Question about the universe [Archive] - Two Plus Two Newer Archives

fifield

02-08-2006, 10:52 AM

Yeah, just keep potential inaccuracies/missteps in mind.

Show discusses parallel universes. The analogy given at the beginning of the show is that our universe, our current reality, is like a bubble in a vast, infinite ocean of bubbles, with infinitely different circumstances (eg. in another reality/universe, Napoleon WON the Battle at Waterloo). The mathematics behind this theory began (it's implied in the show) with Einstein's unfinished "one theory of everything" and has continued along to M THEORY. It defines our universe's physical laws as existing in 11 Dimensions, some trillionths of a mm (tiny). The interesting thing this alludes to is this: universes are continually being created by collisions. The BIG BANG was a creation of a wave like collision between *univereses?* But it is also speculated that HUMANS, yes! HUMAN BEINGS, are CREATORS as an aspect of life, and that, as a part of the physical universe, a collision such as the clapping of our hands may spawn the creation of ?# universes by collision. (By that theory, would that mean I am God, you are God, ...LIFE is GOD?) It theory, such collisions spawn universes that expand in extrasensory dimensions infinitely quickly, and are separate from our universe in an infintessimal amount of time. There are many other points I've missed, so I'd be beneficial to do as I plan to do (if, that is, you are interested in seriously learning more about this fascinating possibility and its implications) and read the books recommended in the other thread or at least catch the show.

fifield

BluffTHIS!

02-08-2006, 11:27 AM

It can also be spatially finite but expanding on the surface of a sphere but without having yet expanded enough so that far away ends connect. But you can also go back to the big bang, and examine the quantum singularity that produced it. It is clear that no matter or energy, even of the dark type, existed outside this singularity until it exploded. Thus there did not exist outside of it what we call the vacuum of space which in fact possesses very minute traces of matter and energy, including dark matter and energy.

So the question is still unanswered as into what is the universe expanding. As a religious believer I of course have a ready answer. And it seems there can never be a scientific explanation, both because there is no observable evidence anywhere in the universe of the conditions that preceded the big bang, and because even if we were able to observe the furthest boundaries of the universe (realizing that such an observation is of things as they were billions of years ago), it remains that a great nothing past those boundaries produces no observable data.

bunny

02-09-2006, 03:08 AM

There is nothing outside the universe - that's how it's defined. It seems to me that you are imagining the universe as a large "bubble" expanding into a void and are asking what's in the void or how far it extends. This is not a correct view of how a cosmologist imagines the expanding universe.

The universe encompasses everything that exists, there is nothing outside and no "border" between the universe and the non-universe. It may be infinite, it may be finite (yet unbounded). Irrespective it is everything and there is nothing "outside" it - the concept of outside the universe doesnt mean anything, in the same way as a square circle doesnt mean anything.

The expansion of the universe is a misnomer really - people usually misinterpret it to mean "getting bigger". A more accurate description is that things within it are getting further apart. This isnt because the galaxies are hurtling off into uncharted void but because the space between galaxies is actually expanding. Some people find it useful to imagine a balloon with 2 dots on it representing galaxies - as it is inflated the dots become further and further apart - yet neither is moving relative to the surface.

Piers

02-09-2006, 01:55 PM

The universe stays the same size, its just that everything inside it is getting smaller. /images/graemlins/wink.gif

_TKO_

02-09-2006, 02:32 PM

[ QUOTE ]
Whats outside of that?

[/ QUOTE ]

More universe.

LadyWrestler

02-09-2006, 06:22 PM

Another universe.

When/if the sciences/we discover that to be true, the word will be redefined to allow for that discovery. Perhaps a cluster of universes would be called a super-universe or something similar.

Have a great day! /images/graemlins/smile.gif

BrickTamlin

02-09-2006, 11:19 PM

jman220

02-10-2006, 12:28 AM

[ QUOTE ]
The universe is expanding, thats how we know there was a big bang. So if its expanding there must be a border, a line where the universe ends, a stop.
Whats outside of that?

[/ QUOTE ]

Serious Question:

I understand that when we see things that are very far away, we are seeing them as they were a long time ago. IE: A star that is 100 light years away we are seeing as it appeared 100 years ago.

Explain this to me:

The edge of our observable universe is something like 15 billion light years away, and that is what we estimate to be the age of the universe (I read this somewhere I believe). But if we observe objects that are 15 billion light years away, and are seeing them as they were 15 billion years ago, well, then, weren't they a lot closer to us 15 billion years ago? As in, weren't they really right next to us, since we are observing them at a time that was very close to when the universe began? But if this is the case, then the light wouldn't have taken 15 billion years to reach us, as 15 billion years ago, they were a lot closer to us. I don't get it.

Gobgogbog

02-10-2006, 01:10 AM

All the light from when we were close to stuff very far away has passed us long ago, because we're moving away from those objects much slower than light moves

jman220

02-10-2006, 01:20 AM

[ QUOTE ]
All the light from when we were close to stuff very far away has passed us long ago, because we're moving away from those objects much slower than light moves

[/ QUOTE ]

Then how is it that the edge of our observable universe are objects that are 15 billionish light years away from us, corresponding to a time very shortly after the "birth" of the universe? 15 billion years ago they would have been much closer to us than 15 billion light years away. It seems like a paradox.

Edit: Obviously I'm wrong somewhere, but I just can't wrap my head around where.

Lestat

02-10-2006, 01:37 AM

[ QUOTE ]
[ QUOTE ]
All the light from when we were close to stuff very far away has passed us long ago, because we're moving away from those objects much slower than light moves

[/ QUOTE ]

Then how is it that the edge of our observable universe are objects that are 15 billionish light years away from us, corresponding to a time very shortly after the "birth" of the universe? 15 billion years ago they would have been much closer to us than 15 billion light years away. It seems like a paradox.

Edit: Obviously I'm wrong somewhere, but I just can't wrap my head around where.

[/ QUOTE ]

Obvioulsy, we do not measure the distance of an object 15 billion light years away, by how long it took the light to reach us.

BluffTHIS!

02-10-2006, 03:22 AM

[ QUOTE ]
The expansion of the universe is a misnomer really - people usually misinterpret it to mean "getting bigger". A more accurate description is that things within it are getting further apart. This isnt because the galaxies are hurtling off into uncharted void but because the space between galaxies is actually expanding. Some people find it useful to imagine a balloon with 2 dots on it representing galaxies - as it is inflated the dots become further and further apart - yet neither is moving relative to the surface.

[/ QUOTE ]

If this is true, and basically the universe rips itself apart and now there are expanses of nothing in the middle created by the expansion of the universe, then that nothing would soon be filled by the vacuum of space, and some sort of detectable movement of matter and energy would be seen to occupy the new space thus created. At least that seems the logical conclusion.

Gobgogbog

02-10-2006, 03:30 AM

[ QUOTE ]
If this is true, and basically the universe rips itself apart and now there are expanses of nothing in the middle created by the expansion of the universe, then that nothing would soon be filled by the vacuum of space, and some sort of detectable movement of matter and energy would be seen to occupy the new space thus created. At least that seems the logical conclusion.

[/ QUOTE ]

Huh?

Toe-Knee

02-10-2006, 03:47 AM

[ QUOTE ]
A McDonalds

[/ QUOTE ]
No, a Starbucks across from a Starbucks- (Lewis Black on Comedy central presents)

Nut4Dawgs

02-10-2006, 04:08 AM

[ QUOTE ]
[ QUOTE ]
A McDonalds

[/ QUOTE ]
No, a Starbucks across from a Starbucks- (Lewis Black on Comedy central presents)

[/ QUOTE ]
I think he first said it in a Houston comedy club. It was after he actually saw a Starbucks across the street from the Starbucks he was leaving.

What does this have to do with the OP? Absolutely nothing. I'm up at an ungodly hour and can't go back to sleep.

BluffTHIS!

02-10-2006, 04:36 AM

[ QUOTE ]
[ QUOTE ]
If this is true, and basically the universe rips itself apart and now there are expanses of nothing in the middle created by the expansion of the universe, then that nothing would soon be filled by the vacuum of space, and some sort of detectable movement of matter and energy would be seen to occupy the new space thus created. At least that seems the logical conclusion.

[/ QUOTE ]

Huh?

[/ QUOTE ]

Let me put it another way. If as he says is possible, the universe doesn't expand into a void but rather merely expands so that the distance between its objects becomes greater internally, then the matter/energy content of the vacuum of space should become more diffuse. Whether we would be able to measure same is a different matter.

Nut4Dawgs

02-10-2006, 04:47 AM

BluffTHIS!

02-10-2006, 04:51 AM

I don't mean the distance not be measurable, but the matter/energy content of the vacuum of space which is already extremely diffuse and should become more so.

fifield

02-10-2006, 05:50 AM

I believe Physics mathematically define all such aspects of our Universe, can't it?

jman220

02-10-2006, 11:47 AM

Lestat

02-10-2006, 03:04 PM

Light is constant. As someone already point out, the first light waves past us a long time ago. Thinks of it this way:

Say I have a water hose capable of spraying a stream of water 100 yards. You are standing next to the hose (which is turned off), and start walking away from it. I now turn the hose on and the water sprays past you because it is traveling faster than you are walking. You look out the corner of your eye and can see a stream of water, but you are NOT seeing the very first drops in the stream. Those drops have already past you.

Light works the same way (for this example). The light we are seeing is not 15 billion years old. Those light waves have already past us.

purnell

02-10-2006, 09:15 PM

[ QUOTE ]
[ QUOTE ]
All the light from when we were close to stuff very far away has passed us long ago, because we're moving away from those objects much slower than light moves

[/ QUOTE ]

Then how is it that the edge of our observable universe are objects that are 15 billionish light years away from us, corresponding to a time very shortly after the "birth" of the universe? 15 billion years ago they would have been much closer to us than 15 billion light years away. It seems like a paradox.

Edit: Obviously I'm wrong somewhere, but I just can't wrap my head around where.

[/ QUOTE ]

The light that we detect was emitted many years ago when the stars were in the position in which they appear to be. They are actually (it is theorized) much farther away now. I suggest Stephen Hawking's book, A Brief History of Time, for further reading. He explains the basics with almost no math, in a way that a layman can understand.

Nut4Dawgs

02-10-2006, 10:02 PM

If the universe is expanding, I'm not questioning/doubting that, does/has Science use(d) any "point" as the center? I understood the analogy about the balloon. I'm trying to absorb (NPI) the water hose comparison about light not returning but passing.

jman220

02-10-2006, 10:26 PM

[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
All the light from when we were close to stuff very far away has passed us long ago, because we're moving away from those objects much slower than light moves

[/ QUOTE ]

Then how is it that the edge of our observable universe are objects that are 15 billionish light years away from us, corresponding to a time very shortly after the "birth" of the universe? 15 billion years ago they would have been much closer to us than 15 billion light years away. It seems like a paradox.

Edit: Obviously I'm wrong somewhere, but I just can't wrap my head around where.

[/ QUOTE ]

The light that we detect was emitted many years ago when the stars were in the position in which they appear to be. They are actually (it is theorized) much farther away now. I suggest Stephen Hawking's book, A Brief History of Time, for further reading. He explains the basics with almost no math, in a way that a layman can understand.

[/ QUOTE ]

So wouldn't this mean that the universe is expanding faster than the speed of light? IE: If we can see something that 15 billion years ago, was 15 billion light years away from us, but the universe is not 30 billion years old, then how did tehy get 15 billion light years away from us 15 billion years ago, without traveling faster than the speed of light?

purnell

02-10-2006, 11:15 PM

[ QUOTE ]
So wouldn't this mean that the universe is expanding faster than the speed of light? IE: If we can see something that 15 billion years ago, was 15 billion light years away from us, but the universe is not 30 billion years old, then how did tehy get 15 billion light years away from us 15 billion years ago, without traveling faster than the speed of light?

[/ QUOTE ]

We get the notion that the universe is expanding by observing the "red shift" in the frequency of radiation that we observe (similar to the doppler effect for sound waves). Theorists estimate the size of the universe by observing the radiation coming from where a star was when it was emitted, and calculating the star's velocity (relative to us) from the red shift. They estimate how far away a star was when the observed radiation was emitted by comparing it's spectrum to other stars to get an idea of the original intensity, from which the distance can be calculated (because the intensity of observed light is proportional to the inverse of the square of the distance traveled). So, given where the star was, it's speed, and the elapsed time, one can estimate where the star is "now". It is from this estimate that the size of the universe is calculated.

I really suggest you read Hawking's book- he is far more eloquent and thorough. (I'm no scientist- I deliver furniture for a living /images/graemlins/crazy.gif)

bunny

02-11-2006, 01:27 AM

[ QUOTE ]
Let me put it another way. If as he says is possible, the universe doesn't expand into a void but rather merely expands so that the distance between its objects becomes greater internally, then the matter/energy content of the vacuum of space should become more diffuse. Whether we would be able to measure same is a different matter.

[/ QUOTE ]

This is a good point and this is indeed what happens. You may have heard about the "background cosmic radiation" which we see, pretty much unvarying any direction we look. The theory is that this is the remnants of the energy released during the big bang. Now this energy (billions of years ago) was extremely high or hot - yet today we measure it as something around 2-3 degrees above absolute zero (which is incredibly cold). The reason is essentially due to the point you made above - namely that space has stretched as the light wave has travelled through space and what was initially a high energy and very short wavelength wave has now been "smeared out" into a lower energy and longer wavelenght wave.

So yes that is what we would expect to happen and it is also consistent with what we observe.

bunny

02-11-2006, 01:39 AM

[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
All the light from when we were close to stuff very far away has passed us long ago, because we're moving away from those objects much slower than light moves

[/ QUOTE ]

Then how is it that the edge of our observable universe are objects that are 15 billionish light years away from us, corresponding to a time very shortly after the "birth" of the universe? 15 billion years ago they would have been much closer to us than 15 billion light years away. It seems like a paradox.

Edit: Obviously I'm wrong somewhere, but I just can't wrap my head around where.

[/ QUOTE ]

The light that we detect was emitted many years ago when the stars were in the position in which they appear to be. They are actually (it is theorized) much farther away now. I suggest Stephen Hawking's book, A Brief History of Time, for further reading. He explains the basics with almost no math, in a way that a layman can understand.

[/ QUOTE ]

So wouldn't this mean that the universe is expanding faster than the speed of light? IE: If we can see something that 15 billion years ago, was 15 billion light years away from us, but the universe is not 30 billion years old, then how did tehy get 15 billion light years away from us 15 billion years ago, without traveling faster than the speed of light?

[/ QUOTE ]

The universe was expanding faster than the speed of light, yes. This is not in any way a violation of the theory of relativity as things within the universe are all moving at less than this "absolute speed limit" relative to the universe.

There is nothing strange about us observing two things moving apart from each other faster than the speed of light - we just dont see them moving faster than that relative to us . As an example (hoepfully helpful) - consider a galaxy above our north pole, receeding from us at very close to the speed of light and another above our south pole, also receeding from us at very close to the speed of light. We notice that they are getting further apart from each other at a rate greater than the speed of light - yet each of them is moving relative to us at below this speed. Where relativity gets weird is when we consider what observers in each of these galaxies would observe. When light from the two eventually reached each other they would disagree with us on the speed with which they are receeding.

Relativity boils down to different observers making different measurements - there is no "absolute" physical frame of reference that represents the "true" motion.

The spots drawn on a balloon then being inflated is a useful mental picture to consider imo. No point on the balloon is special, the dots are immobile relative to the universe, yet they appear to recede (no matter what direction you look) there is no "central point" as another posted asked about. Space itself is expanding.

Reading this back it's a slightly waffly post - my apologies but I just cant be bothered sounding rational today. You'll have to live with it a half-explanation /images/graemlins/tongue.gif

bunny

02-11-2006, 01:48 AM

[ QUOTE ]
Light is constant. As someone already point out, the first light waves past us a long time ago. Thinks of it this way:

Say I have a water hose capable of spraying a stream of water 100 yards. You are standing next to the hose (which is turned off), and start walking away from it. I now turn the hose on and the water sprays past you because it is traveling faster than you are walking. You look out the corner of your eye and can see a stream of water, but you are NOT seeing the very first drops in the stream. Those drops have already past you.

Light works the same way (for this example). The light we are seeing is not 15 billion years old. Those light waves have already past us.

[/ QUOTE ]

This is not actually correct. When we observe light from a star 15 billion light years away - it is light that was emitted 15 billion years ago. Thus, the further out we look distance-wise, the further back we are looking timewise. The stars (or galaxies, quasars, etc) that are 15 billion light years away are stars that existed like that in a much earlier period in the universe's life.

If the modern big bang theory is correct, then the absolute, inviolate limit on how far we can see into the universe is x light years where x is the number of years since the big bang. There is no constraint on how large the universe may be - just on how large the observable (to us) universe is.

madnak

02-11-2006, 01:50 AM

But if we were in one of the galaxies, wouldn't the other galaxy be moving at double the speed of light in relation to us?

bunny

02-11-2006, 01:56 AM

[ QUOTE ]
But if we were in one of the galaxies, wouldn't the other galaxy be moving at double the speed of light in relation to us?

[/ QUOTE ]

It wouldnt yet be in our observable universe. By the time it was and the light reached us it would be moving slower (in our frame of reference) - proven by the fact that the light it emitted has reached us.

madnak

02-11-2006, 02:00 AM

So we can't observe it. But it's still going 2 times faster, right?

bunny

02-11-2006, 02:12 AM

It's more subtle than that. Your question is based on the idea that there is some absolute frame of reference. The best we can do is say that it's possible that there is something beyond the observable universe receeding from us at faster than the speed of light.

A galaxy 10 billion light years from us, for instance was probably receeding from our galaxy at greater than the speed of light 12 billion years ago. We cant know for sure, though since the only things we can see are those which appear to us to be moving slower than the speed of light.

madnak

02-11-2006, 03:16 AM

Okay, but...

What if galaxy a is moving at .75 the speed of light. And galaxy b is moving at the same speed. Now, the Earth can send messages to both galaxies at the speed of light. So we receive something from galaxy b. It is traveling at the speed of light (b to us). Now we send that message to galaxy a. It is traveling at the speed of light (us to a). Now a has information about b, and the message itself also traveled faster than the speed of light (a to b).

bunny

02-11-2006, 08:09 AM

This is true, but by the time we receive a message from galaxy a and relay it to galaxy b: Galaxy b's observable universe has expanded to include galaxy a - so they will never be able to receive information about anything outside of their observable universe. By the time they receive it, it will be faster for them to observe galaxy a directly.

Lestat

02-11-2006, 10:25 AM

First of all, can the most powerful telescopes even see a star 15 billion light years away?

I don't see how what you're saying is possible. It makes me ask the same question as OP. If the universe is 15 billion years old, then how is it possible for light from a star that is 15 billion light years away, to be 15 billion years old as well? The earth and the star didn't start off 15 billion light years away from each other. If the universe is 15 billion years old, then this leaves no time for the earth and the star to have become seperated by a distance of 15 billion light years.

bunny

02-11-2006, 07:43 PM

The oldest stars we see (around 15 billion light years away) are showing us what it was like in the very early universe. You are right that the age of the universe cant also be 15 billion years - otherwise those stars would have existed in the instant of the big bang which is not what current theory would predict at all.

The two numbers are both approximations - perhaps the oldest star is actually 14.8 billion light years away (making it light from 14.8 billion years ago) and the universe is actually 15.2 billion years old. Whatever the actual numbers are - you are correct that light cant have travelled longer than the universe has been in existence.

Perhaps a point worth making is that on the very edge of our observations, that is - the absolute theoretical limit to our observations, there are no stars and nothing but stretched out remnant big bang radiation there are no stars to be seen there as they had not had time to form.

BluffTHIS!

02-11-2006, 08:20 PM

[ QUOTE ]
[ QUOTE ]
Let me put it another way. If as he says is possible, the universe doesn't expand into a void but rather merely expands so that the distance between its objects becomes greater internally, then the matter/energy content of the vacuum of space should become more diffuse. Whether we would be able to measure same is a different matter.

[/ QUOTE ]

This is a good point and this is indeed what happens. You may have heard about the "background cosmic radiation" which we see, pretty much unvarying any direction we look. The theory is that this is the remnants of the energy released during the big bang. Now this energy (billions of years ago) was extremely high or hot - yet today we measure it as something around 2-3 degrees above absolute zero (which is incredibly cold). The reason is essentially due to the point you made above - namely that space has stretched as the light wave has travelled through space and what was initially a high energy and very short wavelength wave has now been "smeared out" into a lower energy and longer wavelenght wave.

So yes that is what we would expect to happen and it is also consistent with what we observe.

[/ QUOTE ]

bunny,

What you have said assumes that the energy content and temperature of the vacuum of space was larger previously, which obviously it was at some point. But your last statement that the theory given is consistent with observation, can only be so if the energy content and temperature of the vacuum is constantly getting smaller than even the small amount that it is now. Are you saying that we do in fact observe such changes in our lives' timeframes, such as decade by decade let alone year to year?

bunny

02-11-2006, 09:52 PM

[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
Let me put it another way. If as he says is possible, the universe doesn't expand into a void but rather merely expands so that the distance between its objects becomes greater internally, then the matter/energy content of the vacuum of space should become more diffuse. Whether we would be able to measure same is a different matter.

[/ QUOTE ]

This is a good point and this is indeed what happens. You may have heard about the "background cosmic radiation" which we see, pretty much unvarying any direction we look. The theory is that this is the remnants of the energy released during the big bang. Now this energy (billions of years ago) was extremely high or hot - yet today we measure it as something around 2-3 degrees above absolute zero (which is incredibly cold). The reason is essentially due to the point you made above - namely that space has stretched as the light wave has travelled through space and what was initially a high energy and very short wavelength wave has now been "smeared out" into a lower energy and longer wavelenght wave.

So yes that is what we would expect to happen and it is also consistent with what we observe.

[/ QUOTE ]

bunny,

What you have said assumes that the energy content and temperature of the vacuum of space was larger previously, which obviously it was at some point. But your last statement that the theory given is consistent with observation, can only be so if the energy content and temperature of the vacuum is constantly getting smaller than even the small amount that it is now. Are you saying that we do in fact observe such changes in our lives' timeframes, such as decade by decade let alone year to year?

[/ QUOTE ]

No, I am not saying that these changes are observable within the timescales of our lifetimes. All I am saying is that if the current cosmological theories are correct then we would expect to see background radiation similar to what we do now. (ie - the theory matches our observations)

madnak

02-12-2006, 12:09 AM

So, while galaxy b is moving at the speed of light in one direction, nothing in the opposite direction exists at all? I'm not sure I follow. It can't observe anything in the other direction (nothing is going fast enough to reach it from that way). Why is that relevant?

bunny

02-12-2006, 12:29 AM

It seems to me (and forgive me if I'm misunderstanding) that you are operating under the false idea that there is an absolute frame of reference, and hence an absolute answer to the question "How fast is object X travelling?"

The fact is this question has no meaning - you can only talk about how fast something is going, whether it exists at a certain point in time, the distance from it to a certain object, etc etc from within a particular frame of reference.

Physics tells us a lot about the observable universe, which is a sphere, centred on the earth with a radius approximately equal to c times the age of the universe. As soon as you start to ask questions about what's really happening you usually find you have misinterpreted relativity and are trying to impose some absolute, special frame of reference.

Going back to the scenario of two galaxies right on the edge of our observations but diametrically opposed. We can see Galaxy A receeding at .75c in one direction and Galaxy B receeding at .75c in the opposite direction so, relative to us, the two objects are zooming apart at 1.5c. That doesnt mean they are "really" moving apart at that speed, just that they seem to be to us. Consider a little green man in a spaceship zooming past earth right now at .75c in the same direction as galaxy a. He will also see galaxy b, but will conclude that galaxy a is stationary, galaxy b is receeding from him at something like .99c, yet he is right next to us!

This is where relativity gets weird. You just cant say they are "really" moving at such and such a speed. The little green man is able to observe both, same as us. The little green man is in the same region of space as us, he is just moving differently. We say they are separating at 1.5c - he says they are separating at .99c. He will agree with us that we are moving apart from galaxy a at a speed of .75c but will disagree that we are moving apart from galaxy b at the same rate. From his perspective, we will be moving away from galaxy b at a much slower rate.

There is no answer to "What's really happening?" other than "It depends who you ask" /images/graemlins/confused.gif

madnak

02-12-2006, 12:35 AM

I don't have a problem with that, per se. I have a problem with how it would all work.

There must be some referential frame that applies to everyone. Even if it doesn't involve time or space. If there were no frame of reference then the end result would be solipsism.

There must be some way to take all the "different" views and parse them into a shared view. I mean, unless the universe is arbitrary. Even if something is moving at a different speed for me than for the litte green man, it seems like there must be some kind of "movement" going on. Whether you define that as displacement or energy levels or just configuration.

bunny

02-12-2006, 12:51 AM

[ QUOTE ]
There must be some referential frame that applies to everyone. Even if it doesn't involve time or space.

[/ QUOTE ]

The theory of relativity says that there isnt. If you are right then relativity is wrong. It is a fundamental tenet of relativity that there is no special frame of reference.

[ QUOTE ]
If there were no frame of reference then the end result would be solipsism.

[/ QUOTE ]

You can believe in relativity - in the idea that there are no special frames of reference and that all physical measurements must be made relative to some arbitrary frame, without being a solipsist. In fact relativity is quite anti-solipsistic (?) in flavour - it says there is nothing special about my frame of reference at all!

[ QUOTE ]
There must be some way to take all the "different" views and parse them into a shared view. I mean, unless the universe is arbitrary. Even if something is moving at a different speed for me than for the litte green man, it seems like there must be some kind of "movement" going on. Whether you define that as displacement or energy levels or just configuration.

[/ QUOTE ]

Relativity does provide a way of parsing them all together - it provides some answers (for instance, you are right that the little green man and us are really moving relative to each other - every observer, any way they look at us will agree on that fact.) It just doesnt answer every question. In the main, this is because we pose poor questions. Our minds and languages have developed to deal with an existence dominated by one frame of reference - the earth. When we speak, we talk about standing still, about the time currently in england, about how fast such and such is moving. All of these questions and statements make sense if we assume that the earth's frame of reference is special and all of us routinely adopt this view. On the scale of the universe, however, it is no longer a helpful frame of reference and you have to be careful not to carry over your underlying assumptions which disregard relativity when you begin talking about the universe on a grander scale.

madnak

02-12-2006, 01:41 AM

[ QUOTE ]
In fact relativity is quite anti-solipsistic (?) in flavour - it says there is nothing special about my frame of reference at all!

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If there is no "common ground" between my universe and your universe, then everything in my universe is based on me. For all intents and purposes, I define everything within my experience. You don't even exist. If I had some way to know that you exist, then there would have to be some connection between our frames.

To put it another way, if you can compare two frames of reference, then they must exist within some greater frame of reference that allows for the comparison.

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Relativity does provide a way of parsing them all together - it provides some answers (for instance, you are right that the little green man and us are really moving relative to each other - every observer, any way they look at us will agree on that fact.)

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In this case I have no problem. It doesn't sound like there is no absolute frame of reference, but rather that the nature and attributes of time and space are not part of that frame.

I still don't exactly understand how to interpret the universe in such a way, but I won't try to on the premise that it involves lots of scary math and non-Euclidean geometry and stuff.

bunny

02-12-2006, 01:47 AM

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If there is no "common ground" between my universe and your universe, then everything in my universe is based on me. For all intents and purposes, I define everything within my experience. You don't even exist. If I had some way to know that you exist, then there would have to be some connection between our frames.

To put it another way, if you can compare two frames of reference, then they must exist within some greater frame of reference that allows for the comparison.

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They do exist within some greater frame of reference, in fact within an infinite number of them. Any frame you choose will allow you to describe your frame and my frame and to make observations from within this new overarching frame. The point of relativity is that there is no way to pick a special frame. Any frame is as good as any other. They are connected - all frames are connected but none are more important or natural than any others.

madnak

02-12-2006, 01:54 AM

Wouldn't an enumeration of those frames represent a "better" overarching frame?

bunny

02-12-2006, 02:09 AM

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Wouldn't an enumeration of those frames represent a "better" overarching frame?

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I dont understand what you mean - there are an infinite number of them (any point in space can be chosen as the "origin" and the frame can be moving in any direction at any speed up to c. You can state that all of these are valid frames (is this what you mean by enumerate?) but it doesnt help pick one out as special - they are all equally special.

madnak

02-12-2006, 02:39 AM

It might be an infinite representation, but it's still a representation.

I don't think it's necessary, regardless. If every frame is connected, a better frame could be identified by looking at how they are connected and representing the information in such a way that you can apply it to different frames arbitrarily. I don't think scientists would try to deny that there is in fact an objective reality.

bunny

02-12-2006, 02:45 AM

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It might be an infinite representation, but it's still a representation.

I don't think it's necessary, regardless. If every frame is connected, a better frame could be identified by looking at how they are connected and representing the information in such a way that you can apply it to different frames arbitrarily. I don't think scientists would try to deny that there is in fact an objective reality.

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Science clearly postulates an objective reality. Some things exist, some things dont. There is an answer to "What exists?" "What determines how that electron interacts with that proton?" etc etc. The point is that a question like "How fast is that object really going?" has no answer as the object has no "real velocity" in the objective universe.

Our language is formed in a way that suggests these questions should have answers - reality is otherwise though (at least if relativity is true). You can translate freely from any frame of reference to any other frame - you will always get an answer but it will always depend on which frame you choose. You cant get around choosing your perspective. At least that's the current theory.

madnak

02-12-2006, 02:49 AM

I would say that the answers to "What exists?" "What determines how that electron interacts with that proton?" etc etc would represent a frame of reference or perception. Saying "I am going such-and-such fast relative to him" also entails such a frame. Maybe we're arguing semantics.

By "frame" I mean "abstract representation of physical laws" while you seem to mean "spatial/temporal point."

bunny

02-12-2006, 03:01 AM

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I would say that the answers to "What exists?" "What determines how that electron interacts with that proton?" etc etc would represent a frame of reference or perception. Saying "I am going such-and-such fast relative to him" also entails such a frame. Maybe we're arguing semantics.

By "frame" I mean "abstract representation of physical laws" while you seem to mean "spatial/temporal point."

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Heh - all philosophy is semantics /images/graemlins/tongue.gif

Basically, I was using frame as it is used in the theory of relativity. Using your definition - it is certainly possible to construct an abstract representation of physical laws and presumably there is a "best" representation - that being the one that most closely represents what occurs in the real world.

Going back to the original problem though - that best representation will only be able to answer certain questions. Questions about absolute velocity will not be answerable (as the concept of absolute velocity is a human illusion), at least if relativity is an integral part of this ultimate representation.

madnak

02-12-2006, 03:08 AM

Okay.

PokerPadawan

02-12-2006, 07:56 AM

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The oldest stars we see (around 15 billion light years away) are showing us what it was like in the very early universe. You are right that the age of the universe cant also be 15 billion years - otherwise those stars would have existed in the instant of the big bang which is not what current theory would predict at all.

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Bunny, those objects at high redshift are not stars. What do you think the magnitude of even an O star 15 billion lyr away would be? We can see galaxies, quasars, and gamma-ray bursts. There is evidence of supernovae very early on, but I don't think we've observed one yet. Your statement makes it sound like you are an expert and that those are really stars.

bunny

02-12-2006, 08:51 AM

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The oldest stars we see (around 15 billion light years away) are showing us what it was like in the very early universe. You are right that the age of the universe cant also be 15 billion years - otherwise those stars would have existed in the instant of the big bang which is not what current theory would predict at all.

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Bunny, those objects at high redshift are not stars. What do you think the magnitude of even an O star 15 billion lyr away would be? We can see galaxies, quasars, and gamma-ray bursts. There is evidence of supernovae very early on, but I don't think we've observed one yet. Your statement makes it sound like you are an expert and that those are really stars.

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I didnt want to confuse the issue by pointing out that the objects we see at such distances are not stars. You are right of course - I just figured the point could be made without correcting a minor inaccuracy.

I also didnt mean to appear as an expert - certainly not in astrophysics. What I said was consistent with modern theory though.