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Posts Tagged ‘big bang’

Vanishing point.

Vanishing point.

The classic example of describing the expanding universe is the inflating balloon.

Imagine that you are on the surface of a half inflated balloon. As the balloon expands you see everything around you moving away even though you are not at the center. If you move around the balloon everything will still be moving away, there is no special center. The two dimensional surface of the balloon is expanding into a three dimensional space for ease of understanding. Likewise one could imagine our three dimensional space expanding into an embedded four dimensional space.

This analogy never really worked for me. I knew what the expanding universe meant but I don’t see how the balloon is the best way to explain it. I heard a better one recently in one of my classes.

Everyone in the room is standing (or sitting) on a particular floor tile. Imagine now that there is an explosion in the room that causes all the floor tiles to fly apart. If someone is at the center they would see everyone flying away from them. But someone sitting elsewhere in the room will see that same person flying away from them. Similarly everyone will see everyone else moving away from them while they are stationary. Except it is not the tiles that are moving apart but space itself.

Of course all of this would easier if we could easily visualize four dimensional space (like a hypercube or 3 sphere).

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Theory

This Phone is Tapped.

This Phone is Tapped.

I always found it hard to find a good example of how a scientific theory differs from the colloquial usage of the word. Professor Plaxco (my astrobiology professor) had a good way of demonstrating the difference.

We have a theory of Angola. Not many people of been to Angola (or if they have pick another small country) so no one can directly confirm the theory. However the theory makes certain predictions we can check. One is that there is a United Nations representative from Angola, we could look up their number and call the representative from Angola. Even though we have never been there we can confirm several phenomena associated with the theory of Angola.

The same is true with many scientific theories. We have Big Bang theory, it predicts several independent aspects of the universe and they are right. It predicts a microwave background radiation, variations in that background caused by phonons in the early universe, the primordial ratios of hydrogen, deuterium, helium and other elements and the expansion of the universe. Even though we cannot see the actually big bang (not yet there is some neat neutrino research being done that may let us see farther back beyond the microwave background) we can clearly see what it predicts should happen, just like the theory of Angola.

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