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...

Space is big, and it’s getting bigger. But where does all that new space actually come from? And is it popping into existence all around you right now? Is that why the remote control is always further away than I thought?

This is a map of the multiverse. Or in physics-ese, it’s the maximally extended Penrose diagram of a Kerr spacetime. And in english: when you solve Einstein’s equations of general relativity for a rotating black hole, the universe does...

I’m going to tell you about the craziest proposal for an astrophysics mission that has a good chance of actually happening. A train of spacecraft sailing the sun’s light to a magical point out there in space where the Sun’s own gravity...

Black holes are a paradox. They are paradoxical because they simultaneously must exist but can’t, and so they break physics as we know it. Many physicists will tell you that the best way to fix broken physics is with string. String...

What if there is no such thing as dark matter? What if our understanding of gravity is just wrong? New work is taking another shot at that Einstein guy. Let’s see if we’ve finally scored a hit with Modified Newtonian Dynamics aka MOND.

We tend to imagine there are connectings between things that we don’t understand. Quantum mechanics and consciousness, aliens and pyramids, black holes and dark matter, dark matter and dark energy, dark energy and black holes. Usually...

How far can you follow a compass needle? As far as the north magnetic pole, where the needle starts spinning wildly? Compass needles align with magnetic field lines, and on the precise spot of magnetic north, those field lines are...

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...

Some see string theory as the one great hope for a theory of everything - that it will unite quantum mechanics and gravity and so unify all of physics into one glorious theory.

Black holes are the result of absolute gravitational collapse of a massive body: a point of hypothetical infinite density surrounded by an event horizon. At that horizon time is frozen and the fabric of space itself cascades inwards at...

In this video Paul Andersen describes the relationship between energy and forces. When objects are directly touching electromagnetic forces can result in forces and energy exchange. When objects are not directly touching fields;...

Between them, general relativity and quantum mechanics seem to describe all of observable reality.

Conservation laws are among the most important tools in physics. They feel as fundamental as you can get. And yet they're wrong - or at least they're only right sometimes. These laws are consequences of a much deeper, more fundamental...

Energy is the most powerful and useful concept in all of physics, but what exactly is it?

The insides of the our gas giant friend, Saturn, might be less of a mystery now that we’ve figured out how to use its rings to indicate its internal makeup. And the light emitted from some very old, very hungry black holes could be...

On this Space Time Journal Club we look at how gravitational waves can be used to search for extra dimensions of space!

Our universe is not a very diverse place when it comes to shapes. Large celestial bodies become spheres, galaxies become discs, and there is little room for variation. Why is this? Well it turns out physics has some pretty strict rules...

We learned how motion gives matter its mass, but how does motion affect time? Let's dive deeper into the true nature of matter and mass by exploring Einstein's photon clock thought experiment, and the phenomenon that is time dilation.

Thanks to some amazing scientific insights, we know a lot about the interior of our planet - even though we’ve never even made it through the crust.

In this video Paul Andersen explains how the electric field between oppositely and equally charged plates is uniform as long as you are far from the edge. The strength of the electric field can be determined by either the charge of the...

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...

This video is about gravitational waves in the weak field limit as discovered by the LIGO collaboration, explained by parallels to electromagnetic radiation, sound waves, water waves, etc. I want to see Cat LIGO ASAP!