Does the expansion of universe effect light?

[swansont]

!

Moderator Note

Since this is essentially the same question, threads have been merged

 

 

You add the vectors. It will accelerate in the direction of the resultant.

The spacetime expansion comment is a red herring (or possibly blue herring if you are moving toward it quickly enough) since expansion will not overcome the intermolecular bonds

[John Conner]

32 minutes ago, swansont said:

!

Moderator Note

Since this is essentially the same question, threads have been merged

 

 

You add the vectors. It will accelerate in the direction of the resultant.

The spacetime expansion comment is a red herring (or possibly blue herring if you are moving toward it quickly enough) since expansion will not overcome the intermolecular bonds

ok. i think i got everything wrong. red herring? you mean a misleading point?

Edited July 19, 2019 by John Conner

[swansont]

1 hour ago, John Conner said:

ok. i think i got everything wrong. red herring? you mean a misleading point?

More like irrelevant. Didn't mean to imply it was intentional.

[John Conner]

9 minutes ago, swansont said:

More like irrelevant. Didn't mean to imply it was intentional. 

ok. another question. we send a light ray to a body far far away. the distance between us (earth) and the body is 1 Mpc. now if the body moves towards us and the light ray with 70km/s would there still be a redshift? or the wavelength won't change?

note: 1- consider the rate of expansion of the metric as hubble's constant. it is believed to be accelerating but in this case consider it constant.

2- the distance is expanding but the body is moving towards us with the exact same rate. so it would appear that the light won't have a redshift but i'm pretty sure it will so why?

[swansont]

If they have an equal magnitude, the shift from the velocity and the shift from the expansion should cancel if the object is moving toward us and far enough away that the expansion is occurring (i.e. gravity is not overriding it)

[John Conner]

11 minutes ago, swansont said:

If they have an equal magnitude, the shift from the velocity and the shift from the expansion should cancel if the object is moving toward us and far enough away that the expansion is occurring (i.e. gravity is not overriding it)

it is reasonable but that doesn't sound right. are you sure there won't be a redshift? do equations support this?

[John Conner]

4 hours ago, swansont said:

If they have an equal magnitude, the shift from the velocity and the shift from the expansion should cancel if the object is moving toward us and far enough away that the expansion is occurring (i.e. gravity is not overriding it)

 

it doesn't sound right because ratio of distance traveled by the body to distance traveled by light is 6/28000. and the redshift definitely won't happen at the destination. it happens through time. so it already happened when they meet (little less than intended but look at the ratio, the damage is done) but it should be like what you said. because if we consider hubble constant (or if we need to, the accelerating rate) the spacetime is expanding with that rate and considering the direction of light toward body and direction of body toward earth and light ray, then expanded distance and time would be accounted for. can some one help me with this?

Edited July 19, 2019 by John Conner

[Mordred]

All forms of redshift are additive. It is plausible to counter cosmological redshift by gravitational or Dobbler shifts. They may have different causes however the effects upon frequency is the same.  It's simply a matter of finding the right combination.

Edited July 19, 2019 by Mordred