Monday, January 30, 2012

Solar mass

Physic master classes puts it nicely and clearly:

There are four interactions known to science, they are called gravity, electromagnetism, weak and strong. These interactions often manifest themselves as forces between particles.
  • The gravitational interaction, for example, is responsible for the attractive force between masses.
  • The electromagnetic interaction is responsible for the attractive or repulsive forces between charges.
Gravity is the most familiar interaction to us, but it is by far the weakest of them all. Gravity acts on mass, and it is because we live next to a very big mass - the Earth - that gravity is so important to us. Gravity holds the planets in orbit around the Sun, it controls the behaviour of galaxies, and it is responsible for the large scale behaviour of the Universe.

The electromagnetic interaction is what brings light and energy to us from the Sun and holds electrons in orbit around nuclei to form atoms. Whereas gravity acts on mass, electromagnetism acts on electric charge - in fact we can think of mass as the charge of the gravitational interaction. Wherever there are electric charges, electromagnetism is at work - bringing electricity into our homes, painting the picture on our television screen, or causing dramatic bursts of lightning like this...

The quoted text helps us students to understand that the Sun has huge mass and so the weak force of gravity holds planets on their orbits around it. And kept those jumping American astronauts on the surface of the Moon.

Well then, how heavy is the Sun?

1,989,000,000,000,000,000,000,000,000,000 kg

Honestly, lots of zeros but I find it difficult to count how many and cannot grasp the meaning of them.

Again, Wikipedia comes to help:

The solar mass () is a standard unit of mass in astronomy, used to indicate the masses of other stars, as well as clusters, nebulae and galaxies. It is equal to the mass of the Sun, about two nonillion kilograms.

This is about 

332,950 times the mass of the Earth or 
1,048 times the mass of Jupiter.

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