ChatterBank4 mins ago
New Paper Appears To Confirm Inflation Theory
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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.
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
I'll make a fool of myself by giving those a try.
Maybe an alternative illustration would be to consider a spinning torch on a contained area, such as a room. The torch spins at less than the speed of light but the spot on the wall, because the wall is a distance away, appears to be moving much faster than the torch. Extend the boundaries of the area far enough away and the spot (assuming it remains) seems to get faster and faster as it completes it circle, until it seems to be going as fast as light itself, and then faster. But the light is still going at light speed, even if the spot appears to be going faster.
Observable universe is the limit we can see as light will have taken all the time since the Big Bang to have reached us. There will be more universe beyond that boundary (presumably) but we can never see it barring some change in our understanding of how it all works.
I don't believe that the speed of light in a vacuum has been exceeded.
IIRC and my memory isn't anything like 100% String Theory says that the basic constituent of everything is not a point but a loop string. It is useful as it allows one to build up a theory of reality that matches well with that observed.
Maybe an alternative illustration would be to consider a spinning torch on a contained area, such as a room. The torch spins at less than the speed of light but the spot on the wall, because the wall is a distance away, appears to be moving much faster than the torch. Extend the boundaries of the area far enough away and the spot (assuming it remains) seems to get faster and faster as it completes it circle, until it seems to be going as fast as light itself, and then faster. But the light is still going at light speed, even if the spot appears to be going faster.
Observable universe is the limit we can see as light will have taken all the time since the Big Bang to have reached us. There will be more universe beyond that boundary (presumably) but we can never see it barring some change in our understanding of how it all works.
I don't believe that the speed of light in a vacuum has been exceeded.
IIRC and my memory isn't anything like 100% String Theory says that the basic constituent of everything is not a point but a loop string. It is useful as it allows one to build up a theory of reality that matches well with that observed.
Lots to reply to here:
LG: The observable Universe/ Not observable Universe thing is in part a direct result of Inflation. If spacetime expands faster than light, naturally some things will be unable to see each other because they were moving apart faster than the light could travel between them (it's a bit more complicated than this, I think redshift enters into it too, but that's the gist -- the Universe is larger in Light Years than it is old, so some places will remain unseen and unseeable).
DTC: Unfortunately, or perhaps not, the "faster than light neutrinos" result disappeared quietly a year or so later, when more measurements were taken and the experimental set-up was rechecked. I think that it was something as simple, after all, as not taking the length of a wire into account properly. A bit of a shame after all the fuss and excitement and there was some feeling that maybe the Scientists involved should have presented the result in a different way, but never mind.
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OG: That would be a nice analogy but I think it fails, sadly. For a subtle reason! The light from the torch is travelling, naturally, at the speed of light, so that means that after a certain distance there will be some noticeable lag between the torch pointing at some part of the wall and the light from it arriving at that point. Not done the maths but intuitively this should mean that the analogy fails and that, after all, the spot on the wall will track around no faster than the speed of light. I'll try to check this at some point. I think the picture that will work better is my (definitely correct) waves on the shore one -- it's just that a picture (or short film clip ideally) is needed. Might get round to drawing one if anyone's still interested.
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humbersloop:
String Theory works roughly as follows:
Instead of everything being made ultimately of particles (with no size) you take the fundamental building block of nature to be strings instead. These have a certain size and structure: they can appear as strings with two ends, or as closed loops (if you tied the two ends together, basically). It turns out that this extra structure allows strings to do rather a lot more than particles can. They can, for a start, vibrate. The vibrations of the string could be thought of as the particles that we actually see (this is a consequence of the whole "waves are particles" idea that runs through Quantum Mechanics), and each individual string can have all sorts of different vibrations on it so that you can describe in principle all particles this way.
There are tonnes of other useful aspects of this idea too, although they are highly technical. What a theory of Nature really is, for example, is not a list of particles (there are electrons and protons and photons...) but it's about how they interact with each other. Invariably this leads to some hideously complex calculations, but it turns out that sometimes these calculations are a lot easier with Strings instead.
Another reason String theory could be useful is that the idea of a Quantum Theory of Gravity naturally pops out of String Theory: something that would look exactly like a graviton (the "photon" for Gravity) is just sitting there, naturally, in the maths.
Unfortunately, String Theory as a fundamental Theory of nature turns out to have a major problem. In order for the theory to make any sense, it turns out that the scale of this strings is something in the region of a hundred thousand million million million million millionth of a metre. This is so stupendously tiny that in order to have an experiment to probe this sort of scale you would need a machine that is something like ten thousand trillion times more powerful than the LHC is. This is just not likely to happen, and so it's likely that String Theory as a fundamental theory of Nature will remain untested and untestable for many decades, if not centuries, to come.
(Continued...)
LG: The observable Universe/ Not observable Universe thing is in part a direct result of Inflation. If spacetime expands faster than light, naturally some things will be unable to see each other because they were moving apart faster than the light could travel between them (it's a bit more complicated than this, I think redshift enters into it too, but that's the gist -- the Universe is larger in Light Years than it is old, so some places will remain unseen and unseeable).
DTC: Unfortunately, or perhaps not, the "faster than light neutrinos" result disappeared quietly a year or so later, when more measurements were taken and the experimental set-up was rechecked. I think that it was something as simple, after all, as not taking the length of a wire into account properly. A bit of a shame after all the fuss and excitement and there was some feeling that maybe the Scientists involved should have presented the result in a different way, but never mind.
* * * * * * * *
OG: That would be a nice analogy but I think it fails, sadly. For a subtle reason! The light from the torch is travelling, naturally, at the speed of light, so that means that after a certain distance there will be some noticeable lag between the torch pointing at some part of the wall and the light from it arriving at that point. Not done the maths but intuitively this should mean that the analogy fails and that, after all, the spot on the wall will track around no faster than the speed of light. I'll try to check this at some point. I think the picture that will work better is my (definitely correct) waves on the shore one -- it's just that a picture (or short film clip ideally) is needed. Might get round to drawing one if anyone's still interested.
* * * * * * * * *
humbersloop:
String Theory works roughly as follows:
Instead of everything being made ultimately of particles (with no size) you take the fundamental building block of nature to be strings instead. These have a certain size and structure: they can appear as strings with two ends, or as closed loops (if you tied the two ends together, basically). It turns out that this extra structure allows strings to do rather a lot more than particles can. They can, for a start, vibrate. The vibrations of the string could be thought of as the particles that we actually see (this is a consequence of the whole "waves are particles" idea that runs through Quantum Mechanics), and each individual string can have all sorts of different vibrations on it so that you can describe in principle all particles this way.
There are tonnes of other useful aspects of this idea too, although they are highly technical. What a theory of Nature really is, for example, is not a list of particles (there are electrons and protons and photons...) but it's about how they interact with each other. Invariably this leads to some hideously complex calculations, but it turns out that sometimes these calculations are a lot easier with Strings instead.
Another reason String theory could be useful is that the idea of a Quantum Theory of Gravity naturally pops out of String Theory: something that would look exactly like a graviton (the "photon" for Gravity) is just sitting there, naturally, in the maths.
Unfortunately, String Theory as a fundamental Theory of nature turns out to have a major problem. In order for the theory to make any sense, it turns out that the scale of this strings is something in the region of a hundred thousand million million million million millionth of a metre. This is so stupendously tiny that in order to have an experiment to probe this sort of scale you would need a machine that is something like ten thousand trillion times more powerful than the LHC is. This is just not likely to happen, and so it's likely that String Theory as a fundamental theory of Nature will remain untested and untestable for many decades, if not centuries, to come.
(Continued...)
Despite that obvious stumbling block of being not really experimentally testable, the maths behind String Theory can also be viewed as a sort of "calculator" for real theories such as the study of how metals work. So really String Theory can mean two different things: a theory of nature (most likely never to be confirmed) and a useful part of the mathematical physicist's toolkit. Sadly the maths is phenomenally hard (indeed, impossibly so for the moment in some ways!), and I don't follow most of it, but it is an interesting and, in its way, beautiful area of maths and physics. It's the sort of thing that, really, I don't think could possibly have been imagined without the mathematics, because really the idea comes as an extension of the maths behind normal particles.
I hope this is clear, and if you have any more questions then feel free to ask.
I hope this is clear, and if you have any more questions then feel free to ask.
@ Jim This may be a topic that merits a separate thread, but I think my confusion over the term "observable universe" was down to some studies that suggested that certain fundamental laws of physics - alpha, for instance, the fine-tuning constant, can vary within different parts of the universe, which in turn implies that some of those laws of physics which we regard as fixed and universal might be nothing more than local bye-laws, as it were.
And I am sure that I read somewhere that people were defining the "observable universe" as a kind of bubble, and that the universe might be considered to consist of millions of these "bubbles", all of which might have variations on the physical laws we have within our own universe. This was, I think, version of the multiverse theory.
http://
And I am sure that I read somewhere that people were defining the "observable universe" as a kind of bubble, and that the universe might be considered to consist of millions of these "bubbles", all of which might have variations on the physical laws we have within our own universe. This was, I think, version of the multiverse theory.
http://
It'd be interesting if you did come to a definitive conclusion re the spinning torch scenario jim. I am having difficulty getting past the thought that regardless of delays on route, the spot of light still has to make a journey right around the perimeter in the same time it takes the torch to rotate. If delays had an affect on that, then instinctively I see light forming a jam trying to get to it's destination but being blocked by the light in front from the last sweep :-) I have no problem with the light showing a 'spiral' pattern as it works its way outwards.
A spot on the wall at a great enough distance can travel faster than the speed of light because the spot itself is not actually anything but a defined location. The photons themselves continue to arrive at the speed of light but the location of their arrival can certainly move faster.
Likewise a shadow. Hence the speed of darkness is infinite. ;)
Likewise a shadow. Hence the speed of darkness is infinite. ;)
Ah there are so many different theories, some with different flavours, to consider, LG, it is very easy to get them confused, especially if trying to answer another's query.
We can not know if the constants and rules we deduce from this part of the universe apply where we can not see, beyond the visible horizon, but I think it probably right to say we have no compelling reason to believe they don't. It'd be interesting to envisage what happens on the boundaries where one area meets/blends with another.
Constants may not even stay constant over long periods anyway. Life/matter may not even be possible here in unimaginably long time into the future if the rules change.
We can not know if the constants and rules we deduce from this part of the universe apply where we can not see, beyond the visible horizon, but I think it probably right to say we have no compelling reason to believe they don't. It'd be interesting to envisage what happens on the boundaries where one area meets/blends with another.
Constants may not even stay constant over long periods anyway. Life/matter may not even be possible here in unimaginably long time into the future if the rules change.
FOR OG: http://
I'm inclined to leave it there. Anyone who was able to look at the torch and wall set-up would surely see all sorts of pretty patterns!
I'm inclined to leave it there. Anyone who was able to look at the torch and wall set-up would surely see all sorts of pretty patterns!
LG: Yes, that's probably a topic that warrants its own thread. I think it's worth testing those sorts of things though probably it won't go anywhere. The implication of a cosmic inflation theory being true ought to be that the Universe is pretty much the same everywhere. There's been an attempt to see if the Universe is as large as it looks by trying to find patterns in the CMB that would look like the same sort of pattern appearing at multiple points, which is probably a similar sort of idea. So far, no-one's found anything to suggest that the Universe isn't large and constant.
(Fine-structure constant, I think you mean?)
(Fine-structure constant, I think you mean?)
I'm impressed by your knowledge of physics, Jim. I'd previously thought that you were mostly a mathematician. But string theory still being useful in related areas ? Yes, so are dispersion relations, which were the forerunner of string theory. No apology is necessary for the physics of yesterday. I'm not sure that you can be so sure of the timescale of when the first particles were formed.
Humbersloop, the idea of string theory developed in the late 1960s, early 1970s, when physicists were still trying to explain why protons stayed so close together in the atomic nucleus. According to the laws of magnetism, they should repel each other, because they are all positively charged. The force that keeps them together is known as the strong force and string theory for a while became a viable explanation.
Well thanks!
My journey through Maths and Physics is a bit of a mess, really. In summary: I started off by doing A-Levels in Maths, Further Maths and Physics; Cambridge, studying the Mathematics "with Physics" option in the first year, studying 3/4 of the first-year Maths course and the whole of the Physics course; second year, I took the Physics and Maths options in the Natural Sciences course, and in the Third year I took the "Experimental and Theoretical Physics" course, only with no actual experimental work (did some in my first and second years only), taking the theoretical physics options. And, last year, I jumped over to the Mathematics department to do Part III of the Tripos, but all of the lecture courses I took were in Theoretical Physics, including String Theory and General Relativity courses -- though, if I'm honest I didn't understand them all that well, and I also didn't take the course in Cosmology.
These days I've ended up in Edinburgh and am starting a PhD in Theoretical High-Energy Physics, mainly focusing on Particle Physics at the LHC.
* * * * * *
Anyway, that's my journey in context. In terms of the timescale of first particles, I'm quoting another source and can't really understand where the numbers come from. Even though I'm used to all these weird small numbers it still seems ludicrously quick how everything happens so that in less than a second you have run through maybe ten different transitions. Presumably the discovery earlier this week appears to mean that the picture and timing are on a lot more solid footing than they were before, but either way it's not the physics I specialise in so I'll leave it to the cosmologists to investigate, understand and explain it. We hope!
My journey through Maths and Physics is a bit of a mess, really. In summary: I started off by doing A-Levels in Maths, Further Maths and Physics; Cambridge, studying the Mathematics "with Physics" option in the first year, studying 3/4 of the first-year Maths course and the whole of the Physics course; second year, I took the Physics and Maths options in the Natural Sciences course, and in the Third year I took the "Experimental and Theoretical Physics" course, only with no actual experimental work (did some in my first and second years only), taking the theoretical physics options. And, last year, I jumped over to the Mathematics department to do Part III of the Tripos, but all of the lecture courses I took were in Theoretical Physics, including String Theory and General Relativity courses -- though, if I'm honest I didn't understand them all that well, and I also didn't take the course in Cosmology.
These days I've ended up in Edinburgh and am starting a PhD in Theoretical High-Energy Physics, mainly focusing on Particle Physics at the LHC.
* * * * * *
Anyway, that's my journey in context. In terms of the timescale of first particles, I'm quoting another source and can't really understand where the numbers come from. Even though I'm used to all these weird small numbers it still seems ludicrously quick how everything happens so that in less than a second you have run through maybe ten different transitions. Presumably the discovery earlier this week appears to mean that the picture and timing are on a lot more solid footing than they were before, but either way it's not the physics I specialise in so I'll leave it to the cosmologists to investigate, understand and explain it. We hope!
http://
This is the best account of the new phenomenon that I can find.
Maybe it's just me but I don't understand why the polarisation of light photons which have no mass should be distorted by the passage of gravitational waves.
Maybe we have to go back to the concept of a blank hard drive being analogously instantaneously formatted by an OS (operating system) called spacetime into the universe we see today.
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.
What we see therefore is another proof for the formatting of our universe by an OS called spacetime billions of years ago in a whizz bang event sarcastically called the 'Big Bang'.
Not much further on really- are we?
This is the best account of the new phenomenon that I can find.
Maybe it's just me but I don't understand why the polarisation of light photons which have no mass should be distorted by the passage of gravitational waves.
Maybe we have to go back to the concept of a blank hard drive being analogously instantaneously formatted by an OS (operating system) called spacetime into the universe we see today.
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.
What we see therefore is another proof for the formatting of our universe by an OS called spacetime billions of years ago in a whizz bang event sarcastically called the 'Big Bang'.
Not much further on really- are we?
Some additional notes and links of possible interest - http://
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