BICEP2 and Gravitational Waves from Inflation (part 2)
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- Опубліковано 6 жов 2024
- In this video we will discuss the recent announcement from the BICEP2 collaboration, the possible discovery of the first direct evidence of cosmic inflation which occurred an incredibly short time after the very start of the big bang.
The BICEP2 announcement:
bicepkeck.org/
A few blog posts about the discovery:
www.preposterou...
motls.blogspot....
philbull.wordpr...
A few good pages on polarization in the CMB:
background.uchi...
cosmology.berke...
Let us know what you think of these videos by filling out our short survey at tinyurl.com/ast.... Thank you!
NANOGrav webpage: www.nanograv.org
Wonderful job of explaining concepts that have no real life connections
These are great, in-depth explanations of the new exciting discoveries. I wish more people in the media would do something like this. Thank you very much!
Do you plan to do other videos?
Another awesome explanation. Thank you.
Instantly subscribed !!! awesome video.
great explanation, thank you indeed and congratulation to all scientists who make this incredible discovery
Sir please explain what is Higgs field, higgs boson, and all sub atomic particles in your words.
As they say, another one bites the dust
could u please post something about the higgs-boson particle?
Very cool presentation. You have a gift for cutting through the clutter to get to the important features of an issue without sacrificing scientific rigor. You and DrPhysicsA are really good at this. Thanks for making these videos and please make more.
Thank you. This one took a long while to write since there are a lot of pieces that come into play with this detection (light polarization, the CMB, gravitational waves, inflation, and then going through the actual data and its interpretation) so I hope that it was all coherent. I'll try to keep posting at least a little more often than I have been, but I'm also trying to write a thesis... so that makes things a little busy. Thanks for watching
really good video
8:50-9:55 Is the 'clincher' in this figure the fact that the black data measurements appear at much higher levels than the effects of gravitational lensing (at those scales - less than '10^2') could produce and so the candidate mechanism of inflation produced B-mode polarization 'fits' the data sufficiently well as to have 'predicted' it?
Very interesting to follow this account. Thank you for sharing.
Pretty much right on. For that figure the left 4 data points are significantly higher than what would be predicted by lensing alone, and when we add in the predicted signal from inflation the data matches quite well for inflation with r=0.2 (if r was lower, the predicted value of the B mode strength would be lower, if r was higher, the predicted value of the B modes would be higher... r=0.2 seems to match best). So inflation in general predicts an excess of B modes with multipoles around 100 or so which was found. So now we see which candidate mechanisms could produce a signal this strong. Also, I think there are some more subtle details in exact shape of the "inflation B mode" line in that graph that depend on the model of inflation. As we get more data and tighten those error bars we'll see if we can identify those feature and further constrain different inflation models (but before that I'll be happy when a second group also finds this signal)
why dont u post now
secondly, if this inflation was so very brief, and gravitational waves propagate at the speed of light, then where would the gravitational waves be to interfere with the radiation from 380,000 years after?
Remember, it is the entire universe that is expanding (it's not expanding into anything, the geometry of space itself expands), and during inflation gravitational waves would be produced throughout the entire universe and propagating in all directions so the gravitational waves wouldn't either propagate out of the universe or leave regions where all the gravitational waves have moved away from (since they'd be incident from all directions for any point).
ok according to theory the universe expanded into nothing becoming something, and being the only something there is the gravitational waves didn't leave the universe.
Though can't they dissipate into heat like everything else tends to do? That is theoretically.
When the geometry of the universe expands, the density of energy and matter dissipates even though the universe is not expanding into anything. Also when the universe expands the wavelength of light in the universe will stretch as well, resulting in the photons of light having lower energy. Gravitational waves will dissipate and stretch in the exact same way as light; this is why the GWs from inflation aren't so strong right now that they're stretching and compressing everything around us (they're just doing this an extremely tiny amount) and why the gravitational waves from inflation are primarily strong at very long wavelengths (they've been stretched throughout the expansion of the universe)
well, this discovery completely went to the garbage can lol
It is unfortunate that the signal that was detected seems to be primarily polluted by the effects of dust in the galaxy. However that does not mean that the BICEP2 project was a waste, it just means that more has to be done to get to the specific signal that I described in these two videos. Specifically, we need to make these kinds of measurements (detecting CMB B modes) when looking at light with different frequencies. The B mode signals produced by dust depend on the frequency of the CMB light in very specific ways. If we can measure this effect at different frequencies then we can filter the effect of the dust out... hopefully to a high enough accuracy that the true primordial gravitational wave signature can be seen.
Ali Rafiq It was more an effect of the dust in OUR galaxy. The BICEP2 team had thought that it was less dusty in that part of the sky then the Planck team showed it was. The good news is that now both groups are working closer together and both looking for clearer areas of the sky to survey, and finding ways to filter out the bad signal from the dust. I should actually put together a new video showing what the next steps are to correct for the dust problem
PhysicistMichael Yes, please. Make a new video showing how the the BICEP2 team is trying to solve the dust issue.
ricArdo, no more videos on this channel?
well, 2022 here, Webb telescope crap things.... and guess what? gravitational lenses proved........
ok, unless we find another plausible way of generating those B-mode polarization patterns
Yes, this is a concern that I discuss. For instance one possible error that has been getting some rumor buzz recently is polarization from dust in our galaxy. The BICEP2 team claims that they have checked how much of their signal could have come from this using a number of dust models, so hopefully this was all done correctly and the dust models they used are accurate. There's some argument about this right now (all a regular and valuable part of the scientific process, vetting new results) but I think the definitive check will come from other missions that are looking for similar CMB B-modes but at different microwave frequencies. The dust in the galaxy should cause different patterns at different frequencies, so if they see the same B-modes then it is highly unlikely that dust is causing the signal.
interesting, I do enjoy the debate, it helps to flesh out evidence and assumptions properly (also makes learning more interesting).
I assume work from LIGO could also help BICEP2's case for gravitational waves. It would be another confirmation of the existence of gravitational waves, making the BICEP2 case stronger. I'm interested to see how it all turns out.
Thanks for the vids btw, very clearly presented.
Thank you. I always feel that understanding the evidence behind a scientific discovery and the process involved in checking that the data and interpretation are valid is just as important (and interesting) as the discovery itself.
LIGO will be sensitive to high frequency (short wavelength) gravitational waves from spinning neutron stars, mergers of low mass black holes, supernovae, etc. The gravitational waves from inflation at these frequencies are expected to be much weaker than the GWs from these sources (though it will contribute a huge amount to our understanding of GWs in general).
GW detection through pulsar timing (what the NANOGrav collaboration is doing, check out the videos for that) is sensitive to much lower frequency GWs, so even though primordial gravitational waves are not the first sources we expect to see even at nanoHertz frequencies, we will be more likely to see them in this way.
Michael, how have you gained your knowledge? Did you study in a university or did you learn everything on your own?
I'm currently finishing up a doctoral degree in physics, specifically focusing on gravitational wave astronomy and it was in grad school that I found that I enjoyed teaching. Hopefully once I finish my degree I'll be able to get a job that involves both teaching and research...
PhysicistMichael I appreciate your lessons and I'm sure many others do, so thank you. Are there any sources online that you recommend to increase my understanding of the universe? And are there any laymen's books you recommend for physics?
@@PhysicistMichael hey, so how did it go, did you find a job that you enjoy? so bad you don't do the videos anymore, i find them very useful for my undergradute degree.
@@kseniachernishov1904 Very nice of you to ask. I did find a good teaching position and I'm actually working on a video series covering topics in intro physics which will hopefully be ready to start rolling out by summer. Glad that you found my videos useful.
MICHAEL JAMESON KOOPA TROOPA UPLOAD A VIDEO *_NOW._*
The most of everything....have 32 likes as of 8 years on youtube.......:-(