Introduction to Astronomy: Crash Course Astronomy #1

Hello, and welcome to Crash Course Astronomy! I’m your host, Phil Plait, and I’ll be

taking you on a guided tour of the entire Universe. You might want to pack a lunch.

Over the course of this series we’ll explore planets, stars, black holes, galaxies, subatomic

particles, and even the eventual fate of the Universe itself.

But before we step into space, let’s take a step back. I wanna talk to you about science.

There are lots of definitions of science, but I’ll say that it’s a body of knowledge,

and a method of how we learned that knowledge.

Science tells us that stuff we know may not be perfectly known; it may be partly or entirely

wrong. We need to watch the Universe, see how it behaves, make guesses about why it’s

doing what it’s doing, and then try to think of ways to support or disprove those ideas.

That last part is important. Science must be, above all else, honest if we really want

to get to the bottom of things.

Understanding that our understanding might be wrong is essential, and trying to figure

out the ways we may be mistaken is the only way that science can help us find our way

to the truth, or at least the nearest approximation to it.

Science learns. We meander a bit as we use it, but in the long run we get ever closer

to understanding reality, and that is the strength of science. And it’s all around us!

Whether you know it or not, you’re soaking in science.

You’re a primate. You have mass. Mitochondria

in your cells are generating energy. Presumably, you’re breathing oxygen.

But astronomy is different. It’s still science, of course, but astronomy puts you in your place.

Because of astronomy, I know we’re standing on a sphere of mostly molten rock and metal

13,000 kilometers across, with a fuzzy atmosphere about 100 km high, surrounded by a magnetic

field that protects us from the onslaught of subatomic particles from the Sun 150 million

km away, which is also flooding space with light that reaches across space, to illuminate

the planets, asteroids, dust, and comets, racing out past the Kuiper Belt, through the

Oort Cloud, into interstellar space, past the nearest stars, which orbit along with

gas clouds and dust lanes in a gigantic spiral galaxy we call the Milky Way that has a supermassive

black hole in its center, and is surrounded by 150 globular clusters and a halo of dark

matter and dwarf galaxies, some of which it’s eating, all of which can be seen by other

galaxies in our Local Group like Andromeda and Triangulum, and our group is on the outskirts

of the Virgo galaxy cluster, which is part of the Virgo supercluster, which is just one