Cycles in the Sky • episode "#3" • Crash Course Astronomy

12:11

Welcome to the first episode of Crash Course Astronomy. Your host for this intergalactic adventure is the Bad Astronomer himself, Phil Plait. We begin with answering a question: "What is astronomy?"

Astronomy

11:16

Today on Crash Course Astronomy, Phil invites you to head outside and take a look at all the incredible things you can see with your naked eye.

Astronomy

9:28

This week we build on our naked eye observations from last week and take a look at the cyclical phenomena that we can see at work in the universe.

Astronomy

9:45

In this episode of Crash Course Astronomy, Phil takes you through the cause and name of the Moon's phases.

Astronomy

10:31

An eclipse is an astronomical event that occurs when an astronomical object is temporarily obscured, either by passing into the shadow of another body or by having another body pass between it and the viewer.

Astronomy

12:00

Today Phil explains how telescopes work and offers up some astronomical shopping advice.

Astronomy

10:02

* Gravity is a Force * Different Types of Orbit * Escape Velocity * Weightless Mass

Astronomy

9:46

Today Phil explores the world of tides! What is the relationship between tides and gravity? How do planets and their moons become tidally locked? What would happen if you were 300km tall? Important questions.

Astronomy

10:16

In today's Crash Course Astronomy, Phil takes a look at the explosive history of our cosmic backyard. We explore how we went from a giant ball of gas to the system of planets and other celestial objects we have today.

Astronomy

12:03

Phil takes us for a closer (eye safe!) look at the two-octillion ton star that rules our solar system. We look at the sun's core, plasma, magnetic fields, sunspots, solar flares, coronal mass ejections, and what all of that means for our planet.

Astronomy

10:13

Phil starts the planet-by-planet tour of the solar system right here at home, Earth.

Astronomy

9:50

Join Phil for a tour of our capital-M Moon, from surface features, inside to the core, and back in time to theories about its formation.

Astronomy

10:17

Mercury is the closest planet to the sun. It has no atmosphere and is, as such, covered in craters. It's also incredibly hot but, surprisingly, has water ice hiding beneath its surface.

Astronomy

10:49

Venus is a gorgeous naked-eye planet, hanging like a diamond in the twilight -- but it’s beauty is best looked at from afar. Even though Mercury is closer to the sun, Venus is the hottest planet in the solar system, due to a runaway greenhouse effect, and has the most volcanic activity in the solar system. Its north and south poles were flipped, causing it to rotate backwards and making for very strange days on this beautiful but inhospitable world.

Astronomy

10:11

The fourth planet from the sun and the outermost of the terrestrial planets, Mars has long been a popular spot for missions and imagination. Phil walks you through the planet's topography, core, and features. We'll take a look back to Mars's past and makes predictions for its future, including the possibilities for human life.

Astronomy

10:43

Jupiter is the biggest planet in our solar system. The gas giant is NOT a failed star, but a really successful planet! It has a dynamic atmosphere with belts and zones, as well as an enormous red spot that’s actually a persistent hurricane. Jupiter is still warm from its formation, and has an interior that’s mostly metallic hydrogen, and it may not even have a core.

Astronomy

10:29

Before moving on from Jupiter to Saturn, we’re going to linger for a moment on Jupiter’s moons. There are 67 known moons, and 4 huge ones that we want to explore in greater detail. Ganymede is the largest - larger, in fact, than any other moon in the solar system and the planet Mercury! Callisto, orbiting the farthest out, is smaller but quite similar to Ganymede in many ways. Io, meanwhile, is most noteworthy for its tremendous volcanic activity. There’s also water on Ganymede and Europa!

Astronomy

12:15

Saturn is the crown jewel of the solar system, beautiful and fascinating. It is a gas giant, and has a broad set of rings made of ice particles. Moons create gaps in the rings via their gravity. Saturn has dozens of moons, including Titan, which is as big as Mercury and has a thick atmosphere and lakes of methane; and Enceladus which has an undersurface ocean and eruptions of water geysers. While we are still uncertain, it is entirely possible that either or both moons may support life.

Astronomy

12:18

Today we’re rounding out our planetary tour with ice giants Uranus and Neptune. Both have small rocky cores, thick mantles of ammonia, water, and methane, and atmospheres that make them look greenish and blue. Uranus has a truly weird rotation and relatively dull weather, while Neptune has clouds and storms whipped by tremendous winds. Both have rings and moons, with Neptune’s Triton probably being a captured iceball that has active geology.

Astronomy

11:32

Now that we’ve finished our tour of the planets, we’re headed back to the asteroid belt. Asteroids are chunks of rock, metal, or both that were once part of smallish planets but were destroyed after collisions. Most orbit the Sun between Mars and Jupiter, but some get near the Earth. The biggest, Ceres is far smaller than the Moon but still big enough to be round and have undergone differentiation.

Astronomy