| MadSci Network: Astronomy |
Yes, the Sun does move through space. We can tell this in a couple of ways.
We know that the Sun orbits around the center of our Galaxy. The best way to measure this is to look at how the Sun is moving relative to a large number of old stars in the Galaxy.
We measure our motion either towards or away from other stars using blueshifts and redshifts. If the Sun is approaching a star, then when we pass the light of that star through a prism and look at the spectrum, it will be blueshifted, that is, the spectrum will look bluer than it would if the star and the Sun weren't approaching each other. The exact reverse happens when the Sun and a star are moving away from each other. In that case, the star's spectrum will be redshifted, it will look redder than if the star and the Sun weren't moving apart.
The oldest stars in our Galaxy move at random around the center of the Galaxy. In fact, they look a lot like a swarm of bees around the Galaxy. When we look at the spectra of these old stars, then, we see mostly blueshifts in one direction, and mostly redshifts in the opposite direction. This is because the orbit of the Sun moves it towards most of the old stars ahead of it (except for the few which just happen to be moving in the same direction as us), and away from most of the old stars that are behind it. The average of the speeds that we see tells us how quickly the Sun is moving in its orbit. The number is about 220 kilometers per second, which means that we move one mile around the Galaxy in less than 1/100th of a second!
We can also look at the Cosmic Microwave Background radiation. This is radiation left over from the Big Bang, and which bathes the entire universe uniformly. When we look at the cosmic microwave background, we see that it is redshifted in one direction and blushifted in the opposite direction. This shift means that our Galaxy (and the Sun along with it) are moving at a speed of several hundred kilometers per second relative to the uniform expansion of the universe.