<p>Well obviously the CMBR arrives (towards us, not receding) at us at the speed of light as it is a form of electromagnetic radiation and local velocities are not affected by expansion.</p>

<p>What I guess you may mean though is the surface of last scattering, which is the surface from which the CMBR that we receive at a given instant was emitted in the early Universe. This surface of course is no longer emitting CMBR in the present cosmological time and it is not a fixed (comoving) surface either as which surface we receive the CMBR from changes with time, however we can give a recession velocity to the comoving set of points which make up the surface of last scattering at any given instant.</p>

<p>In the standard model of cosmology, the Lambda-CDM model, the instantaneous surface of last scattering is receding from us at approximately 3.2c (i.e. a recession velocity 3.2 times the speed of light).</p>

CC BY-SA 3.0
2015-02-04T13:15:10.237Z
Yes, this is what I meant.  Thank you for the clarification, and the answer!
Jonathan
CC BY-SA 3.0
2015-02-04T02:49:19.590Z
2015-02-04T03:16:29.383Z
2015-02-04T03:16:29.383Z
John Davis
<p>Does the cosmic microwave background recede at the speed of light?  Is it possible it recedes even faster because of the stretching of space?</p>

<light><speed><cosmic-microwave-background>
Does the cosmic microwave background recede at the speed of light?
Jonathan
# Does the cosmic microwave background recede at the speed of light?

(Asked by: username_0 on 2015-02-04)

Does the cosmic microwave background recede at the speed of light? Is it possible it recedes even faster because of the stretching of space?

**Tags:** light, speed, cosmic-microwave-background

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## 1 answers

### Answer by username_1 on 2015-02-04. Score: 4 | Accepted answer

Well obviously the CMBR arrives (towards us, not receding) at us at the speed of light as it is a form of electromagnetic radiation and local velocities are not affected by expansion.

What I guess you may mean though is the surface of last scattering, which is the surface from which the CMBR that we receive at a given instant was emitted in the early Universe. This surface of course is no longer emitting CMBR in the present cosmological time and it is not a fixed (comoving) surface either as which surface we receive the CMBR from changes with time, however we can give a recession velocity to the comoving set of points which make up the surface of last scattering at any given instant.

In the standard model of cosmology, the Lambda-CDM model, the instantaneous surface of last scattering is receding from us at approximately 3.2c (i.e. a recession velocity 3.2 times the speed of light).

> **Comments:**
> **username_0**: Yes, this is what I meant.  Thank you for the clarification, and the answer!  

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