I think the best way to tackle this section is to stick to the basics, try to apply what the students have learnt in the rest of the course to the problems of the Olber's paradox and the expanding universe. The problem I find is that students will inevitably ask questions that I can't answer or have recently read some article describing some new theory that I have no clue about.


  • The whole idea of what was there before the big bang is an interesting concept. Itw ould have been impossible to observe the big bang since there was no space or time to observe it from. So what was there? is this question even possible to contemplate.
  • Our universe seems to be made up of a limited number of particles, were these the only particles that could have been created by a big bang or could the universe have been very different?
  • When CMB was first detected it was thought to be uniform but if the universe expanded uniformly then how did galaxies form? The COBE satellite detected variations but was this just because they were looking for them.
  • The big bang does not agree with some religious beliefs but how do they explain the CMB and redshift of galaxies?



 Cosmology answers

 Hubble's law

 Hubbles's law answers

Text Book

Page 358 - 360


problems 22-25

Screenshots of Chris' board



This website has pretty much the whole story

Here is an interesting article on recent refinements of measuring the Hubble constant. After doing this option students should be able to understand what they are on about.

This link is another interesting article about how the Hubble space telescope can look back in time.

Expanding Universe

This applet from Michael Richmond uses an expanding raisin loaf to show how the recessional velocity depends on distance.

 Interactive Physics little bang

Well it can hardly be called a big bang. The spheres in this IP animation move apart because they are charged. Its shows how no matter which particle you take to be the reference particle all the others move away from it. The motion isn't the same as the motion of galaxies since these particles are charges so repel rather than attracting (something to discuss).

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