Naked Science Forum

Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: thedoc on 03/12/2016 19:53:01

Title: How fast did early light travel?
Post by: thedoc on 03/12/2016 19:53:01

Stephen Mac cabe  asked the Naked Scientists:
   After hearing that we can look into space to the extent that we can see the light that was emitted just after the big bang (effectively looking back in time) which I understand as Light from the moon is one minute old and from the sun older and the stars older again all this I understand. Is it then the case then that the material thrown out by the big bang must have been travelling faster than the speed of light for us then now to look back at it, otherwise that light would have passed us by and we would no longer be able to see it?

Stephen Mac Cabe

What do you think?

Title: Re: How fast did early light travel?
Post by: Bill S on 06/12/2016 15:32:27

Hi Stephen. My, very amateur,  understanding is that the Universe inflated faster than light very briefly,  and has been expanding at sub-light speed ever since.  I wrestled for some time with the idea that light from the BB would have passed us by now,  but you need to think that the BB happened everywhere,  so light from it is travelling from everywhere to everywhere all the time. 

Title: Re: How fast did early light travel?
Post by: Bill S on 06/12/2016 15:40:02

BTW, Joao Magueijo has been working for years on the idea that light may have travelled faster in the remote past,  and,  I understand he and Niayesh Afshordi have come up with some interesting ideas recently.  Probably worth looking for.

Title: Re: How fast did early light travel?
Post by: Brad Watson on 06/12/2016 16:53:42

Varying Speed-of-Light Theory (VSL) has been around for about 20 years and is the basis for 'inflation' in the first 10^-36 to 10^-34 after the Big Bang/Bit Bang.

Title: Re: How fast did early light travel?
Post by: evan_au on 06/12/2016 19:17:45

Quote from: Stephen Maccabe

that light would have passed us by and we would no longer be able to see it?

Adding to Bill's first comment...

We are effectively still within the fireball of the Big Bang.
But the light reaching us now is extremely red-shifted.
According to current models, it was last scattered at a temperature of about 3000K, around 380,000 years after the Big Bang.
As we receive it, it occurs in the microwave part of the spectrum, and has an effective temperature of 2.7K (-270C).

See: https://en.wikipedia.org/wiki/Cosmic_microwave_background