Did you grow up thinking there were nine planets in the solar system? You might have been right all along! Today we discuss the possibility of distant worlds in our solar system.

Scientists have spotted a galaxy from the early origins of the universe, and found evidence to support the existence of a 9th planet in our solar system.

A unit is the frequently arbitrary designation we have given to something to convey a definite magnitude of a physical quantity and every quantity can be expressed in terms of the seven base units that are contained in the international...

An introduction to what a derivative is, and how it formalizes an otherwise paradoxical idea.

The meter is the world's ultimate measure, but how did it become "the" meter? What is this measurement based on? The story of this revolution in measurement traces its roots to the French Revolution. Scientists decided that an equal and...

GPS location apps on a smartphone can be very handy when mapping a travel route or finding nearby events. But how does your smartphone know where you are? Wilton L. Virgo explains how the answer lies 12,000 miles over your head, in an...

Meter is the standard unit of length used by most countries around the world. But how did they define it?

You might be benefiting from the weird units you've never heard every time you put on your shoes or read about dark matter.

In this video Paul Andersen shows conceptual thinking in a mini-lesson on proportional relationships. TERMS Quantities - the amount (or number) of a thing Proportional relationship - relation of one dataset to another dataset Directly -...

It's School of YouTube Week! Comic Relief and YouTube are partnering to send students to school! The Bad Astronomer Phil Plait teaches Hank how to measure the distance to the stars.

How can the tiny moon eclipse the sight of the gargantuan sun? By sheer coincidence, the disc of the sun is 400x larger than the disc of the moon, but the sun is 390x farther from Earth -- which means that when they align just right, the...

Thanks to the Heising Simons Foundation (https://www.hsfoundation.org/) for their support of this video, and of short range gravity research. This video is about how little we know about the behavior of gravity at short length and...

All across the world people need to get from one place to another. And sometimes to get to that other place we need bridges. Here are eight bridges that are extraordinary in their own way, from standing the test of time to handling...

Black Holes are known for consuming everything that falls into them, but is there a point where these galactic devourers can't stomach anymore?

In this video Paul Andersen explains how the period is the time between wave and the frequency is the number of waves per second. Period is measured in seconds and frequency is measured in Hertz. Wave period and wave frequency are...

The Andromeda galaxy is heading straight toward our own Milky Way. The two galaxies will inevitably collide. Will that be the very last night sky our solar system witnesses?

With exoplanets, often we want to know if they are Earth-like and whether they might host life, but we can also learn a lot from planets that are nothing like Earth.

In this video Paul Andersen explains how the center of mass of an object represents the average position of matter in an object. The center of mass of a system is a combination of all the objects within the system. As long as no external...

The universe is HUGE. But, there is only so much of the universe we can ACTUALLY see, and if we wanted to measure that FINITE space, how would we do it? A gigantic ruler? One really long car ride? Or maybe it's something even more...

The evil wizard MoldeVort has been trying to kill you for years, and today it looks like he’s going to succeed. But your friends are on their way, and if you can survive until they arrive, they should be able to help stop him. Can you...

Can you ever travel from one place to another? Ancient Greek philosopher Zeno of Elea gave a convincing argument that all motion is impossible - but where's the flaw in his logic? Colm Kelleher illustrates how to resolve Zeno's Dichotomy...

The moon may be 1.3 light-seconds away, but why on earth do we measure distances using time?

In a word, "yes" - space is packed with gravity. Hank explains how Isaac Newton described how gravity works, and why even though it seems that things are floating in space, they're still effected by gravity. Every object in the universe...

How do astronomers make sense out of the vastness of space? How do they study things so far away? Today Phil talks about distances, going back to early astronomy. Ancient Greeks were able to find the size of the Earth, and from that the...