looking into the past???

OK, this is just a thought but... If the nearest star is 4 light years
away then we are seeing light which is 4 years old?? So what we are
looking at is the past??? Is this right? Or am I a plonker?? If this
is right.. then somewhere out there in the universe there is light
from millions of years ago showing how the world began??? Would this
work???

DTWI,

I don't know what a "plonker" is but...


You are correct. Light travels at a finite speed. Viewing more distant
stars and galaxies is implicitly viewing the more distant past. This
is an advantage in that it allows one to test hypotheses about how the
universe evolved from its origins. If all we could see was the current
state of the universe, it would me much harder to figure out how
things have evolved over cosmic timescales.

The universe is a little under 14 billion years old. The universe is
much bigger than 14 billion light-years in diameter. We cannot see it
all. Ever. (Unless we figure out how to base a technology on some
of the solutions to general relativity that do not rule out
superluminal travel. Then maybe we could travel beyond the so-called
light horizon of the portion of the universe centered on Earth. Our
current expectation is that we'd find things over there pretty much
the same as they are here, at least as far as star, galaxy, cluster
and super-cluster formation goes.)

The oldest and hence most distantly originating photons (light) we can
detect is the so-called Cosmic Microwave Background. Studying it
carefully has helped refine theories of the origin of the universe.

This is all elementary stuff (otherwise I could not tell you about it,
'cause I'm an amateur). There are many texts and on-line resources.

Libraries, science teachers and Google are your friends. If you're not
already familiar with them, become so!

Randall Schulz


download the whole internet wrote:

OK, this is just a thought but... If the nearest star is 4 light
years away then we are seeing light which is 4 years old?? So what
we are looking at is the past??? Is this right? Or am I a plonker??
If this is right.. then somewhere out there in the universe there
is light from millions of years ago showing how the world began???
Would this work???

(download the whole internet) writes:

OK, this is just a thought but... If the nearest star is 4 light years
away then we are seeing light which is 4 years old?? So what we are
looking at is the past??? Is this right?

Yes.


If this is right.. then somewhere out there in the universe there is
light from millions of years ago showing how the world began???

That would be BILLIONS, not mere millions, and it is true of =EVERY= point
in the Universe except the points that are inside dust clouds and other
opaque objects. No matter =WHAT= direction you look, there is light left
over from the Big Bang --- the problem is that it has been redshifted to
zero frequency.

Likewise, no matter which direction you look, there is light left over
from just a little bit _after_ the Big Bang. Since the Universe was very
uniform back then, and thick enough that it was effectively opaque, that
leftover light looks about the same in every direction: We call it the
"3 degrees Kelvin Cosmic Background Radiation," or "3 K CBR" for short.

For more on the 3 K CBR and the Early Universe, se Ned Wright's Cosmology
FAQ and Cosmology Tutorial: http://www.astro.ucla.edu/~wright/cosmolog.htm.


-- Gordon D. Pusch

perl -e '$_ = \n"; s/NO\.//; s/SPAM\.//; print;'

"download the whole internet" wrote in message
om...
OK, this is just a thought but... If the nearest star is 4 light years
away then we are seeing light which is 4 years old?? So what we are
looking at is the past???

Correct.

Is this right?

Correct.

Or am I a plonker??

Not yet, at least.

If this
is right.. then somewhere out there in the universe there is light
from millions of years ago showing how the world began???

Not millions - but billions.

Would this
work???

In order to view the beginning of the world, you would have
to travel instantly to a distance of about 5.6 billion light years
and look out your rearview mirror at the earth behind you.

In article , Joe
Strout wrote:

If this
is right.. then somewhere out there in the universe there is light
from millions of years ago showing how the world began???

Well, the world (Earth) formed billions of years ago, not millions. But
otherwise, yes.

Would this work???

Would what work?

If he's asking what I think he's asking...

"If there is light in the universe, showing the formation of the world,
can we use it to see the formation of the world - ie, see 'into the
past'". The short answer to this is "yes, but it wouldn't do you much
good" g - in order to use that light, you have to be vastly far away.

If we had an exceptionally powerful telescope, and it was sited several
billion light-years away, we would be able to see the galaxy as it was
at the era of the Solar System's forming. Getting it there is left as an
exercise to the reader :-)

However... doing some back-of-the-envelope calculations, a hypothetical
one-kilometer diameter telescope situated, say, five billion light-years
away, is (in a perfect situation) going to intersect about one photon
from the Sun every thirty seconds or so. You'd be very hard-pressed to
get an image from that, so I wouldn't bet on being able to see the
formation of the Earth very clearly...

--
-Andrew Gray

then somewhere out there in the universe there is light
from millions of years ago showing how the world began??? Would this
work???

Yes, it works:

http://www.eso.org/outreach/press-re.../pr-24-03.html


Ralph

In article ,
Andrew Gray wrote:

"If there is light in the universe, showing the formation of the world,
can we use it to see the formation of the world - ie, see 'into the
past'". The short answer to this is "yes, but it wouldn't do you much
good" g - in order to use that light, you have to be vastly far away.

If we had an exceptionally powerful telescope, and it was sited several
billion light-years away, we would be able to see the galaxy as it was
at the era of the Solar System's forming. Getting it there is left as an
exercise to the reader :-)

Well, here's a scenario which is rarely mentioned in discussions of this
topic. Suppose friendly and advanced ETs who live roughly 2 billion LY
away have an odd habit of constructing truly enormous, galaxy-sized
mirrors, and one of these mirrors happens to be pointed in the right
direction. By pointing our own giant telescopes at their giant mirror,
we could indeed see light from the formation of our own solar system,
without having to go anywhere.

A minor variation of this would be: the friendly/advanced ETs take
images of our solar system as it's forming, convert this into some sort
of information-bearing signal, and beam it (via a laser?) back in our
direction, just in the off chance that some curious natives evolve here
billions of years later. Perhaps all advanced civilizations do this at
some point, as a way of repaying the cosmic karma of having it done for
them.

OK, so it's ridiculously far-fetched. But from a technical point of
view, it's possible.

Cheers,
- Joe

,------------------------------------------------------------------.
| Joseph J. Strout Check out the Mac Web Directory: |
| http://www.macwebdir.com |
`------------------------------------------------------------------'

download the whole internet wrote:
OK, this is just a thought but... If the nearest star is 4 light years
away then we are seeing light which is 4 years old?? So what we are
looking at is the past??? Is this right? Or am I a plonker?? If this
is right.. then somewhere out there in the universe there is light
from millions of years ago showing how the world began??? Would this
work???

Yep, all true statements. Well, ok, not quite light from when the
universe began, but distant galaxies are shown as they were bilions
of years in the past and not present.

--
Sander

+++ Out of cheese error +++

"Richard Schumacher" wrote in message
...

download the whole internet wrote:

OK, this is just a thought but... If the nearest star is 4 light years
away then we are seeing light which is 4 years old?? So what we are
looking at is the past??? Is this right? Or am I a plonker?? If this
is right.. then somewhere out there in the universe there is light
from millions of years ago showing how the world began??? Would this
work???

Yes, except that that light is going away from us, so we'll never see it.
And it's too dim, and pretty well torn up by dust, garvitty and whatnot so
that it could never be turned into an image.

So, you believe light going away from us is never coming back
to us? That also spells end of story to the 1G constant acceleration
'round the Universe in 50 years' trip which some scientists used to
envisage.

If the great cosmic topology issue is thus all settled, then I shall no
longer have to cross my fingers in the faint hope that a scientific
breakthrough will point to matching patterns of ancient emissions
from a multitude of directions :-)

-Jens