Help! Looking ever further back in time - I just don't get it!

[reactolite]

I have always had an interest in astronomy.  As a young boy I could never understand how it was that people in general had no idea of the vastness of space.  And often I would baulk at some of the terms used in scifi show and films that treated audiences like they were completely ignorant.   But just lately I have been having trouble grasping with the concept that we can, with the aid of very big telescopes and of course Hubble, see back almost to the beginning of the Big Bang...I just don't get it!  If the Big Bang happened some 13.5 or 14 billion years ago, and nothing can travel faster than light, then how could we possibly outrun the 'blast' so fast that we can now look back and see it happening!!!!!  Please, in very simple terms only can someone explain this to me?

[oldpink]

its looking at the effect the big bang had on the universe
particularly the background radiation, you can see it yourself on a TV thats not tuned to a statiuon
its the snow you see on the screen, thats the remnants of the big bang
it cant actually see the bang happen we study the effects and trace it backwards to its start point
thats providing the current theory's are correct, like the search for the predicted gravitational wave it would produce (expansion theory)
that they thought they found now they are not sure about

[dick_dangerous]

People can please feel free to correct me as I try to answer this question - in science terms my expertise are in evolution and zoology, but I was originally going to be a physicist. I had a similar query at a public astronomy event and tried to answer, but referred the person asking the question to a nearby astrophysicist.

He wanted to know what was in the middle of the universe. He'd heard the analogy of the inflating balloon, but this had only confused him - he wanted to know what was inside the balloon. I attempted to clumsily explain that the expansion of the universe is the expansion of space itself, which is happening everywhere at once, so there is no "inside" of the balloon. He wasn't having any of it, but that was essentially the answer.

So you can consider yourself to be the centre of the universe (Ironically most people do). Why don't the stars around us fly apart as the universe expands? Well because we're all gravitationally bound together in a galaxy, something that was worked out in the 19th Century. The debate then raged as to whether the Milky Way represented the whole universe or just an island universe, with many others like it around. It wasn't until Henrietta Leavitt worked out the relationship between the luminosity and period of certain variable stars, Cepheid variables, that the question could be answered - Hubble used her work to prove that the Andromeda Galaxy was over 2 million light years away and therefore not a part of our own galaxy. This then lead to the profound implication that the light from Andromeda had taken 2 million years to get to us because the speed of light is a constant, therefore when we look down our telescopes we see it as it was over 2 million years ago, before even the rise of Homo sapiens (Evolution! I'm back on familiar ground!).

So why isn't Andromeda speeding away from us with the momentum from the Big Bang? Well two huge "Island Universes" produce quite a large gravitational force so we are bound together in a dance of death. One day Andromeda and the Milky Way will collide, merge, and form a giant elliptical galaxy. This is what you'll find if you point your telescope at M87 in Virgo, the result of billions of years of galactic evolution. The Virgo cluster is a great example of a galactic supercluster - a group of galaxies all bound together. In fact quite a lot of modern cosmology is taken up with looking at this large-scale structure of the universe and we can see patterns in the way the galaxies are arranged creating a glorious celestial architecture.

This explains whey we can still see our local galaxies, because our Local Group is in a spur of the larger Virgo supercluster and so we're all linked together by gravitation. But how come some distant quasar from 10 or 11 billion years ago is visible to the Hubble Space Telescope without travelling faster than light? Remember that whatever point in the universe you happen to be in, you appear to be in the centre of that expansion because everywhere is expanding at once. Now consider a galaxy flying away from you at speed - when the light reaches your eyes you see it not only as it was 10 billion years ago, but where it was 10 billion years ago. The fact that it's moving away can be determined by looking at the light - as the galaxy recedes at speed it stretches the wavelength of the light it produces so that the light becomes redder. We call this Redshift, and if the galaxy were moving towards us it would bunch up the wavelengths to make the light bluer - Blueshift - it's similar to the way ambulance sirens sound high-pitched when they're approaching and low-pitched when they moving away from you; the Doppler Effect.

By looking at the spectra of objects in the universe and measuring their redshift or blueshift we can work out their velocity - both the speed and the direction of travel. The technique has shown us that several members of the Virgo cluster are blueshifted, bringing to life the cosmic dance of a large cluster of big galaxies, and has even been used to demonstrate the rotation of galaxies, where one side is redshifted as it spins towards us while the other is blueshifted, spinning away.

The "Shock-wave" of the Big Bang left residual radiation behind too - the Cosmic Microwave Background Radiation which is all around us. As oldpink says above, it contributes to the static you pick up on your radio and television. It's what's left if a massive amount of energy is released all at once then left to cool down and has something to do with the moment that matter and radiation decoupled and the universe became transparent. It's at this point I'd suggest picking up a Brief History of Time or Bill Bryson's Short History of Nearly Everything because I need to go to bed...

As soon as the chap who'd asked me the question about the universe found out I was a Biologist he then started to grill me about dinosaurs and I breathed an audible sigh of relief... Now there's a question - if I wanted to see a Messier galaxy as it was at the time of the dinosaurs, 65MYA+, which one would I have to look at? My researches have shown me that M58 is the only one, but I don't always trust WIkipedia...

DD