How a Frozen Earth Gave the Moon Its Shape

It might look like a perfect circle, but the Moon is actually wider than it is tall. Now, new calculations indicate that the Moon’s shape is a remnant of a time when Earth might’ve been covered in a single, global ice sheet.

Host: Hank Green
Support SciShow by becoming a patron on Patreon:
Dooblydoo thanks go to the following Patreon supporters:
Kelly Landrum Jones, Sam Lutfi, Kevin Knupp, Nicholas Smith, D.A. Noe, alexander wadsworth, سلط الخليفي, Piya Shedden, KatieMarie Magnone, Scott Satovsky Jr, Charles Southerland, Bader AlGhamdi, James Harshaw, Patrick Merrithew, Patrick D. Ashmore, Candy, Tim Curwick, charles george, Saul, Mark Terrio-Cameron, Viraansh Bhanushali, Kevin Bealer, Philippe von Bergen, Chris Peters, Justin Lentz
Like SciShow? Want to help support us, and also get things to put on your walls, cover your torso and hold your liquids? Check out our awesome products over at DFTBA Records:
Looking for SciShow elsewhere on the internet?

Can you power a house with a ShakeWeight?

Using a ShakeWeight, how long would it take to produce enough energy to power a house for a day? Are we making progress toward clean and alternative energy sources?
PBS Digital Studios is grateful to Bill and Melinda Gates for their support. If you’d like to take a look at the 2018 Annual Letter, you can check it out here:

creator: dianna cowern
editor: jabril ashe
research : dianna cowern, sophia chen,
kyle kitzmiller, dan walsh
animations: kyle norby

many thanks to kyle and
dan for creative thinking


For Pacific Mole Crabs It’s Dig or Die | Deep Look

Pacific mole crabs, also known as sand crabs, make their living just under the surface of the sand, where they’re safe from breaking waves and hungry birds. Some very special physics help them dig with astonishing speed.

SUBSCRIBE to Deep Look!

DEEP LOOK is a ultra-HD (4K) short video series created by KQED San Francisco and presented by PBS Digital Studios. See the unseen at the very edge of our visible world. Get a new perspective on our place in the universe. Explore big scientific mysteries by going incredibly small.


Among the surfers and beach-casting anglers, there’s a new visitor to San Francisco’s Ocean Beach shoreline.

Benjamin McInroe is there for only one reason — to find Pacific mole crabs, a creature commonly known as “sand crabs” — and the tiny animals whose burrowing causes millions of small bubbles to appear on the beach as the tide comes in and out.

McInroe is a graduate student from UC Berkeley studying biophysics. He wants to know what makes these little creatures so proficient at digging their way through the wet sand.

McInroe hopes that he can one day copy their techniques to build a new generation of digging robots.

— What are Pacific Mole Crabs?

Pacific mole crabs, also known as sand crabs, are crustaceans, related to shrimp and lobsters. They have four pairs of legs and one pair of specialized legs in the front called uropods that look like paddles for digging in sand. Pacific mole crabs burrow through wet sand and stick their antennae out to catch bits of kelp and other debris kicked up by the breaking waves.

— What makes those holes in the sand at the beach?

When the waves recede, mole crabs burrow down into the sand to keep from being exposed. They dig tail-first very quickly leaving holes in the wet sand. The holes bubble as water seeps into the holes and the air escapes.

— What do birds eat in the wet beach sand?

Shore birds like seagulls rush down the beach as the waves recede to catch mole crabs that haven’t burrowed down quickly enough to escape. The birds typically run or fly away as the next wave breaks and rolls in.

—+ Read the entire article on KQED Science:

—+ For more information:

Benjamin McInroe, a Ph.D. student at UC Berkeley, studies how Pacific mole crabs burrow

Professor Robert Full directs the Poly-PEDAL Lab at UC Berkeley, where researchers study the physics of how animals and use that knowledge to build mechanical systems like robots based on their findings.

—+ More Great Deep Look episodes:

Decorator Crabs Make High Fashion at Low Tide | Deep Look

These Fish Are All About Sex on the Beach | Deep Look

Sea Urchins Pull Themselves Inside Out to be Reborn | Deep Look

There’s Something Very Fishy About These Trees … | Deep Look

—+ See some great videos and documentaries from the PBS Digital Studios!

Why Do We Eat Artificial Flavors? | Origin of Everything

The Facts About Dinosaurs & Feathers

Why Is Blue So Rare In Nature?

—+ Follow KQED Science

KQED Science:

—+ About KQED

KQED, an NPR and PBS affiliate in San Francisco, CA, serves Northern California and beyond with a public-supported alternative to commercial TV, Radio and web media.

Funding for Deep Look is provided in part by PBS Digital Studios. Deep Look is a project of KQED Science, which is supported by the S. D. Bechtel, Jr. Foundation, the Dirk and Charlene Kabcenell Foundation, the Vadasz Family Foundation, the Gordon and Betty Moore Foundation, the Fuhs Family Foundation Fund and the members of KQED.

Why is Special Relativity Hard? | Special Relativity Chapter 1

Thanks to for supporting this video!

Support MinutePhysics on Patreon!
Link to Patreon Supporters:

This is the first in a series of videos about special relativity. This is definitely not an academic course, but it’s going to be a more in depth and developed exploration of a single topic than a typical standalone MinutePhysics video. I’ve been greatly inspired (and heckled) to do this by my friend Grant Sanderson of 3blue1brown who’s set the standard for this kind of thing with his excellent series – serieses? – on calculus and linear algebra.

So, special relativity. Special relativity is one of the most popularly famous ideas in physics – it’s that thing that Einstein figured out about the speed of light and space and time and E=mc^2! It changed our understanding of the universe. And its core ideas are accessible in principle to anyone who understands some basic algebra and geometry – you don’t even need to know calculus!

And yet in spite of this, special relativity is one of the subjects in physics that confuses the most people, and in many cases turns them away from physics altogether.

MinutePhysics is on twitter – @minutephysics
And facebook –
And Google+ (does anyone use this any more?) –

Minute Physics provides an energetic and entertaining view of old and new problems in physics — all in a minute!

Created by Henry Reich

Can you see this type of light?

Polarized light is an unusual form of light. Can humans see when light is polarized?
To learn more about Brilliant, go to

Subscribe to physics girl:

Check out the other YouTubers in this video!
Léo Grasset (Dirty Biology)
William Osman
Allen Pan

Creator: Dianna Cowern
Editing: Jabril Ashe
Animations: Kyle Norby
Research: Sophia Chen
Adviser: Dan Walsh

Thanks to Kyle Kitzmiller and Bill Herrington!

PO Box 9281
San Diego, CA 92169

More instructions for this project:


How I broke a wine glass with my voice (using science!)

If you sing at a wine glass at its exact resonant frequency, you can break the glass without the help of a speaker! Learn the physics behind that.
To learn more about Brilliant, go to
and sign up for free. First 200 people will get 20% off the annual Premium subscription.

Mike Boyd Learning to Break a Glass:
Mike Boyd’s channel:

More Physics Girl:

MIT breaking wine glass video

Creator: Dianna Cowern
Animations: Kyle Norby
Editor: Jabril Ashe
Thanks to Kyle Kitzmiller, Dan Walsh and Mike Boyd!
And to my parents and roommates to endured the screeching.

PO Box 9281
San Diego, CA 92169

Lessons from a solar storm chaser | Miho Janvier

Space physicist Miho Janvier studies solar storms: giant clouds of particles that escape from the Sun and can disrupt life on Earth (while also producing amazing auroras). How do you study the atmosphere on the Sun, which burns at temperatures of up to around 10 million degrees Kelvin? With math! Join the TED Fellow as she shares her work trying to better understand how the Sun affects us here on Earth.

Check out more TED Talks:

The TED Talks channel features the best talks and performances from the TED Conference, where the world’s leading thinkers and doers give the talk of their lives in 18 minutes (or less). Look for talks on Technology, Entertainment and Design — plus science, business, global issues, the arts and more.

Follow TED on Twitter:
Like TED on Facebook:

Subscribe to our channel:

How We Know Black Holes Exist

Thanks to the James Webb Space Telescope (JWST) and Space Telescope Science Institute for supporting this video.

Support MinutePhysics on Patreon!
Link to Patreon Supporters:

This video is about the astronomical amount of astronomical evidence for black holes, ranging from x-ray binaries with accretion disks, supermassive infrared-radiating galactic nuclei black holes, orbital characteristics of high mass binaries, and direct gravitational wave detection of inspiraling merging black hole binaries with LIGO. Yes, they’re real.


Interactive: Masses in the Stellar Graveyard

Galactic Center Orbital Models and Inner Stellar Distributions

Data provided by Andrea Ghez and Sylvana Yelda, UCLA (obtained with the Keck Telescopes)

Visualization by Stuart Levy and Robert Patterson, National Center for Supercomputing Applications, University of Illinois at Urbana-Champaign

Masses of observed black Holes:

Downloadable LIGO Data:

LIGO Neutron Star Binary Merger:

Masses of observed neutron stars:

Cygnus X-1 X-ray binary Black Hole:

Lecture notes on black holes:

Calvera isolated neutron star X-ray source:

Scientific American: pulsar that behaves like a black hole

Largest known neutron star:

Large Neutron Star:

Wandering Black Hole:

Sagittarius A* Black Hole Infrared emissions:

MinutePhysics is on twitter – @minutephysics
And facebook –
And Google+ (does anyone use this any more?) –

Minute Physics provides an energetic and entertaining view of old and new problems in physics — all in a minute!

Created by Henry Reich

Why Is Blue So Rare In Nature?

Duh, except for the sky… and the ocean…
Don’t miss our next video! SUBSCRIBE! ►►
↓↓↓ More info and sources below ↓↓↓

Among living things, the color blue is oddly rare. Blue rocks, blue sky, blue water, sure. But blue animals? They are few and far between. And the ones that do make blue? They make it in some very strange and special ways compared to other colors. In this video, we’ll look at some very cool butterflies to help us learn how living things make blue, and why this beautiful hue is so rare in nature.

Smithsonian Institution – National Museum of Natural History
Bob Robbins, Ph.D. – Curator of Lepidoptera
Juan Pablo Hurtado Padilla – Microscope Educator

Richard Prum, Ph.D. – Yale University
Vinothan Manoharan, Ph.D. – Harvard University



Twitter:@DrJoeHanson @okaytobesmart
Instagram: @DrJoeHanson


It’s Okay To Be Smart is hosted by Joe Hanson, Ph.D.
Director: Joe Nicolosi
Writer: Joe Hanson, Ph.D.
Producer/editor/animator: Jordan Husmann
Producer: Stephanie Noone and Amanda Fox

Produced by PBS Digital Studios
Music via APM