Expert: Jayendra Upadhye - 2/22/2005

Question
Hi, something I just don't get. Bet you probably get this question
a lot.

my problem with m radiation has to do with the timeline of it all.
Bang!  The universe explodes into existence.  Energy and
subatomic
particles race out in every direction.   But only at the speed of
light, yes?  Since nothing may move faster.  Several hundred
thousand
years later (I don't know how long exactly) a huge amount of
microwave
radiation is created and released, the echo of which we can hear
today
and which we are told is roughly 14 billlion years old.  We live on
a
planet which moves far slower than the speed of light (the speed
at
which this microwave radiation travels) so why are we still
receiving
it?  Shoiuldn't the radiation have speed billions of light years
past
the gases which created our solar system into the unchartable
abyss of
the unobservable?  The universe only represents a 14 billion
light
year expanse.  From what point of origin is radiation that is over
14
billion years old originating from when we are not on the cusp of
all
that is?  Moreover, how did we get in front of it when nothing
travels
faster than it?

An adjunct question on looking into the past by way of light.  I
was
at The Hayden Planetarium in NYC today.  There I saw a
photograph of a
galaxy that I was told was 9.5 biillion years old, it is 9.5 billion
light years away from the Milky way.  This means the light left it
and
began travelling to us when the Universe was only 4.2 billion
years
old.  Since the universe can not expand faster than the speed of
light, the greatest distance between our galaxies at the time
would
have been 8.4 billion light years (4.2 plus 4.2 supposing that our
galaxy moved in exactly opposite directions) but even this
seems too
far since radiation, not galaxies travel at the speed of light.  It
seems to me the farthest we miight have been apart would be 4
-6
billion llight years.  But assuming it was 8.4 at the time, the light
begins travelling to Earth..  General relativity teaches us thhat no
matter how fast you move, light will ALWAYS move away and
toward you
at the same speed.  Thus It should have reached us in 8.4 billion
years, or 1.1 billion years ago.  Why did we get this photograph
in
just the last 10 years?  Please help, because I am beginning to
doubt
astronomy makes any sense.

Terry

Answer
Hi,
Terry you have got all worked up!
Relax!
Reminds me of my young days when during cavation i would snooze in the afternoons and "get all worked up" on these type of musings! :)

But IT IS A good thing to do.
First Doubt, then believe.
Faith that emerges after being shaken to its foundations is more enduring! Right? All Science will endure CHEIFLY becasue it has endured the most dispassionate and critical questioning.

Now to your questions no 1
   The big bang was "dark" for some period after the event, cheifly because the radiation temperature was too high for it to be in the visible range. Then came the flash and to call it blinding would be an understatement.
Sometime before that epoch came the instant when temperature was low enough for matter to exist by itself(decoupling of matter and energy).
    One has to understand that the BANG did not start in some "locality" of the universe, from where things 'radiated away"! No such thing happened. What happened was that "all of space" (the universe itself) "happened" at the same time, and began to expand.
The radiation was (and is ofcourse), diffuse, meaning coming from all directions and going in all directions!
Over time, what was radiation in x-ray range, (cooled with the expanding universe, and following the law of black body radiation frequency as a function of temperature, increased in wavelength), became the present day micro-wave radiation (below visible range) corresponding to the coolest temperature anywhere in the universe of about 3 deg kelvin.
    So! there was nowhere that the radiation was NOT there! We will see it coming from all directions, always. (Except, that there is a small lumpiness in its distribution with respect to direction. we know this thanks to COBE SATTELITE experiment).

    Your question 2.
The 9.5 billion years old galaxy! Terry, you have i think made an error in undertsnding what was said or written there. The LIGHT and NOT THE GALAXY was 9.5 billion years old by the TIME IT REACHED US FROM THAT GALAXY. And not the galaxy was 9.5 billion years old!
   Most spiral galaxies are much older than that, as galaxy building process got underway almost immeiately after the energy matter decoupling epoch passed! What with vast clouds of elementary hydrogen swarming the young universe!
   let us work it out in steps.

1 - The ray of light is emitted at time t = 0. Physical separation 9.5 billion light years. The hubble recession rate corresponding to this separation, will impart a red shift to it.
2 - 9.5 billion years later, the object has physically moved much more afield. What we "see" is how it was when 9.5 billion years ago it was 9.5 billion ligh years away from us!
3 - In the intervening 9.5 billion years, the universe has expanded much, and carried the point further away from us. Each new second you watch it, you are seeing how it was 9.5 billion + seconds ago, at some distance more than what it was 9.5 billion years ago!

In a sense, this is much like trying to look thru blinkers and find an aircraft by using the ears to locate the sound when a supersonic aircraft flies past. we will never see the real aircraft as the boom comes later. Similarly, what we "see" as distant objects are NOT the objects themselves but the images of them "as they were" so many years ago! The actual objects have in the mean time moved further on!
I am talking of blinkers as in this case, reality places blinkers on us preventing us from seeing the actual objects, but allowing us to see "images only" instead!
Hope that clarifies things.
If not, do ask followup questions..but not too many!
(just email me for long discussions, you are most welcome, at jupahye_99@yahoo.com).

Also please do rate the answer as it helps me track my responses.
Jayen