JohnW
Posts: 3217
Joined: Aug. 2006
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| Quote (olegt @ Aug. 08 2014,15:59) | An explanation for laymen from Astro 801 at Penn State (which has a superb Astronomy and Astrophysics department).
| Quote | | Does this mean that the Solar System is expanding? What about the Milky Way? Will Pluto get farther and farther from the Sun as the Universe expands? The answer is no, and it is a bit difficult to understand exactly why. Consider again a stable Main Sequence star. We discussed how in order for a star to avoid collapse, the outward force of the radiation pressure created by the nuclear fusion in the core balanced the inward pull of gravity. We can consider all objects and systems of objects in the universe subject to the same kind of balance of forces. The expansion of the universe can be thought of as a global force that is pulling on all objects. However, it is only strong on very large scales. At the scale of a galaxy, the gravitational force binding a galaxy together is much stronger than the "expansion force," so the galaxy does not expand. At the scale of the Solar System, the imbalance is even larger, so the gravitational binding of the Solar System easily overwhelms the "expansion force," keeping Pluto's orbital separation from the Sun the same over time. |
The bottom line: expansion of space is negligible on the scale of a solar system. |
This is way, way over Joe's head. (I know, I know... what are the odds?) He seems to think the expansion is like debris flying away from an explosion At least, that's what his comments about inertia sound like.
Stick to ticks, Joe.
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Math is just a language of reality. Its a waste of time to know it. - Robert Byers
There isn't any probability that the letter d is in the word "mathematics"... The correct answer would be "not even 0" - JoeG
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