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Earth is faster than the speed of light?


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Haha...just kidding. It was a ruse to drag you in here :). 

But I do have a question that I can't seem to articulate enough for Google search engine to give me a useful answer. It is with regards to the big bang theory.

As I have understood it, the entire universe was once compressed into a singularity. All the matter in today's universe was once there. This singularity 'exploded' and the whole universe came into existence. In my mind, I am picturing a grenade that explodes in mid-air, and all the fragments disperse away from the center. This fits nicely with the observation that all solar systems and galaxies are traveling away from each other (you know, the balloon analogy).  

I've often heard it said, that if we had a telescope powerful enough, we could look back to the big bang. But if that light is 12.7 billion years old and we can see it, then how the heck did we get 'out here' to be able to observe our own creation?

It would be like yelling 'hey', run 2 kilometers away and then hear yourself yelling 'hey' from where you came. This is theoretically possible. If you can run faster than the speed of sound. But since we cannot move faster than the speed of light, how can we see anything from the big bang?

Am I even making any sense?

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Because the Universe expanded faster than the speed of light while light travelled through it. And only information cannot move faster than the speed of light, other things can, like the fabric of space-time and the galaxies attached to it.

Galaxies at opposite sides of the observable Universe move faster than light relative to each other but that's not a violation because light (information about them) emitted by those galaxies respects its speed limit.

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Because of spacetime curvature between "over there" and "over here", it is difficult to define the speed of an object "over there" with respect to us "over here" in a way that respects all of our everyday experiences with speed. This leads to a first explanation for the possibility of recessional speeds greater than the speed of light.

Special relativity prohibits speeds greater than the speed of light. Cosmology, however, is governed by the curved spacetime of general relativity, to which special relativity is a good *local* approximation. Consequently, we will never see anything moving faster than the speed of light in our local neighbourhood, where special relativity is a good approximation. Stuff at the edge of the universe is not in our local neighbourhood, and thus is not governed by the laws of special relativity.

Alternate (more technical) explanation for recessional speeds greater than the speed of light.

speed = distance/time, so if different definitions of distance and time are available, we can have have differing definitions of speed. The definitons of distance and time used in cosmology lead to cosmological recessional velocities that correspond not to velocity in special relativity, but to something different called rapidity (sometimes called the "velocity parameter"). In special relativity, there is a relationship between velocity and rapidity, which, for some reason is not used in cosmology. If this relationship were uswed in cosmology than a recession rapidy of 3.4 corresponds to a recessional speed of 0.998 times the speed of light.

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As I understand it (a) the universe didn't start as a singularity, it was already infinite, just infinitely dense as well. (b) it's a rising fruit b read full of raisins, not an inflating balloon covered with dots.

Our observable universe appears as if it all expanded out from where we are (i.e. it looks the same in all directions and the further away you look the older you see) but the same is true of anywhere else. So the observable universe from that far away galaxy over there may overlap with ours but includes things we can't see AND from that galaxy it looks like they are in the middle not us...)

No doubt I'm as wrong on this occasion as with my previous interpretations...

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2 hours ago, Anthonyexmouth said:

The balloon analogy is ok to a point

... but not to a singularity!

(Ow! I've cut myself on my razor-sharp wit).

Edit - actually I think you said what I said, but in considerably fewer words. Next time I'll quote you ?

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The universe has always been 'all of space'.

The singularity is one in time, not in space.

Space may have been infinite from the start. If it was, it still is.

The observable universe is not infinite: it once was  very small. 

If space was finite from the start, it sill is finite. This because it has expanded only for a finite amount of time and to grow to infinity it would need an infinite amount of time. An infinite speed would also do, but that would  reduce its density to zero in an instant, and it's density is higher than zero.

For a while space expanded ridiculously fast (inflation) which limits our horizon: we can't see all of space. 

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14 minutes ago, Ruud said:

For a while space expanded ridiculously fast (inflation) which limits our horizon: we can't see all of space. 

More accurately, we can't see all of the space that was once close enough to us to have 'communicated' with our space before inflation.

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Wow, I've really hit the jackpot with this forum. Thank you so much to all who have responded.

I can't claim to have fully grasped the concept (yet). It is quite difficult to wrap your head around. But one thing I have understood is that it is my linear thinking that has gotten me into trouble in the first place. Given my initial approach to the problem, I am sure you can understand why I was struggling with it and why the paradox arose, to begin with. Just goes to show why a little knowledge is a dangerous thing :).

Appreciate ALL who have contributed. But a special shout-out goes to Ben the Ignorant who was kind enough to post a 'astrophysics for dumbasses' video. It's right up my alley :).

Ok, I have some thinking to do. Might take a while...haha.

 

 

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The 'Big Bang Theory' is a theory but it relies on a hypothetical concept of inflation to make it work. In truth, nobody knows how the universe came into being or whether there was anything 'before'. We may never know the facts of creation or whether our universe is infinite (probably not, imho) or whether there may be any so-called parallel universes. But I'm sure people will keep asking questions. Maybe one day we'll have more answers - who knows?

Louise

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Came across this interview with Dr Penrose regarding his thoughts on the nature of the universe and whether we will ever be able to offer any definition to its nature prior to the big bang .  It's the type of video that you may need to watch 2 or 3 times but it is well worth persevering with. 

Jim 

 

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The Big Bang “theory” best one we have, but a theory at that, the Big Bang would imply that time itself began with it. Anyone who pretends to have the answer to that, (ALREADY) has surrendered to their own need for gratification.

We understand the beginning of the universe as we see it, as close as an ant is to understanding it’s place on earth.

 

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18 hours ago, Sunshine said:

The Big Bang “theory” best one we have, but a theory at that

 

We need to be careful with the use of the word "theory".  The layman often means the same thing by "theory" and "hypothesis".  Science rarely does.

James

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The Roger Penrose interview is very interesting, but I find his "anthropomorphisation" of the universe is, for me, unhelpful in understanding what he actually meansand glosses over some of the most fascinating detail.  For example, what does he actually mean when he says "the universe forgets how big it is"?

He seems to be saying that the dimensions of space are ever-increasing and time is always passing, up to a point when if we were able to wait long enough, suddenly they'd stop existing.  Errrm.  I'll have to give that one some more thought.

James

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Actually, here's an alternative way I might think about what he says.  It's almost as though he's saying that spacetime exists and expands until there's nothing left that requires the existence of spacetime (in a way, until there's nothing left to "observe" it), at which point it ceases to exist.

I think I'd best go to bed now, before my head undergoes exponential inflation :D

James

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21 minutes ago, JamesF said:

Actually, here's an alternative way I might think about what he says.  It's almost as though he's saying that spacetime exists and expands until there's nothing left that requires the existence of spacetime (in a way, until there's nothing left to "observe" it), at which point it ceases to exist.

I think I'd best go to bed now, before my head undergoes exponential inflation :D

James

I have read that it's possible that spacetime could undergo a spontaneous phase shift thus destroying everything at the speed of light. At least it wouldn't be painful :)

Louise

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2 hours ago, JamesF said:

We need to be careful with the use of the word "theory"

Agreed, any theory must first be backed by a hefty dose of evidence, unfortunately though, many very enlightened people cannot agree on what is defined as a "Big Bang" some say the visible universe began from a single infinitely small point.

Others say the big bang occurred everywhere at once, BANG! not like an explosion which throws material in an expanding sphere.  What's beyond the visible universe?, if the big bang has occurred some 14billion years ago, from where did all the matter required for there to be a big bang come from? what was before everything we know was? some things we may never know. 

 What if the entire universe as we know it, is about the size of a marble actually, lost within a much more vast universe. A microscopic organism, crawling on the ocean floor, must believe that the ocean is endless if asked, this organism, i'll call them sea peas, because they're green and cute like peas, has made great strides in exploring its ocean, has sent explorers abroad, and discovered that their world is far larger than they have ever imagined. They developed all kinds of theories attempting to explain what may be beyond their ocean? there must be something surely! 

For thousands of years, the great sea pea civilization flourished, colonizing other reefs and even travelled upwards off the ocean floor, they found a way to harness the power of bubbles, lifting them to great heights above the ocean floor!!

THEN! one day, a great sea pea explorer while riding a great big bubble, broke free of the ocean and was thrown into the air! what is this place??? he thought! there is more than just down there?!! the ocean! IMPOSSIBLE!! our math does not allow for this!! the great sea pea civilization had to come to terms with a new reality. lol (yes i'm bored)

My point is, our science as it has evolved throughout the ages, is tailored to explain what we can see, touch, examine, experience, within our universe, like an auto mechanics toolkit is not designed to repair computers, so our current scientific arsenal may be useless in explaining the centre of a black hole, let alone what may be beyond our expanding universe. Just like the great sea pea, one day we may land in the fourth dimension by accident, oops!! whats this place?? AHHH MY MATH DOESN'T WORK GOOD HERE!!!

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15 hours ago, JamesF said:

We need to be careful with the use of the word "theory".  The layman often means the same thing by "theory" and "hypothesis".  Science rarely does.

James

 

I like what Robert Geroch wrote (in his non-technical book "General Relativity from A to B about physics theories and "proofs" of theories:

Quote

It seems to me that "theories of physics" have, in the main, gotten a terrible press. The view has somehow come to be rampant that such theories are precise, highly logical, ultimately "proved". In my opinion, at least, this is simply not the case - not the case for general relativity and not the case for any other theory in physics. First, theories, in my view, consist of an enormous number of ideas, arguments, hunches, vague feelings, value judgements, and so on, all arranged in a maze. These various ingredients are connected in a complicated way. It is this entire body of material that is "the theory". One's mental picture of the theory is this nebulous mass taken as a whole. In presenting the theory, however, one can hardly attempt to present a "nebulous mass taken as a whole". One is thus forced to rearrange it so that it is linear, consisting of one point after another, each connected in some more or less direct way with its predecessor. What is supposed to happen is that one who learns the theory, presented in this linear way, then proceeds to form his own "nebulous mass taken as a whole". The points are all rearranged, numerous new connections between these points are introduced, hunches and vague feelings come into play, and so on. In one's own approach to the theory, one normally makes no attempt to isolate a few of these points to be called "postulates". One makes no attempt to derive the rest of the theory from postulates. What, indeed, could it mean to "derive" something about the physical world? One makes no attempt to "prove" the theory, or any part of it. I don't even know what a "proof" could mean in this context. I wouldn't recognize a "proof" of a physical theory if I saw one.

 

Geroch was a very deep thinking, very good, professor in the departments of mathematics and physics at the University of Chicago.

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Cosmology has the advantage over other branches of science that,. in general, you only have observations from which to derive theory and testing can be no more than making predictions and testing them.

Humble Earth-bound science is generally able to undertake controlled experiments (with some notable exceptions, like plate tectonics, although you could call fracking an experiment in that area...).

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I lay in bed last night pondering more on the Roger Penrose interview (Yeah, I know, ok?  My brain just does this sometimes.) and a number of thoughts randomly crossed my mind...

Perhaps mass and spacetime are somehow interrelated, in that they can't exist independently of each other.  I'd assume having mass with no space to put it in might be tricky, but can spacetime exist without mass?  I wonder if that's partly where he's going when he talks about the equivalence between mass and the universe "having a clock".  In "The Elegant Universe" I think Brian Greene talks about there being many possible dimensions (or degrees of freedom) not all of which are necessarily exposed to our perception of it.  Could the creation of mass be related to which of those dimensions do become extant?

And could the expansion of the universe and the existence of mass also be related?  Is it possible that as the amount of mass in the universe decreases as Penrose suggests, being converted into photons in black holes, that the expansion may reverse and the universe shrinks back down to where we started and begins all over again?

I'm no cosmologist nor particle physicist so clearly there may be fundamental objections to these ideas based on what we already have good evidence for being true.  There is however a certain emotional appeal in the idea that "heat death" isn't just the end of the universe, but the start of a new one.

James

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1 hour ago, JamesF said:

  I wonder if that's partly where he's going when he talks about the equivalence between mass and the universe "having a clock".  In "The Elegant Universe" I think Brian Greene talks about there being many possible dimensions (or degrees of freedom) not all of which are necessarily exposed to our perception of it.  Could the creation of mass be related to which of those dimensions do become extant?

 

What, I think, Penrose is saying is consider mass as equivalent to energy (condensed energy) or rather energy with a particular frequency (quantum field theory).  Now frequency is a time derived unit hence the linkage he makes between mass and time; more correctly I guess between energy and time.

Regarding his statement "the universe forgets what size it is"  I struggled with that as well. I think what he is referring to is the consequence of the mathematical model (conformal geometry ) he is using in which size (distance) is not is not recognised.  

I must admit I found the interview intriguing , I only wish I understood it better :)  

 

Jim 

 

  

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