Which Way Is Down? ─ Vsauce

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Links to sources and to learn more below!

my twitter https://twitter.com/tweetsauce
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Thanks to Eric Langlay (https://www.youtube.com/user/ericdrav...) for producing, editing, and animating this episode with me. Thanks also to Henry Reich (https://www.youtube.com/user/minuteph...) for his advice and guidance.

Mass vs weight:

https://en.wikipedia.org/wiki/Mass_ve...
Great Veritasium video: https://www.youtube.com/watch?v=_Z0X0...
two other great videos: https://www.youtube.com/watch?v=6ccIj... and https://www.youtube.com/watch?v=aCqQz...

baseballs coming together under gravitational attraction can be simulated in Universe Sandbox 2. More math behind it can be found here: https://www.reddit.com/r/explainlikei...

Weight to mass (on surface of Earth) convertor: https://www.convertunits.com/from/kil...

pencil and Earth falling numbers: https://www.quora.com/When-we-drop-a-...

NASA HD footage: https://archive.org/details/NASA-Ultr...

Buoyancy: https://en.wikipedia.org/wiki/Buoyancy

Earth’s spin and its effect on ‘down’: http://www.freemars.org/jeff/Earth/do...

The measurement of Earth and its gravity:

https://en.wikipedia.org/wiki/Geodesy
https://en.wikipedia.org/wiki/Physica...

Movement of Earth’s center of mass:

http://www.aiub.unibe.ch/research/slr...
http://www.massentransporte.de/index....
http://citeseerx.ist.psu.edu/viewdoc/...

you get heavier before you get lighter as you descend into Earth: https://www.reddit.com/r/askscience/c...

vertical deflection:

https://en.wikipedia.org/wiki/Vertica...
file:///Users/michaellaptop/Downloads/tv_21_2014_4_697_705%20(1).pdf

practical uses of measuring gravity: https://en.wikipedia.org/wiki/Gravimetry

geoid:

https://en.wikipedia.org/wiki/Geoid
https://oceanservice.noaa.gov/facts/g...
https://www.youtube.com/watch?v=jOQl8...

Interactive Earth geoid: https://experiments.withgoogle.com/ch...

your weight when moon is overhead: https://www.thenakedscientists.com/fo...

Hammer and feather drop on moon: https://nssdc.gsfc.nasa.gov/planetary...

Why things fall at the same rate: https://www.quora.com/If-an-object-ha...

Wolfram Alpha cone geodesic tool: http://demonstrations.wolfram.com/Con...

General Relativity:

simple animation showing geodesic on cone and how it causes motion DOWN in space: https://www.youtube.com/watch?v=DdC0Q...
GREAT pbs spacetime video (watch the whole channel): https://www.youtube.com/watch?v=AwhKZ...
http://www.askamathematician.com/2009...
https://www.av8n.com/physics/geodesic...
http://www.pitt.edu/~jdnorton/teachin...
http://www.einstein-online.info/spotl...

time and gravity:

https://www.youtube.com/watch?v=jlTVI...
https://youtu.be/1ENkP0h8nAg
https://youtu.be/gcvq1DAM-DE
https://www.reddit.com/r/askscience/c...
https://www.reddit.com/r/AskScienceDi...

tests of general relativity: https://en.wikipedia.org/wiki/Tests_o...

RECOMENDED BOOKS:

great introductory texts:

“Relativity Visualized” by Lewis Carroll Epstein https://www.amazon.com/Relativity-Exp...

There’s also this PDF that takes Epstein’s diagrams into more detail: http://www.relativity.li/uploads/pdf/...

“Relativity Simply Explained” by Martin Gardener https://www.amazon.com/Relativity-Exp...

great intro to the math of general relativity:

“A Most Incomprehensible Thing: Notes Towards a Very Gentle Introduction to the Mathematics of Relativity” by Peter Collier https://www.amazon.com/Most-Incompreh...

Requires some background in relevant math topics (see above) but very very good:

“Spacetime And Geometry: An Introduction To General Relativity” by Sean Carrol https://www.amazon.com/gp/product/933...