Some five billion years ago, when the Sun was young and spinning some two hundred times faster than it spins at

present, its magnetic field, which extends far beyond its surface, had to spin with it. That's because electrical

conductors like the Sun drag their magnetic fields around with them when they move or spin. And you can think of the

Sun's magnetic field as a "great magnetic egg beater," spinning through the electrical particles in its

neighborhood, like a great wire egg beater spinning through the eggs.

Now stars get hot by falling together by gravity, not by nuclear fusion, and the bigger they are, the hotter they get.

And the Sun is big enough to shine in the ultraviolet, and this ultraviolet radiation knocks the electrons off the atoms

in the region round about. Those electrical particles are what I think of as the eggs. But there are different kinds of

eggs. There would be different kinds of atoms in the gas around the Sun. There would be hydrogen and helium of course,

because they are the main ingredients in the Sun. But there would be all sorts of other atoms in smaller amounts, like

carbon and oxygen, silicon and sulfur, and heavier atoms like iron, and each with a single electron knocked off by the

ultraviolet light.

Now the magnetic push on the particles is in proportion to the charge on the particles, so it's the same push for all of

them, no matter how heavy they are. But the heavier ones are harder to push, so they stay in closer to the Sun. That's why

the planets near the Sun are made of iron and rock while the planets farther out are made of the lighter materials. But

most of the stuff of the cloud is blown far away. Much of it may join what's known as the "dark matter" in the halo of the

galaxy.

It is probable that the Sun's magnetic egg beater is largely responsible for sorting the material in theSolar System so

that the denser planets would be near the Sun. But you can think of Jupiter and Saturn, as stars, partly because they

are made of the same stuff as the Sun, but mostly because they spin so fast. Eighty percent of the angular momentum of

the Solar System is in Jupiter, and most of the rest is in Saturn. And we also know that where we are in the disc of the

Milkyway, things are spinning too fast for a single star to pull together alone.

When a cluster of stars is formed from a cloud of dusty gas in the disc of the Milkyway, most of the gas and dust of the

cloud is blown away by the stellar winds of the stars. And most of the angular momentum of the cloud is transferred away

by their great magnetic egg beaters. The spinning magnetic fields of the stars transfer most of the angular momentum of

the cloud to the material which is blown away. And this transfer slows down the spins of the stars. The reason that

the discs of the galaxies are so flat is because the angular momentum of the globular cluster stars and the stars of the

central bulge has been transferred to the material which later formed the disc.