Maximum distance between two points

[kamil]

OK now this is just an idea to solve the problem raised in the previous post. Because the Universe is expanding, then we would also be expanding, so we would be moving away from the incoming light beam. :)

[my brain hurts]

OK now this is just an idea to solve the problem raised in the previous post. Because the Universe is expanding, then we would also be expanding, so we would be moving away from the incoming light beam. :)

 

It would still be coming in at the speed of light (ie- it would measure c), whether we were moving toward it or away from it.

 

 

Please try to limit replies to the question I posed.

[TheBigDog]

A third astronomer claims to have found a quasar that is 12 billion light years away.

Did the astronomer claim the the quasar is 12 billion light years away now, or was 12 billion light years away when the current light was sent? Could his answer been an estimate of its current position?

 

Bill

[my brain hurts]

Did the astronomer claim the the quasar is 12 billion light years away now, or was 12 billion light years away when the current light was sent? Could his answer been an estimate of its current position?

 

Bill

 

Umm, the example was illustrative- there is no third astronomer. I refer to any claim regarding an object 12 billion light years away, or any other number higher than 10 billion.

[kamil]

It would still be coming in at the speed of light (ie- it would measure c), whether we were moving toward it or away from it.

 

 

Please try to limit replies to the question I posed.

:evil:

But we would be moving away from the quasar, and yes, we would measure the light to be moving at the same speed but we would see it arrive at earth later. Edwin Huble said that the Expansion of the Universe is like the expansion of a balloon, so if the Universe expands so does earth! moving away from the quasar.

 

BTW how do astronomers measure the distance of distant quasars? The speed of light is known but the time is also needed to measure the distance:confused:

If I would know this I might then be able to come up with better ideas on this.

[woog]

Very interesting question

 

If the universe sprang into being from a singularity, with particles (whatever they may be) hurtling away from each other at no greater than the speed of light, after one year the furthest a particle could be from the point of origin would be one light year. Okay so far? The farthest particle from this location would be one that travelled from the origin one light year in a diametrically opposed direction, and the resulting distance between them would be two light years.

 

The first thing to do is work out what model of the universe we are talking about. I assume that the universe you imagine is something like an expanding gas cloud in an empty room, with the origin of the gas being the singularity?

 

Based on this view I think your problem makes perfect sense, and seems to imply one should not be able to "see" anything greater than 2/3 the age of the universe away in light years.

 

However, if we consider different geometric models (hypersphere, torus, hypercone...) of the universe then I think your problem can be overcome. A higher limit than 2/3 might even be set. These depend on the fact that the direction of expansion may not be along one of the dimensions of our universe.

 

I'll assume that the universe is on the surface of an expanding balloon as mentioned in a previous post. After 7.5 years, the radius of this balloon is 7.5 light years. Objects can be on opposite ends of the balloon, and be 7.5*pi light years away from each other.

 

If the universe is the surface of a torus, this distance may even be greater.

 

I would like to point out that my reasoning is purely geometrical and I've ignored many things such as relativity that would probably make my simple reasoning flawed. For instance recently it has been thought that the speed of light may have slowed down since the big bang.

 

Sorry its a bit long.

[my brain hurts]

Very interesting question

 

 

 

The first thing to do is work out what model of the universe we are talking about. I assume that the universe you imagine is something like an expanding gas cloud in an empty room, with the origin of the gas being the singularity?

 

Based on this view I think your problem makes perfect sense, and seems to imply one should not be able to "see" anything greater than 2/3 the age of the universe away in light years.

 

However, if we consider different geometric models (hypersphere, torus, hypercone...) of the universe then I think your problem can be overcome. A higher limit than 2/3 might even be set. These depend on the fact that the direction of expansion may not be along one of the dimensions of our universe.

 

I'll assume that the universe is on the surface of an expanding balloon as mentioned in a previous post. After 7.5 years, the radius of this balloon is 7.5 light years. Objects can be on opposite ends of the balloon, and be 7.5*pi light years away from each other.

 

If the universe is the surface of a torus, this distance may even be greater.

 

I would like to point out that my reasoning is purely geometrical and I've ignored many things such as relativity that would probably make my simple reasoning flawed. For instance recently it has been thought that the speed of light may have slowed down since the big bang.

 

Sorry its a bit long.

 

Not long at all, Woog, and thanks for the thoughtful reply. I understand your point regarding the geometry, but I don't think it answers the underlying problem. If, as you say in your example, the two points were on opposite ends of a balloon, they still couldn't be more than 15 light years apart (after a period of 7.5 years) without violating relativity.

 

The easiest way to think of my conumdrum is this- go way, way back in time (which we claim to do by looking at very distant objects), say 14 billion years. If we assume the universe to be 15 billion years old (merely for argument's sake), then the universe back then was much different than it is today, not the least of which was its size. If it was only one billion years old, how could it have been big enough for two objects to be so distant from each other that they required 14 billion years for light to pass between them?

 

So far, I believe that you're the only one (in here, at least) to have latched onto the general predicament to which I refer. Thanks for the input.

[TIDUSGIYA]

What is the maximum distance between any two points in the universe. Would it be twice the age of the universe in light years, or otherwise?

 

Please give your answer and a brief explaination as to why, and I will present an interesting point. Thanks.

 

All caps post deleted by Tormod.

[woog]

You're welcome :rainbow: . Your problem was too intriguing to ignore.

 

Not long at all, Woog, and thanks for the thoughtful reply. I understand your point regarding the geometry, but I don't think it answers the underlying problem. If, as you say in your example, the two points were on opposite ends of a balloon, they still couldn't be more than 15 light years apart (after a period of 7.5 years) without violating relativity.

Your reasoning is correct but I think we have a slight misunderstanding here.

 

I was assuming that our four dimensional universe exists on the four dimensional surface of a five dimensional balloon -- quite a mouthful. The shortest distance between two opposite points on that "balloon" is certainly the diameter but that would mean travelling through the balloon. This implies moving through another dimension, something which I don't think is possible based on what I have assumed.

 

The point is that objects in our universe can only travel on the surface of that balloon, and hence the furthest two points can be is on opposite ends of the balloon. What appears as straight lines to us may be curved in a higher dimension.

 

As a side note this also means that the singularity that kicked off the big bang cannot be located in our universe. So when the universe expands, everything becomes further apart from everything else because there is no point of origin where things are stretching away from.

 

The easiest analogy is to imagine two dimensional beings living on the surface of a three dimensional sphere.

 

The easiest way to think of my conumdrum is this- go way, way back in time (which we claim to do by looking at very distant objects), say 14 billion years. If we assume the universe to be 15 billion years old (merely for argument's sake), then the universe back then was much different than it is today, not the least of which was its size. If it was only one billion years old, how could it have been big enough for two objects to be so distant from each other that they required 14 billion years for light to pass between them?

A good point, and I can only think of one explanation for now.

 

The first is that those two may not have been very distant from each other initially, but after 14 billion years they happen to be in the situation that the light from one object has just reached the other. For example if an astronaut detects an object 14 billion light years away, it is not to say that she has been waiting there for 14 billion years, only that she has just detected the light from an object that emitted it 14 billion years ago.

 

The universe may also have some mechanism to prevent such problems from occuring that we are not aware of. Nature often has exhibited clever ways to disallow paradoxes and such from coming to pass. I have suspicion this may be one of those cases.

 

Thanks for listening.

[virtualmeet]

As a side note this also means that the singularity that kicked off the big bang cannot be located in our universe. So when the universe expands, everything becomes further apart from everything else because there is no point of origin where things are stretching away from.

 

The easiest analogy is to imagine two dimensional beings living on the surface of a three dimensional sphere.

 

Saying that we live in a 4D surface and, as consequence, we can't locate the origin of the big bang because it doesn't belong to our universe is really a good idea...but even in this case the distance can be mathematicly computed because it's definition is well defined for heigher dimension too(http://en.wikipedia.org/wiki/Distance) !!!

for example, the 2D being can compute this distance even if he can't locate the origine of the sphere : d = sqrt(x*x + y*y + z*z)

For us it'll look something like this : d = sqrt (x*x + y*y+z*z +f(t)*f(t)) where f is a function. :rainbow:

[Boerseun]

When we look at the edge of the visible universe, we see a point roughly 15 billion light years away.

 

Imagine for a second what you'd see right there, right now. At this moment in time. If you could stand on a planet right on the edge of Earth's visible universe, and you look back towards Earth, you'd see what this corner of the universe looked like 15 billion years ago. The region where Earth is today, would be speckled with quasars and all kinds of funny things that existed here 15 billion years ago. And what would you see when you look in the opposite direction, i.e. beyond Earth's visible horizon? Pretty much the same. And if you could go there, to the visible edge that would exist at the point of Earth's visible edge, you'd see the same! And at that edge, the same! Ad infinitum.

 

This is my personal belief. And it holds true with the notion that every single cubic millimetre, every conceivable point in space is the exact center of the universe, and the exact point of origin of the Big Bang.

[TIDUSGIYA]

All caps post deleted by Tormod. (From TidusGiya, I did not use the caps lock, if this mesg is missing.)

 

Even though my theory has been deleted.....those of you that did get to read it, would have found it to be rational and true.

 

so, here it is once more.

 

There is no possible way to measure the distance between the maximum length. The maximum lenght would be the universal stucture.

 

example.

 

find the most distant particle at the edge of the universe and find the second most distant particle at the edge of the universe, and measure the distance from one to the other.

Next....rational answer....

 

the universe is expanding continuously, so when you have measured the distance of those paticles, you would continualsy have to record the distance. you would never get a true maximum distance until the universe stops expanding.....Remember this.

 

The universe itself is not space, because if the universe did not exist the there would only be space, and there would be no maximum distance.

 

thank you for reading this. please do not delete this text.

[Tormod]

Even though my theory has been deleted.....those of you that did get to read it, would have found it to be rational and true.

 

1) Yes, it was ALL CAPS, as were most of your posts up until now. It was deleted because I warned you to not post in ALL CAPS anymore (but you didn't care to listen).

 

2) Your "theory" was perhaps rational from your point of view, but it was not "true". There is no such thing as a "true theory". A theory is by definition not true, it is only an explanation of something, and as such it is biased.