Cosmology Monroe February 30, 2008

Cosmology pages 847 – 851 Astronomy and Cosmology are terms that can almost be used interchangeably. They almost always mean the same thing. There are three big questions we are going to look at. 1.What is the Universe made of? 2.What does the Universe look like? 3.How did the Universe start? 4.How will the Universe end?

What is the Universe made of? Unfortunately, it is sad that the only we are quite sure of, is that we really don ’ t know. This is the best guess of some of the best in the field. It is sure to change, but how much I am sure I do not know.

1.Dark Energy 75% -- It is an irony of nature that the most abundant form of energy in the universe is also the most mysterious. Since the breakthrough discovery that the cosmic expansion is accelerating, a consistent picture has emerged indicating that two-thirds of the cosmos is made of “dark energy” - some sort of gravitationally repulsive material. **physicsworld.com**

2.Dark Matter 20% -- This is really creepy matter. It does not interact with anything but gravity (it attracts), but other than that, it is unseen and undetectable.

3.Normal Matter 5% -- This is what we are, and can easily detect.

What does the Universe look like? 1.Steady State – this theory states that the universe is unmoving, and goes on forever. The problem is, however, that if this were true, then the night sky would be bright, because in any direction, if you went far enough, you would see a star.

2.Expanding State – This theory states that the universe is expanding in all directions. To be correct, two things must be true. a.Things farther away must be traveling faster. They are. b.Things must have, at some point in the past, been at the same place, at the same time. They were.

3.No one really knows what the actual shape of the universe is. I personally believe it is shaped like a basketball, and it seems that the data backs up this conclusion.

From top to bottom: a spherical universe, a hyperbolic universe, and a flat universe. 1.The shapes would look like this.

How did the Universe start? 1. A deity created it. This may be so, but as a theory it cannot be used, because is includes a non-reproducible, and untestable conclusion. It is not scientific.

2. The Big Bang. This theory is now the most widely accepted idea of how it all began.

a. About 15 billion years ago, all things seen and unseen developed and grew out of a single mathematical point. This point, smaller than an atom, had infinite temperature, infinite density, and zero volume.

b. This was the time when all physical forces, as well as time, started to develop. Gravity, Electricity, Magnetism, Strong and Weak nuclear forces, were all intertwined. They would come apart later. This was also when dimensions gained meaning. I. Background radiation shows predicted cooling of the universe. II. Stars fall away are moving faster, and we can tell this because the Doppler effect stretches the light out.

How will the Universe end? 1. The big crunch. If the total amount of gravity in the universe is high enough, then it will quit expanding, start coming together, and we will have a big crunch.

2. The big flat. If the forces of expansion equal the forces of compaction, the universe will be really big, and just kind of stay that way. This is unstable equilibrium, and I don’t see it happening.

3. The big open. The forces of expansion just keep doing their thing, and the universe just keeps getting bigger, colder and darker.