Expert: Jayendra Upadhye - 8/18/2009

Question
Hello -

My question focuses on how we are in a position within the universe to see light from ancient objects billions of light years away; despite all mass emanating from a single source and moment.

Assuming as scientific truths: (1) that all matter emanated from a single mass which exploded (big-bang); (2) that light travels faster than all known matter (186K m/s); and (3) that light does not travel in a single plane from its source; how is that we are in a position on Earth to see or "receive" light from objects that took billions of light years to reach Earth.  In particular, how can we see light objects which existed at the beginning of the universe, which is often explained as having light that took billions of years to reach us.

Did we somehow race ahead of light from these objects to be in a position to receive that light at a later point?

Or, in peering deep into the universe via telescope, are we seeing a static light signature from on object that exists infinitely?

Or, is it something all-together different?

Thanks for any guidance.

Best,
Jeffrey



Given this, how is it possible for us to see from Earth the light of objects that are up to 13 billion light-years away  is the fastest known

Answer
Hi,
No No, Jeffry, hold your horses!

Its not as if the bang happened and events preceeded our existence and then suddenly we sped up and over took that light and lo and behold we SAW!

The universe went through an inflation in the first split second of a split second!
It expanded in leaps and bounds faster than the speed of light!
Thus the bang happened over a large "volume" (I am talking of a 4 dimensional equivalent, as 3 d space represented the skin of that volume. It is all analogy only, no one has visualised any 4 dim object yet).

Then matter and energy decoupled when the temperature had cooled enough to allow matter to survive independently of energy. That was when the flash we call the CMB occured. It was the snapshot of the universe just in ithe last stages of that decoupling.

Then came the dark ages, until the primordial hydrogen coalesced to form the first stars.
Whatever light we see as the oldest light is from these "firstborns".
But by the time they flashed on, the universe must have been 100s of kiloparsecs wide.
Since that time, their light has been reaching us, our light to them, but it was light that got progressively redder and redder (either way), till now some galaxies (abell cluster) is showing us starlight of galaxies it is gravitationally lensing into arcs, which is billions of years old. (red shifted 7 I think).

So you see, there is NO suddenness any where in this process.
10 billion years ago, we would be seeing galaxies, but with may be just a bit of a shift.
Galaxies that were close enough for their light to reach us in a few billion years.

Light has been travelling either way throughout this time, light from the entities that we see today as 13 billion years away, may be reaching us only now, thanks to the space differential of an expanding space and inflation.

If we continue watching, we will find stars evolving and going super nova, stars of low metallicity, being first gen stars.

There is one more angle that flashed in my mind just now.
Light that started its journey with a red shift x, would arrive with red shift y, where y > x, because, space would expand in the time it took to travel, and its red shift would be increased.
The lightwaves would be stretched as they travelled "embedded" in a mtrix of expanding space!
The added doppler shift would have nothing to do with the doppler shifting due to recession rate of the body when the light was emitted.

We need to see if light undergoes red shifting "inflight"! Thanks to prolonged time of travel and the expansion space undergoes in that period.

Regarding the issue "that light does not travel in a single plane from its source"..how should that matter? stars are diffuse sources (that is why we have limb darkening), and that is all the more reason for us to be able to see them. Plus their radiating surface is 100s to 1000 times larger than the cross sections of obscuring planets. Over large distances, all we see is the star, and "no planets". (except periodical dimming due to occultation, but this dimming is nominal).


regards
Jayen