What Physics Teachers Get Wrong About Tides! | Space Time | PBS Digital Studios

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We all know tides have something to do with gravity from the Moon and Sun, but if gravity affects the motion of all objects equally, then how come oceans have large tides while other bodies of water don't? It's because your mental picture of the tides is probably WRONG!!! Join Gabe on this week’s episode of PBS Space Time as he sets the record straight on tidal force, gravitational differential and what role the moon actually plays in tides. Why don't lakes have tides? Watch the episode to find out!

Emily Rice (NASA Space Apps Challenge talk on Exoplanet Atmospheres):

Sean Carroll (lecture notes on general relativity):

For Additional Info on tides:

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COMMENTS:

Johan 't Hart

Marcos MH

Campbell McLauchlan

Pedro Gusmão

Michael Winter

Anthony Englert (antenglert)

Ciroluiro

electrocat1

dligac

KRIGBERT

Mark G

Arunabha D.

Iwon't tellmyname

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Let us know what topics you want to learn more about:

[ScienceAsylum]

Dude, you just blew my mind. I'm a physics teacher. Thank you for the correction. I will not make this mistake in the future. I've only had moments like this a few times in my life, but they have a way of making you feel enlightened and guilty at the same time.

[tibees]

awesome to see so many people updating their knowledge based on new information and not being salty about it

[friendlyfire]

Two things: 1. You would have done well to show why the arrows go left on the left side of the screen. It seems by your logic they would go out. 2. Why do you have the tides occurring at the north and south

[crystalclark]

I will now not cover tides and gravity in my class today, as I need to watch this video again - I found it hard to follow the fast talking, but I obviously need to learn more and not be so confused before attempting to teach it! Thank you.

[mylesmackey]

The extent to which you guys interact with channel followers is incredible. I've never seen a channel attempt to answer so many viewer's questions and with such detail and genuine interest. Keep up the great work, this channel is amazing!

[mickblock]

This guy speaks so clearly. I don't always understand what he's explaining, but I'm always impressed about how well he speaks. I seriously am curious to know if this guy has ever mispronounced a word or uttered "uuuuhm."

[AshPragasam]

6:53 "A human is basically a big sack of water" I had to pause and look at the wall for a few hours

[Morningstar]

I still Dont get this, they all say the bulge is already there, if bulge of water is always there how come entire earth is rotating under that bulge without being drowned? Does this also means that all fishes and turtles stays on the same bulge and earth just is sweeping under them.
My head is spinning 😅

[fiveohfivethree]

"Everything I just said is oversimplified" I didn't understand a word you just said. I've never felt so stupid.

[jhettema]

Man, forced staying home really gives the possibility to learn things. Thanks!

[Amamos]

I've been trying to understand the two tides a day for over an hour now from many sources.

I clearly see you know what you are talking about.

But I still can't understand the most important part, the directions of the tidal vectors.

I can see the 0 degree, point A, vector being a rotation inward, but not a direct 180 degree arrow.

Also, can't understand a 350 degree vector pointing away from the moon side, neither the 270 degree one totally opposing the moon.

Can you or any other viewer help me with this?

Thanks!

[ultimatedeatrix]

Wow this channel never fails to impress me. I just watched a video on how tides work which was similar to the description he gave in the first 4 minutes and left confused why do the effects only occur in oceans. This video cleared it up so well.

[brianxx]

I watched until 2:30, then missed the rest because I switched Earth's gravity off and had to swim very far to reach any air.

[MarshmallowRadiation]

This confirms what I've thought for a while: fluid dynamics is frickin weird.

[DavidHeizer]

The bit around 7:09, where the surface of the Earth lifts up to meet the elevated swimming pool water, also explains how planets with no liquid oceans can become tidally-locked (as, in fact, is the Moon itself): these forces operate on the whole planet, not just the water. (The oceans just react to it more dramatically.)

[garysmith]

I liked when you talked about the nooks and crannies having larger tides. It's comparable to what makes the windy city so windy.

[SharksfootSoup]

OK, then, the mind of this physics teacher changed! I will (a) revise my explanation of tides and (b) mention tides when I talk about pseudoforces, which I never thought of before. It's an awesome example!

[nothingnewhere]

Great video! I was a physics major. My class was taught that there were imperceptible tidal effects on both land and inland water bodies because of tidal forces. There is a mathematical approach to this in the undergraduate text Thorton's Classical Dynamics of Particles and Systems using similar assumptions -- for anyone who is interested. It gives functions for these tidal forces that can be used to calculate a vector at any point - using those assumptions. Going through it you will get math for what the man in the video is presenting. Although I think the title is a bit misleading, partially because I wasn't taught the incorrect way he mentioned at the Community College, Undergraduate, or Graduate level, the detail he stresses is an important one and often left out. I really enjoyed this video, thanks!

[siobhangraham]

The force isnt "fake, " it exists - you can find terms for it in the frame of the earth when you derive Newton's laws of motion. It's a fictive force - which means it arises as an interaction between an object and the frame, rather than between objects.

[NativeSonDC]

After about five and a half minutes into this video I decided that tides aren't important enough for me to understand.