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Which Way Is Down?: summary

Which Way Is Down?

Vsauce · Nov 2, 2017 · about 26 min

Uploaded Nov 2, 2017 · 31.8M views (as of Oct 30, 2026)

Good value given

Mass is how hard something is to accelerate. Weight is the pull between you and something else.
Astronauts in orbit still feel about 90% of Earth's gravity. They float because they're falling around the Earth.
You weigh about half a percent less at the equator than at the poles because of Earth's spin.
Einstein's equivalence principle says falling feels the same as floating in space with no forces.
A straight line on a curved surface is called a geodesic, and falling objects follow geodesics through space-time.

Which way is down?

Down is the direction gravity pulls you, toward the center of mass of what you're on, but it shifts slightly from place to place and over time. In the deeper answer from general relativity, gravity isn't a force at all. Mass curves space-time, and objects just follow straight paths through that curve. Since time runs slower closer to a massive object, down always points toward slower time.

Worth watching?Good value given. Starts with simple questions about weight and ends with a clear, hands-on explanation of Einstein's view of gravity. The ribbon and cone demos make a hard idea click.

ActionableLessons

Actionable

Drop a heavy and a light object that both have small surface areas and watch them land together.
Try the ribbon or paper strip test on a ball to see why lines of latitude aren't straight.
Look up the geoid map of Earth to see how gravity varies.

Lessons

Everyday words like weight and down hide surprisingly deep physics.
A good analogy, like the cone, can make an abstract idea concrete.
Newton described gravity well, and Einstein explained why it happens.

Quick answer

Vsauce posted this video on Nov 2, 2017. Here's our summary in our own words: the answer to the title, a verdict, 5 takeaways, and Actionable and Lessons tabs.

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Watch on YouTube: Which Way Is Down?

Channel: Vsauce. Published Nov 2, 2017. About 26 minutes.

No advice, but there's a fun experiment: try the ribbon test from the video on a ball or cone to see what a truly straight line looks like on a curved surface.

Quotes from the video

“mass is intrinsic, whereas weight depends on what's around”
“Bertrand Russell called this the law of cosmic laziness”
“a straight line on a curved surface is called a geodesic”

A note on this summary

This page reports what the video says, in our own words. Quotes are copied word for word from the video's transcript. Views are as of Oct 30, 2026.

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FAQ: questions people ask

Why do astronauts float if there's gravity in orbit?

They're moving sideways so fast that they fall around the Earth, so nothing pushes back on them and they feel weightless.

Is gravity a force?

In general relativity, no. Mass curves space-time and objects follow straight paths through it, which looks like falling.

Is the video worth watching?

Good value given. It's long but the demos are worth it.