How much do we actually know?

It isn't a question that you see asked much, which is in a way more worrying to me than any wrong assumption people might have. The world isn't a science fiction movie, but for all intents and purposes it doesn't matter. Just because the way black holes are portrayed in movies, and so how most people think about them, is wrong doesn't make a difference at the end of the day.

However I think the title question is something that does matter, and it should be asked more often. How much do we know about the universe?

The truth is, we don't actually -know- much at all. The blog title is more than a coy, arrogant reference to my own perceived level of knowledge. It is also a bit of an in-joke about how much we can say for sure that we know about the world around us.

We can't do experiments on other stars or other worlds (outside our solar system). We can't make the universe repeat itself so we can see if thing happen the same way every time. All we can do is watch and make observations. Then we make assumptions based on those observations.

We look at the spectra of stars, and see it looks very much like spectra from the Sun. They are massive, bright, hot objects. We can tell all of that from looking at stars. So we assume that they are like our sun. But we can't say for sure. We haven't gone up to another star and done tests on it. All we can do is make observations of the stars we can see.

So far, they all appear to behave similar to the sun. But even if we look at billions of stars, or trillions of stars, there is nothing to say that the next one won't be something completely different. It's happened before. What we thought were stars at one point turned out to be distant clusters of thousands of stars, or galaxies, or even Blazars, giant jets of energy released as the 'last gasp' of matter falling into a black hole. They all looked like stars until we started looking harder. With better instruments, better detectors, with better resolution.

We very well could be wrong again.