ChatterBank1 min 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
Obviously that was rather too speedy a response.
No I don't think this discovery impacts on String Theory in any meaningful way -- nor did the Higgs Boson discovery if it comes to that. There are two reasons for this. In the first place "String Theory" doesn't have to be a fundamental Theory of Nature in order to be useful -- in recent years it's become clear that certain calculations in very real topics such as Quantum Chromodynamics (the theory of quarks and gluons, the constituent particles of protons and neutrons and therefore of virtually all of matter), and Condensed Matter (the study of how real-world matters behave). So in that sense String Theory has undergone something of a revolution as it's been seen to be extraordinarily useful in many other fields.
In the second case, the Discovery of the Higgs Boson confirmed that our understanding of matter up to about TeV scales (where 1 TeV = 1000GeV = 1000 times the mass of a proton) is correct. On the other hand, today's discovery tells us that there is some new energy scale, about one thousand billion times more energetic than anything at the LHC, where new Physics responsible for inflation kicks in. The race will now be on to investigate this physics anew, now that we know where it is and now that today's paper has some more concrete idea of what it is.
But String Theory as a fundamental Theory would operate at an energy scale higher still, I think another factor of 1,000, and might be responsible for the Physics before Inflation starts. A rough history of the Universe would go something like:
time=0 Big Bang starts
time = 0 to about 10^-36 seconds: some sort of bizarre Quantum Theory of Gravity gets things going, while the Universe expands, leading to some sort of Qunatum-scale variation in the shape of the Universe. Possibly there's also some sort of time here when all the forces of nature (excluding Gravity) behaved as one.
time = 10^-36 seconds onwards: Inflation. The Universe grows at some ridiculous rate, essentially the same rate in all directions, so that all those weird bumps from earlier get "locked in" at large scales.
time = 10^-32 seconds later: Inflation ends, and over the next few seconds particles start to form.
In this picture, all the String Theory stuff occurs before inflation, and all the LHC stuff occurs afterwards. Today's paper essentially implies that this picture is correct, and that we now have the chance to probe Physics back to about 0.00000000000000000000000000000000001 seconds after the Universe started! (I think that's the right number of zeroes.) Like I've said before, though, String Theory would be important even earlier than that.
No I don't think this discovery impacts on String Theory in any meaningful way -- nor did the Higgs Boson discovery if it comes to that. There are two reasons for this. In the first place "String Theory" doesn't have to be a fundamental Theory of Nature in order to be useful -- in recent years it's become clear that certain calculations in very real topics such as Quantum Chromodynamics (the theory of quarks and gluons, the constituent particles of protons and neutrons and therefore of virtually all of matter), and Condensed Matter (the study of how real-world matters behave). So in that sense String Theory has undergone something of a revolution as it's been seen to be extraordinarily useful in many other fields.
In the second case, the Discovery of the Higgs Boson confirmed that our understanding of matter up to about TeV scales (where 1 TeV = 1000GeV = 1000 times the mass of a proton) is correct. On the other hand, today's discovery tells us that there is some new energy scale, about one thousand billion times more energetic than anything at the LHC, where new Physics responsible for inflation kicks in. The race will now be on to investigate this physics anew, now that we know where it is and now that today's paper has some more concrete idea of what it is.
But String Theory as a fundamental Theory would operate at an energy scale higher still, I think another factor of 1,000, and might be responsible for the Physics before Inflation starts. A rough history of the Universe would go something like:
time=0 Big Bang starts
time = 0 to about 10^-36 seconds: some sort of bizarre Quantum Theory of Gravity gets things going, while the Universe expands, leading to some sort of Qunatum-scale variation in the shape of the Universe. Possibly there's also some sort of time here when all the forces of nature (excluding Gravity) behaved as one.
time = 10^-36 seconds onwards: Inflation. The Universe grows at some ridiculous rate, essentially the same rate in all directions, so that all those weird bumps from earlier get "locked in" at large scales.
time = 10^-32 seconds later: Inflation ends, and over the next few seconds particles start to form.
In this picture, all the String Theory stuff occurs before inflation, and all the LHC stuff occurs afterwards. Today's paper essentially implies that this picture is correct, and that we now have the chance to probe Physics back to about 0.00000000000000000000000000000000001 seconds after the Universe started! (I think that's the right number of zeroes.) Like I've said before, though, String Theory would be important even earlier than that.
Some sort of bizarre Quantum Theory of Gravity ? Apparently it was just the universe getting a bit cold thus created latent heat :-)
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I don't think so, sometimes the unknown is the most fascinating stuff of all. All those fields of study that I know little or nothing about, I do have a certain sense of fascination about, not least the "How did anyone think of this? How could anyone study it?" That sense of wonder at the achievements of others.
If you have any questions I can try to answer them for you?
If you have any questions I can try to answer them for you?
QM man - Jim that is - am I right... the inflation epoch is where the standard laws DIDNT hold ( so you could travel faster than the speed of light etc )
and this was quickly succeeded by the Planck epoch where they ( the standard laws) did hold.
or is it back to Fundamental Arithmetic for me ?
Oh, and did you feel sorry for the girlie on University Cock-up this week who said " inflation " when she should have said 'nucleosynthesis' ?
and this was quickly succeeded by the Planck epoch where they ( the standard laws) did hold.
or is it back to Fundamental Arithmetic for me ?
Oh, and did you feel sorry for the girlie on University Cock-up this week who said " inflation " when she should have said 'nucleosynthesis' ?
Yes, it was rather unfortunate, the first minute or so of the life of the Universe -- the first second, even! -- is full of all sort of different "epochs" (though how an epoch can last for a fraction of a second I don't know) and I doubt many people know them all of by heart, in order. I can't remember which physicist it was who said something like "If I could remember the names of all these particles I would have become a botanist." -- similar thing here!
Not quite, PP. The normal laws of Physics hold even during Inflation. Rather than any object moving faster than light, space expanded at a rate faster (many times faster!) than the speed of light! This doesn't break any laws at all, even though it might seem that way.
To see why, one common analogy is to think of waves against the shore. You can imagine that if the waves came in at some angle, then you should be able to see the point where the crest of the wave arrives at the beach, and define some speed for how fast that point moves along the beach. As the angle of approach changes, this speed will vary -- but, critically, it won't depend on the wave speed all that much at all, and in fact must always be equal to or greater than the wave speed (where it's equal in the case where the waves are travelling parallel to the shore). If the waves are coming in at an angle almost 90 degrees to the beach, then the point at which the wave first makes contact with the beack would zip from one side of the beach to the other almost instantly -- corresponding to a speed that approaches infinity! (You can calculate this using High-School Trigonometry... someone really ought to introduce problems like that at school. The speed goes as v/sin(x), where v is the normal wave speed and x is the angle between the beach and the wavefront.)
Anyway, this example shows that speeds that are faster than light are entirely possible after all. The reason this is not a problem is because, in this case, the point of contact between wave and beach is somehow "not real". Certainly the physical stuff, the water and the wave, aren't moving that fast. It's a sort of "virtual point" and this virtual point is carrying no information, and no mass, and no nothing really -- but still, its speed can easily be whatever you like.
And, in essentially the same sort of way, space itself has no substance exactly, and is as a result free to move at any speed -- including speeds faster than light, because nothing really is travelling, and no information is being carried. This is what happened during Inflation. Space itself expanded at a rate many times faster than the speed of light, but all the energy (and any matter) within it would have stayed travelling at normal speeds.
Really a couple of diagrams would have been helpful, but I hope the explanation above is useful.
Not quite, PP. The normal laws of Physics hold even during Inflation. Rather than any object moving faster than light, space expanded at a rate faster (many times faster!) than the speed of light! This doesn't break any laws at all, even though it might seem that way.
To see why, one common analogy is to think of waves against the shore. You can imagine that if the waves came in at some angle, then you should be able to see the point where the crest of the wave arrives at the beach, and define some speed for how fast that point moves along the beach. As the angle of approach changes, this speed will vary -- but, critically, it won't depend on the wave speed all that much at all, and in fact must always be equal to or greater than the wave speed (where it's equal in the case where the waves are travelling parallel to the shore). If the waves are coming in at an angle almost 90 degrees to the beach, then the point at which the wave first makes contact with the beack would zip from one side of the beach to the other almost instantly -- corresponding to a speed that approaches infinity! (You can calculate this using High-School Trigonometry... someone really ought to introduce problems like that at school. The speed goes as v/sin(x), where v is the normal wave speed and x is the angle between the beach and the wavefront.)
Anyway, this example shows that speeds that are faster than light are entirely possible after all. The reason this is not a problem is because, in this case, the point of contact between wave and beach is somehow "not real". Certainly the physical stuff, the water and the wave, aren't moving that fast. It's a sort of "virtual point" and this virtual point is carrying no information, and no mass, and no nothing really -- but still, its speed can easily be whatever you like.
And, in essentially the same sort of way, space itself has no substance exactly, and is as a result free to move at any speed -- including speeds faster than light, because nothing really is travelling, and no information is being carried. This is what happened during Inflation. Space itself expanded at a rate many times faster than the speed of light, but all the energy (and any matter) within it would have stayed travelling at normal speeds.
Really a couple of diagrams would have been helpful, but I hope the explanation above is useful.
@Jim I must admit to struggling with that "waves against the seashore" analogy, Jim :) Sounds like the sort of analogy that is in need of an illustration :)
Mind you, I still get confused when people talk about the "observable universe" and "the universe", which I think might have something to so with the multiverse theory...
Mind you, I still get confused when people talk about the "observable universe" and "the universe", which I think might have something to so with the multiverse theory...
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