So, have you ever wondered why we have seasons? Or maybe where the sun goes when it's night time? *Hint: It doesn't actually go anywhere* In this episode of Crash Course Kids, Sabrina talks about the Earth's rotation and revolution and...

There are four fundamental forces - the strong and weak nuclear forces, electromagnetism, and gravity. Except maybe gravity is no more fundamental than the force of a stretched elastic band. Maybe gravity is just an entropic byproduct—an...

It’s been 120 years since Henry Cavendish measured the gravitational constant with a pair of lead balls suspended by a wire. The fundamental nature of gravity still eludes our best minds - but those secrets may be revealed by turning...

You may have heard that a kilogram of feathers weighs the same as a kilogram of steel, but that all depends on where you weigh them. This video is all about the difference between mass and weight, and how weirdly awesome Earth’s gravity...

Challenge question: if 1kg of apples is $5 and 2kg is $10, how much is -1kg of apples? The answer? Priceless. Because you could use negative-mass apples to build warp drives, travel in time, and construct a perpetual motion machine. In...

Fact: in a black hole, all of the mass is concentrated at the singularity at the very center. Fact: every black hole singularity is surrounded by an event horizon. Nothing can escape from within the event horizon unless it can travel...

In this episode, we discuss the basic nature of gravity, one of the four fundamental forces in our universe.

At the beginning of the 20th century, many scientists thought that we had learned all there was to know about physics. The problem is, the better we get at measuring things and building models of our universe, the more we discover that...

In this video Paul Andersen explains why astronauts are weightless. He also explains how Newton's Universal Law of Gravitation can be used to calculate the gravitational force between objects.

The universe gets a little weirder, and more dangerous, every time we study it. Understanding space weather, which can mess with our communications systems, will take strategic planning to monitor.

Like positive and negative, or debit and credit, matter and antimatter are equal and opposite. So if matter falls down, does antimatter fall up? Chloe Malbrunot investigates that question by placing two atoms - one made of matter, and...

Gabe breaks down the steps for how he determined the density of the moon in Majora's Mask.

We've been through the first few episodes of our crash course on general relativity, and came out alive! But it's officially "time" for CURVED spacetime. Join Gabe on this week's episode of PBS Space Time as he discusses Newton and...

In this episode, we discuss the basic nature of gravity, one of the four fundamental forces in our universe.

In this video Paul Andersen explains how the gravitational mass is a measure of the force on an object in a gravitational field. The gravitational mass is based on the amount of material in an object and can be measured to a standard kg...

In this video Paul Andersen explains how an object with mass placed in a gravitational field experiences a gravitational force. On the Earth this gravitational force is known as weight. The gravitational force is equal to the product...

Every star, black hole, human being, smartphone and atom are all constantly pulling on each other due to one force: gravity. So why don’t we feel pulled in billions of different directions? And is there anywhere in the universe where...

In this episode of Crash Course Kids, Sabrina talks about why things on the bottom of the Earth, don't just fall off into space. Plus... PENGUINS! This first series is based on 5th grade science. We're super excited and hope you enjoy...

Paul Andersen explains how objects interact when touching and at a distance. Electromagnetic forces are very important when objects are touching and fields explain both electromagnetic and gravitational forces. The strong and weak...

Most of us take gravity as an assumed part of our living realities, but why? Basic physics introduces us to the concept of gravity from a Newtonian sense, but when you start factoring Einstein into an understanding of gravity, things get...

In this video Paul Andersen explains how gravitational forces differ from the other three fundamental forces; electromagnetic, strong, and weak. Gravitational forces are always attractive and operate at all scales. Even though...

I'm sure you've all heard about Isaac Newton and that apple that fell on his head and how that was a huge deal to our understanding of gravity. Well... let's talk about that. In this episode of Crash Course Physics, Shini sits down to...

In this video Paul Andersen explains how conservative forces can be used to store potential energy in an object or a system. The work done is equal to the amount of potential energy in the object. The following conservative forces are...

Thanks to the Heising Simons Foundation ( for their support of this video, and of short range gravity research.



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