Science Mystery: Where Did the Spin Go?

by Roger Bourke White Jr., copyright December 2017


This is a science mystery that just came to mind.

The sun and planets of the solar system were created from a cloud of gas and dust that existed in this area before the sun and planets were created. The cloud condensed into the sun, planets and other icy and rocky bodies that orbit the sun.

Here is the mystery: What happened to all the angular momentum of this gas and dust -- its spin -- as all this condensing into planets and the sun was occurring? If it was conserved then the sun in particular should be spinning like a furious top, not rotating placidly in a way that takes 20+ days to complete a rotation. By comparison, Jupiter seems to a conserved its spin. It rotates in about ten hours.

So this is the mystery: Where did all the spin go?

Creating a Solar System

Conventional wisdom is that the sun and solar system were created from a cloud of gas and dust. The cloud was a slowly orbiting mass that for some reason, perhaps because of getting compressed by a mass of debris blowing in from a nearby supernova, began condensing rather than continuing it timeless spinning.

Most of the mass that condensed ended up in the sun. A small amount condensed into orbiting planets and their moons and a teensy amount condensed into smaller rocky objects such as asteroids.

As the sun heated up and began shining the gas which had not condensed into the sun or any of the orbiting objects was heated up and driven off into interstellar space.

As an explanation: so far, so good. Now comes the mystery that I just came up with.

Where did the spin go?

When a spinning object contracts its rate of spin increases. This is conserving angular momentum. You can feel this happening personally if you spin on a chair with your legs spread out, then pull them in so they are close to the chair. Your rate of spin will increase. It's an exciting feeling.

So, this big, diffuse cloud of gas and dust is going to contract into a much smaller sun and planets. This contraction should be amplifying the spin -- things should be spinning a lot faster. In the case of Jupiter and Saturn it seems to have done so. These planets have rotation periods of just a few hours. But the sun and the other orbiting bodies haven't followed their example. The sun, instead of rotating in just a few minutes, rotates in 20+ days. (there isn't a single number because the rotation rate is different between the equator and the poles)

So, what happened to all that angular momentum? Where did it go, or what transformed it into some other form of energy, such as heat?

Adding to the mystery: whatever transformed the angular momentum in the sun's rotation didn't affect orbiting planets or asteroids. They have conserved their angular momentum for 4.5 billion years now.


This is a mystery. There is probably a good explanation, but I haven't encountered it yet. Now I will be researching.



--The End--