The conservation of angular momentum (Unit 20 ) says that a contracting gas cloud must spin faster as it gets smaller.
a. Suppose the material orbiting today at 1 AU began 1 ly away. By what factor has its orbital radius changed?
b. Material orbiting at 1 AU today (like the Earth) is moving at $30 \mathrm{km} / \mathrm{sec} .$ According to the conservation of angular momentum, how fast was its rotation speed when it was at a radius of 1 ly?.