I'm sure you've heard of Isaac Newton and maybe of some of his laws. Like, that thing about "equal and opposite reactions" and such. But what do his laws mean? And how do they help us understand the world around us? In this episode of Crash Course Physics, Shini talks to us about just that.

***
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This week Hank introduces skepticism, exploring everything from the nature of reality through the eyes of a 17th century philosopher and, of course, The Matrix.

--

PBS Digital Studios wants to get to know you better! If you have 10 minutes, we'd really appreciate it AND you'll be entered for a chance to win a t-shirt! https://www.surveymonkey.com/r/pbsds2016

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Images and video via VideoBlocks or Wikimedia Commons, licensed under Creative Commons by 4.0: https://creativecommons.org/licenses/by/4.0/

"The Matrix" stills copyright 1999 Warner Bros. Entertainment Inc.

“Crowd with Violin Playing” by Freesound user alukahn: http://freesound.org/people/alukahn/sounds/144139/


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Crash Course Philosophy is sponsored by Squarespace.
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This week on Crash Course Theater, Mike is acting like theater started in Greece. Well, for the western theater, this is true. The earliest recorded drama in the west arose in Athen, and these early plays grew out or religious ritual. Namely, they evolved from the worship of Dionysus, god of wine, fertility, and RITUAL MADNESS. That's right. I said RITUAL MADNESS

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Anatomy & Physiology continues with a look at your biggest organ - your skin.

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Chapters:
Introduction: All About Skin 00:00
Skin Layers: Epidermis, Dermis, & Hypodermis 1:30
Types of Epidermal Cells: Keratinocytes, Melanocytes, Langerhans Cells, and Merkel Cells 2:15
Layers of Skin: Stratum Corneum, Stratum Lucidum, Stratum Granulosum, Stratum Spinosum, and Stratum Basale 4:15
Layers of the Dermis: Papillary, Reticular, and Hypodermis 6:59
Review 8:48
Credits 9:18

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Next stop in our tour of your sensory systems? VISION. With a little help from an optical illusion, we take a look inside your eyes to try to figure out how your sense of vision works -- and how it can be tricked.

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Chapters:
Introduction: Optical Illusions 00:00
How Does Light Work? 1:31
Structure of the Eye 2:31
Layers of the Eye: Fibrous, Vascular, and Inner Layers 3:33
The Retina 4:56
Rods and Cones 6:07
How do Optical Illusions Work? 7:15
Review 8:33
Credits 9:14

***
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Slavery was inherently cruel and unjust, and it was cruel and unjust to different people in different ways. Today, Clint Smith teaches you about the experience of enslaved women, and how their experience of slavery was different than men. Women had a unique vantage point to understand slavery, and were particularly vulnerable to some terrible abuses under the institution.

Clint's book, How the Word is Passed is available now! https://bookshop.org/a/3859/9780316492935

SOURCES
- Samuel H. Williamson & Louis Cain, "Measuring Slavery in 2016 dollars," MeasuringWorth, 2020.
-"A Prelude to War: The 1850s." African American Lives: The Struggle for Freedom, by Clayborne Carson et al., Pearson Longman, 2005, pp. 221-222.
-Modern History Sourcebook: Sojourner Truth: "Ain't I a Woman?", December 1851
-Quoted in Deborah Gray White, Ar' n't I a Woman? Female Slaves in the Plantation South, rev. ed. (New York: Norton, 1999), 102.

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#crashcourse #history #blackhistory

Today we conclude our unit on Philosophy of Religion and Hank gets a little help from Indiana Jones to explain religious pragmatism and Pascal’s Wager, fideism, and Kierkegaard’s leap to faith.

--

“Indiana Jones” © Copyright Walt Disney Studios
All other images and video via VideoBlocks or Wikimedia Commons, licensed under Creative Commons BY 4.0: https://creativecommons.org/licenses/by/4.0/

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Hank calls in a friend to do his push-ups for him today to explain how skeletal muscles work together to create and reverse movements. Hank and Claire also demonstrate the role size plays in motor units, the three-phase cycle of muscle twitches, and how the strength and frequency of an impulse affect the strength and duration of a contraction. This episode also explains twitch summation, tetanus, and isotonic vs. isometric movements.

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Chapters:
Introduction: Heavy Lifting 00:00
How Muscles Push & Pull 1:13
Functional Muscle Groups: Prime Movers, Antagonists, and Synergists 2:27
Motor Units 3:49
3 Phases of Muscle Twitches: Latent, Contraction, Relaxation 4:41
Graded Muscle Responses 5:22
Temporal Summation vs Tetanus 6:19
Multiple Motor Unit Summation (Recruitment) 7:07
The Size Principle of Recruitment 7:52
Isotonic vs Isometric Movements 8:50
Review 9:28
Credits 9:59


***

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***SUBBABLE MESSAGES***

TO: Ariela
FROM: Gavi

I love you so much, stay awesome as always!

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I love you!

***SUPPORTER THANK YOU!***

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In this episode, Hank welcomes you to the new age, to the new age, welcome to the new age. Here he'll talk about transmutation among elements, isotopes, calculating half-life, radioactive decay, and spontaneous fission.

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--
Table of Contents

Radioactivity
Transmutation Among Elements and Isotopes
Calculating Half-Life
Radioactive Decay
Spontaneous Fission
--

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Empire, imperialism, and colonialism are all interrelated tactics of geopolitics that are used to achieve similar goals of one state maintaining economic, political, or even cultural dominance over other territories. Today, we’re going to unravel the impacts of colonialism at different times throughout history from Taiwan to Myanmar as we examine the longstanding impacts of these relationships. We’ll also take a look at how some countries today, like Thailand, have taken the control of the narrative through culinary colonization.

SOURCES

General:
Getis, Bjelland, and Getis. Introduction to Geography, 15 ed. McGraw-Hill Education. 2017. ISBN: 978-1-259-57000-1

Gregory, Derek, Ron Johnston, Geraldine Pratt, Michael Watts, and Sarah Whatmore, eds. 2009. The Dictionary of Human Geography. 5th ed. Willey-Blackwell. ISBN: 978-1-4051-3288-6

For a free and open source option for Intro to Human Geography, see: https://humangeography.pressbooks.com/

For a free and open source option for World Regional Geography, see: https://worldgeography.pressbo....oks.com/front-matter

Cracking the AP Human Geography Exam: 2020 edition.  The Princeton Review.

Taiwan: 
http://dlc.dlib.indiana.edu/dlc/bitstream/handle/10535/7376/402.pdf?sequence=1&isAllowed=y
http://d-scholarship.pitt.edu/16493/
https://www.brookings.edu/rese....arch/taiwans-economi
https://www.cia.gov/the-world-....factbook/countries/t
https://eh.net/encyclopedia/th....e-economic-history-o
https://journals.openedition.o....rg/chinaperspectives

Condensed history of Asian Empire:
http://afe.easia.columbia.edu/....main_pop/kpct/kp_190

Mongolia:
https://www.nationalgeographic.....com/culture/article
https://geohistory.today/mongo....l-empire-effects-rus

Myanmar:
https://www.cia.gov/the-world-....factbook/countries/b
https://www.bbc.com/news/world....-asia-pacific-129928
https://www.newmandala.org/col....onialism-and-ethnic-
https://newint.org/features/2008/04/18/history/
https://en.wikipedia.org/wiki/History_of_Myanmar

Thailand
https://www.cia.gov/the-world-....factbook/countries/t
https://arrow.tudublin.ie/cgi/viewcontent.cgi?article=1140&context=dgs

Qing Dynasty
https://en.m.wikipedia.org/wiki/Qing_dynasty

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#CrashCourse #Geography #Colonization

What is an underground economy? Whether you call it a black market, a grey market, or just the shop down the street, its about connecting people with goods outside of official channels. Some stuff happens in the underground economy because it's illegal, but a lot of the money that moves around this way is exchanged for pretty mundane goods and services. We'll talk about how these things work, and the awesome ways that economists figure out where all that money is.

In the penultimate episode of Crash Course Anatomy & Physiology, Hank explains your adaptive immune system. The adaptive immune system's humoral response guards extracellular terrain against pathogens. Hank also explains B cells, antibodies, and how vaccines work.

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Chapters:
Introduction: Adaptive Immune Responses 00:00
How B Cells Identify Antigens 2:14
B Cells Become Effector Cells & Memory Cells 4:05
How Antibodies Fight Antigens 5:22
Active and Passive Humoral Immunity 6:03
How Vaccines Work 6:27
Review 8:30

***

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How did we get here? Well, in terms of Atomic Chemistry, Hank takes us on a tour of the folks that were part of the long chain of other folks who helped us get to these deeper understandings of the world. From Leucippus to Heisenberg to you - yes, YOU - the story of Atomic Chemistry is all wibbly-wobbly... and amazing.

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--
Table of Contents

Leucippus, Democritus & Atomic Theory 0:09
Discharge Tubes 1:52
Ernest Rutherford & The Nucleus 4:22
Chemistry = Math 7:22
Niels Bohr Model 5:32
Heisenburg & Quantum Theory 6:35
--

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Hank tries not to stress you out too much as he delves into the functions and terminology of your sympathetic nervous system.

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Chapters:
Introduction: Physiology of Stress 00:00
How Signals Travel to Effectors 1:48
Hormones & Neurotransmitters Communicate Stress 2:15
Preganglionic Fibers Release Acetylcholine (ACh) 3:42
Postganglionic Fibers Release Norepinephrine 4:34
Adrenal Glands Release Norepinephrine and Epinephrine as Hormones 5:10
Neurotransmitters vs. Hormones 6:01
How Norepinephrine Works: Alpha and Beta Receptors 6:29
Review 9:29
Credits 10:18

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Why do we sleep? Well... that's a tricky question. More easily answered is the question, "How do we sleep?" In this episode of Crash Course Psychology, Hank discusses some of the ways our brain functions when sleeping and how it can malfunction as well.

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

--
Chapters:
Introduction: What Happens When We're Sleeping? 00:00
What is sleep and why do we do it? 1:20
How do we sleep? 1:56
Rapid Eye Movement (REM) 2:38
4 Stages of Sleep 3:08
Sleep Deprivation 4:28
Sleep Disorders 4:47
What do we dream about? 6:08
Why do we dream? 7:26
Review & Credits 9:46
--

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In this episode of Crash Course Film History, we talk about the development of the language of films by filmmakers like Edwin S. Porter and his films; Life of an American Fireman and The Great Train Robbery.


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Images and Video Used are in the Public Domain and from the Library of Congress.

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In today's episode, Phil looks at how gravity plays out across the universe.

This episode is sponsored by Squarespace: http://www.squarespace.com/crashcourse

Check out the Crash Course Astronomy solar system poster here: http://store.dftba.com/product....s/crashcourse-astron

--
Chapters:
Introduction 00:00
Understanding Mass 1:11
What is Gravity? 2:17
Different Types of Orbit 3:41
Escape Velocity 5:30
Why Are Astronauts Weightless? 7:03
Gravity Warps Space 8:17
Review 8:43
--

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PHOTO/VIDEO CREDITS
First photo by Roscosmos / NTSOMZ/ SRC "Planeta" / zelenyikot.livejournal.com
http://www.slate.com/blogs/bad...._astronomy/2013/09/2
http://commons.wikimedia.org/w....iki/File:Portrait_of
http://en.wikipedia.org/wiki/I....saac_Newton#mediavie
http://en.wikipedia.org/wiki/J....ohannes_Kepler#media
http://en.wikipedia.org/wiki/K....aren_L._Nyberg#media
https://www.youtube.com/watch?v=doN4t5NKW-k

Today we're talking about the heart and heartthrobs -- both literal and those of the televised variety. Hank explains how your heart’s pacemaker cells use leaky membranes to generate their own action potentials, and how the resulting electricity travels through the cardiac conduction pathway from SA Node to Purkinje fibers, allowing your heart to contract. He's also going to make you better able to spot inaccuracies in medical dramas by explaining how defibrillators work to reset the rhythm of your heart.

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Chapters:
Introduction: Cardiac Arrest 00:00
Cardiac Muscle Tissue Structure 1:24
Pacemaker Cells - The Brain of Your Heart 2:49
The Intrinsic Cardiac Conduction System 3:56
How Defbrilators Work 6:46
Review 8:33
Credits 9:07

***

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TO: Beth
FROM: Joey

I Love You Beth Ronie With All Of My Heart!

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TO: The WORLD
FROM: Future Is The Future

Awesome gender neutral vintage clothing: http://futureisthefuture.com

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From towering mountains to pebbles along a river, the Earth is made of a huge variety of rocks. In today's episode, we're going to follow the rock cycle of a piece of granite in the Himalayan mountains, and as you'll see, every rock has a far-reaching story to tell often millions of years in the making.

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#CrashCourse #Geography #Rocks

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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