Why are we getting fatter?

[This is a transcript of the video embedded below. Some of the explanations may not make sense without the animations in the video.]



Today I want to talk about personal energy storage. I don’t mean that drawer we all have that’s full of batteries in the wrong size, I mean our expanding waistlines that store energy in form of fat. What are the main causes of obesity, how much of a problem is it, and what are you to make of the recent claims that obesity is caused by plastic? That’s what we’ll talk about today.

Obesity is common and becoming more common, so common in fact that the World Health Organization says “the issue has grown to epidemic proportions.” The proportions of the issue are, I guess, approaching that of a sphere, and the word “epidemic” just means it’s a widely spread health problem. Though, interestingly enough, obesity is in some sense infectious. Not because it’s spread by a virus, but because eating habits spread in social networks. If your friends are obese, you’re more likely to be obese too.

In the past decades, the fraction of people who are obese has steadily increased everywhere. In the United States, more than a third of adults are now obese. Canada, the UK, and Germany are not far behind. The United States by the way are not world-leaders in obesity, that title goes to a pacific island by name Nauru where 60 percent of adults are obese. I have no idea what is going on there, but I want to move there when I retire.

Jokes aside, the economic burden of obesity is staggering. According to an estimate from the Milken Institute for the United States alone, obesity and overweight account for direct health care costs of at least four-hundred eighty billion dollars per year. The indirect costs due to lost economic productivity are even higher, about 1 point two four trillion dollars per year. Together that’s more than 9 percent of the entire American GDP.

But what, exactly, is obesity? The World Health Organization defines obesity as an “abnormal or excessive fat accumulation that may impair health”. I believe that an “excessive fat accumulation” does not mean stuffing your fridge with so much cheese that it hits you in the face when you open the door. They probably mean an accumulation of fat in the human body. This is why obesity is most commonly measured with the body mass index, BMI for short, that’s your weight in kilogram divided by the square of your height in meters. For adults, a BMI over 25 kilogram per square meter is overweight, and over 30 it’s obese.

The BMI is widely used because it’s easy to measure, but it has several shortcomings. The biggest issue is that it doesn’t take into account how much of your body weight is fat. You can put on muscle rather than fat and your BMI goes up. A more reliable measure is the amount of body fat.

There are no accepted definitions for obesity based on the percent of body fat, because academia wouldn’t be academia if people could just agree on definitions and move on. But a commonly used indicator for overweight is more than 25 percent fat for men and more than 35 percent for women. Turns out that about 12 percent of men who have a BMI about 25 have a normal amount of body fat, so probably just a lot of muscles. And on the flip side, about 15 percent of women with a BMI below 25 have an abnormally high percentage of body fat.

But using body fat as a measure for obesity is also overly simplistic because the problem isn’t actually the fat, it’s where you store it.

You see, the body removes fat from the blood and then tries to store it in fat cells. But in adults the number of fat cells doesn’t increase, it’s just the size of the cells that increases. And there’s only so much fat that a single cell can store. The problem begins when all the fat cells are full. Because then the body has to store the fat in places where it doesn’t belong and it does that notably around the liver and in muscle tissue. That’s right, the fat isn’t the problem, it’s the lack of fat cells that’s the problem. I would like to add that for the same reason books aren’t the problem, it’s the lack of bookshelves that’s the problem.

The out-of-place storage of fat seems to be the major reason for most of the health problems associated with obesity. Among others, that’s an increased risk for heart attacks and strokes, type 2 diabetes, breathing problems, knee, hip, and back problems, and an increased risk for certain types of cancer. But since there are individual differences in how much fat the body can store in the available fat cells, the onset of disease doesn’t happen at any particular amount of fat. About 20 percent of people with a BMI above thirty appear to be metabolically healthy.

This is why researchers have tried to figure out specifically where too much fat is a problem. But it’s not as easy as saying, if your waist circumference is more than so-and-so then that’s too much. To begin with, as you have undoubtably noticed, men and women store fat in different places. Men store it mostly at the belly, women store it primarily at the breasts, thighs (!th), and bottom, which is why you never get to see my bottom. It doesn’t fit on the screen. So, if you use a measure like waist circumference, at the very least you have to use a different one for men and women. To make matters more complicated, the onset of metabolic disease with waist circumference seems to depend on the ethnic group.

To return to the definition from the WHO, we see that it’s not all that easy to figure out when “an accumulation of fat impairs health”. It’s clearly not just the number on your scale that matters and it’s true that some obese people are healthy. Still, after all is said and done, the BMI is very strongly correlated with the ill effects of obesity.

So what are the possible causes of this obesity epidemic? Yes, the universe also expands, but it’s the space between galaxies that expands, not planets, or people on planets. So I’m afraid we can’t blame Einstein for this one. But if not Einstein, then what?

The first possible cause of obesity is too much food. Bet you didn’t think of this one.

Food has become more easily accessible to almost everyone on the planet, but especially in the developed world. It doesn’t help that food companies have an incentive to make you want to eat more. In a familiar pattern, the sugar industry has tried to play down evidence that sugar contributes to coronary heart disease for decades, though the evidence is now so overwhelming that they’ve given up denying it.

But just saying obesity is caused by easy access to food is a poor explanation because not everyone who has food in abundance also gets fat. Let’s therefore look at the second possible cause, the wrong type of food.

Modern food is nothing like the food our ancestors ate. A lot of the stuff we eat today is highly processed, which means for example that meat is shredded to small pieces, mixed with saturated fats and preservatives, and then formed to shapes. Processed food also often lacks fiber and protein and is instead rich in salt, sugar and fat, possibly with chemical compositions that don’t occur in nature.

The issue with processed food is that we may say we’re “burning energy” but, I mean I’m just a physicist, but I believe the human body doesn’t literally burn food. It’s rather that we have to take apart the molecules to extract energy from them. And taking apart the food requires energy, so the net turnout depends on how easy the food is to digest. Processed food is easy to digest, so we get more energy out of it, and put on weight faster.

The correlation between processed food and overweight is well-established. For example, in 2020 a a study looked at a sample of about 6000 adults from the UK. They found that the highest consumption of processed food was associated with 90 percent higher odds for being obese. Another paper from a just a few weeks ago analyzed data from adolescents who had participated in a Health and Nutrition Survey in the United States. They too found that the highest consumption of ultra-processed food was associated with up to 60 percent higher odds of being obese.

A particular problem are trans fats, that are fats which don’t identify with the hydrogen bonds they were assigned at birth. Trans fats are chemically modified so that they can be produced in solid or semi-solid form which makes them handy for the food industry. The consumption of trans fats is positively correlated not only with obesity but also with cardiovascular diseases, disorders of the nervous system, and certain types of cancer, among others. Forty countries have banned or are in the process of banning trans fats. I’m not a doctor but I guess that means they really aren’t healthy.

Let’s then look at the third possible cause, lack of exercise. Just last year, a group of European researchers published a review of reviews on the topic, so I guess that’s a meta-meta-review. They found that exercise led to a significant weight loss in obese people. But when they say “significant” they mean statistically significant not that it’s a lot of weight. If you look at the numbers they are referring to fat loss of about 2 kilogram on average, a difference that most obese people would hardly notice. Part of the reason may be that exercise has a rebound effect. If people start exercising, they also eat more.

Don’t get me wrong, exercise has a lot of health benefits in and by itself, so it’s a good thing to do, but it seems that its impact on reducing obesity is limited.

The next cause we’ll look at are your genes. Obesity has a strong genetic component. Twin, family, and adoption studies show that the chance that obesity is passed down the family line lies between 40 and 70 percent.

The genetic influence on obesity comes in two types, monogenic and polygenic. The monogenic type is caused by only one of a number of genes that affect the regulation of food intake. Monogenic obesity is rare and affects fewer than 5 percent of obese people. Those who are affected usually gain weight excessively already as infants.

Polygenic obesity has contributions from many different genes, though some of them stand out. For example, the so-called FTO gene affects the production of a hormone called ghrelin. Ghrelin is often called the “hunger hormone” because it regulates appetite. The ghrelin level is high if you’re hungry and decreases after you’ve eaten. A study in 2013 found that people with the obesity variant of the FTO gene showed less reduction of ghrelin levels after they’d eaten. So they’ll stay hungry longer, and you don’t need to be Einstein to see how this can lead to weight gain.

How many obese people are obese because of their genes? No one really knows. For one, not all genes that contribute to obesity are known, not all people who carry those genes are obese, and the prevalence of certain genes depends strongly on the population you look at. For example, the variation of the FTO gene that’s correlated with an increase of BMI is present in about 42 of people with European ancestry, but only 12 percent of those with African ancestry. So, it’s complicated, but that’s why you’re here, so let’s make things more complicated and look at the next possible cause of obesity, the microbiome.

The microbiome, that’s all those bacteria, viruses, and fungi that live in your gut. They strongly affect what you can digest and how well. Several studies have shown that obese people tend to have a somewhat different microbiome. However, some other studies seem to contradict that, and it’s also again unclear whether this is a cause or an effect of obesity. So my conclusion on this one is basically, more work is needed. The next suspect is your circadian rhythm.

Your inner clock regulates metabolic processes, that includes digestion. If you mess with it and eat or sleep at the wrong time, you might extract more or less energy from food. A 2018 review paper reported strong evidence that disrupted sleep and circadian misalignment, such a working night shifts, contributes to obesity.

However, while the correlation is again statistically significant, the effect isn’t particularly large. A survey by the American Cancer Society found that in women, missing out on sleep is associated with a BMI that’s greater by 1.39 kilogram per square meter, while in men it’s a difference of up to 0 point 57 kilogram per square meter. That typically converts to one or two kilogram in weight.

Another possible cause of obesity is stress. For example, a 2019 paper looked a group of about 3000 adult Americans and their exposure to a wide range of psychosocial stressors, such as financial strain, relationship trouble, people who believe in the many worlds interpretation of quantum mechanics, etc. They found that stress increased the risk of obesity by 15 to 25 percent.

But correlation doesn’t mean causation. For one thing, stressed people don’t sleep well, which we’ve seen also makes obesity more likely. Or maybe they are stressed because they’re obese to begin with?

Yet another possible cause of obesity that researchers have looked at are vitamin and mineral deficiencies. These are indeed common among overweight and obese individuals. That’s been shown by a number of independent studies. But in this case, too, the direction of causation remains unclear because excess body weight alters how well those nutrients are absorbed and distributed.

Another option to explain why you’re fat is to blame your mother. Indeed, there’s quite convincing evidence that if your mother smoked while pregnant, you’re more likely to be obese. For example, a 2016 meta-review from a group in the UK found that children born to smoking mothers had a 55 percent increased risk of being obese. A similar meta-analysis from 2020 came to a similar conclusion. However, these meta-reviews are difficult to interpret because there are many factors that have to be controlled for. Maybe your mother smoked because she’s stressed and that’s why you didn’t get enough sleep and now you’re fat. This is all getting very confusing, so let’s talk about the two newest ideas that scientists have come up with to explain the obesity epidemic, viruses and plastic.

Did I say obesity is not caused by a virus, oops!

Turns out that a number of viruses are known to cause obesity in chickens, mice, and rats. And it’s not just animals. A meta-analysis from 2013 showed that a previous Adenovirus 36 infection is correlated with an increased risk of obesity of about 60 percent. A few other viruses are suspect, too, but this Adenovirus 36 seems to be the biggest offender. An infection with adenovirus 36 has the symptoms of a common cold but can also lead to eye infections.

A review published in 2021 in the International Journal of Obesity found that 31 out of 37 studies. reported a positive correlation between Adenovirus 36 antibodies and weight gain, obesity, or metabolic changes. However, this virus is incredibly common. About every second person has antibodies against it, not all of them are obese, and not all obese people have had an infection. So this might play a role for some people but it’s unclear at the moment how relevant it is. In any case, face masks also protect from obesity, just don’t take them off.

This finally brings us to the headlines you may have seen some weeks ago claiming that plastic makes us fat. These headlines were triggered by three review papers that appeared simultaneously in the same journal about the role of obesogens in the obesity epidemic.

“Obesogen” is a term coined in 2006 by two researchers from UC Irvine. They are a type of “endocrine disrupting chemicals” that resemble natural hormones and can interfere with normal bodily functions. About a thousand chemicals are currently known to have, or are suspected to have endocrine disrupting effects. About 50 of those are believed to be obesogens that affect the metabolic rate, the composition of the microbiome, or the hormones that influence eating behavior.

Obesogens are in cosmetics, preservatives, sun lotion, furniture, electronics, plastics, and the list goes on. From there they drift into the environment. They have been found also in dust, water, and even in medication and processed foods.

The review papers report fairly convincing evidence that obesogens affect the development of fat and muscle cells in a petri dish, not to be confused with a peach tree disk. There is also some evidence that obesogens affect the development of mice and other animals. However, the evidence that they play a significant role for obesity is not quite as convincing.

The majority of studies on the topic show a positive correlation between obesogen exposure and an elevated BMI, especially when exposure occurs during pregnancy or in childhood. However, as we saw earlier, just because a correlation is statistically significant doesn’t mean the effect is large. How large the effect may be is at present guess work. In a recent interview with The Guardian the lead author of one of the reviews, Robert Lustig, said “If I had to guess, based on all the work and reading I’ve done, I would say obesogens will account for about 15 to 20 percent of the obesity epidemic. But that’s a lot.”

Maybe. If it was correct. But maybe asking the lead author isn’t the most objective way to judge the relevance of a study. There are also some studies which didn’t find correlations between obesogen exposure and obesity risk and again, the results are difficult to interpret, because exposure to certain chemicals depends on living conditions that are correlated with all kinds of demographic factors.

Despite that, the researchers claim that “epidemiological studies substantiate a causal link between obesogen exposure and human obesity”. They don’t stop there but put forward a new hypothesis for the cause of obesity.

In their own words: “This alternative hypothesis states that obesity is a growth disorder, in effect, caused by hormonal/enzymatic defects triggered by exposures to environmental chemicals and specific foods in our diet.” You can see how this would make big headlines. It’s such a convenient explanation, all those damned chemicals are making us fat. However, until there’s data on how big the effect is, I will remain skeptical of this hypothesis.

So, let’s wrap up. The best evidence for factors that make obesity more likely are genetics and the consumption of processed food. Factors that may make the situation worse, are stress, lack of sleep, exercise, or essential vitamins and minerals, and an abnormal microbiome, but in all those cases it’s difficult to tell apart cause and effect. When it comes to viruses and exposure to certain chemicals, the headlines are bigger than the evidence.

If you’re interested in a video on possible treatment options for obesity, let us know in the comments.

Science News Oct 12

Cold Fusion is Back (there's just one problem)

[This is a transcript of the video embedded below. Some of the explanations may not make sense without the animations in the video.]



Cold fusion could save the world. It’d be a basically unlimited, clean, source of energy. It sounds great. There’s just one problem: it’s not working. Indeed, most physicists think it can’t work even in theory. And yet, the research is making a comeback. So, what’s going on? What do we know about cold fusion? Is it the real deal, or is it pseudoscience? What’s cold fusion to begin with? That’s what we’ll talk about today.

If you push two small atomic nuclei together, they will form a heavier one. This nuclear fusion releases an enormous amount of energy. There’s just one problem: Atomic nuclei all have a positive electric charge, so they repel each other. And they do so very strongly. The closer they are, the stronger the repulsion. It’s called the Coulomb barrier, and it prevents fusion until you get the nuclei so close together that the strong nuclear force takes over. Then the nuclei merge, and boom.

The sun does nuclear fusion with its enormous gravitational pressure. On earth, we can do it by heating a soup of nuclei to enormous temperatures, or by slamming the nuclei into each other with lasers. This is called “hot nuclear fusion”. And that indeed works. There’s just one problem: At least so, far hot fusion eats up more energy than it releases. We talked about the problems with hot nuclear fusion in this earlier video.

But nuclear fusion is possible at far lower energy, and then it’s called cold fusion. The reason this works is that atomic nuclei don’t normally float around alone but have electrons sitting in shells around the nucleus. These electrons shield the positive charges of the nuclei from each other and that makes it easier for the nuclei to approach each other.

There’s just one problem: If the atoms float around freely, the electron shells are really large compared to the size of the nucleus. If you bring these nuclei close together, then their electron shells will be much farther apart than the nuclei. So the electron shells don’t help with the fusion if the nuclei just float around.

One thing you can do is strip off the electrons and replace them with muons. Muons are basically heavier versions of electrons, and since they are heavier, their shells are closer to the nucleus. This shields the electric fields of the nuclei better from each other and makes nuclear fusion easier. It’s called “muon catalyzed fusion”.

Muon catalyzed fusion was theoretically predicted already in the 1940s and successfully done in experiments in the 1950s. It’s cold fusion that actually works. There’s just one problem: muons are unstable. They must be produced with particle accelerators and those take up a lot of energy. The muons then get mostly lost in the first fusion reaction so you can’t reuse them. There’s a lot more to say about muon catalyzed fusion, but we’ll save this for another time.

There’s another type of “cold fusion” that we know works, which is actually a method for neutron production. For this you send a beam of deuterium ions into a metal, for example titanium. Deuterium is a heavy isotope of hydrogen. Its nucleus is a proton with one neutron. At first, the beam just deposits a lot of deuterium in the metal. But when the metal is full of deuterium, some of those nuclei fuse. These devices can be pretty small. The piece of metal where the fusion happens may just be a few millimeters in size. Here is an example of such a device from Sandia Labs which they call the “neutristor”.

The major reason scientists do this is because the fusion releases neutrons, and they want the neutrons. It’s not just because lab life is lonely, and neutrons are better than no company. Neutrons can also be used for treating materials to make them more durable, or for making radioactive waste decay faster.

But the production of the neutrons is quite an amazing process. Because the beam of deuterium ions which you send into this metal typically has an energy of only 5-20 kilo electron Volt. But the neutrons you get out, have almost a thousand times more energy, in the range of a few Mega electron Volt. It’s often called “beam-target fusion” or “solid-state fusion”. It’s a type of cold fusion, and again we know it works.

There’s just one problem: The yield of this method is really, really low. It’s only about one in a million deuterium nuclei that fuse, and the total energy you get out is far less than what you put in with the beam. So, it’s a good method to produce neutrons, but it won’t save the world.

However, when physicists studied this process of neutron production, they made a surprising discovery. When you lower the energy of the incoming particles, the fusion rates are higher than theoretically expected. Why is that? The currently accepted explanation is that the lattice of the metal helps shielding the charges of the deuterium nuclei from each other. So, it lowers the Coulomb barrier, and that makes it more likely that the nuclei fuse when they’re inside the metal. This isn’t news, physicists have known about this since the 1980s.

But if putting the deuterium into metal reduces the Coulomb barrier, maybe we can find some material in which it’s lowered even further? Maybe we can lower it so far that we create energy with it? This idea had been brought up already in the 1920s by researchers in the US and Germany. And it’s what Pons and Fleischman claimed to have achieved in their experiment that made headlines in 1989.

Pons and Fleischman used a metal called palladium. The metal was inside a tank of heavy water, so that’s water where the normal hydrogen is replaced with deuterium. Ponds and Fleischman then applied a current going through the palladium and the heavy water. They claimed this created excess heat, so more than what you’d get from the current alone. They also said they’d seen some decay products of fusion reactions, notably neutrons and tritium. Everyone was very excited.

There was just one problem... Other laboratories were unable to reproduce the claims. It probably didn’t help that Pons and Fleischmann were both chemists, but nuclear fusion has traditionally been territory of physicists. And physicists largely think that chemical reactions simply cannot cause nuclear fusion because the typical energies that are involved in chemical processes are far too low.

A few groups said they’d seen something similar to Ponds and Fleischman, but the findings were inconsistent, and it remained unclear why it would sometimes work and sometimes not. By the early nineties, the Pons and Fleischmann claim was largely considered debunked. Soon enough, no scientist wanted to touch cold fusion because they were afraid it would damage their reputation. The philosopher Huw Price calls it the “reputation trap”. In fact, while I was working on this video, I’ve been warned that I, too, would be damaging my reputation.

Of course not everyone just stopped working on cold fusion. After all, it might save the world! Some carried on, and a few tried to capitalize on the hope.

One such case is that of Andrea Rossi who already in the 1970s said he knew how to build a cold fusion device. In 1998, the Italian government shut down his company on charges of tax fraud and dumping toxic waste into the environment. In the mid 1990s, Rossi moved to the USA and by 2011, he claimed to have a working cold fusion device that produced excess heat.

He tried to patent it, but the international patent office rejected the application arguing that the device goes “against the generally accepted laws of physics and established theories”. A rich Australian guy offered $1 million to Rossi if he could prove that the device produces net power. Rossi didn’t take up the offer and that’s the last we heard from him. There’s more than one problem with that.

In 2019, Google did a research project on cold fusion and they found that the observed fusion rate was 100 times higher than theoretically expected. But it wasn’t enough to create excess heat.

The allure of cold fusion hasn’t entirely gone away. For example, there are two companies in Japan, Technova Inc. and Clean Planet Inc, which claim to have produced excess heat. Clean Planet Inc has a very impressive roadmap on their website, according to which they’ll complete a model reactor for commercial application next year. There’s just one problem: No one has seen the world-saving machine, and no one has reproduced the results.

The people who still work on cold fusion have renamed it to “Low Energy Nuclear Reactions”, LENR for short. Part of the reason is that “cold” isn’t particularly descriptive. I mean, these devices may be cold compared to the interior of the sun, but they can heat up to some hundred degrees Celsius, and maybe that’s not everybody’s idea of cold. But no doubt the major reason for the rebranding is to get out of the reputation trap. So make no mistake, LENR is cold fusion reborn.

I admit that this doesn’t sound particularly convincing. But I think it’s worth looking a little closer at the details. First of all, there are two separate measurements that cold fusion folks usually look at. That’s the production of decay products from the nuclear fusion, and the production of excess heat.

An experiment that tried to shed light on what might be going on comes from a 2010 paper by a group in the United States. They used a setup very similar to that from Fleischmann and Pons but in addition they directed a pulsed laser at the palladium with specific frequencies. They claimed to see excess power generation for specific pulse frequencies, which suggests that phonon excitations have something to do with it. There’s just one problem: a follow-up experiment failed to replicate the result.

Edmund Storms who has been working on this for decades published a paper in 2016 claiming to have measured excess heat in a device that’s very similar to the original Ponds and Fleischman setup. In this figure you see how the deuterium builds up in the palladium, that’s the red dots, and the amount of power that Storms says he measured.

He claims that the reason that these experiments are difficult to reproduce is that the nuclear reactions happen in appreciable rates only in some regions of the palladium which have specific defects that he calls nano-cracks. These could be caused by the treatment of the metal, so some samples have them and others not, and this is why the experiments sometimes seem to work and sometimes not. At least according to Storms. There’s just one problem: No one’s been able to replicate his findings.

There is also a 2020 paper from the Japanese company, Clean Planet Inc which I already mentioned. They use a somewhat different setup with nanoparticles of certain metals that are surrounded by a gas that contains deuterium. The whole thing is put under pressure and heated. They claim that the resulting temperature increase is higher than you’d expect and that their device generates net power. In this figure you see the measured temperature increase in their experiment with Helium gas and with a gas that contains deuterium. The Helium gas serves as a control. As you see there’s more heating with the deuterium. There’s just one problem: No one’s been able to replicate this finding.

The issue with these heat measurements is that they’re incredibly difficult to verify. For this reason it’s much better to look at the decay products. Those are in and by themselves mysterious. In a typical nuclear fusion reaction, there is a very specific amount of energy that’s released, and so the energy distribution of the decay products is very sharply peaked. In deuterium fusion, the neutrons in particular should have an energy of 2.45 MeV. In those cold fusion reactions, however, they see a fairly broad distribution of neutron energies and at higher energies than expected.

Here is an example. The red bars show the number of deuterium ions as a function of energy, the black ones are the background. As you can see the spectrum looks nowhere like the expected peak at about 2.5 MeV. Something is going on and we don’t know what. Forget saving the world for a moment, it’s much simpler, there’s an observation that we don’t understand.

In a recent paper, a group from MIT has put forward two different hypotheses that could explain why nuclear fusion happens more readily in certain metals than you’d naively assume. One is that there are some unknown nuclear resonances which can become excited and make fusion easier. The other one is that the lattice of the metal facilitates an energy transfer from the deuterium to some of the palladium nuclei. So then you have excited Palladium nuclei and those decay. Since the Palladium nuclei have more decay channels than are typical for fusion outputs, this can explain why the energy distribution looks so weird. There’s just one problem: We don’t know that that’s actually correct.

What are we to make of this? The major reason cold fusion has been discarded as pseudoscience is that most physicist think it can’t possibly be that chemical processes cause nuclear reactions. But I think they overestimate how much we know both about nuclear physics and chemistry.

Nuclear physics is dominated by the strong nuclear force which holds quarks and gluons together so that they form neutrons and protons. The strong nuclear force has the peculiar property that it becomes weaker at high energies. This is called asymptotic freedom. Arvin Ash recently did a great video about the strong nuclear force, so check this out for more details.

The Large Hadron Collider pumps a lot of energy into proton collisions. This is why understanding the strong nuclear force in LHC collisions is quite simple, by which I mean a PhD in particle physics will do. The difficult part comes after the collisions, when the quarks and gluons recombine to protons, neutrons, and other bound states such as pions and rhos and so on. It’s called hadronization, and physicists don’t know how to calculate this. They just extract the properties of these processes from data and parameterize it.

I am telling you this to illustrate that just because we understand the properties of the constituents of atomic nuclei doesn’t mean we understand atoms. We can’t even calculate how quarks and gluons hold together.

Another big gap in our understanding are material properties because we often can’t calculate electron bands. That’s especially true for materials with irregularities that, according to Storms, are relevant for cold fusion. Indeed, if you remember, calculating material properties is one of those questions that physicists want to put on a quantum computer exactly because we can’t currently do the calculation. So, is it possible that there is something going on with the nuclei or electron bands in those metals that we haven’t yet figured out? I think that’s totally possible.

But, let me honest, I find it somewhat suspicious that the power production in cold fusion experiments always just so happens to be very close to the power that goes in. I mean, there isn’t a priori any reason why this should be the case. If there is nuclear fusion going on efficiently, why doesn’t it just blow up the lab and settle the case once and for all?

So, well, I am extremely skeptical that we’ll see a working cold fusion device in the next couple of years. But it seems to me there’s quite convincing evidence that something odd is going on in these devices that deserves further study.

I’m not the only one who thinks so. In the past couple of years, research into cold fusion has received a big funding boost, and that’s already showing results. For example, in 1991, a small group of researchers proposed a method to produce palladium samples that generate excess heat more reliably. And, I hope you’re sitting, research groups at NASA and at the US Navy have recently been able to reproduce those results.

A project at the University of Michigan is trying to reproduce the findings by the Japanese companies. The Department of Energy in the United States just put out a call for research projects on low energy nuclear reactions, and also the European research council has been caught in the act of supporting some cold fusion projects.

I think this is a good development. Cold fusion experiments are small and relatively inexpensive and given the enormous potential, it’s worth the investment. It’s a topic that we’ll certainly talk about again, so if you want to stay up to date, don’t forget to subscribe. Many thanks to Florian Metzler for helping with this video.

The First Ever Episode of Science News Without the Gobbledygook

One thing I miss about the blogging days is the ability to comment on current events short notice. It's much harder with video than in writing. This is why on my YouTube channel, we now have a weekly Science News episode. 


I hope we will all have some fun with this :o)

I have 6 other people involved in the production of this weekly news show (it's more difficult than you might think). We will only be able to continue with this if we find sponsors, and we will only find sponsors if we have sufficiently many views. That is to say, if you like our science news and would like them to continue, please help us spread the word!

Can we make flying "Green"?

[This is a transcript of the video embedded below. Some of the explanations may not make sense without the animations in the video.]



“Flight shaming” is a social movement that originated in Sweden a few years ago. Its aim is to discourage people from flying because it’s bad for the environment. But let’s be honest, we’re not going to give up flying just because some Swedes think we should. I mean, we already shop at IKEA, isn’t that Swedish enough?

But seriously, maybe the flight shamers have a point. If aliens come to visit us one day, how are we supposed to explain this mess? Maybe we should indeed try to do something about airplane emissions. What are airlines doing anyway, isn’t it their job? What are the technological options, and will any of them give you a plausible excuse if flight shamers come for you? That’s what we’ll talk about today.

Flying may be good for watching four movies in a row, but it really isn’t good for the planet. It’s the third biggest contribution to carbon emissions from individuals, after having children and driving a car. Altogether, flying currently accounts for around 2 point 5 percent of global carbon dioxide emissions, that’s about a billion tons each year. 81 percent of this comes from passenger flights, and another 60 percent of that, so about half of the total, are international flights.

Most of the flights, not so surprisingly, come from high-income countries. If flying was as a country itself, it would rank sixth in carbon dioxide emissions, and it would congratulate the new British Prime Minister by reminding her that “The closest emergency exit may be behind you.”

The total carbon dioxide emissions from flying have been increasing steeply in the past decades, but the relative contribution has remained stable at 2 point 5 percent. This is partly because everybody is emitting more with everything, but also because planes have become way more fuel efficient. Planes consume today about half as much fuel as they did in the mid 1960’s.

Carbon dioxide emissions are not the only way that flying contributes to climate change. It also adds some other greenhouse gasses, and it creates clouds at high altitude that trap heat. But in this video, we’ll focus on the carbon dioxide emissions because that’s the biggest issue, right after the length of this video.

There are four ways that airlines are currently trying to reduce their carbon emissions, that’s electric planes, hydrogen, biofuel, and synthetic fuel. We’ll talk about each of those starting with electric planes.

1. Electric planes

The idea of electric planes is pretty obvious, charge a battery with a carbon neutral source of energy, use the battery to drive a propeller, try to not fall off the sky. Then you can partly recharge the battery when you’re landing.

And at first sight it does sound like a good idea. In 2016, the Swiss aircraft Solar Impulse 2 completed its first trip around the world. Its wings are covered with solar cells with a wingspan that is comparable to that of a Boeing 747.

A Boeing 747 typically flies at about one thousand kilometers per hour and carries 500 or so people. The Solar Impulse carries two and it flies about 70 kilometers per hour. At that speed it would take about 4 days to get from Frankfurt to New York which requires more in-flight entertainment than the CDC recommends.

You might think the issue is the solar panels, but the bigger problem is that electric batteries are heavy, and you don’t need to be Albert Einstein to understand that something that’s supposed to fly better not be heavy.

One way to see the problem is to compare batteries to kerosene, which is illustrated nicely in this figure. On the vertical axis you have the energy per mass and on the horizontal axis the energy per volume. Watch out, both axes are logarithmic.

You want energy sources that are as much in the top right corner as possible. Kerosene is up here, And lithium-ion batteries down here. You can see that kerosene has 18 times more energy in the same volume as a typical lithium-ion battery and sixty times more energy in the same mass. This means it’s difficult to pack power onto an aircraft in form of electric batteries. Consequently, electric planes are slow and don’t get far.

For example, in 2020, the Slovenian aircraft company Pipistrel brought the first electric aircraft onto the market. It’s powered by lithium-ion batteries, can carry up to 200 kilogram, and flies up to 50 minutes with a speed of about 100 kilometers per hour. It’s called Velis Electro which sounds like a good name for a superhero. And indeed, carrying 200 kilograms at 100 kilometers per hour is great if you want to rescue the new British Prime Minister from an oncoming truck, I mean, lorry. Though there isn’t much risk of that happening because the lorries are stuck at the French border. Which, incidentally, is farther away from London than this plane can even fly.

Nevertheless, some other companies are working on electric planes too. The Swedish start-up Heart Aerospace plans to build the first electric commercial aircraft by 2026. They ambitiously want to reach 400 kilometers of range and hope it’ll carry up to 19 passengers. Presumably that’s 19 average Swedes, which is about the same weight as 2 average Germans.

So, unless there’s a really big breakthrough in battery technology, electric planes aren’t going to replace kerosene powered ones for any sizeable share of the market, though they might be used, for example, to train pilots. Train them to fly, that is, not to rescue prime ministers.

A plus point of electric planes however is that they are more energy-efficient than kerosene powered ones. An electric system has an efficiency of up to ninety percent, but kerosene engines only reach about fifty percent efficiency. To this you must add other inefficiencies in the gearbox and the mechanics of the propeller or fan and so on. The total efficiency is then around 70-75 percent for electric engines and between thirty and forty percent for kerosene engines.

The technological developments that are going to have the biggest impact on electric planes are new types of batteries, that are either lighter or more efficient or, ideally, both. Lithium-sulfur and lithium-oxygen batteries are two examples that are currently attracting attention. They pack three to ten times more energy into the same mass as than Lithium-ion batteries.

2. Hydrogen

Let’s then talk about hydrogen. No, we don’t want to bring the Zeppelin back. We are talking about planes powered by liquid hydrogen. If we look back at this handy figure, you can see that liquid hydrogen really packs a lot of energy into a small amount of mass. It has, however, still a fairly large volume compared to kerosene. And volume on an airplane means you must make the plane bigger which makes it heavier, so the weight-issue creeps back in.

Also, hydrogen usually isn’t liquid, so you have to either cool it or keep it under pressure. Cooling requires a lot of energy, which is bad for efficiency. But keeping hydrogen under pressure requires thick tanks which are heavy. It’s like there’s a reason fossil fuels became popular.

The downside of hydrogen is its low efficiency, which is only around 45 percent. Still, together with the high energy density, it’s not bad, and given that burning hydrogen doesn’t create carbon dioxide it’s worth a try.

Hydrogen powered airplanes aren’t new. Hybrid airplanes that used hydrogen were being tested already in the 1950’s. Airbus is now among the companies who are developing this technology further. Just a few months ago, they presented what they call the ZEROe demonstrator. It’s a hydrogen powered engine, that will be tested both on the ground and in flight, though in the test phase the plane will still be carried by standard engines.

They recently did a 4-hour test flight for the hydrogen engine. The plane they used was an A380, that’s a two-deck plane that can transport up to eight hundred passengers or so. They used this large plane because it has plenty of room for the hydrogen tanks plus the measurement equipment plus a group of engineers plus their emotional support turkeys. However, the intended use of the hydrogen engine is a somewhat smaller plane, the A350. Airbus wants to build the world’s first zero-emission commercial aircraft by 2035.

The Airbus competitor Boeing is not quite so enthusiastic about hydrogen. Their website explains that hydrogen “introduces certification, infrastructure, and operational challenges”. And just to clarify the technical terms, “challenge” is American English for “problem”. Because of those challenges, Boeing focusses on sustainable fuels. According to its CEO, sustainable fuels are “the only answer between now and 2050”. So let’s look at those next.

3. Biofuel

Bio-fuels are usually made from plants. And when I say plants, I mean plants that have recently deceased and not been underground for a hundred million years. Bio-fuels still create carbon dioxide when burned, but the idea is that it’s carbon dioxide you took out of the air when you grew the plants, so the carbon just goes around in a cycle. This means unlike regular jet fuel, which releases carbon dioxide that was long stored underground in oil, bio-fuels don’t increase the net amount of carbon dioxide in the atmosphere.

The most common bio-fuel is ethanol, which can be made for example from corn. It can and is being used for cars. But ethanol isn’t a good choice for airplanes because it’s not energy dense enough, basically, it’s too heavy. In the figure we already looked at earlier, it’s up here.

Another issue with bio-fuel is that, to be used for aircraft, it must fulfil a lot of requirements, in particular it must continue to flow well at low temperatures. I’m not much of an engineer but even I can see that if the fuel freezes midflight that might be a challenge.

A bio jet fuel which fits the bill is synthetic paraffinic kerosene, which can be made from vegetable

oils or animal fats, but also from sugar or corn. Paraffinic kerosene is in some sense better than fossil kerosene. For example, it generates less carbon dioxide and less sulfur.

The International Airport Transport Association considers bio-jet fuel a key element to get off fossil fuels. Indeed, some airlines are already using biofuels. The Brazilian company Azul Airlines has been using biofuel from sugarcane on some of their flights for a decade. British Airways has partnered with the fuel company LanzaJet to develop biofuels that are suitable for aircraft. The American Airline United is also investing into biofuels. And the Scandinavian airline SAS has the goal to use 17 percent biofuel by 2025.

The problem, I mean challenge, is that bio jet fuels still cost three to six times more than conventional jet fuel. Moreover, researchers from the UK and Netherlands have estimated that the start-up cost for a commercial bio jet fuel plant is upwards of 100 million dollar which is a barrier to get things going.

But making the production of bio jet fuel easier and more affordable is a presently a very active research area. An approach that’s attracting a lot of attention is using microalgea. They produce a lot of biomass, and they do so quickly. Microalgae reach about three to eight percent efficiency in transforming solar energy to chemical energy, while conventional biofuel crops stay below 1 percent. Take that, conventional biofuel crops!

Algae also generate more oil than most plants, and genetic engineering can further improve the yield. A few years ago, ExxonMobil partnered with Craig Venter’s Synthetic Genomics and they developed a new strain of algae using the gen editing tool CRISPR. The gene engineered algea had a fat content of 40-55 percent compared to only 20 percent in the naturally occurring strain.

But bio fuels from algae also have a downside. They have a high nitrogen content so the fuel produced from them will release nitrogen oxides. If you remember, we talked about this earlier in our video on pollution from diesel engines. Then again, you can try to filter this out, at least to some extent.

Another way to make biofuels more affordable is to let the customer pay for it. SAS for example says if you pay more for the ticket, they’ll put more biofuel into the jet. So, it’s either more legroom or saving the planet, though times for tall people.

4.Synthetic jet fuel

Finally, you can go for entirely synthetic jet fuel. For this, you take the carbon from the atmosphere using carbon capture, so you get rid of the plants in the production process. Instead, you use a renewable energy source to produce a chemical that’s similar to kerosene from the carbon dioxide and water.

The resulting fuels are not completely carbon neutral because of the production process but compared to fossil fuels they have small carbon footprint. According to some sources, it’s about 70 to 80 percent less than fossil fuels though those number are at present not very reliable.

Synthetic kerosene is already in use. Since 2009, it can be blended with conventional jet fuel. The maximum blending ratio depends on the properties of the synthetic component, but it can be up to fifty percent. This restriction is just a precautionary requirement and it’s likely to be relaxed in the future. The problem, I mean challenge, is that at the moment synthetic kerosene is about 4 to 5 times more expensive than fossil kerosene.

Nevertheless, a lot of airlines have expressed interest in synthetic kerosene. For example, last October, Lufthansa agreed on of annual purchase of at least 25 thousand liters for at least five years. That isn’t a terrible lot. Just for comparison, a single A380 holds up to three hundred twenty thousand liters. But it’s a first step to test if the synthetic stuff works. Quantas announced a few months ago that they’ll invest 35 million dollars in research and development for synthetic jet fuel. They hope to start using it in the early 2030s.

But let me give you some numbers to illustrate the… challenge. In 2020 the market for commercial jet fuel was about 106 billion gallons globally. Twenty-one billion-gallon in the US alone. According to the US Energy Information Administration, it is expected to grow to 230 billion gallons globally by 2050.

At current, the global production of synthetic kerosene is about 33 *million gallons per year. That’s less than a tenth of a percent of the total jet fuel. Still, the International Air Transport Association is tentatively hopeful. They recently issued a report, according to which current investments will expand the annual production of synthetic kerosene to 1 point three billion gallons by 2025. They say that production could reach eight billion gallons by 2030 with effective government incentives, by which they probably mean subsidies.

So, even if we’re widely optimistic and pour a lot of money into it, we might be able to replace 5 percent of jet fuel with synthetic fuel by 2030. It isn’t going to save the planet. But maybe it’s enough to push transatlantic flight down on the sin-list below eating meat, so the Swedes can move on from flight-shaming to meat-shaming.

I’ve said it all before but here we go again

[I didn't write the title and byline
and indeed didn't see it until it
appeared online.]

For reasons I don’t fully understand, particle physicists have recently started picking on me again for allegedly being hostile, and have been coming at me with their usual ad homimen attacks.

What’s going on? I spent years trying to understand why their field isn’t making progress, analyzing the problem, and putting forward a solution. It’s not that I hate particle physics, it’s rather to the contrary, I think it’s too important to let it die. But they don’t like to hear that their field urgently needs to change direction, so they attack me as the bearer of bad news. 

But trying to get rid of me isn’t going to solve their problem. For one thing, it's not working. More importantly, everyone can see that nothing useful is coming out of particle physics, it’s just a sink of money. Lots of money. And soon enough governments are going to realize that particle physics is a good place to save money that they need for more urgent things. It would be in particle physicists’ own interest to listen to what I have to say.

And I have said this all many times before but I hate long twitter threads, so let me just summarize it in one blogpost:

a) Predictions for fundamentally new phenomena made from new theories in particle physics have all been wrong ever since the completion of the standard model in the 1970s. You have witnessed this ongoing failure in the popular science media. All their ideas were either falsified or they have been turned into eternally amendable and fapp unfalsifiable models, like supersymmetry.

b) Saying that “it’s difficult” explains why they haven’t managed to find new phenomena, but it doesn’t explain why their predictions are constantly wrong. 

c) Scientists should learn from failure. If particle physicists’ method of theory-development isn’t working, they should analyze why, and change their methods. But this isn’t happening.

My answer to why their current method isn’t working is that their new theories (often in the form of new particles) do not solve any problems in the existing theories. They just add unnecessary clutter. When theoretical predictions were correct in the past, they solved problems of consistency (example: the Higgs, anti-particles, neutrinos, general relativity, etc).

Two common misunderstandings: Note that I do NOT say theorists in the past used this argument to make their predictions. I am merely noting in hindsight that’s what they did. It’s what the successful predictions have in common, and we should learn from history. Neither do I say that theoretical predictions were the ONLY way that progress happened. Of course not. Progress can also happen by experimental discoveries. But the more expensive new experiments become, the more careful we have to be about deciding which experiments to make, so we need solid theoretical predictions.

In many cases, particle physicists have made up pseudo-problems that they claim their new particles solve. Pseudo-problems are metaphysical misgivings, often a perceived lack of beauty. A typical example is the alleged problem with the Higgs mass being too small (that was behind the idea that the LHC should see supersymmetry). It’s a pseudo-problem because there is obviously nothing wrong with the Higgs-mass being what it is, seeing that they can very well make predictions with the standard model and its Higgs as it is. 

(I sometimes see particle physicists claiming that supersymmetry “explains” the Higgs-mass. This is bluntly wrong. You cannot calculate the Higgs-mass from supersymmetric models, it remains a free parameter.)

Other pseudo-problems are the baryon asymmetry or the smallness of the cosmological constant etc. I have a list that distinguishes problems from pseudo-problems here.

So my recommendation is that theory development should focus on resolving inconsistencies, and stop wasting time on pseudo-problems. Real problems are eg the lacking quantization of gravity, dark matter, the measurement problem in quantum mechanics, as well as several rather technical issues with quantum mechanics (see the above mentioned list).

When I say “dark matter” I refer to the inconsistency between observation and theory. Note that to solve this problem one does NOT need details of the particles. That’s another point which particle physicists like to misunderstand. You fit the observations with an energy density and that’s pretty much it. You don’t need to fumble together entire “hidden sectors” with “portals” and other nonsense. Come on, people, wake up! This isn’t proper science!

There are several reasons why particle physicists can’t and don’t want to make this change. The most important one is that it would dramatically impede their capability to produce papers. And papers are what keeps grant cycles churning. This is a systemic problem. Next problem is that they can’t believe that what I say can possibly be correct because they have grown up in a community that has taught them their current methods are good. That’s group think in action.

There are solutions to both of these problems, but they require changes from within the community.

Particle physicists, rather unsurprisingly, don’t like the idea that they have to change. Their responses are boringly predictable.

They almost all attack me rather than my argument. Typically they will make claims like I’m just “trying to sell books” or that I “want attention” or that I “like to be contrarian” or that, in one way or another, I don’t know what I am talking about. I yet have to find a particle physicists who actually engaged with the argument I made. Indeed most of them never bother finding out what I said in the first place.

A novel accusation that I recently heard for the first time is that I allegedly refuse to argue with them. A particle physicist claimed on twitter that I had been repeatedly invited to give a seminar at CERN but declined, something she had been told by someone else. This is untrue. I have to my best knowledge never declined an opportunity to talk to particle physicists, even though I have been yelled at repeatedly. I was never invited to give a seminar at CERN. 

The particle physicist who made this claim actually went and asked the main seminar organizers at CERN and they confirmed that I was never invited. She apologized. So it’s all good, except that it documents they have been circulating lies about me in the attempt to question my expertise. (Another symptom of social reinforcement.)

There have also been several instances in the past where particle physicists called senior people at my workplace to complain about me, probably in the hope to intimidate me or to get me fired. It speaks much for my institution that the people in charge exerted no pressure on me. (In other words, don't bother calling them, it’s not going to help.)

The only “arguments” I hear from particle physicists are misunderstandings that I have cleared up thousands of times in the past. Like the dumb claim that inventing particles worked for Dirac. Or that I’m “anti-science” because I think building a bigger collider isn’t a good investment right now.

You would think that scientists should be interested in finding out how their field can make progress, but particle physicists just desperately try to make me go away, as if I was the problem. 

But hey, here’s a pro-tip: If you want to sell books, I recommend you don’t write them about theoretical high energy physics. It’s not a topic that has a huge market. Also, I have way more attention than I need or want. I don’t want attention, I want to see progress. And I don’t like being contrarian, I am just not afraid of being contrarian when it’s necessary.

As a consequence of these recent insults targeted at me, I wrote an opinion piece for the Guardian that appeared on Monday. Please note the causal order: I wrote the piece because particle physicists picked on me in a renewed attempt to justify continuing with their failed methods, not the other way round. 

It's not that I think they will finally see the light. But yeah I’m having fun for sure.

Book Review “The Biggest Ideas in the Universe: Space, Time, and Motion” by Sean Carroll

The Biggest Ideas in the Universe
Space, Time, and Motion
By Sean Carroll
Dutton, Sep 20, 2022

The first time I heard Sean Carroll speak was almost 20 years ago in Tucson, Arizona, where he gave a physics colloquium. He had just published his first book, a textbook on General Relativity. His colloquium was basically an introduction to modern cosmology, dark matter, dark energy, and the cosmic microwave background.

It was a splendidly delivered talk; the students loved it. But later I overheard several faculty members remarking they had found it “too simple” and that Sean didn’t seem to be doing much original work. To them, the only good talk was an incomprehensible one. Those remarks, I would later come to realize, are symptomatic of academia: You impress your colleagues by being incomprehensible.

Sean had begun blogging the same year I heard him speak in Tucson, 2004. I would begin blogging not much later, though for unrelated reasons (I originally didn’t intend to write about science), and naturally I kept track of what he was up to.

Since then, it has made me very happy to see Sean making a good career both in research and in science communication, on his own terms. I have met him a few times over the years, read most of his books, and reviewed a few. But I didn’t anticipate he’d pop up on YouTube in 2020, stuck at home during the first COVID lockdowns, like all of us. There he was, green screen as crappy as mine had been a year earlier, promising to cover “The Biggest Ideas in the Universe”, when I had just decided to put more effort into my own YouTube channel.

To my relief it became clear quickly that Sean’s YouTube ambitions were much different from mine. He went for the basics where I prioritized brevity. If my YouTube channel is a buffet, then his is the farmer’s market. And luckily his YouTube appearance remained temporary.

His newest book is the first of three to summarize his YouTube series, focused on dynamical laws, space, and time. It gradually builds up from functions to equations of motions, to concepts like energy, velocity, and momentum, space-time and its geometry, and finishes with black holes in General Relativity. He uses the most essential equations and explains how they work, but you can follow the explanation just by reading the text.

This isn’t your usual popular science book. It doesn’t discuss speculative new ideas, but it’ll give you the background to understand them. It’s a timeless book that I am sure will become a classic, a go-to reference for the interested non-expert who wants to see how the gears of the machinery turn underneath the superficial stories you find in popular science books.

If the three volumes are complete, they’ll presumably cover the classes you’d take for a master’s degree in physics. There aren’t many books like this, which fill the gap between textbooks and popular science books. The only other example that comes to my mind is the “Theoretical Minimum” series by Susskind, Hrabovsky, Friedman, and Cabannes. Sean’s is more focused on the essentials and somewhat lighter in the maths. I have also found Sean’s to be better written.

I’ve always admired Sean for ignoring the unwritten dictum of academia that inaccessibility makes you move valuable, and for his enthusiasm in helping people understand physics, despite the fact that, 20 years ago, most senior academics considered this a waste of time. Today the situation is entirely different. I think Sean was one of the people who changed this attitude.

What is "Nothing"?

[This is a transcript of the video embedded below. Some of the explanations may not make sense without the animations in the video.]


Like most videos on YouTube, this is a video about nothing. But we’re a science channel, so we’ll talk about nine levels of nothing. What are the nine levels of nothing? Can you really make a universe from them? And if someone asks you why there is something rather than nothing, what’s a good answer? That’s what we will talk about today.

First things first, what do we mean by “nothing”? A first attempt to define nothing is to look at how we use the word in everyday language. Suppose your birthday is coming up and you say “Oh, I want nothing.” So when I give you a box for your birthday, you expect it to be empty It’s nothing, in the sense that it doesn’t contain any objects. We will call this the level 1 nothing. It’s a pre-science nothing, the nothing you might refer to before you’ve ever heard of physics.

But of course, you have heard of physics, and so you know that even a box full of level one nothing still contains air, and air is made of something. You wanted nothing for your birthday, and certainly you’ll be disappointed to get air instead. Let’s therefore pump all the air out of this box. We’ll call what’s left the level 2 nothing. It’s what was called a vacuum in the 17th century, no objects, and no air either.

Okay you might say, but we don’t live in the 17th century, and when you said you want nothing for your birthday you really meant it. If we just pump out the air, there’s still the occasional cosmic ray inside, or neutrinos, or dark matter particles, if they exist. So, we go one step further and remove all types of matter, this gives us the level 3 nothing. Indeed, since objects and air are made of particles, removing particles includes the previous two nothings.

But even if the box is closed, there would still be radiation in the box, for example in the infrared, which is maybe not much, but it’s something. And the magnetic field of the earth would also still go through the box. Therefore, we now also remove all types of radiation and all fields. Because you wanted nothing for your birthday and of course I want you to be happy. Now we have a level four nothing: no particles, no radiation, no fields. What you have left then is what you could call the 21st century vacuum.

The level 4 nothing is however is still something. For one thing, many physicists argue that the vacuum has an energy density and pressure and associate this with the cosmological constant. As I explained in this earlier video, I think this doesn’t make sense, the cosmological constant is just a constant of nature which determines the curvature of empty space. Empty space just isn’t necessarily flat. Talking about the curvature of empty space as if it was energy density and pressure is just a weird interpretation of geometry.

Even leaving aside the cosmological constant, the 21st century vacuum isn’t nothing because in quantum field theories, like the standard model of particle physics, the vacuum contains virtual particles that are created in pairs but quickly destroy each other again. They come out of the vacuum and disappear back into it. Virtual particle pairs are like couples you’ve never heard of that pop up in your news feed, destroy each other, and disappear back into nothing. Except with maths.

We can’t directly measure virtual particles, that’s why they’re called virtual. But we can infer their presence because we can measure their influence on other particles. Or we could, if we hadn’t removed those from the box already.

For example, if we look at the energy levels of electrons around an atomic nucleus, these are slightly shifted in the presence of virtual particles. This can be measured, and it has been measured. That’s one way we know virtual particles exist.

You could argue that the phrase “virtual particle” is really just a name for a mathematical expression that we use to calculate measurement outcomes, and I would agree. But be that as it may, we can observe their effects and nothing has no effects so it’s got to be something. And you wanted nothing for your birthday, not a box full of virtual particles. Besides, virtual particles can sometimes become real, for example near black holes, so they can actually kick us back from level four to level three.

To get to level 5 nothing we therefore remove the twenty-first century vacuum too. Now we have neither virtual nor real particles nor radiation nor fields and there’s also no way that any of them can reappear from the vacuum. What’s left in the box now? Well. There’s still space and time in it. And time is money, and money is the root of all evil, and that’s a terrible joke, but still something rather than nothing.

This is why for level 6 of nothing, things get decidedly weird because we remove space and time, too. And just to make sure, we will also remove all other equations and laws of nature that might give rise to space and time, such as strings or quantum gravity, or whatever other idea you believe in. Remove all of it. At this point there is nothing left from our theories of physics.

So why is there any physics at all? This question is one of the reasons we’ll never have a theory of everything, because even the best theory can’t explain its own existence. Scientific explanations end at this level, and it’s probably where this video should end, but I admit I enjoy talking about nothing, so let’s see what else there is to say.

I have taken inspiration for this video from an essay by Robert Lawrence Kuhn. He also talks about it in this video. My first six levels of nothing are similar to his, though not exactly the same because I’ve looked at it from the perspective of a physicist. But Kuhn doesn’t stop there, he has three more levels of nothing.

Taking away everything physical still leaves us with something in your birthday box because you might grant the existence of non-physical entities. For example, some people believe in god, or other religious ideas, like the belief that consciousness is non-physical. In level 7 we remove those, too. Theological explanations end at this level. If you think that god necessarily has to exist then you have to get off the bus at level 7 and accept that the question why god exists doesn’t have an answer.

Is the box finally empty? Not quite. There’s still mathematics that could be said to exist in some sense. That is, we have abstract ideas and objects, numbers, sets, logic, truths and falsehoods, and the entire platonic world of ideals. For the 8th level of nothing, we remove those too.

Has this finally removed everything? Are you finally happy with your birthday gift? Well, there’s still the possibility that something comes into existence even if that something doesn’t exist. And a possibility is something in and by itself. So, for level 9, we also remove all possibilities. This is Kuhn’s final level of nothing. It’s the best nothing I can give you for your birthday. I hope you’re happy now.

The ninth level of nothing leaves us with the always interesting question whether the absence of something is also something, which is why philosophers like to discuss whether holes in cheese exist. Personally, I’m more interested in the cheese. I guess that’s why I’m a physicist and not a philosopher, but I found Kuhn’s classification of nothings useful because it explains why we sometimes talk past each other apropos of nothing.

For example, “inflation” is a currently popular theory in physics according to which our universe was created by a quantum fluctuation from a vacuum. We have no evidence that this is correct, but let us leave this aside for today, and just ask what kind of creation this would be if it was correct. The idea of inflation is that you have a big space that’s filled with a quantum vacuum, and every once in a while a quantum fluctuation succeeds in becoming so large that it begins to grow. Indeed, it grows into an entire universe like ours, with cheese, and holes in it, and all.

In such a vacuum there are many fluctuations, and therefore the creation of a universe doesn’t happen only once, it happens over and over again. It’s a type of multiverse called “eternal inflation”. We just talked about this some weeks ago. The beginning of our universe in this eternal inflation would be a creation from a level four nothing.

Physics can get you a little further than this because you can write down a theory in which space and time is created from a state without space and time. It’s arguably somewhat hard to imagine what this means, but you can certainly write down mathematics for it.

You see, I just define a symbol for a state without space and time, and an operator that creates space and time, then I let the operator act on the state, and voila, I’ve created space and time. Ok, I have oversimplified this a little, but basically this is how it works. I really think people are way too respectful of all the stuff that physicists made up and get away with just because their maths is incomprehensible.

Lawrence Krauss’ book “A Universe from Nothing” is about this idea of creating space and time from nothing. And this would be a creation from a level 5 nothing. But even if you don’t believe in God, a level 5 nothing is still something. To begin with it has the mathematics that give rise to all the rest.

If physics doesn’t answer the question why there is something rather than nothing, then what could? Philosophers have discussed that back and forth. I’m not much of a philosopher and have a nothing worthwhile to add. That’s a ninth level nothing. But just in case someone stops you on the street and asks “why is there something rather than nothing”, let me tell you the three most popular answers that I have come across.

The most popular answer at the moment seems to be that nothing is absurd. It doesn’t make sense in and by itself and can’t be. It’s just a confusion of human language that we have inflicted on ourselves. The difficulty becomes apparent if you try to explain what nothing is, because any statement about it requires something. I mean if I can talk about nothing, then nothing it’s the thing that I talk about and it's therefore something?

Another answer is that no explanation is needed, or there is no explanation. God made it, que sera, sera, please move on, nothing to see here. See what I did there?

A third answer might be that our universe, or at least any universe, is in some sense the best option, and nothing doesn’t live up to the requirement because nothing can’t be any good.

If someone asked me on the street why there is something rather than nothing, I’d probably just shrug. I can’t think of any way to answer the question, and I also don’t see what difference it would make if we could answer it. I mean, suppose someone came tomorrow with a 2000 page proof that something must exist, what would it be good for? I guess I could do a video about it.

More seriously, just because it’s not a question that I want to spend my time on doesn’t mean I think no one should. In fact, I am glad that we are not all interested in the same questions and I’m happy to leave this one to philosophers. Do you have an answer that I didn’t mention? Let me know in the comments.

The New Meta-Materials for Superlenses and Invisibility Cloaks

[This is a transcript of the video embedded below. Some of the explanations may not make sense without the animations in the video.]


Meta is the Greek prefix for “after” and Aristotle used the phrase “metaphysics” for the stuff in his writing that came literally “after” he was done with the physics. Metaphysics is concerned with some of the most important questions we face at this critical moment in human history. Questions like whether the holes in cheese exist, whether cheese exists, or whether only the atoms that make up the cheese exist.

But this is not what we’ll talk about today. This video is about metamaterials which, I assure you, have nothing to do with cheese. Though, maybe, a little bit. Metamaterials are the next technological stage “after” materials. It’s a research area that has progressed incredibly quickly in the past decade, and that includes superlenses, invisibility cloaks, earthquake protection, and also chocolate. What are metamaterials, and what are they good for? That’s what we’ll talk about today.

First things first, what are metamaterials? A linguistic approach might lead you to think a metamaterial is what comes after the material, so I guess, that’d be the bill. But that’s not quite right. A metamaterial has custom-designed micro-structures which give a material new properties. These micro-structures are typically arrays that resonate at specific frequencies, and that interact either with acoustic waves or with electromagnetic waves. This way, metamaterials can be used to control sound, heat, light, and even earthquakes.

This sounds pretty abstract, so let us start with a concrete example, the superlens.

When you take an image of an object, with your eyes or with a camera, you collect light that reflects off the surface of an object with a lens. Lenses work by “refraction” which means they change the angle at which the light travels. If an object is too close to the lens, the refraction can no longer converge the light. For this reason, you can’t take images of things that are too close to the lens.

But not all the light that reflects from an object gets away. The part that gets away is called the far field, but there is another part of the light called the near field, which stays near the surface of the object. The electromagnetic waves in the near field are oscillating like usual, but they don’t travel into the distance, they decay exponentially. It’s also called an “evanescent wave”.

This figure shows how waves enter a medium at a surface, which is the red line. The top image is a normal, refracted wave, which continues traveling through space but the angle changes when it enters the medium. The bottom image shows an evanescent wave, which decays with distance from the surface. The evanescent waves contain tiny details of the structure of the object, but since they don’t reach the camera, those details are lost. And you can’t get the camera arbitrarily close to the object, because then you couldn’t refocus the light. And that’s a shame because you might not be able to count the hairs in my eyebrows after all.

But in 2000, the British physicist Sir John Pendry of Imperial College in London found a way to use the information in the near field. He said, it’s easy enough, you just use a material that has a negative refractive index.

What does it mean for a material to have a negative refractive index? Normal materials don’t have this, but metamaterials can. When a ray of light enters a medium, then the refractive indexes of the two media relate the angles. This is called Snell’s law. If the refractive index of the medium is negative, then this means the continuation of the ray in the medium is also reflected from the normal to the surface. So, it goes back into the direction it comes from. How would that look like?

Well, as I said, stuff that we normally encounter in daily life doesn’t have a negative refractive index, so I can’t show you a photo. But we can illustrate what it would look like. You probably remember the “broken pencil” illusion. If you put a pencil half into a glass of water, then the part in the water appears shifted to the side. It’s because the light is refracted in the water but the brain interprets the visual input as if the light travels in straight lines. If the water had a negative refraction index, then the lower part of the pencil wouldn’t just seem shifted, it’d also be reflected to the other side.

Aaron Danner had the great idea to use a raytracer to create a 3-d image of a pool filled with water that has a negative refraction index. Here is the image of the pool with normal water. And here is the image with the negative refractive index. The thing to pay attention to are those three black lines, which indicate the corner of the pool. You’d normally expect this to be out of sight, but since this strange water mixes refraction with reflection, you can now see it. If there were fish in the pool they’d appear to be floating on top of the water. Which, I don't know if you know this, but it’s not what a fish is supposed to do.

What’s this got to do with lenses? Well remember that you need lenses to collect rays of light. But if you put a sheet of a medium with negative refractive index between two with normal refractive index, that’ll basically turn the light rays around and effectively focus them. It acts like a lens. And, here comes the important bit, this also works for evanescent waves which usually get lost. They get focused too, and are prevented from decaying. This is why metamaterials with a negative refraction image can reach a resolution that’s impossible to reach with normal lenses.

A superlens was built for the first time in 2005 by researchers at UC Berkeley. Their lens was made of a silver sheet that was merely 35 nanometers thick. In this case, the structure of the material comes from oscillations in the electron density in the silver which amplifies the evanescent waves coming from the object. You have to put the object directly into contact with the silver surface for that to work.

This image (A) is a lithograph taken with a focused ion beam, so this is the control image. This image (C) is the optical control without superlens. And this one (B) is the superlens image. You can clearly see that the superlens image has a higher resolution. This graph D shows the difference in accuracy between imaging with the superlens, that’s the blue curve, compared to imaging without the superlens, that’s the red curve.

Though this jump in resolution might sound good, these lenses are rather impractical. You have to put the metamaterial directly into contact with whatever you want to image and then your camera on top. So it does away with selfie sticks, but unfortunately also ruins your makeup. This is why, last year, a group of researchers from Iran and Switzerland published a paper in Scientific Reports, in which they propose to use a metamaterial to turn the near field into a far field, so you can put your camera elsewhere.

They call this device a “hyperlens” which to me sounds like it’s a superlens that’s had too much coffee, but they mean a grid of aluminum nanorods that resonate at wavelengths in the visible part of the spectrum. For now, this is just a computer simulation, but the idea is that the resonance converts the evanescent modes into propagating modes, so then you can capture them elsewhere. The researchers claim that at least in their numerical simulations this structure can image biological tissues with a resolution of a tenth of the wave-length of the light. The resolution limit of conventional lenses is about a quarter of a wave-length.


Let’s then talk about what’s the probably best known application of metamaterials, the invisibility cloak. You may have read the headlines a few years ago about this. Metamaterials make invisibility cloaks possible because with a negative refraction index you can bend light in the opposite direction to what normal materials do. This means that, at least in theory, with the right combination of materials and metamaterials, you can bend light around an object. This appears to us as if the object isn’t there, again because the brains assume that light travels in straight lines.

This sounds pretty cool, and indeed scientists have some things to show, or maybe in this case it’s better to say *not show. Early experiments in the mid-2000’s mainly used microwaves. But in 2015, a team of researchers from China made an invisibility cloak that works in the infrared. In this Figure (Figure 1f) you see how the light is redirected. They used several triangles of germanium and put them in a very precise geometric configuration so that it creates a hidden area inside. You might say that this isn’t much of a metamaterial, but it’s the same idea: you custom-design structures to redirect waves as you want. Into this hidden region they put a mouse. (Figure 2b). Then they took an image with and without the cloak (Figure 4a and 4b). Half of the mouse is gone!

Invisibility cloaks in the visible part of the spectrum haven’t yet been made, but some semi-invisibility shields exist, for example this one from a company named Hyperstealth Corp. These don’t work by bending the light around objects, but by spreading the light in the horizontal plane. If you have a narrow object, then its image will be overpowered by the light coming from the sides of the object which blurs out what is behind. This works particularly well when the background is uniform. However, it’s not really an invisibility shield. Easiest way to build an invisibility shield is put a camera behind you and project that on a screen in front of you.

You can also use metamaterials to manipulate electromagnetic fields that are not in the optical range. For example, as I explained in this earlier video, the main problem with wireless power transfer is that power decreases with very rapidly with distance from the sender. A “magnetic superlens”, however, could extend this reach.

That this works was shown in a paper by a group of American researchers in 2014. This figure shows the difference between wireless power transfer using a magnetic superlens compared to wireless power transfer through free space. On the y-axis, we have wireless power transfer efficiency, and on the x-axis, we have distance in meters. The solid black line represents wireless power transfer through free space, which drops quickly to near-zero values as distance increases.

The colored lines represent wireless power transfer with the use of a magnetic superlens made up of metamaterials. You see that at best you can extend the reach by a few centimeters. And notice that the efficiency is in all cases in the single digits. So, nice idea, but in practice it doesn’t make much of a difference.

Another type of wave you can manipulate are acoustic waves. Acoustic metamaterials aren’t really a new thing. Sound absorption foam like this one uses basically the same idea. It has a lot of tiny holes. So you see, it’s kind of like cheese. The holes make it very difficult for sound waves in certain frequencies to bounce back which basically kills echo. If I wrap this around my head, you’ll hear the difference. Wrapping your head into one of those will generally improve your experience of the world, highly recommended.

Metamaterials are more sophisticated versions of this. You can for example design them so that they only absorb particular frequencies, this is called a sonic or phononic crystal. Another thing you can do is to reflect the signal back without spreading it out. This was done by a team of researchers from China and the USA in 2018. The material they used was just a plastic dish with a spiral structure that effectively changes the refractive index. They say an application could be to make vehicles easier to detect. Though I suspect that their metamaterial would sell better if it made a car less easy to detect.

You can also use acoustic metamaterials to build an acoustic type of superlens, which has been done for ultrasound, but it’s the kind of solution still looking for a problem. And, as you can guess, they are trying to build acoustic invisibility shields. This has been done for example underwater with ultrasound which is great if you want to hide from dolphins. And in 2014, a group from Duke University used a pyramid with a special surface structure that makes it reflect sound as if it was an empty plane. Here is how this pyramid would look looks like if you could see sound. The pyramid is hollow, so you can hide stuff inside. Maybe they’ve finally figured out what the Egyptians were up to?

Another application of metamaterials is earthquake protection. Like you can use structures in materials to change how light and sound propagates, you can change the properties of the ground to change how seismic waves propagate. For this you embed structures around or under buildings so that seismic waves are diverted around the building. You basically make the building invisible to earthquakes.

For example, a group at MIT’s Lincoln lab use arrays of boreholes that are either filled or empty to redirect seismic waves. They haven’t actually build a real world example, but they have made measurements on downscaled physical models and they have done computer simulations.

This image is an illustration for how seismic barriers could work in theory. The green squiggly lines are the surface waves, the blue squiggly lines are P-waves, and the black arrows are the S-waves. All these waves get partly redirected and diffused.

At least in a computer simulation, the cloaking effect is quite impressive as you can see in this image from a 2017 paper. For this, they used data from a real earthquake, the Hector Mine earthquake that happened in Southern California in 1999. It had a magnitude of 7.1. The metamaterial barriers effectively reduced it to an earthquake of magnitude 4.5. And just a few months ago, a group from China proposed another metamaterial to dampen seismic waves. They want to use steel embedded with cylinders of foam.

Image A of this figure shows an aerial view of a seismic wave moving through unprotected soil – without protection, the wave moves without losing energy, exposing any infrastructure atop the soil to the full power of the seismic wave. In Image B, the metamaterial array effectively neutralizes the wave. Here you see the effectiveness of the metamaterial array from a side view – in Image A, the seismic wave travels across the surface uninterrupted, while in Image B, the metamaterial array dissipates the wave at Line C. The authors claim that their system can dampen seismic surface waves in the range of 0 point 1 to 20 Hertz with up to 85 percent efficiency.

And as promised, a tasty example to finish. A team of researchers from the Netherlands have created an edible metamaterial. It’s made of chocolate in multiple s-shaped pieces that makes the chocolate more or less crunchy, depending on the direction you chew it. And if you think about it YouTubers do this too when they cut breaths out of their videos and zoom back and forth in every other sentence. This structural changes affects how you travel through a video. So we’re really doing meta-videos.

Metamaterials have opened a whole new dimension to material design, and as you can see, they are well on the way to application already. We will certainly come back to this topic in the future, so if you want to stay up to date, don’t forget to subscribe.