ChatterBank7 mins ago
New Paper Appears To Confirm Inflation Theory
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A rough summary of this paper is well-provided by the BBC, I think, but for the record this paper provides the claim that we have seen for the first time a direct sign of the existence of "Gravitational Waves". These are just about the only piece of the General Relativity Jigsaw left to be discovered to confirm the full predictions of Einstein's theory, so in that alone this is a hugely significant announcement.
But more than that: these are the gravitational waves that were emitted when the Universe itself was coming into existence, emitted some tiny fraction of a second after the Big Bang, during a period called "Inflation" when the Universe grew in size by something like 10^24 times larger than it started out, in some phenomenally small time scale. Essentially, then, this discovery not only means that our theories of Physics are correct, but allows us to claim with more conviction than ever before that those laws apply to the entire Universe for (almost) its entire history.
If this is true, this is one of the most significant announcements that there has been in Physics.
http://
A rough summary of this paper is well-provided by the BBC, I think, but for the record this paper provides the claim that we have seen for the first time a direct sign of the existence of "Gravitational Waves". These are just about the only piece of the General Relativity Jigsaw left to be discovered to confirm the full predictions of Einstein's theory, so in that alone this is a hugely significant announcement.
But more than that: these are the gravitational waves that were emitted when the Universe itself was coming into existence, emitted some tiny fraction of a second after the Big Bang, during a period called "Inflation" when the Universe grew in size by something like 10^24 times larger than it started out, in some phenomenally small time scale. Essentially, then, this discovery not only means that our theories of Physics are correct, but allows us to claim with more conviction than ever before that those laws apply to the entire Universe for (almost) its entire history.
If this is true, this is one of the most significant announcements that there has been in Physics.
Answers
"Photons have no mass. They travel at c (the speed of light). Why would their polarisation be affected by gravitational waves when Newtonian gravity would have them unchanged as they have no mass."
Not just you, this is surely one of the key questions. Answer is that gravitational waves don't affect photons directly -- rather, gravitational waves (and gravity itself) distort the shape of spacetime in which photons, and everything else, travel. Photons in particular always take the "shortest possible path" between two points. As a gravitational wave travels, it will change the nature of this shortest possible path and so change the path that photons take. And, presumably, will change other properties as well such as polarisation.
This indirect effect of Gravity on even those things that are massless is one of the triumphs of General Relativity.
Not just you, this is surely one of the key questions. Answer is that gravitational waves don't affect photons directly -- rather, gravitational waves (and gravity itself) distort the shape of spacetime in which photons, and everything else, travel. Photons in particular always take the "shortest possible path" between two points. As a gravitational wave travels, it will change the nature of this shortest possible path and so change the path that photons take. And, presumably, will change other properties as well such as polarisation.
This indirect effect of Gravity on even those things that are massless is one of the triumphs of General Relativity.
Yes, from my previous posts on related discussions you know I agree with you that the existence of spacetime, the operating system format of the universe I compare to an infinite hard drive in my analogy, is now undisputable.
The pretty polarisation patterns in the cosmic background radiation revealed by Bicep2 are stunning, but scientists will now be busily engaged in ensuring that the B mode 'cosmic curl' cannot possibly be attributable to other more mundane influences on the photons in question. I try to be patient before I sign up to the hyperbole of theoretical cosmologists that follows every new discovery.
That said the image generated by the data is simply stunning in and of itself. We can all be rightly awestruck by it whatever it does or doesn't imply about the process that made the universe what we observe it to be.
I have a framed original copy of the Nature poster that celebrated the publishing of the human genome hanging on my wall. I'd have no reservations about putting a similar poster of the BICEP2 data generated cosmic image of the CBR polarisation right next to it.
The pretty polarisation patterns in the cosmic background radiation revealed by Bicep2 are stunning, but scientists will now be busily engaged in ensuring that the B mode 'cosmic curl' cannot possibly be attributable to other more mundane influences on the photons in question. I try to be patient before I sign up to the hyperbole of theoretical cosmologists that follows every new discovery.
That said the image generated by the data is simply stunning in and of itself. We can all be rightly awestruck by it whatever it does or doesn't imply about the process that made the universe what we observe it to be.
I have a framed original copy of the Nature poster that celebrated the publishing of the human genome hanging on my wall. I'd have no reservations about putting a similar poster of the BICEP2 data generated cosmic image of the CBR polarisation right next to it.
"I try to be patient before I sign up to the hyperbole of theoretical cosmologists that follows every new discovery. "
Good call. Let's hope that this doesn't disappear, but obviously there have in the past been major announcements followed by quiet but embarrassing climb-downs. The "faster-than-light neutrinos" claim is the most notable in my field; a few days before this paper was published there was a story about the claim of stem cells in acid baths, which went from this:
http://
to this:
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to this:
http://
Anyone who got excited about that one will have ended up embarrassed...
The peer-review process is important, though, as it almost always exposes mistakes and dodgy results. Let's hope that the course of the next year or so resolves whether or not this is a legitimate discovery.
Good call. Let's hope that this doesn't disappear, but obviously there have in the past been major announcements followed by quiet but embarrassing climb-downs. The "faster-than-light neutrinos" claim is the most notable in my field; a few days before this paper was published there was a story about the claim of stem cells in acid baths, which went from this:
http://
to this:
http://
to this:
http://
Anyone who got excited about that one will have ended up embarrassed...
The peer-review process is important, though, as it almost always exposes mistakes and dodgy results. Let's hope that the course of the next year or so resolves whether or not this is a legitimate discovery.
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