One of my students, Jacob, just popped open the door and said"Question! When a space shuttle docks onto the International Space Station...does it bring its orbit closer to Earth...because of the mass change?"
Whew. I have to chew on that for a while. Here is what I am thinking....the difference in mass is so minute in comparison with the scale of the orbit of the station that it doesn't really affect the orbit distance. Kind of like the idea that technically I have a gravitational pull on the Earth, but since my mass is so much smaller than the Earth's it doesn't really matter. Hmmm....
Then the conversation turned to whether or not satellites naturally fall to the Earth. My first thought was, yes, they do. However, upon further reflection...and some searching...I realized that it has a lot to do with centripetal acceleration. A satellite reaches an optimum speed and the centripetal force outward balances the pull of Earth's gravity. Kind of like when something is swung on the end of a string. If its not fast enough it won't move in a circle and all is lost.
I guess when you breed critical thinking...your morning gets completely turned upside down in one question.
Jacob....want to comment?
1 comment:
Recently, I found an interesting answer to the question had posed when reading A Brief History of Time by Stephen Hawking. In one of the chapters he discusses the properties of the four fundamental forces in the Universe: the Strong, Weak, Electromagnetic, and Gravitational forces. He informs the reader that we can think of these fundamental forces as particles with specific integer "spins" that act on all particles of matter in the universe with non-integer "spins" and that these force particles come in two states. The state were are not so familiar with is when the force particles act as "virtual" particles and cannot be observed or directly detected. For instance, a proton, having positive charge, and an electron, having a negative charge, attract each other by exchanging the Electromagnetic force carrying particle, the photon. These exchanging photons are virtual and cannot be directly observed, we can only indirectly observe their effects on the charged particles. However, we can change the state of the force carrying particles from virtual to a state when it becomes real and acts as a wave. This is done every time we get an x-ray. When a charged particle such as a proton suddenly changes its direction, it leaves the virtual photons that surround it behind, far away from any charged particle, they have to become real and act as waves.
Now, In the case of a satellite whizing around the earth, or the earth traveling around the sun, every particle in the each of the bodies of matter exchange a force carrying particle of Gravity, called the graviton. We all know that stuff... whether it be a neutron, an electron orbital, or earths ecosystem, naturally behaves in order to attain a stable state. In the case of stars, planets and satellites, the most stable state possible that two bodies orbiting each other can attain, is a single body of mass. In order to do this, the bodies emit gravitational waves which were once in the form of virtual gravitons, at very slow and weak paces. Eventually, they fall into each other.
I find this very interesting, and I'm glad I could find out and understand why this happens.
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