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Gravitational Waves!!! [and old Inflation Thread]
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| Watsisname | Date: Wednesday, 19.03.2014, 04:08 | Message # 1 |
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| Surprised this hadn't been mentioned yet. This may end up being Nobel-Prize winning stuff!
Universe Today
PhysicsWorld
For those unfamiliar with Inflation, Wikipedia has a pretty good overview of it, and Alan Guth's work in producing this theory.
To put it briefly, we're looking at the Cosmic Microwave Background (CMB), a relic radiation field from when the universe was ~300,000 years old and the first atoms formed. Inflation is a theoretical period which preceded that -- it happened within a tiny fraction of a second after the Big Bang, and lasted just as briefly, but during that instant the size of the universe grew exponentially, doubling in size some ridiculous number of times:
I believe this image is from one of Guth's papers, but I grabbed it from here, which is also a good but technical primer on this topic.
Inflation was hypothesized as a solution to a number of weird observations about the universe, like why is the mass density so close to the critical density, and how did widely separated regions of the universe come to thermal equilibrium? Inflation provides a mechanism which naturally explains these, and if it is correct, then it should have left behind an imprint in the CMB via gravitational waves, which would show up as certain polarization modes. That evidence has now, apparently, been found!
This detection comes with a high degree of confidence but of course it will have to be replicated. I was actually waiting for this announcement to happen for almost a year, expecting it to come from the Planck telescope data revealed last March. I wasn't aware of this group working on making the same detection out of Antarctica -- BICEP2. Congrats to them! 
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| neutronium76 | Date: Wednesday, 19.03.2014, 08:12 | Message # 2 |
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| Yes I heard about this in local news. A few weeks/months ago watched a documentary about gravity waves which mentioned LIGO as the most ambitious project to detect them. Apparently their colleagues in Antarctica stole their glory  . I can't remember the name of the documentary but it is in YT somewhere.
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| Watsisname | Date: Wednesday, 19.03.2014, 08:48 | Message # 3 |
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| Ah, not quite -- LIGO is a project whose goal is to detect gravitational waves directly, as they pass through the instrument. Nobody has achieved this yet because these waves are extraordinarily weak.
What happened here with BICEP2 involves indirect evidence for gravitational waves (as they are the mechanism by which inflation leaves an imprint on the CMB). But we've also had indirect evidence of their existence since the 1980s, from watching the orbits of binary pulsars. The emission of gravitational waves slowly carries off their orbital energy, causing them to spiral in and eventually merge together. As pulsars, we can monitor their orbits very precisely, and the observed orbital decay very closely matches general relativity's prediction.
So LIGO's glory is still there to be won. 
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| apenpaap | Date: Wednesday, 19.03.2014, 15:03 | Message # 4 |
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| It's fantastic news! Does anyone know what caused the sudden inflation, or is that still a mystery?
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| HarbingerDawn | Date: Wednesday, 19.03.2014, 16:08 | Message # 5 |
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| Quote apenpaap (  ) still a mystery
Yup
All forum users, please read this!
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| Spyro | Date: Thursday, 29.05.2014, 01:16 | Message # 6 |
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| Here is a theory that isn't based on any math I did, just a wild guess:
Maybe it was that some kind of higher-dimensional rift caused by the crazy amounts of energy in the young universe caused the Quantum Foam to "unfoam" into a more line-like feature, letting all of the particles expand in an extremely fast fashion until the dimensions regulated themselves.
Am I onto something, or just letting my imagination run wild?
I'm back, but am I here to stay? Hopefully!
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| Watsisname | Date: Thursday, 29.05.2014, 10:10 | Message # 7 |
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| Probably the latter, although what you're describing does have some similarities to a concept in physics known as symmetry breaking.
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| midtskogen | Date: Thursday, 29.05.2014, 11:51 | Message # 8 |
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| I've seen these results taken as support for the multiverse idea. I've very sceptical. Not of the multiverse concept, but of it discussed as science.
The results are Nobel prize stuff, but I hope that a prize is put on hold for several years to allow others to reproduce and criticise the work. Like the faster-than-light neutrinos, mistakes or oversights are easy to make, so for now what we need is a lot of people trying to find flaws in the results and patience.
NIL DIFFICILE VOLENTI
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| Watsisname | Date: Thursday, 29.05.2014, 19:47 | Message # 9 |
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| I am not aware of any link between Inflation and multiverse theories, though I'm not the most knowledgeable on the subject.
I've seen that the initial results on the mass of the Higg's puts it right in the middle of the range where, on the light side, favors supersymmetries, and on the heavier side, favors multiverses. Physicists are really hoping that supersymmetry turns out to be correct, as it is very elegant and much of the last few decades of theoretical work have followed this avenue. If it is wrong then it's essentially back to the drawing board for the next version of the standard model.
If the multiverse on the other hand is correct then it becomes extremely difficult to think of ways to advance our understanding of particle physics, as the theories are nearly untestable.
The BICEP2 results will definitely have to be reproduced, even aside from Nobel considerations. I anticipate this coming from Planck data before too long.
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| midtskogen | Date: Friday, 06.06.2014, 21:16 | Message # 10 |
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| Gravitational waves turn to dust after claims of flawed analysis
NIL DIFFICILE VOLENTI
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| Watsisname | Date: Saturday, 07.06.2014, 00:01 | Message # 11 |
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| Yup. One of the funny things with studying the CMB is that instead of capturing a signal and subtracting the backgrounds, we want to do the opposite and subtract the foreground. This makes it much more difficult.
As with studying CMB's anisotropy, which was a major objective of modern work in cosmology from COBE to Planck, it is very important to characterize and subtract contribution from galactic foregrounds when looking for b-mode polarization caused by gravitational waves from the Inflationary Epoch. Dust grains in our own galaxy radiate in wavelengths that overlap the CMB signal, and their polarization can also produce the same b-mode patterns that we are looking for. If these were not properly accounted for, we may very well have a false detection. Rather, we may have confused a foreground signal for the background signal that we wanted. This is what Steinhardt and others are claiming. Again, we'll really have to wait for Planck data results to be sure.
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| midtskogen | Date: Saturday, 07.06.2014, 08:35 | Message # 12 |
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| It's perfectly fine to make bold claims and be wrong, that's how science progresses, but when doing so one needs to be very careful about how it's presented. When wrong there is a delicate tipping point between being applauded and having your scientific career seriously dented or destroyed. I think perhaps they were a bit too sure in this case, but not as bad as in the case of the arsenic life discovery, which to me seems like a schoolbook example of how to ruin your scientific career (NASA should have learned their lesson after the Martian meteorite fossile episode). A fine example of how to present incorrect results and yet have your reputation intact or even increased is the faster than light neutrinos case. It's all about whether you present all your data, invite anyone to prove the results wrong and accepting new arguments and evidence.
NIL DIFFICILE VOLENTI
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| midtskogen | Date: Tuesday, 12.01.2016, 11:21 | Message # 13 |
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| Here we go again.
NIL DIFFICILE VOLENTI
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| Watsisname | Date: Tuesday, 12.01.2016, 23:22 | Message # 14 |
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| WOW! 60% confidence that a rumor is true! By independent sources! YEAH, SCIENCE!
Edit:
More seriously, I'm really displeased with the media right now. And with Krauss. Actually, more with Krauss than theguardian; the article is actually good. So yeah, Krauss apparently has some inside word about a possible gravitational wave detection, and he's really excited about it because if it's correct then it's a big deal. That's cool. I get the enthusiasm. But come on, he should know exactly what happens when he starts shouting out stuff like this. Reporters will pick up on it, some inevitably over-hype it--
"Alien 'MEGASTRUCTURE' found as bizarre star is blocked by huge object | Daily Mail Online"
--and people can get an unrealistic expectation. But 9 times out of 10 stuff like this falls through. Then people are disappointed and public perception of science is tarnished.
I'll wait for a formal announcement and submitted papers.
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| parameciumkid | Date: Wednesday, 13.01.2016, 09:17 | Message # 15 |
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| We're not saying it was aliens... because we're saying it's not aliens ;P
Intel HD Graphics 4000 ;P
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