# Thread: Where does a pendulum get the energy to spin relative to the ground?

1. ## Where does a pendulum get the energy to spin relative to the ground? var addthis_config = {"data_track_clickback":false};

Or, where does the energy, which is the difference between the pendulum's rotation, and the Earth's rotation, come from? Empty space?

2. from the air with the guide of commanding force!

3. gravity ?? maybe I dunno

4. You need no energy to turn the pendulum's swing direction relative to the ground. Foucault's pendulum is initially deflected manually and swings forth and back in its initial direction. Then the earth keeps spinning around its north-south axis by 15.04°/h.
Between the plane of the swing of the pendulum, and the line on ground which indicates the direction of the plane of swing at the pendulum's release time, there is an angular motion of
1-cos(lattitude)*15.04°/h
But this angular motion between initial and initial and actual direction of swing needs no energy - it is just an indication of slowly increasing angle between a fixed line (the pendulum swing) and a moving line (the one on the earth's surface)

5. The pendalum doesn't rotate - the earth rotates. We are rotating with the earth, so from our perspective, it will appear to rotate, even though it actually doesn't.

The energy that causes the earth to rotate is the same residual energy that makes the galaxies move away from each other - whatever that initial impetus may have been (I'm not going to get into a religion vs science discussion here!) It's also the same energy that makes the solar system spin, and the galaxy spin, etc...

In my opinion, Foucault's Pendalum in France is the best empiracle evidence of the earth's rotation - before that, we only had mathematical evidence (which can be suspect at times.)

6. hey dude