ChatterBank1 min ago
Einstein Said Nothing Can Move Faster Than Light?
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Einstein's theory states nothing can move faster than light. How did we get all the way out here with images from the beginning of time still arriving? It is also accepted that the big bang pushed everything out instantaneously. Surely, the big bang theory proves Einstein wrong.
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At the instant of 'creation' I guess you could say everything was pushed out instantaneously, but the term means little if referring to a single point in time, thus removing the time factor. Over time there was no instantaneous push by definition.
You can find the answer to your query in other threads here. It wasn't so much an expansion as per our day to day experience. There was nowhere for a universe to expand into. It was a case of space being created throughout the existing universe, and space can be created fast enough to give the appearance of "stuff" apparently moving apart faster than light speed, even though neither bit of "stuff" actually is.
So no problem between 'Big Bang' and relativity.
You can find the answer to your query in other threads here. It wasn't so much an expansion as per our day to day experience. There was nowhere for a universe to expand into. It was a case of space being created throughout the existing universe, and space can be created fast enough to give the appearance of "stuff" apparently moving apart faster than light speed, even though neither bit of "stuff" actually is.
So no problem between 'Big Bang' and relativity.
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First, let's just debunk the whole "just a theory" point. This is one of those times where the technical meaning of a theory and the public's meaning clash. The technical meaning of "theory" is, in essence, something that is as close to factual as it is possible to be in Science. Obviously no theory is ever perfect, but at the moment there is nothing that fits the experimental data better than Einstein's Theory of Relativity. Thus, to all intents and purposes, it's factual, and you would be hard-pressed to find a single reputable Scientist who did not accept Relativity as a correct description of Gravity on large/ strong scales.
The same is essentially true of the "Big Bang" Theory. Up to the details of whether or not there was anything before, all competing theories such as in particular the "Steady State" Theory, or some young Universe model, have failed to fit the data and are for the time being discarded as explanations. As with everything else in Science, this is subject to the current status of experiment. We've just had a paper published last week that appears to cement the two theories of General Relativity and the Big Bang as the correct ones; if this result turns out to be wrong, and if at the same time some new and verifiable experiment showed that in fact an alternative model was correct, then the understanding of what is the "correct" Theory would change.
It seems that when members of the public talk about things as being "theories", they are using the word in the same way that a scientist would talk about a "hypothesis" -- which is to say, an idea that hasn't really been tested properly yet. If you wanted then to dismiss an idea as "only a Theory", you really ought to talk about it being "only a hypothesis". Completely different things: Hypotheses are untested, Theories have been tested and found to pass the test; for now, at least, but even then theories that pass one test but fail another are often still useful. Think of Newton's Theory of Gravity, which must after all be wrong because of the fact that we need Einstein's Relativity -- but is still useful because, as far as it goes, it is a very good description of how Gravity works. If you wanted to send a rocket to the Moon, for example, it's enough to use Newton's Gravity, and you lose virtually nothing and gain simplicity in doing so. On the other hand, describing Mercury's orbit about the Sun needs the upgraded Theory of Einstein. Presumably, at some point, describing Gravity in the earliest stages of the Universe, or at the tiniest scales, will need a better Theory still -- we are still looking for this. But each Theory is a more accurate version of the ones that precede it, and doesn't make previous ones wrong.
The name "theory", anyway, doesn't tell you that the idea is under dispute; indeed, almost exactly the opposite, as only those ideas that have passed the stringent tests of experiment receive the lofty honour of being called "Theories".
The Mathematical equivalent is a "Theorem", which is to say, something that has been proven to be true. As I've said, Theories are the best Scientific equivalent, ideas that are empirically true in present status.
Anyway, to dismiss Relativity, or the Big Bang, as "just a Theory" is a misunderstanding of the word.
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The same is essentially true of the "Big Bang" Theory. Up to the details of whether or not there was anything before, all competing theories such as in particular the "Steady State" Theory, or some young Universe model, have failed to fit the data and are for the time being discarded as explanations. As with everything else in Science, this is subject to the current status of experiment. We've just had a paper published last week that appears to cement the two theories of General Relativity and the Big Bang as the correct ones; if this result turns out to be wrong, and if at the same time some new and verifiable experiment showed that in fact an alternative model was correct, then the understanding of what is the "correct" Theory would change.
It seems that when members of the public talk about things as being "theories", they are using the word in the same way that a scientist would talk about a "hypothesis" -- which is to say, an idea that hasn't really been tested properly yet. If you wanted then to dismiss an idea as "only a Theory", you really ought to talk about it being "only a hypothesis". Completely different things: Hypotheses are untested, Theories have been tested and found to pass the test; for now, at least, but even then theories that pass one test but fail another are often still useful. Think of Newton's Theory of Gravity, which must after all be wrong because of the fact that we need Einstein's Relativity -- but is still useful because, as far as it goes, it is a very good description of how Gravity works. If you wanted to send a rocket to the Moon, for example, it's enough to use Newton's Gravity, and you lose virtually nothing and gain simplicity in doing so. On the other hand, describing Mercury's orbit about the Sun needs the upgraded Theory of Einstein. Presumably, at some point, describing Gravity in the earliest stages of the Universe, or at the tiniest scales, will need a better Theory still -- we are still looking for this. But each Theory is a more accurate version of the ones that precede it, and doesn't make previous ones wrong.
The name "theory", anyway, doesn't tell you that the idea is under dispute; indeed, almost exactly the opposite, as only those ideas that have passed the stringent tests of experiment receive the lofty honour of being called "Theories".
The Mathematical equivalent is a "Theorem", which is to say, something that has been proven to be true. As I've said, Theories are the best Scientific equivalent, ideas that are empirically true in present status.
Anyway, to dismiss Relativity, or the Big Bang, as "just a Theory" is a misunderstanding of the word.
* * * * * * * * *
Now, to answer the original question.
There are two further misunderstandings here: firstly, of what Einstein's Theory says, and secondly, of what the Big Bang Theory says. OG's answer is pretty close to the mark, and I've also provided an analogy over in the thread on inflation that should help answer the question, so I'll link to that thread and you can find my answer there.
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Not sure I can improve on that at the moment, but a brief Summary follows:
1. Einstein didn't state that nothing can move faster than light in a vacuum; rather, that things that have mass and energy and information cannot move faster than light in a vacuum.
2. Spacetime isn't really mass or energy. Things without mass or energy, and are in some sense just some "reference point", are at perfect liberty to move at any speed they like.
3. For the purposes of inflation, Spacetime is essentially a set of arbitrary reference points. Therefore there is nothing stopping spacetime from expanding at arbitrarily large speeds, which is precisely what is said to have happened. So there isn't a contradiction between the two statements.
4. " images from the beginning of time still arriving"... the images in question are actually from something like 400,000 years after the Beginning of Time. By this time most of the rapid expansion of the Universe was long finished (inflation lasted a tiny fraction of a second within the first second of the Universe), and the images were sort of "locked in" to everywhere within the Universe. What this means is that all observers everywhere in the Universe will see essentially the same pattern as we do when we look back. The "image" is all around us, everywhere.
There are two further misunderstandings here: firstly, of what Einstein's Theory says, and secondly, of what the Big Bang Theory says. OG's answer is pretty close to the mark, and I've also provided an analogy over in the thread on inflation that should help answer the question, so I'll link to that thread and you can find my answer there.
http://
Not sure I can improve on that at the moment, but a brief Summary follows:
1. Einstein didn't state that nothing can move faster than light in a vacuum; rather, that things that have mass and energy and information cannot move faster than light in a vacuum.
2. Spacetime isn't really mass or energy. Things without mass or energy, and are in some sense just some "reference point", are at perfect liberty to move at any speed they like.
3. For the purposes of inflation, Spacetime is essentially a set of arbitrary reference points. Therefore there is nothing stopping spacetime from expanding at arbitrarily large speeds, which is precisely what is said to have happened. So there isn't a contradiction between the two statements.
4. " images from the beginning of time still arriving"... the images in question are actually from something like 400,000 years after the Beginning of Time. By this time most of the rapid expansion of the Universe was long finished (inflation lasted a tiny fraction of a second within the first second of the Universe), and the images were sort of "locked in" to everywhere within the Universe. What this means is that all observers everywhere in the Universe will see essentially the same pattern as we do when we look back. The "image" is all around us, everywhere.
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If it were not proven, then the phrase would be "just a hypothesis", as I have just pointed out at length...
And like I've said, the paper from last week would appear to be the final confirmation of the idea. But before that, there is the CMB itself, the evidence of an expanding Universe, the proportions of light elements in the Universe, cosmic redshift, large-scale structure formation, etc., etc. There is no other idea that fits the evidence so well, although rightly this hasn't stopped people from looking.
And like I've said, the paper from last week would appear to be the final confirmation of the idea. But before that, there is the CMB itself, the evidence of an expanding Universe, the proportions of light elements in the Universe, cosmic redshift, large-scale structure formation, etc., etc. There is no other idea that fits the evidence so well, although rightly this hasn't stopped people from looking.
There is nothing within our visible horizon of the universe that violates the limitation of c, otherwise we would not be able to see it. The closest thing to travelling the speed of light we see is that extremely red shifted part of the cosmic microwave background (which was liberated during the recombination phase of the universes evolution, long after inflation) that has not exceeded c. If anything this only offers additional support to the theory of relativity.
https:/
In some sense nearly everything in motion we see in the universe 'exceeds the speed of light' because nothing is where (or when) we see it due to the propagation of its light being a limited quantity. For instance, the Sun has moved about 2 full degrees across the sky from where we see it in the eight plus minutes it takes for its light to reach us.
https:/
In some sense nearly everything in motion we see in the universe 'exceeds the speed of light' because nothing is where (or when) we see it due to the propagation of its light being a limited quantity. For instance, the Sun has moved about 2 full degrees across the sky from where we see it in the eight plus minutes it takes for its light to reach us.
Jim - Please excuse my ignorance on this matter but I think I understand where the OP is coming from as the same thought has occurred to me.
I imagine the big bang as an instantaneous event that ejected all the matter in the universe outwards. Intuitively then, here we are far away from the "centre" and yet if we look back towards the origin we see light that is still heading towards us. Therefore, in my ignorance, it seems that we travelled here faster than the light.
I know this probably doesn't make sense but a "simple" explanation would be appreciated.
I imagine the big bang as an instantaneous event that ejected all the matter in the universe outwards. Intuitively then, here we are far away from the "centre" and yet if we look back towards the origin we see light that is still heading towards us. Therefore, in my ignorance, it seems that we travelled here faster than the light.
I know this probably doesn't make sense but a "simple" explanation would be appreciated.
Personally, I think that is why the term "the big bang" often creates the wrong impression in peoples heads. People tend to think of it as an event where there was a huge explosion of incredibly compressed matter into the surrounding vacuum that was the universe - but it actually was the universe itself and everything that it contains expanding at this incredible rate.
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