Friday, August 02, 2013

Video about Loop Quantum Cosmology

The below YouTube video on Loop Quantum Cosmology was brought to my attention.

I'm not sure who this video is aimed at. It seems to me you'll only understand what they are talking about when you already know what they are talking about, in which case you're not learning anything new, except possibly that Abhay Ashtekar's family moved a lot. The visuals are pretty much useless, the audio is on occasion extremely bad, and who is that person with the flipboard? They somehow fail to mention that Loop Quantum Gravity isn't the same as Loop Quantum Cosmology, so there's a glaring gap in the narrative. I don't know what the CMB anomalies mentioned at the end have to do with anything and why are people still discussing black holes at the LHC, that topic is as dead as dead can be, not to mention that Loop Quantum Gravity didn't have much if anything to do with it anyway. At around 32 minutes, they start talking about phenomenology and it gets more interesting then. Note how very careful they avoid making predictions...

That having been said, I'm not at all sure you want to spend 45 minutes on this. But please ignore my opinion and make up your own. I'm just in a foul mood because I couldn't find my favorite socks this morning.


skydivephil said...

Hi Sabine
I am one of the makers of the film you linked to. First off many thanks for mentioning it on your blog. We appreciate that. But I have to say I’m a little upset your focus seems to be so negative. The film’s target audience is the educated layman; I think you are mistaken to say that no one will learn anything who doesn’t already know the field..
I studied astronomy and many people I spoke to believed LQC was a cyclic model that was surely disproved by dark energy. An impression perhaps created when Scientific American had a front cover image that seemed to imply many bounces. If we clear up only that misconception I think we have achieved something. That is spelt out very clearly in the film. Others thought results from Integral ruled out LQC. There are many other issues regarding entropy, the probability of inflation, whether the universe has a beginning, eternal inflation etc which have not been discussed in the layman’s literature.
One of the reasons we made this film was because we wanted to know the answers to these questions and we couldn’t find them anywhere. There are lots of online videos for other models of the early universe such as eternal inflation, CCC, ekpyrotic and very little about LQC.
The reason we mentioned black holes at the lHC is the papers are still being produced on it, here is a Google scholar search I did for black holes at the LHC since 2013, and I got 297 results:
An arxiv search found papers as recent as June 2013 on the subject.

You are right the audio is not as good as we would have liked. When we interviewed Ivan there was a fan in the room, a noise I thought I could get rid of with software, but it was a real nightmare to deal with. That is why we spent our own money getting a professional media company to do close captioning, so I’m not sure that it matters. Anything that is not clear is provided as these subtitles.
We have spent a lot of our personal time and money making this film, promoting exciting scientific ideas to the public and trying to clearing up misconceptions about them. Something I hope you would support. Of course you have supported it by linking to it; I just hope you find your socks.

Nemo said...

Hahaha Bee :-D,

thanks for this review, since I am not a native English speaker I would probably have too large difficulties in understanding what they say, as the audio quality is bad.

Your comment about the socks made me LOL :-D

Phillip Helbig said...

"a noise I thought I could get rid of with software"

"We'll fix it in the mix" is one of the three lies of rock and roll. Another one is "the cheque is in the mail". I'll leave out the third one here.

Uncle Al said...

"I'm just in a foul mood because I couldn't find my favorite socks this morning." This is a terse yet complete summary of both quantum gravitation and SUSY since Lenny Suskind got stuck in a 1970 Coral Gables, FL elevator with Murray Gell-Mann.

Murray Gell-Mann laughed at string theory. Way to go, Murray!

johnduffieldblog said...

This looks interesting. I fancy I know a bit about this kind of stuff. Or maybe not. I'll watch the video.

Giotis said...

Skydivephil that is a noble cause of yours and well done (although you have chosen the wrong theory to present :-)). Your effort is not in vain; small things like that make the world go around. I’m sure Sabine’s intention was not to offend you.

Sabine Hossenfelder said...


Having engaged in the production of several videos about theoretical physics during the last year and faced with several more this year, I totally believe that it took you some time and money. I also totally believe that you don't like that I don't like your video, because I'd also not like if you didn't like our videos, which you probably didn't even watch though. At least I watched yours.

With that preamble, by and large I think you could have been a little more selective in the messages you wanted to get across. In any case, as you noted I did mention your video, and I did that because I approve of the intention and I appreciate general educational outreach efforts, esp in theoretical physics where it's very difficult. I'll not go so far to pretend I like a video which I in fact, well, didn't like. Sorry about that. Next time, if you prefer, I can just be polite and not mention it at all.

Regarding the black holes at the LHC: I know that there are *still* papers being produced on the topic and that people *still* give talks about it, and to make matters worse there is funding for the topic (probably because it still gets published) and so on. And if they haven't found anything at the LHC, they'll move onward to produce papers about it for the next-big-thing, whatever it'll be called. Yes, you can count that as a prediction.

No, I didn't find my socks. Which is why I have a blister on my big toe now and that didn't exactly improve my mood. Best,


Sabine Hossenfelder said...


The video has subtitles. It is somewhat beyond me why anybody would want to watch the video if they could as well read the text in a fraction of the time given that the visuals are pretty much useless, but anyway. All I wanted to say is that you can read through the bad-audio passages. Best,


Stephen Paul King said...

Does not the resent observation of ultra high energy gamma rays contraindicate any discrete structure of spacetime?

Sabine Hossenfelder said...

Stephen Paul,

The brief answer to your question is no, but you have some confusions there. Importantly, Loop Quantum Gravity does not predict any signature in gamma ray bursts, though this has on occasion been deliberately or accidentally presented as such. (Thus my comment about carefully not making any predictions.) Besides this, the signature that people have been looking for (are still looking for) does not actually have anything to do with discreteness. Rather, it's a modification of Lorentz-invariance, but there's nothing explicitly discretized about it. Unfortunately, it has often been presented as if it was a test for discreteness, so your confusion is understandable. Best,


johnduffieldblog said...

Phil: I watched video, and thought it was good. It gave a nice overview of what these guys are doing, and what they think. I didn't have any problems with the sound quality. And I feel sympathetic about loop quantum gravity, see comment 4 on this physicsworld article for my attempt to outline quantum gravity.

But I have to say I'm not keen on the big bounce. That doesn't really square with general relativity, and I get the feeling that the guys have been seduced by that instead of treating the early universe as something similar to the original "frozen star" black hole interpretation. Imagine you've squeezed the sponge down in your hand, and then you let go. It expands, but there's no way its going to squeeze itself back down. Also there was no mention of infinite time dilation or the gravastar, and overall I have to say that it came over as rather speculative. I think this somehow undermined the quantum gravity. I think the LHC black holes undermined Ivan a bit too.

Overall I liked the video, but wasn't keen on the cosmology.

Shantanu said...

Just to press on to Sabine's question, what specific predictions does LQC make about black holes at LHC?

The Tunneller said...

Just a digression is this the long sought after Equation of Quantum Gravity?

Megan Reynolds said...

Part of the problem is that Ashtekar talks in such a vague way, that it is difficult to determine what specifics he's actually talking about. Being a physicist who is not an expert in any of this, I agree with Sabine. I didn't really learn anything.

B Yen/Getty Images [ iTunes demo ] said...

"The Power of the Press relies on the Ignorance of the Masses"

Science Outreach ("Dissemination of Science" at layman level, in America to "science-challenged" Masses) has been reduced to

"pandering to the Masses-are-Asses"

"I have never catered to the Elite, I go after Bigger Game..the Masses"
"The masses are Asses"
-- Mark Twain

Heck, I couldn't have detected the non Consistency you mentioned (this is your field/sector), as an outsider.

There was that Universe series on History Channel (uses artsy-fartsy Computer Animation in conjunction with abstract statements), which sunk to a new level of "lowest common denominator", to which Peter Woit on "Not Even Wrong" said

"what the BLEEP [ insert obscenity ]?"

"The participants [ Filippenko/Berkeley, Johnson/USC ] should be DEEPLY ASHAMED of themselves"

Even Johnson/USC said "What was THAT?" [ crazy nonsensical Computer Animation ].

Basically, the Producers "chopped up" interviews of various Physicists, made their own (incorrect) interpretation, coupled with fanciful (incorrect) Computer Animation -- JUNK result.

Part of the anti-Intellectualism movement in USA, Science-challenged journalists don't help..

See Dr Craig Venter (Biotech pioneer, co-sequenced Human Genome with Celera startup) comments on anti-Intellectualism culture in US Govt

" I think the new anti-intellectualism that’s showing up in politics today is a symptom of our not discussing these issues enough. We don’t discuss how our society is now 100 percent dependent on science for its future. We need new scientific breakthroughs—sometimes to overcome the scientific breakthroughs of the past. A hundred years ago oil sounded like a great discovery. You could burn it and run engines off it. I don’t think anybody anticipated that it would actually change the atmosphere of our planet. Because of that we have to come up with new approaches. We just passed the 7 billion population mark. In 12 years, we’re going to reach 8 billion. If we let things run their natural course, we’ll have massive pandemics, people starving. Without science I don’t see much hope for humanity."

Zephir said...

Quantum Gravity in under five minutes