Gravitation: The Four Fundamental Forces of Physics #3
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Hank continues our series on the four fundamental forces of physics with a description of gravitation - the interaction by which physical bodies attract with a force proportional to that of their masses, and which is responsible for keeping planets in orbit, among other things.
Jun 14, 2012 1:44 PM
Re: Gravitation: The Four Fundamental Forces of Physics #3
They say that gravity travels at the speed of light. So I guess if our sun magically and suddenly became ten times more massive then the Earth's orbit wouldn't start to be affected at all until eight minutes later when the increased number of gravitons hit us?
By: KeyserSosay
Re: Gravitation: The Four Fundamental Forces of Physics #3
That's right.
But we don't need magic to see it. If gravity propagates at the speed of light, the direction of the sun's gravitational influence always would be exactly parallel to the sunlight; if it propagates instantaneously or faster than light, its direction would be "leading" the sunlight, somewhere toward where the sunlight will be coming from eight minutes in the future. From our inertial frame, where we see the light from the sun or distant stars in our sky "now," is where those objects "really are now" for all physical purposes, including gravitation.
But we don't need magic to see it. If gravity propagates at the speed of light, the direction of the sun's gravitational influence always would be exactly parallel to the sunlight; if it propagates instantaneously or faster than light, its direction would be "leading" the sunlight, somewhere toward where the sunlight will be coming from eight minutes in the future. From our inertial frame, where we see the light from the sun or distant stars in our sky "now," is where those objects "really are now" for all physical purposes, including gravitation.
