The stars....

[Improvision]

are really used as a base to estimate the age of the universe? The oldest stars we see are "some of the first"?

 

Thats like looking at the oldest living human who is say 115 years old and using them to estimate that the human race started 115 years ago.

[GDG]

are really used as a base to estimate the age of the universe? The oldest stars we see are "some of the first"?

 

Thats like looking at the oldest living human who is say 115 years old and using them to estimate that the human race started 115 years ago.

 

It would be more accurate to say that the most distant stars are used to estimate the age of the universe. If the most distant star is (for example) 90 billion light years away, then we know that the universe is at least 90 billion years old. And since the light from the star that we observed took 90 billion years to get here, that should make it one of the oldest as well.

[NowThatWeKnow]

are really used as a base to estimate the age of the universe? The oldest stars we see are "some of the first"?

 

Thats like looking at the oldest living human who is say 115 years old and using them to estimate that the human race started 115 years ago.

 

I see it as looking at light that took 13+ billion years to get here and seeing a new born.

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...If the most distant star is (for example) 90 billion light years away, then we know that the universe is at least 90 billion years old. And since the light from the star that we observed took 90 billion years to get here, that should make it one of the oldest as well.

 

Don't forget about the expansion of space. Light that took 13 billion years to get here was emitted from a galaxy when it was 3.3465 billion light years away and is now 29.701 billion light years away.

[Improvision]

I see it as looking at light that took 13+ billion years to get here and seeing a new born.

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Don't forget about the expansion of space. Light that took 13 billion years to get here was emitted from a galaxy when it was 3.3465 billion light years away and is now 29.701 billion light years away.

Galaxies move 2x faster than the speed of light?

 

How does the galaxy move ~26 billion light years in 13 billion years?

[NowThatWeKnow]

Galaxies move 2x faster than the speed of light?

 

How does the galaxy move ~26 billion light years in 13 billion years?

 

Galaxies are basically at rest in space relative to the cosmic microwave background radiation. There is little movement relative to the speed of light but local gravitational forces do cause some local movement. Hubble's law talks about space expanding. Every light year in open space is getting bigger causing galaxies to spread out. At the edge of the observable universe, galaxies are separating from us at near the speed of light. Galaxies much further away, because of the expansion of space, exceeds light speed and we can not see them. Nothing is moving that fast, it is all because of expansion.

 

There are a couple of other threads next to this one talking about the same stuff. You may want to join in there.

[Improvision]

Galaxies are basically at rest in space relative to the cosmic microwave background radiation. There is little movement relative to the speed of light but local gravitational forces do cause some local movement. Hubble's law talks about space expanding. Every light year in open space is getting bigger causing galaxies to spread out. At the edge of the observable universe, galaxies are separating from us at near the speed of light. Galaxies much further away, because of the expansion of space, exceeds light speed and we can not see them. Nothing is moving that fast, it is all because of expansion.

 

There are a couple of other threads next to this one talking about the same stuff. You may want to join in there.

How do they know that space is "expanding"?

 

What is the current scientific definition of "space"?

[petebro]

stating the obvious the" big bang "if the universe was,nt expaning and perhaps slowing down the universe would,nt exist , the light that has been emmitted from varying light sources stars are a window into the past its how they used to be so it tells us just that.

space that is to be occupied is anti matter it is yet to be created so therefore expanding

universes are to occupy space that is being created . Black Holes are what confuse me .

the elusive holes in the universe with a no entry sign like some kind of potholers entry point.

[NowThatWeKnow]

How do they know that space is "expanding"?

 

What is the current scientific definition of "space"?

 

It has been determined that the temperature,in different directions, of the cosmic microwave background radiation

http://en.wikipedia.org/wiki/Cosmic_microwave_background_radiation

tells us we are at rest and it is the universe that is expanding. Check out Hubble's law for info on the expansion of space.

 

Most believe that space is just a metric and nothing else. The link in my signature may be a good source of basic information.

[Martin]

How do they know that space is "expanding"?

 

What is the current scientific definition of "space"?

 

It has been determined that the temperature,in different directions, of the cosmic microwave background radiation

http://en.wikipedia.org/wiki/Cosmic_microwave_background_radiation

tells us we are at rest and it is the universe that is expanding. Check out Hubble's law for info on the expansion of space.

 

Most believe that space is just a metric and nothing else. The link in my signature may be a good source of basic information.

 

I agree with the general tenor of what NowThat is saying here.

I think it is merely a figurative expression to say "space expands" when mathematically what we are talking about is a pattern of increasing distances.

 

Physics does not need to have space defined, as if it were a substance.

Defining space is more an issue for philosophy. Practically speaking what matters IMHO is that we can measure distances, angles, areas, volumes---that we can observe geometry. The distance function that summarizes this kind of information is called the metric.

 

I halfway suspect that Impro knows this already and is just being "Impish" when he asks "what is the current definition of space".

For a sympathetic listener it is not so hard to recognize a figure of speech and to understand what the speaker is trying to say.

 

Personally I often try to avoid saying "space expands". If there's a perceived risk of being misunderstood, I prefer to talk about increasing distances instead. Find other ways to say the same thing.