All you need to know about 5G

The new 5G network technology is currently being rolled out in the United States, Germany, the United Kingdom, and many other countries all over the world. What’s new about it? Does it really use microwaves? Like in microwave ovens? Is that something you should worry about? I began looking into this fully convinced I’d tell you that nah, this is the usual nonsense about cellphones causing cancer. But having looked at it in some more detail, now I’m not so sure.


First of all, what is 5 G? 5 G is the fifth generation of wireless networks. The installation of antennas is not yet completed, and it will probably take at least several more years to complete, but in some places 5G is already operating, and you can now buy cellphones that use it. What’s it good for? 5G promises to deliver more data, faster, by up to a factor one hundred, optimistically. It could catapult us into an era where driverless cars and the internet of things have become reality.

How is that supposed to work? 5 G uses a variety of improvements on the data routing that makes it more efficient, but the biggest change that has attracted the most attention is that 5G uses a frequency range that the previous generations of wireless networks did not use.

These are the millimeter waves. And, yes, these are the same waves that are being used in the scanners at airport security, the difference is that in the scanners you’re exposed for a second every couple of months or so, while with 5G you’d be sitting in it at low power but possibly for hours a day, depending on how close you live and work to one of the new antennas.

As the name says, millimeter waves have wavelengths in the millimeter range, and the ones used for 5G correspond to frequencies of twenty-four to forty-eight Giga-Hertz.

If that number doesn’t tell you anything, don’t worry, I will give you more context in a moment. For now, let me just say that the new frequencies are about a factor ten higher than the highest frequencies that were previously used for wireless networks.

Another thing that’s new about 5G are directional phased-array antennas. Complicated word that basically means the antennas don’t just radiate the signal off into all directions, but they can target a particular direction. And that’s an important difference, if you want to know how the signal strength drops with distance to the antenna. Roughly speaking, it becomes more difficult to know what’s going on.

Because of these new features, conspiracy theories have flourished around 5G and there have been about a hundred incidents, mostly in the Netherlands, Belgium, Ireland, and the UK, where people have burned down or otherwise damaged 5G telephone towers. Dozens of cities, counties, and nations have stopped the installing. There have been protests against the rollout of the 5G technology all over the world. And groups of concerned scientists have written open letters twice, once in 2017 and once in 2019. Each letter attracted about a few hundred signatures from scientists. Not a terrible lot, but not nothing either.

Before we can move on, I need to give you some minimal background on the physics, so bear with me for a moment. Wireless technology uses electromagnetic radiation to encode and send information. Electromagnetic radiation is electric and magnetic fields oscillating around each other creating a freely propagating wave that can travel from one place to another. Electromagnetic radiation is everywhere. Light is electromagnetic radiation. Radio stations air music with electromagnetic radiation. If you open an oven and feel the heat, that’s also electromagnetic radiation. These seem to be different phenomena, but physically, they’re all the same thing. The only difference is the wavelength of the oscillation. Commonly, we use different names for electromagnetic radiation depending on that wavelength.

If we can see it, we call it light. Visible light with long wavelengths is red, and at even longer wave-lengths when we can no longer see it, we call it infrared. We can’t see infrared light, but we often still feel that it’s warm. At even longer wavelengths we call the radiation microwaves, and if the wavelengths are even longer, they are called radio waves.

On the other side of visible light, at wavelengths shorter than violet, we have the ultraviolet, and then the X-rays, and gamma-rays. The new millimeter waves are in the high frequency part of microwaves.

Now, we may call electromagnetic radiation a “wave” but those waves are actually quantized, which means they are made of small packs of energy. These small packs of energy are the particles of light, which are called “photons”. You may think it’s an unnecessary complication, to talk about quantization here, but knowing that electromagnetic radiation is made of these particles, the photons, is extremely helpful to understand what the radiation can do.

That’s because the energy of the photons is proportional to the frequency of the radiation, or equivalently, the energy is inversely proportional to the wavelength.

So, a high frequency means a short wavelength, and a large energy per photon. A small frequency means a long wavelength, which means small energy. Again that’s energy per photon.

That the frequency of electromagnetic radiation tells you the energy of the particles in the radiation is so useful because if you want to damage a molecule, you need a certain minimum amount of energy. You need this energy to break the bonds between the atoms that make up the molecule. And so, the most essential thing you need to know to gauge how harmful electromagnetic radiation is, is whether the energy per photon in the radiation is large enough to break molecular bonds, like the bonds that hold together the DNA.

Breaking molecular bonds is not the only way electromagnetic radiation can be harmful, and I will get to the other ways in few minutes, but it *is the most direct and important harm electromagnetic radiation can do.

So how much energy do you need to damage a molecule? Damage begins happening just above the high-energy-end of visible light, with the ultraviolet radiation. That’s the light that gives you a sunburn and that you’ve been told to avoid. It has wavelengths that are just a little bit shorter than visible light, or frequencies and energies that are just a little bit higher.

In terms of energy, ultraviolet radiation has about three to thirty electron volts per photon. An electron Volt is just a unit of energy. If that’s unfamiliar to you, doesn’t matter, you merely need to know that the binding energy of most molecules also lies in the range of a few electron volts.

If you want to break a molecule, you need energies above that binding energy, so you need frequencies at or above the ultraviolet. That’s because the energy for the damage has to come with the individual photons in the radiation. If the individual photons do not have enough energy to actually damage the molecule, they either just go through or, sometimes, if they hit a resonance frequency, they’ll wiggle the molecule. If you wiggle molecules that means you warm them up.

So, what matters for the question whether you can damage a molecule is the energy per photon in the radiation, which means the frequency of the radiation, *not the total energy of all the particles in the radiation, of which there could be many. If you take more particles, but *each of them has an energy below what’s necessary for damaging a molecule, you’ll just get more wiggling.

All the radiation used for wireless networks, including 5G, uses frequencies way below those necessary to break molecular bonds. It is below even the infrared. So in this regard, there is clearly nothing to worry about.

But. As I mentioned, breaking molecular bonds is not the only way that electromagnetic radiation can harm living tissue. Because tissue is complicated. It’s not just physics. You can also harm tissue just by warming it.

And how much warming you can get from electromagnetic radiation is not determined by the energy per photon, it is determined by the total energy per time that is transferred by all the photons and on the fraction that is absorbed by the tissue. That total energy transfer per time is called the “power” and it’s commonly measured in Watts. So: The frequency tells you the energy per photon. The power tells you the total energy in photons per time.

For example, if you look at your microwave oven, that probably operates at about 2 GigaHertz, which is a really small energy per photon, about a million times below the energy required to break molecular bonds.

But a microwave oven operates at maybe four hundred or up to a thousand Watts. And that’s high in terms of power. So, a lot of photons per time. On the other hand, if you have a wireless router at home, it quite possibly operates at a similar frequency as your microwave oven. But a wireless router typically uses something like one hundred milli Watts, that’s ten thousand times less than the microwave oven, and the router radiates into space, not into a closed cavity.

That’s a relevant difference for a simple geometric reason. If the photons in the electromagnetic radiation distribute in all of the directions, as they do for antennas like your wireless router, then the density of particles will thin out, meaning the power will drop very quickly with distance to the sender. This is why, in wireless communication, the highest power you’ll be exposed to is if you are close to the sender and that is usually your cell phone, not an antenna, because the antennas tend to be on a roof or a mast or in any case, not on your ear.

Ok, to summarize: The frequency tells you the energy per particle and determines the what type of damage is possible. The power tells you the number of particles and it drops very quickly with distance to the source. The power alone does not tell you how much is absorbed by the human body.

Back to 5G. What the 5G controversy is about is whether the electromagnetic radiation from the new antennas poses a health risk.

5G actually uses electromagnetic radiation in three different parts of the spectrum, called the low band, the mid band, and the high band. The frequency of the radiation in all these bands is below that which is required to damage molecules. The frequency of the mid band is indeed comparable to the one your microwave oven is using, but actually, there’s nothing new about this, microwaves have been used by wireless networks for more than two decades.

The radiation in the high band are the new millimeter waves. This band has so far been largely unused for telecommunication purposes simply because it’s not very good for long-range transmission. The electromagnetic waves in this range do not travel very far and can get blocked by walls, trees, and even humans.

Therefore, the idea behind 5G is to use a short-range network, made of the so-called “small cells” for the millimeter waves. These small cells have to be distributed at distances of about one hundred meters or so.

The small cells communicate with macro cells that use the mid and low bands with antennas that operate at higher power and that do the long range transmission. So, a fully functional 5G network is likely to increase the exposure to millimeter waves, which have not before been used for cell phones.

This means the people who are citing the lack of correlation between cell phone use and cancer incidence in the past 20 years missed the point. These studies don’t tell you anything about the 5G high band because that wasn’t previously in use.

Now the thing is if you look what is known about the health risks from long-term exposure to the new millimeter waves band, there are basically no studies. We know that millimeter waves cannot penetrate deeply into the human body, but we know that at high power, they warm the skin and irritate eyes. Exactly what power is too much in the long run no one knows because there just hasn’t been enough research.

Here is for example a Meta-review published about a year ago, which came to the conclusion:

“The available studies do not provide adequate and sufficient information for a meaningful safety assessment.”

And here we have Rob Waterhouse, vice president of a telecommunication company in the United States:

Waterhouse admits that although millimeter waves have been used for many different applications—including astronomy and military applications—the effect of their use in telecommunications is not well understood… “The majority of the scientific community does not think there’s an issue. However, it would be unscientific to flat out say there are no reasons to worry.”

That’s not very reassuring. And the World Health Organization writes:

“no adverse health effect has been causally linked with exposure to wireless technologies… but, so far, only a few studies have been carried out at the frequencies to be used by 5G.”

So the protests that you see against 5G, I am afraid to say, are not entirely unjustified. Don’t get me wrong, damaging other people’s property is certainly not a legitimate response. But I can understand the concern. We have no reason to think 5G *is a health risk. Indeed, it is reasonable to think it is *not a health risk, given that this radiation is of low energy and scatters in the upper layers of the skin, but there is very little data on what the effects of long-term exposure may be.

How should one proceed in such a situation? Depends on how willing you are to tolerate risk. And that’s not a question for science, that’s a question for politics. What do you think? Let me know in the comments.

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