How Do We Know What Is Going on in the Universe?

How is it that we know all these different methods for galaxies to da? You know, how are you actually studying these? There are a variety of ways to do it. You can look at galaxy populations. So red verses blue, for instance. That's how this was done to start with. We just looked at the colours of galaxies and found there were more red galaxies in dense environments. And that told us something about environment is important. Then we can go further and look at what that might be. What we do a lot nowadays is look at the gas in galaxies. As i said, it's really the crucial component in all this,. cause it's that fuel for future star formation