Travelling to the edge of the universe is impossible
Discussion
People often ask what is at the edge of the universe and what is beyond....
I think this turns out to be a non-relevant question as the edge of the universe is also the edge of time.
Its hypothesised, even measured, that as you travel further away from any single point in space that time dilates (shown by red-shifting), and that this dilation increases with distance until time basically stops.
Its a hard concept to break down, the fact that time slows and stops. But essentially the so called 'edge' of the universe is impossible to reach or pass and the non-existence of time (never mind space), means that the concept of what is beyond the universe becomes meaningless.
So like with black holes, an outside observer would see a traveller head out in to the distance but gradually slow down to a stand still as they approach the 'edge' of the universe.
For the traveller it would seem that distance becomes incredibly long, time would pass as per normal but the distance covered in one second would be incredibly minimal to the point of not moving at all. As from the traveller's perspective its the rest of the universe that seems to have time stopped.
(Please feel free to rip that apart, I created this post to also try and get my own head around the question).
I think this turns out to be a non-relevant question as the edge of the universe is also the edge of time.
Its hypothesised, even measured, that as you travel further away from any single point in space that time dilates (shown by red-shifting), and that this dilation increases with distance until time basically stops.
Its a hard concept to break down, the fact that time slows and stops. But essentially the so called 'edge' of the universe is impossible to reach or pass and the non-existence of time (never mind space), means that the concept of what is beyond the universe becomes meaningless.
So like with black holes, an outside observer would see a traveller head out in to the distance but gradually slow down to a stand still as they approach the 'edge' of the universe.
For the traveller it would seem that distance becomes incredibly long, time would pass as per normal but the distance covered in one second would be incredibly minimal to the point of not moving at all. As from the traveller's perspective its the rest of the universe that seems to have time stopped.
(Please feel free to rip that apart, I created this post to also try and get my own head around the question).
AA999 said:
So like with black holes, an outside observer would see a traveller head out in to the distance but gradually slow down to a stand still as they approach the 'edge' of the universe.
That hypothesis assumes the universe has an "edge" though.There may be no edge - in much the same way as the surface of the earth has no edge.
It could well be the case that if you travelled far enough in a single direction - you'd end up back where you started - much as you would if you did the same on earth.
Moonhawk said:
That hypothesis assumes the universe has an "edge" though.
There may be no edge - in much the same way as the surface of the earth has no edge.
It could well be the case that if you travelled far enough in a single direction - you'd end up back where you started - much as you would if you did the same on earth.
Yes - I was careful to put 'edge' in quotes/hyphens..... as there is no defined edge as time dilates towards infinity.There may be no edge - in much the same way as the surface of the earth has no edge.
It could well be the case that if you travelled far enough in a single direction - you'd end up back where you started - much as you would if you did the same on earth.
Its just that the question is often posed "what's beyond the edge of the universe?"
I've also been trying to get my head around "flat space-time" and "curved space-time".
"Space-time" is not a 3D postion co-ordinate with time added as the 4th dimension..... "Flat space-time" is a whole other entity in as much as it plots 'events'.
"Curved space-time" again is more complex and one hypothesis is indeed that if space-time is curved in such a way then heading off in one direction could lead you back to the origin. But the problem we have here is that we can not see or measure the entire universe, only the observable part is 'known'.
anonymous said:
[redacted]
It's a function of speed but also of gravitational potential (i.e. time runs slower the closer you are to a large mass).https://en.wikipedia.org/wiki/Gravitational_time_d...
The question makes the assumption that we know what the universe is, that we can describe it and, more difficult still, predict.
When we have no idea what makes up the majority of the universe, cannot detect it and would no know if it all suddenly turned blue. Therefore we can only make uninformed guesses.
The current theory is that we could never attain the speed of light so, as the universe is expanding at the speed of light, we've missed the boat.
This is shorn of technical language and the maths of course, but generally it is correct.
My theory is that the universe will come at us in years to come, just when we least expect it. Which is now, I suppose.
When we have no idea what makes up the majority of the universe, cannot detect it and would no know if it all suddenly turned blue. Therefore we can only make uninformed guesses.
The current theory is that we could never attain the speed of light so, as the universe is expanding at the speed of light, we've missed the boat.
This is shorn of technical language and the maths of course, but generally it is correct.
My theory is that the universe will come at us in years to come, just when we least expect it. Which is now, I suppose.
Derek Smith said:
My theory is that the universe will come at us in years to come, just when we least expect it. Which is now, I suppose.
Yep! http://www.rawstory.com/2015/10/christian-group-sa...The universe has an 'horizon' the maximum distance and time we can ever see. Consider the speed of light, multiplied by the age of the universe. This gives an absolute maximum distance we can ever 'see', the universes event horizon. This is actually just the same thing as the event horizon normally associated with black holes. This event horizon is actually smaller than the size of the universe, the universe is also expanding relatively fast. This means you can never actually every reach the edge of the universe even if you had infinite time.
Edited by Martin4x4 on Sunday 11th October 11:19
ash73 said:
Derek Smith said:
the universe is expanding at the speed of light
It's expanding a lot faster than that.Martin4x4 said:
The universe has an 'horizon' the maximum distance and time we can every see into the past. Consider the speed of light, multiplied by the age of the universe. This gives an absolute maximum distance we can ever 'see', the universes event horizon. This is actually just the same thing as the event horizon normally associated with black holes. This is actually smaller than the size of the universe, the universe is also expanding very fast. This means you can never actually every reach the edge of the universe even if you had infinite time.
Yeah, but, what about those entities fortunate enough to be at the edge as the universe expands? Do they get dragged along with it, or does it expand away from them as well, and if so, why? If something has an edge, then there is something at the edge, isn't there? Hoofy said:
Since the universe is expanding...
(resisted temptation to add more space here)
... you'd better leave now.
I wonder if this has a part to play in the Fermi Paradox(resisted temptation to add more space here)
... you'd better leave now.
Some of the comments on these threads always confuse me. I try and be humble and never know whether they're ahead of my reading or massively behind, I fear often it's the latter.
The universe is flat and expanding into infinity. You can check the maths for yourself but it's not curving off or looping or coming back in itself. This is why the universe will end cold and dark.
The universe expands faster than "c" or the universal constant (or "speed limit") which is coincidentally also the speed of light. If you think about it the universe has to expand faster that "c" or else where would the light from the big bang go?
This rate of expansion, travels faster the further out you go, faster than light, which is faster than matter can travel as demonstrated by the universal constant.
So even if you can reach almost light speed, which is pure fantasy, then you've still to catch something moving faster than you, and it has at least a 46 billion light year head start.
So yes. Probably no need to phone ahead for the Milliways just yet.
The universe is flat and expanding into infinity. You can check the maths for yourself but it's not curving off or looping or coming back in itself. This is why the universe will end cold and dark.
The universe expands faster than "c" or the universal constant (or "speed limit") which is coincidentally also the speed of light. If you think about it the universe has to expand faster that "c" or else where would the light from the big bang go?
This rate of expansion, travels faster the further out you go, faster than light, which is faster than matter can travel as demonstrated by the universal constant.
So even if you can reach almost light speed, which is pure fantasy, then you've still to catch something moving faster than you, and it has at least a 46 billion light year head start.
So yes. Probably no need to phone ahead for the Milliways just yet.
The more it is studied the less is understood. It's almost, almost, as if the philosophers build in a futility quotient just to be awkward. To the lay person (me, for instance) it's a guess, compounded by an assumption and supported by invention. Then backed up with a convenient mathematical construct that can't be argued with because nobody knows. But hugely entertaining. Help, I'm disa
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Thorodin said:
The more it is studied the less is understood. It's almost, almost, as if the philosophers build in a futility quotient just to be awkward. To the lay person (me, for instance) it's a guess, compounded by an assumption and supported by invention. Then backed up with a convenient mathematical construct that can't be argued with because nobody knows. But hugely entertaining. Help, I'm disa
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Another plastic philosopher talking bpp
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ks then hiding behind the caveat of 'I'm a layman but...'.This is a science forum, leave that crap for a creating writing exercise. Don't make a baseless attack on something you don't understand.
Prof Prolapse said:
Another plastic philosopher talking bks then hiding behind the caveat of 'I'm a layman but...'.
This is a science forum, leave that crap for a creating writing exercise. Don't make a baseless attack on something you don't understand.
Thanks for that. Your inability to recognise self deprecation is proof of your closed mind. And on a science thread as well! Not worried about credibility then. ks then hiding behind the caveat of 'I'm a layman but...'.This is a science forum, leave that crap for a creating writing exercise. Don't make a baseless attack on something you don't understand.
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