(October 4, 2012 at 9:56 pm)Polaris Wrote:

(October 4, 2012 at 9:19 pm)Stimbo Wrote: Perhaps you misspoke there; the geologic timescale is a heartbeat in comparison with cosmic time.

Not really much difference as both deal in billions of years. Only way I would see a real significant difference would be if I still believed in the collapsing universes theory.

It is not believed to be constant because of the believed exponential effects of dark energy.

I don’t know if it has been proven, but is believed that the rate of expansion is accelerating therefore not a constant. But, is it accelerating at a constant exponential rate?

(October 4, 2012 at 8:33 pm)Cthulhu Dreaming Wrote: A team of astronomers, using NASA's Spitzer space telescope has confirmed cosmological inflation and has refined the error range of acceleration to 74.3 +/- 2.1 km/megaparsec (the Hubble constant).

Do you mean cosmological expansion, I thought cosmological inflation was the extremely rapid exponential expansion of the early universe.

Grimesy

(October 4, 2012 at 10:09 pm)popeyespappy Wrote: I don’t know if it has been proven, but is believed that the rate of expansion is accelerating therefore not a constant. But, is it accelerating at a constant exponential rate?

Yes, the units above should have been 74.3 +/- 2.1 kilometers per second per megaparsec, which is the rate of acceleration of expansion.

(October 5, 2012 at 3:18 pm)Tino Wrote:

(October 4, 2012 at 10:09 pm)popeyespappy Wrote: I don’t know if it has been proven, but is believed that the rate of expansion is accelerating therefore not a constant. But, is it accelerating at a constant exponential rate?

Yes, the units above should have been 74.3 +/- 2.1 kilometers per second per megaparsec, which is the rate of acceleration of expansion.

Oops, mea culpa. You are correct.

OK here is one for you math whiz types.

Assuming the most distant object visible in the Hubble ultra deep field image is 13 billion light years old (I don't know that number to be correct so if you have a more accurate one please feel free to substitute); How far from Earth was it when the light captured by Hubble was emitted? How far from Earth was it when the light captured by Hubble was detected?

It was 13 bilion light years away?

It took the light 13 billion years to get here. But unless I'm missing something (wouldn't be unusual) due to expansion it was closer than 13 billion light years when the light was emitted and is further than 13 billion light years now.

I think....

Nope, you are looking at the object were it was 13 bilion years ago, the light it is emmiting now will arive in more than 13 bilion years, since it is farther away than it was. And it will take above 13 bilion years for us to see its progress untill this exact moment.

Since the speed of light is a constant, a light year is a measure of both time and distance.

If it is 13 billion light years from here now it will take light emitted today more than 13 billion years to get here because the distance between the light and Earth will increase over time due to expansion.

My understanding.

Could be wrong....

That is why the light red-shifts. Its a good question anyway. I guess they do take that into acount making the calculations.

Anyway I'm getting out of my league, mabe someone more Physics savvy can shed some light into the matter <--- see what I did there?