Last week, I teased you with the idea that it’s actually easy to estimate distances to galaxies.
I do mean estimate–and distance indicators are still important.
The Hubble Law is named for Edwin Hubble, the astronomer who was first able to settle the debate over what galaxies were–using the new Hale Telescope, the largest in the world at the time. But the Hubble Law is undoubtedly what he’s most famous for.
In order to understand the Hubble Law, though, we first need a little review of the Doppler effect…
Well, I’ll give you a spoiler: they’re ridiculously far away.
Let’s consider for a moment what a light-year actually means. It sounds like a unit of time, but it’s actually the distance that light travels in one Earth year.
Think of it this way: if your name is Bob, and you can travel a certain distance in one year, that distance could be called a Bob-year.
I know it’s strange to think of light traveling at a certain speed. When you flip a light switch, the room immediately brightens. When you shine a flashlight, its beam immediately falls across the nearest surface.
But that just goes to show how insanely fast light travels. If it takes 2 million years for light to get from one object to another…imagine how far apart those objects are?
Well, that’s the case for our home galaxy, the Milky Way, and our nearest galactic neighbor, the Andromeda Galaxy.