Expert: Tom Whiting - 1/27/2009

Question
How can telescopes see back to almost the Big Bang?

Answer
Hi Areail,
Even looking at the night sky with naked eye, you are actually
"looking backward" in time. You see the moon from 1.3 seconds
ago...the sun 8.33 minutes ago, the brighter stars anywhere from
16 to nearly 1500 years ago.  Indeed, if I am standing say one
meter from you, you aren't seeing me "now"...you're seeing me something like one nanosecond later.  
Light {all light including the entire electromagnetic spectrum...
radio, Infrared (heat), visible light, Ultraviolet, X-Ray, and
Gamma rays) speed is finite (not infinite) and travels thru space
at about 186000 miles per second, so it takes time to travel,
say 25 trillion miles (distance to the nearest star, Alpha Centauri)
which 25 trillion miles is also the same distance as about 4.3 lightyears.
{One lightyear, a unit of distance, equals about 5.8 trillion miles}.

So a telescope is basically a "look back in time" machine...the
bigger your scope, the dimmer....read that farther....the object
we can see, so the farther back in time you are looking.
And since we are in the Big Bang influence and result, it doesn't
matter which direction you look...it's all 'backward' in time.
We cannot see forward in time.

OK, there is this light still existing from the Big Bang of 'only'
13.7 billion years ago; it was such a large region and super bright and super hot.  But due to the expansion of the Universe (I suppose you've read or heard about that one at some point)....all the light has been redshifted (the wavelengths of light shifts to a longer wavelength with velocity of the expansion, similar to the Doppler effect with sound).....down into the microwave portion of the radio spectrum. So with a radio telescope, we actually see (hear) "light"...redshifted into the microwave portion of the radio
spectrum....of the Big Bang....well, actually it's the remnant radiation which occurred about 380,000 years after the Big Bang...but it's still radiation from that initial cooling of that huge event.

You can actually see it too...just tune your TV to antenna, and choose a channel that does not have an active TV signal. See all that hissing and static and snow on your TV picture?  That's it.
But it wasn't recognized until 1965 by two Bell Lab scientists
(not even connected with astronomy)..Arno Pensias and Robert Wilson.
(Google it....discovery of the CBR -Cosmic background radiation)
using a primitive radio telescope in 1965. They later received the
Nobel prize for their accidental discovery.

So that's how we "see" the light of the original Big Bang...and that's a hard piece of evidence that you could take into a court
of law to verify and substantiate...the Big Bang.
Hope this helps,
Clear Skies,
Tom Whiting
Erie PA