I just wanted to say thanks to Greg and Steve both. Excellent Q&A!

John

Quoth Greg Neill :
Steve Trellert wrote:
Greetings all,

Some questions I have but before that I want to say that I have always had
alot of intellectual curiosity and love history, political science,
religion, philosophy etc. I must say that i have a tremendous respect for
those interested in science as I find it particularly hard to grasp. Kudos
to all of you. Now for the questions which I hope some of you can answer:

1) Since looking into deep space from a telescope is in fact looking back
deep into the past, I presume that at the edges of our visibility these
areas appear more primitive in terms of the formation of galaxies etc? Now
if this is the case, has any astonomer actually witnessed the birth of a
sun
(star)?

Young stars can be seen much closer to hand than at the edge of
the visible universe; our galaxy is still forming new stars from
gas and dust. Google: stellar nurseries . In particular, have a
look at some pictures at:

http://apod.nasa.gov/apod/stellar_nurseries.html

Note that the gas and dust in the star forming regions can make it
difficult to see details of the individual stars being formed, but
infra red and radio wavelengths can do much better.

2) For astronauts going into space:

a) The earth's atmosphere is mostly Nitrogen and Oxygen, are astronauts
breathing apparatus 100% oxygen? Is there any harm in breathing in this
high
a concentration? Or is it beneficial? Would we all be healthier if we
could
breathe in 100% oxygen at all times?

Breathing 100% oxygen for any long period of time is not good; oxygen
in that concentration tends to be toxic. The cabin is pressurized
with a fairly normal atmospheric mix. For special cases, such as
spacewalks where the astronaut is going to be working in conditions
of much reduced pressure, they may breath a much higher concentration
oxygen mixture in order to flush nitrogen from their systems prior to
"stepping out". This prevents nitrogen bubbles from forming in their
blood (nitrogen narcosis, the bends) when they go from cabin pressure
to lower pressure.

b) In a spacecraft there is always a lack of gravity (in general). Is it
possible to make the interior of a spacecraft equivalent to the gravity
level on earth?

Sure, build a really big spaceship and spin it. Centrifugal effect
can mimic gravity. But the ship will have to be very large indeed
to keep the spin rate within reasonable values.

3. I believe proximy centauri is the closest star to us..4.5 light years
from what i remember. How long would it take our fastest known spacecraft
to
reach it? Anyone knows if there are any planets orbiting that star?

Our fastest spacecraft? The ultimate velocity depends upon a combination
of available fuel and time. The Voyagers used gravity assist manoeuvres
around planets to get up the speed required to leave the solar system.
Nothing we currently have available will do much better for quick escapes.

However, continuous drive ion thrusters, while taking a long time
to get up to speed, have high specific impulse and make the best
use of their available reaction mass. It may take more time for
them to get up to speed, but their ultimate speed is higher.

Voyager 1 is cruising along at about 17 km/second. Let's say for the
sake of argument that our ion drive craft can do five times better,
but will take 50 years to build up to cruising speed (it has a very
small acceleration).

A Voyager type craft could travel 4.5 light years in about 80,000 years.
The ion drive craft would do 5 times better, about 16,000 years.

As far as we know (so far), Proxima Centauri doesn't have any planets.

4. I heard the Andromeda galaxy is heading for a collision with the Milky
Way. I thought the big bang implied that everything is expanding away from
everything else. Which is right?

Both. Gravitationally bound systems, like the our solar system, our
galaxy, and our local cluster of galaxies and globular clusters, are
not subject to the general expansion (because they are gravitationally
bound together).

5. On the periodic table the lightest elements are Hydrogen and Helium. We
they both immediately arise upon the big bang? How? I know some of the
other
elements (nitrogen, oxygen etc) derive from the intense nuclear reactions
within a star, how did they get away from a star..are they spewed forth
form
the solar wind? Or do they only arise once a supernova happens and a star
explodes?

Subatomic particles were created from the energy of the early universe.
These included protons and electrons, which subsequently got together
as hydrogen when things cooled down enough. Things were still hot
enough to drive some of the hydrogen to fuse into heavier bits, like
helium and lithium.

Some heavier elements come off of stars, driven by the solar wind,
but this is a minor contribution compared to the scattering of much
of the mass of an entire giant star when it goes supernova.

6. Some people claim there are multiple universes. Is this just conjecture
or is there any evidence for this?

It can only be conjecture, since by definition another universe would
have no connection to ours, and hence entirely unobservable.