Tag Archives: John Green

Saturn: Crash Course Astronomy #18

This episode of Crash Course is brought to you by Squarespace. So now we’ve come to the last of the naked eye planets in the solar system: Saturn. It’s the second largest planet, but ironically the least dense. In fact, if you could find a bathtub big enough, Saturn would float in it! But it… Read More »

Comets: Crash Course Astronomy #21

Hey, Phil Plait here and this is Crash Course Astronomy. Since humans have been human we’ve looked to the skies for portents of the future. The Sun, the Moon, the planets, the stars; they’ve all been used for prognostication. And so have comets. A fuzzy blob, moving slowly across the stars? How could soothsayers resist?… Read More »

Galaxies, part 1: Crash Course Astronomy #38

We live in a pretty cool neighborhood: the Milky Way galaxy. We’re out in the suburbs, sure, but it’s still an interesting place, buzzing with activity. Stars, nebulae, stellar clusters of various sorts, the occasional supernova. It’s a happening place. In the earliest part of the 20th century, astronomers were just starting to figure this… Read More »

Outtakes #5: Crash Course Astronomy

[music] The universe will be dark — dark to human eyes, at least assuming we have eyes in a trillion years or we’re even around that long. Wow, that– yeah. OFF-SCREEN: Yeah. I was trying to be a little more jocular. [intro] OFF-SCREEN: I am rolling. Are you? Are you? Are you hating? OFF-SCREEN: They… Read More »

Galaxies, part 2: Crash Course Astronomy #39

Hey astronomers, Phil Plait here. In our last episode, I talked about galaxies: vast collections of gas, dust, and upwards of hundreds of billions of stars. We live in one, the Milky Way, a gigantic disk galaxy with sprawling spiral arms. Other galaxies are elliptical, or irregular, or peculiar. But those are classifications based on… Read More »

Uranus & Neptune: Crash Course Astronomy #19

This episode of Crash Course is brought to you by Squarespace. You run us. YOU run us. You RAN us. You ran us. Ooo- Ooo ran ose. There are five planets in our solar system you can see without a telescope; well, six if you include the one you’re sitting on. But there are two… Read More »

Black Holes: Crash Course Astronomy #33

As we’ve seen over the past few episodes, a lot of really epic stuff happens when a star dies. If the star’s core is less than 1.4 times the mass of the Sun, it becomes a white dwarf—a very hot ball of super-compressed matter about the size of the Earth. If the core is heftier,… Read More »

Dark Energy, Cosmology part 2: Crash Course Astronomy #43

The previous episode of Crash Course Astronomy was a bit of a brain-stretcher. We saw that the Universe is expanding, space is expanding, and it’s carrying galaxies along with it. That means it was denser in the past, and at some point — 13.82 billion years ago, to be fairly precise — all of space,… Read More »

The Gravity of the Situation: Crash Course Astronomy #7

We live — and stop me if I’m going too fast — on a planet. I mean, sure, duh. But this isn’t the natural state of the Universe; or, at least, it’s not the way things usually are. Most of the Universe is pretty empty — that’s why we call it “space” — and if… Read More »

Light: Crash Course Astronomy #24

Hey, Phil Plait here and this is Crash Course Astronomy. In last week’s episode, I mentioned that nearly all the information we have about the Universe comes in the form of light. But how does that light get made? What can it tell us about these astronomical objects? And honestly, what is light? Here’s a… Read More »