Dartmouth Professor Discusses Foucault's Pendulum

Physics and astronomy professor Jim LaBelle discusses the science behind a classic physics experiment, Foucault's pendulum, while seated next to Dartmouth's pendulum in Fairchild Tower.

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[VcTrification]

some people just want to watch the world turn

[Tocsin-Bang]

One of my earliest memories in science was of the Foucault's pendulum in the London Science Museum, it was suspended down the stairwell in the entrance. Sadly no longer there. Many years later after taking a physics class on a visit, and finding it was gone, we set one up in a stair well in the science block.

[haloodst]

The scientist explaining the pendulum: ^
The pendulum: “i came in like a WREEECKING

[salinayacovone]

explains this better in 3 mins than my professor does in a class period 👏

[carnafillian]

To the doubters:
Step 1: sit in office chair
Step 2: make pendulum using a string and weight (or just headphones).
Step 3: sitting still, hold the string end up and drop the weight so it swings freely (it goes back and forth in a plane)
Step 4: repeat step 3 but this time spin yourself in the chair first. When u drop the weight this time, the plane of the pendulum's motion will now rotate (at least it will appear to in the "chair" frame of reference) and the pendulum motion will appear erratic.
This is analogous to the earth-pendulum subject.

Note: if the pendulum motion in Step 4 results the weight hitting u in the face, just know that's physics hitting u in the face.

[rvdende]

It will stop eventually, its just very heavy and the air doesn't slow it down fast enough to notice. I imagine there will also be some friction at the top of the cable where it is hanging from.

Now, if you could encase this inside a vacuum chamber, reducing air friction, it will swing much much longer.

[eertlmontag]

Thank you, Dr. Gregory House. Lovely explanation

[milindayapa]

The best explanation possible! No one talks about how the pendulum is mounted which is the most important detail.

[gliddeninstructionalvideos]

thank you for the upload, that last excerpt "like blew my mind man"

[aswathip.v.]

Thank you so much for the video. Really liked the way of talking and teaching. Expect more videos about various physics topics

[bigboam]

One of the best explanations of this experiment I've ever heard. Thanks and aloha!

[TheMinion]

At least he was honest at the end. May we all have peace at heart.

[TedJerome]

Short answer: it's powered.
Longer answer, from Dartmouth's website:
The pendulum uses an electronic mechanism to keep it going; otherwise it would lose its energy due to friction and stop after a few hours.

[arsenic]

Doesn't it stand to reason that there is an "absolute" in angular velocity? There is no absolute linear motion, but this pendulum kinda shows that there is an "absolute" value to be derived for angular velocity. Analogous to "the universe as a whole" is just the zero reference of rotation.
Am I missing something?

[RaytheonNublinski]

It’s so simple and so undeniable. Flat earthers foiled again by a ball on a string. 😂

[StaticBlaster]

I just read The Accidental Universe by Alan Lightman and he briefly mentioned this experiment in the last chapter of his book. He was talking about all the great revolutions of science and how we came to our current understanding of the universe as a whole. Brilliant book. It's a riveting and engaging read. You'll enjoy it.

[anandg]

One question on the North Pole situation. Since the pendulum is hung from a structure connected to earth and initially the structure and pendulum are all rotating with earth, shouldn't the plane of oscillation also rotate and for an observer on earth, it should appear as if the plane of oscillation appear to be static?

[OudeicratAnnachrista]

2:18 he says it can be used to detect "the rotation -- the revolution of the earth around the sun" or even the solar system around the galaxy. But what is he talking about?
The orbit around the sun or around the galaxy is not a "rotation", it's freefall - it shouldn't be possible to detect in any local way without an external reference (like the stars, galaxies or CMB)

[rbspider]

Wish they would show the other end of that cable.

[SnoverDS]

I took the liberty of paraphrasing the Professor's question, a bit:

"How does this pendulum, here, on our little spinning planet, going around its sun, going around the Milky Way, etc, know something about the wider universe?"

It doesn't. Like the ratio of pi (or any other constant you care for), it only illustrates the nature of the universe itself. By building the pendulum, we just gave ourselves a tool to see what the universe is doing; what is otherwise too small an effect for us to perceive in our daily lives, but, nonetheless, has been there all along because it's just the way the universe works. Foucault gave us a brilliant way to illustrate the action of the universe.

Maybe that's why these Foucault Pendulum exhibits commands such attention? Because at some instinctive level we know we are seeing something amazing, even if we can't explain why. Watching a ball swing back and forth? Not most people's first idea for something interesting to do. But set one up and watch: most people will stop and observe, at least for a few minutes. Or in my case, hours.