Expert: Philip Stahl - 11/9/2010

Question
Long have we been told that the universe is actually moving away from us,,...and thats it. We are told nothing more.  It leaves the amateur mind wandering to areas of...well " In what direction" Is the universe moving away from us in ALL directions. That seems immpossible as then the earth would have to be the exact CENTRE of the universe wouldnt it. The area where the big bang first banged so to speak.  So then we must be moving away WITH the universe, in the same direction. We are  part of the remnants of the big bang going along its merry way. So we must be moving AWAY from the big bang area. >> Seems logical to me. So then other bits of the universe must be closing in on us from behind if the bits ahead of us are moving away. Right. Surely the earth cannot be the centre of the universe where its moving away from us in ALL dirctions.  Right.. Why cant science be more specific when making statements to the amateur public like me. regards. Paul

Answer
Hello,

First, of all let me attend to your last query first: science (in this case cosmology-astrophysics) can't be more "specific" because the topic itself is inherently complex and a detailed understanding requires not only familiarity with advanced physics (e.g. General Relativity- which most lay folk lack) but advanced math (topology, non-Euclidean geometry, which most lay folk also lack).

Indeed, in the course of tensor analysis (Google!)of Einstein’s field equations (from GR), the Big Bang emerged naturally as a solution with matter present. The key equations are usually written: G_uv = 0 (for empty space) and G_uv  = K_uv for matter- see e.g. Sir Arthur Eddington, 'Space, Time and Gravitation', Cambridge University Press, 1920, Chapter XII. While somewhat dated, the principles behind GR are enunciated better than most current books, provided one has some background in intermediate algebra, geometry.

Thus, the problem is that if we were as specific as many "amateurs" demanded, no one would understand us! So, we have to resort to crude cartoon analogies and often absurd translations which don't do the theory justice.

The problem, as you have guessed, is that when we adopt these over-simplified approaches, many misconceptions arise! Well, guess we just can't win!

Anyway, I think the majority of your other questions are dealt with in the link below.

http://en.allexperts.com/q/Astronomy-1360/2009/8/Big-Bang-17.htm

Pay special attention to the text  (by Karen C. Fox) referenced on the Big Bang itself. It's probably the best to gain an understanding at the basic level.

If you still have questions after going through this material, please feel free to ask!