using redshift of light from far galaxy

If we use the redshift of light from a far galaxy to calculate its
radial velocity away from us then use the Hubble Law to find a
distance, what is this distance really? Is it A: distance from
position of galaxy when it emitted its light to position of us AT THAT
TIME or B: distance from position of galaxy when it emitted its light
to position of us RIGHT NOW? Thank you.

On 4/17/10 11:22 PM, Lax wrote:
If we use the redshift of light from a far galaxy to calculate its
radial velocity away from us then use the Hubble Law to find a
distance, what is this distance really? Is it A: distance from
position of galaxy when it emitted its light to position of us AT THAT
TIME or B: distance from position of galaxy when it emitted its light
to position of us RIGHT NOW? Thank you.

Distance is more typically determined by brightness and the inverse
square law. Cosmic expansion (apparent radial velocity) by red shift.

BTW, you may be interested in:
http://www.astro.ucla.edu/~wright/CosmoCalc.html

On Apr 18, 8:08*am, Sam Wormley wrote:
On 4/17/10 11:22 PM, Lax wrote:

If we use the redshift of light from a far galaxy to calculate its
radial velocity away from us then use the Hubble Law to find a
distance, what is this distance really? Is it A: distance from
position of galaxy when it emitted its light to position of us AT THAT
TIME *or B: distance from position of galaxy when it emitted its light
to position of us RIGHT NOW? *Thank you.

* *Distance is more typically determined by brightness and the inverse
* *square law. Cosmic expansion (apparent radial velocity) by red shift.

* *BTW, you may be interested in:
* * *http://www.astro.ucla.edu/~wright/CosmoCalc.html

If we take the apparent radial velocity and divide it by the hubble
constant, what distance do we get?

On Apr 19, 9:35*pm, Lax wrote:
On Apr 18, 8:08*am, Sam Wormley wrote:

On 4/17/10 11:22 PM, Lax wrote:

If we use the redshift of light from a far galaxy to calculate its
radial velocity away from us then use the Hubble Law to find a
distance, what is this distance really? Is it A: distance from
position of galaxy when it emitted its light to position of us AT THAT
TIME *or B: distance from position of galaxy when it emitted its light
to position of us RIGHT NOW? *Thank you.

* *Distance is more typically determined by brightness and the inverse
* *square law. Cosmic expansion (apparent radial velocity) by red shift.

* *BTW, you may be interested in:
* * *http://www.astro.ucla.edu/~wright/CosmoCalc.html

If we take the apparent radial velocity and divide it by the hubble
constant, what distance do we get?

Quasars have two redshift sources. The first is gravitational the
other is distance. Quasars are distributed equally throughout the
universe.

Mitch Raemsch

On 4/19/10 11:35 PM, Lax wrote:
On Apr 18, 8:08 am, Sam wrote:
On 4/17/10 11:22 PM, Lax wrote:

If we use the redshift of light from a far galaxy to calculate its
radial velocity away from us then use the Hubble Law to find a
distance, what is this distance really? Is it A: distance from
position of galaxy when it emitted its light to position of us AT THAT
TIME or B: distance from position of galaxy when it emitted its light
to position of us RIGHT NOW? Thank you.

Distance is more typically determined by brightness and the inverse
square law. Cosmic expansion (apparent radial velocity) by red shift.

BTW, you may be interested in:
http://www.astro.ucla.edu/~wright/CosmoCalc.html

If we take the apparent radial velocity and divide it by the hubble
constant, what distance do we get?

One need to know absolute brightness. Type Ia supernovae make
reasonable "standard candles".