outward faster than the current speed of light. This explanation is known as inflation theory, and has widespread advocacy within the astrophysics community because it reconciles theory with observation. It should be noted, however, that inflation theory is not directly verifiable.Whether you believe inflation theory or not, galaxies did form. And since they formed from matter that was moving rapidly, they also move rapidly. Due to a phenomenon called doppler shifting, the wavelength emitted by something moving away from us is shifted to a lower frequency, and the wavelength of something moving towards us is shifted to a higher frequency. A good example of this is the sound of a fire truck siren as it drives by; the pitch of the siren is higher as the fire truck moves towards you, and lower as it moves away from you. Although this example illustrates the effect for sound waves, the same effect occurs for all wavelengths (incuding light), the result being that visible wavelengths emitted by objects moving away from us are shifted towards the red part of the visible spectrum, or redshifted. And the faster they move away from us, the more they are redshifted. Thus, redshift is a reasonable way to measure the speed of an object (this, by the way, is the principal by which radar guns measure the speed of a car or baseball). Here's the point: When we observe the redshift of galaxies outside our local group, every galaxy appears to be moving away from us. We are therefore lead to the conclusion that our Universe is expanding. This is called hubble expansion, after Edwin Hubble, who discovered the phenomenon in 1929.Here's a subtle point that you may have wondered about: If we look out into the Universe and every galaxy we see is moving away from us, doesn't that mean that we are at the center of the Universe? The obvious answer seems to be 'yes', but actually the answer is 'no'. Hopefully the following analogy will explain why. Image a loaf of...
