Time comparison

[JaKiri]

I suspect JaKiri isnow being deliberately misleading....

 

No, it's just that he's quoting my counterargument for the existance of a 'fixed universe center' and using it to construct a counterargument for the existance of the same.

[Jacques]

What I think is that there is no 'fixed universe center' .

[JaKiri]

What I think is that there is no 'fixed universe center' .

 

Yes, that's what I think too. You'd have thought that my posts saying just that would have been evidence enough.

[Jacques]

OK

The confusion came from the word 'certain' that I interpreted has a particular point.

[ed84c]

So hypothitically the sun could still be in the center of the universe?

 

The movement of the Milkyway, may just be ajustment for the universes uneven expansion?

[Saint]

Just a quick question about the expansion of the universe. What is the largest unit of cosmic classification (solar system, galaxy etc...) for which the expansion does not apply? I mean, does the expansion of the universe only imply that galaxies are moving away from each other? Are the galaxies themselves expanding by some smaller factor as well?

[nur_agus_ipftiuii]

I'm a newbie...but let's try...

 

What we are debating is still the concept of "now", I think. As Relativity said, there is no absolute "now".

 

Example:

Jim and Jack bring a very-very big flare that can be detonated, and also a clock. They fly from earth, jim goes to sun, and Jack goes to Mars. They stop when the ship inform that they have travelled 3s of lightspeed. Then, as promised before, they explode each flare when the clock show the time. And...bang...but, who's bang. Of course, they can see their flare, but they still need to wait 6 second to see another's flare. "Now" is different in each person's point of view.

 

It's my thought.

Thanks, and sorry for bad English.

[5614]

maybe, or maybe that is similar to a reaction.

 

if i hit you hard it'd take a few micro seconds for you register it whilst the electrical impulses form the nerves went to your brain etc... so if i punch you NOW you will feel it NOW+0.001 seconds or something like that, if you see what i mean.

 

i dont think you can say the 'reaction time' or 'travelling time' for your light wave is redefining thw word 'now'.

 

do you see what i mean?

 

there's a now for the initial explosion, a now for when you see it (which varies on how far away from the explosion source you are).

[Severian]

I mean, does the expansion of the universe only imply that galaxies are moving away from each other?

 

Yes. The galaxies themselves are not expanding.

[Saint]

Severian - thanks for the response. I guess my question then continues: if everything was flying away from everything else very early on - before galaxy formation could occur, and the galaxies, as they are currently understood, are in fact still flying away from each other (even accelerating?), what enabled them to form in the first place? It seems that they would have required a pretty solid chunk of mass to start with in order to attempt to pull together the particles that were expanding away from each other.

[Severian]

Well, that is a very good question. In fact, this is what the COBE satelites answered. You are correct - if the pre-galaxy plasma was completely homogenous and isotropic, there would be no structure formation. Everything would get gravitational pulsl from everything else, which would all cancel out, and there would be no movement. What the COBE satelite showed (and WMAP later) was that the universe was not completely homogenous after all - there were very tiny amounts of structure. As soon as you have some structure, it will start to magnify (because the forces no longer balance) and eventually one gets galaxies.

 

What caused the original (very small) structure is a different question...

[Saint]

OK - so the universe started out non-homogeneous. It would seem difficult for a singularity (the thing that got "banged"), to be non-homogeneous would it not? Wouldn't all the non-homogeneity have been "squeezed" out the singularity by definition? I guess the question is: where did the non-homogeneity come from? How would it arise from a homogeneous singularity?

[Asimov Pupil]

Think of it as a grid and you have the tree spacial dimentions on the Y axis and time on the X Axis and speed as your slope. If you increase your slope/speed then then the time it takes to cross the same amount of space is shortened compared to the the one doing it at a slower speed.

[Mart]

Actually, the big difference with Newton was entirely relative space

 

Newton wouldn't entirely agree with you. He wrote Absolute space, in its own nature, without relation to anything external, remains always similar and immovable.

[Mart]

OK - so the universe started out non-homogeneous. It would seem difficult for a singularity (the thing that got "banged"), to be non-homogeneous would it not? Wouldn't all the non-homogeneity have been "squeezed" out the singularity by definition? I guess the question is: where did the non-homogeneity come from? How would it arise from a homogeneous singularity?

 

Maybe there are varieties of singularities like there are of infinities. I expect somebody will drive themself mad trying to figure it out.

[JaKiri]

Newton wouldn't entirely agree with you. He wrote [i']Absolute space, in its own nature, without relation to anything external, remains always similar and immovable.[/i]

 

Absolute space, in its own nature, without relation to anything external, remains always similar and immovable. Relative space is some movable dimension or measure of the absolute spaces, which our senses determine by its position to bodies and which is commonly taken for immovable space; such is the dimension of a subterraneous, an aerial, or celestial space, determined by its position in respect of the earth. Absolute and relative space are the same in figure and magnitude, but they do not remain always numerically the same. For if the earth, for instance, moves, a space of our air, which relatively and in respect of the earth remains always the same, will at one time be one part of the absolute space into which the air passes; at another time it will be another part of the same, and so, absolutely understood, it will be continually changed.

 

From the start of the Principia, I believe.

 

Oh, and it seems you've missed off the rather critical second sentance, and beyond.

[Mart]

From the start of the Principia' date=' I believe.

 

Oh, and it seems you've missed off the rather critical second sentance, and beyond.[/quote']

 

.

 

Your assertion was "Actually, the big difference with Newton was entirely relative space" So what do you mean?

[JaKiri]

Your assertion was "Actually, the big difference with Newton was entirely relative space" So what do you[/i'] mean?

 

Space which is entirely relative. Durr.

[Mart]

Space which is entirely relative. Durr.

 

Entirely? So what was Newton thinking when he wrote about Absolute space?

[JaKiri]

Entirely? So what was Newton thinking when he wrote about Absolute space?

 

You appear to be having a problem with the english language.

[Mart]

You appear to be having a problem with the english language.

 

Try to be more specific.

[JaKiri]

Newton introduced the concept of a relative spatial system.

 

See now?

[Mart]

Newton introduced the concept of a relative spatial system.

 

See now?

 

So no one before Newton had thought of the concept?

[JaKiri]

So no one before Newton had thought of the concept?

If they had, it certainly lacked any mathematics to go with it.

[Mart]

If they had, it certainly lacked any mathematics to go with it.

 

If they had? Does that mean that you don't know whether they did or they didn't?

But you're certain about some aspect of their mathematics. What aspect would that be?