00:00Our galaxy is enormous. It's 100,000 light years wide.
00:05Just think for a second about how big our galaxy really is.
00:08To really understand that, it's only 8.3 light minutes from the Sun to Earth.
00:12One light day would take you way beyond our solar system.
00:16But hang on, if we're here, how do we know how big our galaxy is?
00:19Well, we started measuring the distances to different stars, and by filling in this map,
00:23we discovered that there are way more that way and that way than that way and that way.
00:27So we understood its shape.
00:29But how do you figure out how far away a star is?
00:31This is cool.
00:32For the close ones, we can measure their apparent location in the sky,
00:35and then measure it again six months later when the Earth is on the other side of the Sun.
00:38And based on their slight change in location, we can calculate how far away it is.
00:42For farther stars, we look at a special category that pulse at a consistent rate.
00:46We know the ones that pulse faster are actually smaller and less bright,
00:49and our galaxy has 100 billion stars in it.
00:52We're learning new things about them all the time.
00:54If you want more optimistic science and tech stories, subscribe.
