What does it mean to say that angular momentum is conserved? Give an example you might see on Earth. How could conservaton of angular momentum help astronomers understand the development of the solar system?
When we say that angular momentum is conserved, it means that the total angular momentum of a system remains constant unless acted upon by external torques or net external forces. Angular momentum is a property of rotating objects and is defined as the product of an object's moment of inertia and its angular velocity.
An example of conservation of angular momentum on Earth can be seen in a figure skater. When a figure skater is spinning, if they pull their arms inward, their angular velocity increases, making them spin faster. This happens because the skater's moment of inertia decreases due to the reduction in the distribution of mass away from the axis of rotation. By conserving angular momentum, the product of moment of inertia and angular velocity remains constant.
In astronomy, conservation of angular momentum plays a crucial role in understanding the development of the solar system. According to the solar nebula theory, the solar system formed from a rotating, flattened cloud of gas and dust called the solar nebula. As the nebula collapsed under its own gravity, it started to spin faster due to the conservation of angular momentum. The increased rotation caused the nebula to flatten into a spinning disk, with the Sun forming at the center.
This disk then gradually evolved into the individual planets as particles collided, coalesced, and formed larger bodies. The conservation of angular momentum explains why most planets in our solar system orbit the Sun in roughly the same plane and in the same direction. It also plays a role in shaping the orbits and rotations of moons, asteroids, and other celestial bodies.
By studying the distribution of angular momentum in the solar system today and comparing it to theoretical models, astronomers can gain insights into how our solar system developed and evolved over billions of years.