We’ve covered a lot of incredible stuff, but this week we’re talking about the weirdest objects in space: BLACK HOLES. Stellar mass black holes form when a very massive star dies, and its core collapses. The core has to be more than about 2.8 times the Sun’s mass to form a black hole. Black holes come in different sizes, but for all of them, the escape velocity is greater than the speed of light, so nothing can escape, not matter or light. They don’t wander the Universe gobbling everything down around them; their gravity is only really intense very close to them. Tides near a stellar mass black hole will spaghettify you, and time slows down when you get near a black hole — not that this helps much if you’re falling in.

Crash Course Astronomy Poster: http://store.dftba.com/product....s/crashcourse-astron

--

Table of Contents
How Stellar Mass Black Holes Are Formed 1:03
The Core 1:43
Nothing Can Escape Once It’s Inside 2:29
Gravity Intensifies The Closer You Get 3:33
Spaghettification 6:01
Time Will Slow Down Near A Black Hole 8:01

--

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--

PHOTOS/VIDEOS
White Dwarf Pulses Like a Pulsar http://www.nasa.gov/centers/go....ddard/news/topstory/ [credit: NASA, Casey Reed]
Swift Reveals New Phenomenon in a Neutron Star http://www.nasa.gov/mission_pa....ges/swift/bursts/new [credit: NASA's Goddard Space Flight Center]
Black Holes - Monsters in Space https://en.wikipedia.org/wiki/....File:Black_Holes_-_M [credit: NASA/JPL-Caltech, Wikimedia Commons]
What if the Sun became a black hole? (artist's impression) http://www.spacetelescope.org/....videos/hubblecast43g [credit: ESA/Hubble (M. Kornmesser)]
Black Hole Animation http://chandra.harvard.edu/pho....to/2003/0203long/ani [credit: NASA/SAO/CXC/D.Berry]
Star Destroyer http://svs.gsfc.nasa.gov/cgi-b....in/details.cgi?aid=1 [credit: Space Telescope Science Institute (STScI) and NASA's Goddard Space Flight Center]
Black hole deforms space http://www.spacetelescope.org/....videos/hst15_blackho [credit: ESA/Hubble (M. Kornmesser & L. L. Christensen)]
Black hole close-up (artist's impression) http://www.spacetelescope.org/videos/heic0211c/ [credit: European Space Agency, NASA and Felix Mirabel (the French Atomic Energy Commission & the Institute for Astronomy and Space Physics/Conicet of Argentina)]

•••SUBBABLE MESSAGE•••

TO: Jordan Schoonover
FROM: Mom, Dad & Madison

Happy Birthday Jordan! We love you sweetheart!!

***

You can directly support Crash Course at http://www.subbable.com/crashcourse Subscribe for as little as $0 to keep up with everything we're doing. Also, if you can afford to pay a little every month, it really helps us to continue producing great content.

***

In this episode of Crash Course Anatomy & Physiology, Hank gives you a brief history of histology and introduces you to the different types and functions of your body's tissues.

--

Table of Contents:

Nervous, Muscle, Epithelial & Connective Tissues 1:23
History of Histology 2:07
Nervous Tissue Forms the Nervous System 5:17
Muscle Tissue Facilitates All Your Movements 7:00
Identifying Samples 9:03

--

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Hank resists the urge to devour a slice of pizza so that he can walk you through the way we experience our major special senses. It all boils down to one thing: sensory cells translating chemical, electromagnetic, and mechanical stimuli into action potentials that our nervous system can make sense of. Today we're focusing on smell (olfaction) and taste (gustation), which are chemical senses that call on chemoreceptors. As usual, we'll begin with a quick look at how these things can go wrong.

Table of Contents
Anatomy and Physiology of Smell 2:26
The Olfactory Sensory Neurons 3:01
Receptors → Glomerulus → Mitral Cells → Brain 3:47
Taste Receptor Epithelial Cells 7:30
Receptors Trigger Action Potentials to Four Different Cranial Nerves 8:26


***

Crash Course is now on Patreon! You can support us directly (and have your contributions matched by Patreon through April 30th!) by signing up at http://www.patreon.com/crashcourse

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***SUBBABLE MESSAGES***

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***SUPPORTER THANK YOU!***

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Today Phil explains that YES, there are other planets out there and astonomers have a lot of methods for detecting them. Nearly 2000 have been found so far. The most successful method is using transits, where a planet physically passes in front of its parent star, producing a measurable dip in the star’s light. Another is to measuring the Doppler shift in a star’s light due to reflexive motion as the planet orbits. Exoplanets appear to orbit nearly every kind of star, and we’ve even found planets that are the same size as Earth. We think there may be many billions of Earth-like planets in our galaxy.

This is a reupload of last week's episode to correct an error in the way we covered reflexive motion.
For more information on the change and reflexive motion, you can check out Phil's blog: http://www.slate.com/blogs/bad...._astronomy/2015/08/0
--

Table of Contents
Other Planets Orbit Other Stars 2:10
Nearly 2000 Have Been Found 9:29
Transits 5:44
Doppler Shift 3:30
Exoplanets Orbit Nearly Every Kind of Star 8:44
Billions of Earth-Like Planets 9:33

--

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--

PHOTOS/VIDEOS
Stars as viewed from ISS https://www.youtube.com/watch?v=TOQrx-7qgak [credit: Alex Rivest & NASA]
Jupiter http://www.nasa.gov/centers/go....ddard/multimedia/lar [credit: NASA]
Mars http://mars.jpl.nasa.gov/multi....media/images/?ImageI [credit: NASA/JPL-Caltech/MSSS]
Mercury http://solarsystem.nasa.gov/multimedia/display.cfm?Category=Planets&IM_ID=7543 [credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington]
Earth https://www.nasa.gov/topics/ea....rth/overview/index.h [credit: NASA]
Uranus http://photojournal.jpl.nasa.gov/catalog/PIA18182 [credit: NASA/JPL-Caltech]
Lost in the Glare http://planetquest.jpl.nasa.gov/video/23 [credit: NASA Kepler Mission/Dana Berry]
Reflexive Motion gifs http://spaceplace.nasa.gov/barycenter/en/ [credit: NASA]
Artist's conception of PSR B1257+12's system of planets https://en.wikipedia.org/wiki/....Pulsar_planet#/media [credit: NASA/JPL-Caltech/R. Hurt (SSC)]
Artist’s impression of the exoplanet 51 Pegasi b (image) http://www.eso.org/public/usa/images/eso1517a/ [credit: ESO/M. Kornmesser/Nick Risinger (skysurvey.org)]
Artist’s impression of the exoplanet 51 Pegasi b (video) http://www.eso.org/public/usa/videos/eso1517b/ [credit: ESO/M. Kornmesser/Nick Risinger (skysurvey.org)]
Kepler Transit Graph http://planetquest.jpl.nasa.gov/video/22 [credit NASA Kepler Mission/Dana Berry]
Kepler “Beauty Shot” http://planetquest.jpl.nasa.gov/video/2 [credit: NASA/Kepler mission/Dana Berry]
The Brown Dwarf 2M1207 and its Planetary Companion https://www.eso.org/public/usa/images/eso0515a/ [credit: ESO]
Beta Pictoris b http://www.eso.org/public/arch....ives/images/screen/e [credit: ESO]
A size comparison of the planets in the Kepler-37 system and objects in the Solar System http://photojournal.jpl.nasa.gov/catalog/PIA16694 [credit: NASA/Ames/JPL-Caltech]
Water World http://planetquest.jpl.nasa.gov/video/39 [credit: NASA Kepler Mission/Dana Berry]
Earth-like World http://planetquest.jpl.nasa.gov/video/42 [credit: NASA Kepler Mission/Dana Berry]

In which John Green teaches you about Imperialism. In the late 19th century, the great powers of Europe were running around the world obtaining colonial possessions, especially in Africa and Asia. The United States, which as a young country was especially suceptible to peer pressure, followed along and snapped up some colonies of its own. The US saw that Spain's hold on its empire was weak, and like some kind of expansionist predator, it jumped into the Cuban War for Independence and turned it into the Spanish-Cuban-Phillipino-American War, which usually just gets called the Spanish-American War. John will tell you how America turned this war into colonial possessions like Puerto Rico, The Philippines, and almost even got to keep Cuba. The US was busy in the Pacific as well, wresting control of Hawaii from the Hawaiians. All this and more in a globe-trotting, oppressing episode of Crash Course US History.

Our Subbable Dooblydoo message today is from James Williams. He writes, "Gracie Mckenna, luck is, indeed, for suckers."

You can support Crash Course directly by subscribing and pledging a monthly gift at https://www.patreon.com/crashcourse. You could even have your own message in the Dooblydoo. If you subscribed via Subbable when the service first launched, you may need to go back and resubscribe. Thanks for your support.

Hey teachers and students - Check out CommonLit's free collection of reading passages and curriculum resources to learn more about the events of this episode. As America transitioned from the 19th to the 20th century, she experimented with imperialism through war and annexation; one of the most lasting effects of this time was the annexation of Hawaii, America's 50th state: https://www.commonlit.org/text....s/the-1897-petition-
America’s imperial aims continued for decades, particularly with the Monroe Doctrine: https://www.commonlit.org/text....s/the-monroe-doctrin

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In which Jacob Clifford and Adriene Hill launch a brand new Crash Course on Economics! So, what is economics? Good question. It's not necessarily about money, or stock markets, or trade. It's about people and choices. What, you may ask, does that mean. We'll show you. Let's get started!

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Culpzilla's students are amazing! You guys rock!

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DFTBA and keep being the exception like the Mongols.

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In which John Green teaches about filthy, filthy lucre. Money. And Debt. So, what is money? And what is it for? And why do we use money? And why does it all disappear so quickly after payday? John will look into 75% of these questions, and if he doesn't come up with answers, we'll get into some interesting ideas along the way, at least. This week we'll investigate whether money displaces barter, then leads to war, slavery, and what we think of as civilized social orders. We'll also see what old Adam Smith thinks of big money, no whammies, this week on Crash Course.

We'll also talk quite a bit about Debt: The First 5000 Years by David Graeber. You can buy that book here: http://dft.ba/-debt5000

You can directly support Crash Course at https://www.patreon.com/crashcourse Subscribe for as little as $0 to keep up with everything we're doing. Also, if you can afford to pay a little every month, it really helps us to continue producing great content.

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.

This episode is brought to you by Squarespace http://www.squarespace.com/crashcourse

--

Table of Contents
Venus’s Size and Atmosphere 3:09
Hottest Planet in the Solar System 4:04
Slow Clockwise Rotation 6:02
Tremendous Volcanic Activity 8:31

--

PBS Digital Studios: http://youtube.com/pbsdigitalstudios

Follow Phil on Twitter: https://twitter.com/badastronomer

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--

PHOTOS/VIDEOS
Naked-eye Venus photo taken by Phil Plait
Phases of Venus http://commons.wikimedia.org/w....iki/File:Phases-of-V [credit: Wikimedia Commons]
2012 Venus Transit https://www.youtube.com/watch?v=34mXua1n_FQ [credit: NASA]
Black drop effect in 2004 http://en.wikipedia.org/wiki/B....lack_drop_effect#med [credit: Vesta]
Venus Transit http://www.nasa.gov/images/con....tent/657111main_1-SO [credit: JAXA/NASA/Lockheed Martin]
Venus in real colors http://en.wikipedia.org/wiki/V....enus#mediaviewer/Fil [credit: NASA]
Earth http://visibleearth.nasa.gov/view.php?id=57723 [credit: NASA Goddard Space Flight Center, Image by Reto Stöckli]
Venus http://www.msss.com/images/sci....ence/venus180hem_mag [credit: NASA/JPL-Caltech/Magellan Project]
Atmospheric Drag on Venus https://www.youtube.com/watch?v=aRAonBSIBck [credit: NASA]
Lakshmi Planum and Maxwell Montes http://en.wikipedia.org/wiki/V....enus_snow#mediaviewe [credit: NASA/JPL]
Artist's impression of the surface of Venus http://sci.esa.int/science-e-m....edia/img/59/VenusSur [credit: ESA]
Venera Images http://planetimages.blogspot.com/ [credit: Ted Stryk]
Venus Globe http://en.wikipedia.org/wiki/V....enus#mediaviewer/Fil [credit: NASA]
Impact craters on the surface of Venus http://en.wikipedia.org/wiki/V....enus#mediaviewer/Fil [credit: Wikimedia Commons]
Idunn Mons http://photojournal.jpl.nasa.g....ov/figures/PIA13001_ [credit: NASA/JPL-Caltech/ESA]
Pancake Volcanoes http://en.wikipedia.org/wiki/P....ancake_dome#mediavie [credit: NASA/Jet Propulsion Laboratory]

You can directly support Crash Course at https://www.patreon.com/crashcourse Subscribe for as little as $0 to keep up with everything we're doing. Free is nice, but if you can afford to pay a little every month, it really helps us to continue producing this content.

In which John Green teaches you about the New Deal, which was president Franklin D. Roosevelt's plan to pull the united States out of the Great Depression of the 1930's. Did it work? Maybe. John will teach you about some of the most effective and some of the best known programs of the New Deal. They weren't always the same thing. John will tell you who supported the New Deal, and who opposed it. He'll also get into how the New Deal changed the relationship between the government and citizens, and will even reveal just how the Depression ended. (hint: it was war spending)

Hey teachers and students - Check out CommonLit's free collection of reading passages and curriculum resources to learn more about the events of this episode. President Roosevelt developed his New Deal policies to ease the economic burdens of the Great Depression, a grim reality he began to tackle with his first fireside chat: https://www.commonlit.org/text....s/president-roosevel
In his Economic Bill of Rights, FDR tried to get the country to trust its banks again: https://www.commonlit.org/text....s/the-economic-bill-

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In which John Green kicks off Crash Course US History! Why, you may ask, are we covering US History, and not more World History, or the history of some other country, or the very specific history of your home region? Well, the reasons are many. But, like it or not, the United States has probably meddled in your country to some degree in the last 236 years or so, and that means US History is relevant all over the world. In episode 1, John talks about the Native Americans who lived in what is now the US prior to European contact. This is a history class, not archaeology, so we're mainly going to cover written history. That means we start with the first sustained European settlement in North America, and that means the Spanish. The Spanish have a long history with the natives of the Americas, and not all of it was positive. The Spanish were definitely not peaceful colonizers, but what colonizers are peaceful? Colonization pretty much always results in an antagonistic relationship with the locals. John teaches you about early Spanish explorers, settlements, and what happened when they didn't get along with the indigenous people. The story of their rocky relations has been called the Black Legend. Which is not a positive legend.

Turn on the captions. You'll like it!

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Want more videos about psychology every Monday and Thursday? Check out our sister channel SciShow Psych at https://www.youtube.com/scishowpsych!

So how do we apply the scientific method to psychological research? Lots of ways, but today Hank talks about case studies, naturalistic observation, surveys and interviews, and experimentation. Also he covers different kinds of bias in experimentation and how research practices help us avoid them.
--
Table of Contents

The Scientific Method 2:06
Case Studies 3:05
Naturalistic Observation 3:48
Surveys and Interviews 4:15
Experimentation 6:35
Proper Research Practices 8:40
--
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Want more videos about psychology every Monday and Thursday? Check out our sister channel SciShow Psych at https://www.youtube.com/scishowpsych!

How would you measure a personality? What, exactly, is the self? Well, as you've come to expect, it's not that easy to nail down an answer for those questions. Whether you're into blood, bile, earth, wind, fire, or those Buzzfeed questionnaires, there are LOTS of ways to get at who we are and why.

--
Table of Contents

Trait & Social-Cognitive Personality 01:35:01
Measuring Personality 02:57:03
Who or What is the Self? 09:16:14
How Self Esteem Works 09:42:04

--
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In which John Green teaches you about the War of 1812. The War of 1812 was fought between the United States and its former colonial overlord England. It started in, you guessed it 1812. The war lasted until 1815, and it resolved very little. John will take you through the causes of the war, tell you a little bit about the fighting itself, and get into just why the US Army couldn't manage to make any progress invading Canada. And yes, Canadians, we're going to talk about the White House getting burned down. The upshot: no territory changed hands, and most of the other bones of contention were solved prior to the actual war. Although nothing much changed for the US and England, the Native Americans were the big losers. Tecumseh was killed, and the Indian tribes lost a lot of territory. Watch as John lays it all out for you. Also, check out #1812problems on Twitter. It's awesome.

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In which John Green teaches you about the European Renaissance. European learning changed the world in the 15th and 16th century, but was it a cultural revolution, or an evolution? We'd argue that any cultural shift that occurs over a couple of hundred years isn't too overwhelming to the people who live through it. In retrospect though, the cultural bloom in Europe during this time was pretty impressive. In addition to investigating what caused the Renaissance and who benefitted from the changes that occurred, John will tell you just how the Ninja Turtles got mixed up in all this.

Crash Course World History is now available on DVD! http://store.dftba.com/product....s/crashcourse-world-

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In which John Green teaches you about Iran's Revolutions. Yes, revolutions plural. What was the1979 Iranian Revolution about? It turns out, Iran has a pretty long history of unrest in order to put power in the hands of the people, and the most recent revolution in 1979 was, at least at first, not necessarily about creating an Islamic state. It certainly turned out to be about that, but it was initially just about people who wanted to get rid of an oppressive regime. Listen up as John teaches you about Iran's long history of revolution.

Citation 1: Caryl, Christian. Strange Rebels: 1979 and the Birth of the 21st Century. New York, Basic Books. 2014, p. 11
Citation 2: Axworthy, Michael, Revolutionary Iran: A History of the Islamic Republic. Oxford U. Press. 2014, p. 62
Citation 3: Quoted in Axworthy, p. 81
Citation 4: Axworthy, p. 114
Citation 5: Axworthy, p. 163

You can directly support Crash Course at https://www.patreon.com/crashcourse Subscribe for as little as $0 to keep up with everything we're doing. Free is nice, but if you can afford to pay a little every month, it really helps us to continue producing this content.

In which John Green teaches you about the tumultuous 2000's in the United States of America, mainly the 2000's that coincide with the presidency of George W Bush. From the controversial election in 2000, to the events of 9/11 and Bush's prosecution of the War on Terror, the George W. Bush presidency was an eventful one. John will teach you about Bush's domestic policies like tax cutting, education reform, and he'll get into the wars in Afghanistan and Iraq. The event that came to pass during Bush's presidency are still very much effecting the United States and the world today, so listen up!

Hey teachers and students - Check out CommonLit's free collection of reading passages and curriculum resources to learn more about the events of this episode. Much of President Bush's term was defined by the events following the terror attack on September 11, including his support for the Patriot Act: https://www.commonlit.org/text....s/president-bush-on-
President Bush also sought to prevent discord with Muslim Americans following the 9/11 attacks in his Islam is Peace” Speech: https://www.commonlit.org/text....s/president-bush-s-i

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.

This episode was brought to you by Squarespace http://www.squarespace.com/crashcourse

--

Table of Contents
Ice Giants With Small Rocky Cores 2:18
Thick Mantles of Ammonia, Water, and Methane 1:53
Atmospheres Makes Them Look Green And Blue 2:53
Uranus Has Dull Weather 3:35
Neptune Has Active Weather 7:19
Both Have Rings And Moons 5:12

--

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--

PHOTOS/VIDEOS
Uranus http://en.wikipedia.org/wiki/V....oyager_2#/media/File [credit: NASA/JPL/Voyager mission]
Neptune https://www.nasa.gov/content/2....5-years-ago-voyager- [credit: NASA]
King George III http://en.wikipedia.org/wiki/G....eorge_III_of_the_Uni
Uranus from Earth picture by Phil Plait
Uranus, Earth size comparison http://en.wikipedia.org/wiki/F....ile:Uranus,_Earth_si [credit: NASA]
Uranus core, reconstructed from http://en.wikipedia.org/wiki/F....ile:Uranus-intern-en [credit: Wikimedia Commons]
Uranus http://www.spacetelescope.org/....static/archives/imag [credit: NASA, ESA, L. Sromovsky and P. Fry (University of Wisconsin), H. Hammel (Space Science Institute), and K. Rages (SETI Institute)]
Uranus storms http://www.keckobservatory.org..../images/made/images/ [credit: Imke de Pater (UC–Berkeley)/Keck Observatory]
Uranus and rings (tilt demonstration) http://en.wikipedia.org/wiki/U....ranus#/media/File:Ur [credit: Hubble Space Telescope - NASA Marshall Space Flight Center]
Uranus with rings and moons http://www.eso.org/public/images/eso0237a/ [credit: ESO]
Miranda http://en.wikipedia.org/wiki/M....oons_of_Uranus#/medi [credit: NASA]
Verona Rupes http://apod.nasa.gov/apod/ap110404.html [credit: NASA]
Neptune’s Interior https://solarsystem.nasa.gov/m....ultimedia/display.cf [credit: Lunar and Planetary Institute]
Neptune clouds http://en.wikipedia.org/wiki/F....ile:Neptune_clouds.j [credit: NASA]
Neptune’s Great Dark Spot http://en.wikipedia.org/wiki/N....eptune#/media/File:N [credit: NASA / Jet Propulsion Lab]
Neptune’s Rings http://www.rolfolsenastrophoto....graphy.com/Astrophot [credit: Rolf Wahl Olsen / NASA/JPL (Voyager 2, NASA Planetary Data System)]
Triton http://en.wikipedia.org/wiki/T....riton_(moon)#/media/ [credit: NASA / Jet Propulsion Lab / U.S. Geological Survey]
Triton flipped http://en.wikipedia.org/wiki/F....ile:PIA01538_Triton_ [credit: NASA/JPL]
Triton Nitrogen Geysers http://en.wikipedia.org/wiki/T....riton_(moon)#/media/ NASA]

Hank introduces us to biogeochemical cycles by describing his two favorites: carbon and water. The hydrologic cycle describes how water moves on, above, and below the surface of the Earth, driven by energy supplied by the sun and wind. The carbon cycle does the same... for carbon!

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Table of Contents

1) Hydrologic Cycle - 1:15
A) Clouds - 2:13
B) Runoff - 3:06
C) Oceans - 3:41
D) Evapotranspiration - 4:25

2) Carbon Cycle - 5:12
A) Plants - 5:48
B) Fossil Fuels - 6:40
C) Oceans - 7:12
D) Global Warming - 7:35


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What is a trade deficit? Well, it all has to do with imports and exports and, well, trade. This week Jacob and Adriene walk you through the basics of imports, exports, and exchange. So, you remember the specialization and trade thing, right? So, that leads to imports and exports. Economically, in the aggregate, this is usually a good thing. Globalization and free trade do tend to increase overall wealth. But not everybody wins.

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Mark, Eric Kitchen, Jessica Wode, Jeffrey Thompson, Steve Marshall, Moritz Schmidt, Robert Kunz, Tim Curwick, Jason A Saslow, SR Foxley, Elliot Beter, Jacob Ash, Christian, Jan Schmid, Jirat, Christy Huddleston, Daniel Baulig, Chris Peters, Anna-Ester Volozh, Ian Dundore, Caleb Weeks

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Today, Carrie Anne is going to take a look at how those transistors we talked about last episode can be used to perform complex actions. With the just two states, on and off, the flow of electricity can be used to perform a number of logical operations, which are guided by a branch of mathematics called Boolean Algebra. We’re going to focus on three fundamental operations - NOT, AND, and OR - and show how they were created in a series of really useful circuits. And its these simple electrical circuits that lay the groundwork for our much more complex machines.

*CORRECTION* AT 1:27 the graph says "Quinary System" but then the graph shows 10 possible states - which is actually decimal. Technically, there should be only 5 possible values there, but the overall concept is still the same.


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