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Astronomy Cast, episode 181 from Monday, March 15, 2010. Rotation.

Welcome to Astronomy Cast, our weekly facts-based journey through the cosmos to help you understand not only what we know, but how we know what we know.

My name is Fraser Cain, I'm the publisher of the universe today, and with me is Dr. Pamela Gay at Professor at Southern Illinois University.

Hi Pamela, how are you doing?

I'm doing well, how are you doing?

Excellent, as usual.

Alright, so everything in the universe is spinning.

In fact, without this rotation, life on Earth wouldn't even exist.

We need the conservation of angular momentum to flatten out galaxies and solar systems and to make planets possible.

Let's find out about the physics involved with everything that spins and finally figure out the difference between centripetal and centrifugal force.

Man, there is nothing that makes physics geeks matter than to misuse centrifugal and centrifugal force.

Honestly, I have no idea the difference, barely care, but I know that if I'm going to be having polite conversations with physicists and I don't want to get sucked and knows, I dare not make this difference.

You know, when I am spinning a bucket of water and the water is sitting inside the bucket, that's centrifugal force.

Is that right?

So the water staying in the bucket is centrifugal force.

centrifugal force.

The bucket moving in a circular motion is because it's experiencing a centrifugal force.

Okay, all right, so start from the beginning.

Start wherever you like.

So I have to admit, when I teach class, over fear of saying the wrong thing and everyone in my class knows the difference because they read XKCD, I actually say it's the MV squared over our force.

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