Jump to content
Edisonian

Where Does Space End? It Must End Somewhere!

Recommended Posts

personally, i think WMAP was a waste of money. it is based on a small part of our universe.

 

By that argument, all research is a waste of money, since it is all based on a small part of our universe.

Share this post


Link to post
Share on other sites

no, physical laws are the same in every part of the universe. that is an axiom on which almost all physical theories are based. what I am saying is that you cannot tell the size/shape of the universe when you have no clue how much of it you can actually see. we can only see so far. if that is the entire universe, the we must be the center, and i doubt that we are.

Share this post


Link to post
Share on other sites
no, physical laws are the same in every part of the universe.

Aren't we forgetting something?

Share this post


Link to post
Share on other sites

how does that mean we can tell how big/what shape the universe is?

Share this post


Link to post
Share on other sites
no, physical laws are the same in every part of the universe.

 

So could the speed of light be different? If the speed of light was to be differ, then there could be systems farther away, but ther light is half the speed so it has not reached out system yet.

Share this post


Link to post
Share on other sites
Everything ends somewhere.

 

That's a rather shaky premise. Can you prove that? It may be weakly empirically true, but it certainly isn't a priori conclusive.

Share this post


Link to post
Share on other sites

surely the entire arg depends upon What you define as "Space".

if by space you mean an area sparsely occupied with mater in which there will be a measurable distance between objects, then yes the Universe under these definitions has a Border so to speak. if include in your deffinition the area that this Universe is expanding into as "Space" also, then there`s no reason for it to have ANY limit at all :)

Share this post


Link to post
Share on other sites
how does that mean we can tell how big/what shape the universe is?

What?

 

That vaguely-related question of your own is not a reply to the question I asked you.

Share this post


Link to post
Share on other sites
no, physical laws are the same in every part of the universe. that is an axiom on which almost all physical theories are based. what I am saying is that you cannot tell the size/shape of the universe when you have no clue how much of it you can actually see. we can only see so far. if that is the entire universe, the we must be the center, and i doubt that we are.

 

There is no centre of the universe. Why would there be?

 

The only assumption which goes into the astrophysical experiments is that we are not in an exceptional part of the universe. That all the other bits of the universe that we can't see (because they are outside our lightcone) are much the same as the stuff we can see. This is completely akin to the assumption that the parts of the universe that we cannot see have the same physical laws as the bits we do see - an assumption which you seem happy with. So why do you have a problem with one assumtion but not the other?

Share this post


Link to post
Share on other sites
There is no centre of the universe. Why would there be?

 

The only assumption which goes into the astrophysical experiments is that we are not in an exceptional part of the universe. That all the other bits of the universe that we can't see (because they are outside our lightcone) are much the same as the stuff we can see. This is completely akin to the assumption that the parts of the universe that we cannot see have the same physical laws as the bits we do see - an assumption which you seem happy with. So why do you have a problem with one assumtion but not the other?

 

This "no centre of the universe" used to do my head in, there was a big bang, all explosions have a central point.

BUT I think I've cleared it up in my mind now...

For the time before the big bang the universe was compressed into it's miniscule size so the big bang happened all over the universe at the same time. Is that the right way to look at it??

 

I watched a documentary recently that mentioned WMAP and showed the photo/map...

I don't understand which microwaves it's picking up.

The m/waves that went out from the sphere (radius = distance we can see) in that miniscule universe have travelled away now so the m/waves WMAP's picking up must be the ones still travelling from other spots in that miniscule universe, is that right??

How can it be right because with the universe being so small in its early days it wouldn't have taken EM waves long to travel right across the universe. Was the speed of light slower then??

 

And I think that's what yourdadonapogo meant by us being at the centre of this sphere, distance we can see. So if all we can see is that sphere of microwaves that haven't reached our part of the universe yet how does it tell us the shape of it?? If it was a cube, we'd still only be able to see X lightyears away in any direction, wouldn't we??

 

The other thing was the dark patches represented areas where matter must have been denser, so gravity could take effect and build up bigger masses.

But how do they get to that conclusion?

If these microwaves are travelling from X lightyears away wouldn't they be absorbed by other bodies in the universe before they reached us leaving darker regions??

http://map.gsfc.nasa.gov/m_mm/mr_whatsthat.html

To use their own analogy of light passing through clouds, the clouds absorb some of the light waves.

Share this post


Link to post
Share on other sites

I think I just realised something you all take for granted. ;)

 

Electromagnetic waves travel at the speed of light and EM waves were/are the energy given out by the big bang, so the universe must be expanding at the speed of light.

 

Matter can't travel at the speed of light so no matter will ever reach the edge of the universe, so that's my previous idea of tachyons being matter bouncing off the edge of the univere with more energy than the speed of light out the window, faster than the speed of light. ;)

 

Is that why we'll never be able to see the edge of the universe, because there can never be anything that far out for us to see??

Share this post


Link to post
Share on other sites
This "no centre of the universe" used to do my head in' date=' there was a big bang, all explosions have a central point.

BUT I think I've cleared it up in my mind now...

For the time before the big bang the universe was compressed into it's miniscule size so the big bang happened all over the universe at the same time. Is that the right way to look at it??

[/quote']

 

Yes, that is a fair way to look at it.

 

How can it be right because with the universe being so small in its early days it wouldn't have taken EM waves long to travel right across the universe. Was the speed of light slower then??

 

You are almost correct. If we imagine a big bang with matter moving apart slower than 'c', you are right to start with: the light will travel more quickly and pass the matter, so that the light from the big bang would already be gone. But actually it is not like that because you have to wait a little while for the matter in the universe to become transparent to light. Initially we have just one big soup, and the photons will be absorbed and re-emitted continuously. Eventually the 'soup' will clump into galaxies with space between and the universe will become 'transparent' allowing light to travel freely. You may have noticed that in previous posts I have been careful not to say that the photons from furthest away are coming from the Big Bang...

 

After a little bit of time, these galaxies are far enough away that your problem does not occur. But eben if it did, many cosmolgists beleive the universe underwent a period of 'inflation' where the universe grew incredibly quickly (faster than 'c', but not violating special relativity since it is space-time itself stretching faster than 'c', so allowing no information flow). Then galaxies which are far away would move outside out light cone anyway...

 

And I think that's what yourdadonapogo meant by us being at the centre of this sphere, distance we can see. So if all we can see is that sphere of microwaves that haven't reached our part of the universe yet how does it tell us the shape of it?? If it was a cube, we'd still only be able to see X lightyears away in any direction, wouldn't we??

 

WMAP is not measuring the shape of the galaxy as such, but using physical measurements and laws to deduce it. For example, if there were a lot of mass, the gravitational attraction would pull space-time back in on itself, making the universe closed. They have measured the mass (locally, or in other words, measured the density), and found that there is not enough to do this, so they deduce that the universe is open, etc. What circumstance could possibly result in the universe being a cube?

 

The other thing was the dark patches represented areas where matter must have been denser, so gravity could take effect and build up bigger masses.

But how do they get to that conclusion?

If these microwaves are travelling from X lightyears away wouldn't they be absorbed by other bodies in the universe before they reached us leaving darker regions??

 

This should now be clear from my earlier comments....

 

As for your second post about light charging away from us anyway, that was the point I was trying to make (clearly unsuccessfully) earlier, when mumbling on about light cones.

Share this post


Link to post
Share on other sites
What?

 

That vaguely-related question of your own is not a reply to the question I asked you.

 

And the answer to the vauge question you asked would be...... what am I forgetting? Please enlighten me oh sarcastic one.

Share this post


Link to post
Share on other sites
I think I just realised something you all take for granted. ;)

 

Electromagnetic waves travel at the speed of light and EM waves were/are the energy given out by the big bang' date=' so the universe must be expanding at the speed of light.

 

Matter can't travel at the speed of light so no matter will ever reach the edge of the universe, so that's my previous idea of tachyons being matter bouncing off the edge of the univere with more energy than the speed of light out the window, faster than the speed of light. ;)

 

Is that why we'll never be able to see the edge of the universe, because there can never be anything that far out for us to see??[/quote']

 

light travels slower than c through a medium because of defraction, since space is teeming with virtual particles not to mention gaseous nebula and galaxies wouldn't light be defracted and traveling slower than c?

Share this post


Link to post
Share on other sites
WMAP is not measuring the shape of the galaxy as such, but using physical measurements and laws to deduce it. For example, if there were a lot of mass, the gravitational attraction would pull space-time back in on itself, making the universe closed. They have measured the mass (locally, or in other words, measured the density), and found that there is not enough to do this, so they deduce that the universe is open, etc. What circumstance could possibly result in the universe being a cube?

 

Hmmm so what does the local mass (in our hubble volume) have to do with the universal mass? Is the assumption that the universe is uniform? Isn't this assumption refuted by the fact matter has condensed into galaxies?

Share this post


Link to post
Share on other sites
Hmmm so what does the local mass (in our hubble volume) have to do with the universal mass? Is the assumption that the universe is uniform? Isn't this assumption refuted by the fact matter has condensed into galaxies?

 

The assumption is that the universe is uniform on a much much larger scale, so that galaxies are distributed more or less randomly etc. In fact the COBE and WMAP experiments showed that this is actually a much better assumption than anyone had previously thought. This is supporting evidence for inflation, since inflation would tend to smooth out any un-uniformity.

Share this post


Link to post
Share on other sites
Yes, that is a fair way to look at it.

Good, I'm catching up slowly. ;)

 

You are almost correct. If we imagine a big bang with matter moving apart slower than 'c', you are right to start with: the light will travel more quickly and pass the matter, so that the light from the big bang would already be gone. But actually it is not like that because you have to wait a little while for the matter in the universe to become transparent to light. Initially we have just one big soup, and the photons will be absorbed and re-emitted continuously. Eventually the 'soup' will clump into galaxies with space between and the universe will become 'transparent' allowing light to travel freely. You may have noticed that in previous posts I have been careful not to say that the photons from furthest away are coming from the Big Bang...

 

Thanks for reminding me about the soup, I'd forgotten to take that into consideration. It was shown quite clearly in the documentary I watched just a few days ago too. :-/

So the actual photons of light/energy created by the big bang have all been absorbed and emitted many times since their creation, recycling the energy and the process is still ongoing, right??

 

When you say we have to wait for the matter in the universe to become transparent to light, I assume that includes other forms of wave energy too, is that correct??

 

After a little bit of time, these galaxies are far enough away that your problem does not occur. But eben if it did, many cosmolgists beleive the universe underwent a period of 'inflation' where the universe grew incredibly quickly (faster than 'c', but not violating special relativity since it is space-time itself stretching faster than 'c', so allowing no information flow). Then galaxies which are far away would move outside out light cone anyway...

 

Got that, also mentioned in the same documentary I watched and seen references to in other places.

Out of curiosity - is the inflation theory already established as being correct or are people finding holes in it??

 

WMAP is not measuring the shape of the galaxy as such, but using physical measurements and laws to deduce it. For example, if there were a lot of mass, the gravitational attraction would pull space-time back in on itself, making the universe closed. They have measured the mass (locally, or in other words, measured the density), and found that there is not enough to do this, so they deduce that the universe is open, etc. What circumstance could possibly result in the universe being a cube?

 

Ahhhh... A new piece I can put into my jigsaw puzzle. ;)

The universe would act like a huge black hole, enough mass to generate enough gravity to pull even light and everything else in. Its event horizon would be the edge of the universe, right??

 

Sorry about mentioning the cube, I meant it as an example of another shape the universe could be. I realise my mistake now, energy would be thrown out in all directions with the same amount of force. Whoops, things just got foggy again...

In my visualisation of how things happened the big bang threw out energy in all directions at the same time, something like the outer casing of a grenade, I see that outer casing of energy as being space. As that energy wave travels outwards it pushes out the boundaries of our space.

Or is space-time just something else the BB threw out along with everything else??

 

That would seem to make more sense to me now. Because space-time grows outwards, the fundamental particles form the soup and the electromagnetic energy is trapped in the soup bouncing around. As that matter is spread out the gaps between each particle lessens the amount of heat transference from particle to particle - the matter cools. Another contributing factor to the cooling is the EM waves can escape through the now wider gaps in the particles. Basically the energy in the particles is lowered because it's now allowed to roam freely between the gaps, there is more energy travelling through space than stored in particles...

I had this vision that if you could magically escape the universe and look at it you would see a large sphere of EM wave energy from the big bang, I'll cross my fingers and say "That's nonsense." isn't it??

 

If any of that's correct and space-time isn't EM energy pushing the universe outwards, does that mean ST can be travelling at a different speed??

It would have to have a variable speed to allow for inflation wouldn't it??

 

Perhaps I should have done some more scouting about on the net to see how the new jigsaw piece fits in with things I didn't understand before. ;)

 

This should now be clear from my earlier comments....

 

Let's find out... ;)

The microwaves WMAP is picking up aren't the ones from the big bang.

Each microwave WMAP receives has been travelling towards us for a very long time without being absorbed and emitted again.

The dark patches (if those are the denser areas of matter) they're the areas where the microwaves were absorbed by matter, right??

The lighter areas would obviously be the microwaves travelling unimpeded.

 

Yet there are other bodies within that sphere of WMAPS visibilty that emit microwaves, the way I'd have to explain why those aren't on the map is that the older microwaves from further away would have more energy stored in them, WMAP then filters out microwaves from the sun by ignoring low energy microwaves. Would that be correct??

 

 

BTW thanks for taking the time to explain all this, much appreciated.

I sometimes feel like a caveman looking at the stars when I read some of this stuff on the net.

Share this post


Link to post
Share on other sites
What?

 

That vaguely-related question of your own is not a reply to the question I asked you.

 

what was i forgetting?

Share this post


Link to post
Share on other sites

Singularities.

 

I was quite shocked you left them out to be honest.

Share this post


Link to post
Share on other sites

We don't really know what goes on inside them, but we're pretty sure that physics does some colourful things. And they're in the universe.

Share this post


Link to post
Share on other sites

Hmmm we cant observe whats inside a singularity so does it exist in the universe? Isn't the only thing that exists which is part of a singularity the event horizon and the gravitational distortion of space?

Share this post


Link to post
Share on other sites

As a graphic designer, I think i have a good perspective of this topic. When you start a new model, you have a big empty space. You can build this anywhere you could ever want. Space is not limited to where it stops or starts, but to how far we can go into it. Here are some other responses:

1.) Numbers are infinite. How is there a start and an end to them?

2.) If space ended somewhere, wouldn't there have to be something on the other side of it? You see, space is nothing, with something in it. Therefore it doesnt end. Nothing can't end... Because if it did... What would you be left with? Nothing.

Share this post


Link to post
Share on other sites
Guest
This topic is now closed to further replies.

×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.