On Mon, 18 Oct 2004 23:54:42 +0200, Albert
wrote:

Can someone help me understand this ?

The powerful telescopes are supposed to see in the past.
OK, I get thet. If you look at a distant star, you catch the light it
emitted one year ago if it is at one light-year distance.

Absolutely. Actually, the speed of light is constant but finite. If
we were in the same room, you would see me as I was just a few
billionth of a second ago!! No matter how close, there is always a
delay.

It is just like the ( delicate ) sound of thunder during a
thunderstorm: there is a delay between the time we see the lightning
and the time we HEAR it depending on how far away it is (sound travel
at 340 meters per second). Remember that there is already a delay
between the time the lighting does happen and the time we see it!

So, because Alpha Centauri is 4.3 light-years away, we see it as it
was 4.3 years ago. The most distant quasars are about 13 billions
light-years away so we know that there was something in the universe
13 billions years ago.

But you cannot see the light it emitted 2 years ago, for that light has
already travelled past you.
Correct ?

Absolutely again!

Now, some say they can watch light coming from stars created just after
the big bang.

From quasars actually, here is an example:
http://antwrp.gsfc.nasa.gov/apod/ap000419.html


This I cannot understand, because that light should have travelled past
us already, from the original point.


There was an original point but as the universe is expanding, that
point is now a sphere all around us. There is a misconception that
the Big Bang exploded into space. It did not. There was no space at
that time: the Universe create it's own space during it's expansion...
If you think that one day, with a super-super telescope we will be
able to see some kind of Big Bang like a super-super novae then think
again: it can not happen because at that time we were INSIDE the
"cosmic egg". All we can expect to see is a kind of shell of light
around us. And yes, there is one:
http://map.gsfc.nasa.gov/m_uni/uni_101Flucts.html

Please explain ...

It took thousands of years for humankind to understand that ( and yet
we are not sure ). Don't be sorry if you can't understand in just a
few minutes....


Have a good night!

Benoît...