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Man made climate change vs meteor question...

Discussion in 'Environmental Discussion' started by burritos, Feb 19, 2013.

  1. Corwyn

    Corwyn Energy Curmudgeon

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    You might start with Newton's First Law, which states (roughly) "An object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force." This will help you get rid of the notion that light is 'constantly maintaining its speed'. If it were diminishing on the other hand that would require a force, and an explanation.
     
  2. FL_Prius_Driver

    FL_Prius_Driver Senior Member

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    Light's speed varies within the material it is propagating. In some very highly engineered materials, it travels at only 15 mph.
     
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  3. austingreen

    austingreen Senior Member

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    When I took modern physics in school it was theorized that the speed limit for gravity would be the speed of light, but there was not any experimental evidence. We now have some evidence that the speed of gravity is around the speed of light.

    Chinese scientists find evidence for speed of gravity
    Kind of cool. In case you were wondering you should not be able to sense a disturbance in the force much faster than the speed of light either.:(;)

    Now we have redefined pluto to not be a planet - see tyson for that - but if the sun suddenly disapeared its warp in space time would take around 6 hours for this change to be felt by pluto. The string would be cut in your words, and pluto would continue on its way unimpeded by the sun's gravity.. Now if the sun exploded instead of disappeared this would take much longer, as the pieces of the exploded sun - mainly hydrogen, would take time to disperse, and until they did they would cause a similar warp in space time.
     
  4. Corwyn

    Corwyn Energy Curmudgeon

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    The center of mass of an exploded sun would remain the same (and thus so would Pluto's orbit) until some pieces got beyond the orbit of pluto. Pluto would likely have evaporated by then from the increased energy.
     
  5. dbcassidy

    dbcassidy Toyota Hybrid Nation, 8 Million Strong

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    You mean if the sun implodes. The star, going super nova is ending its' life in the universe. The center of mass becomes totally different compared to pre-super nova. Rapid increase in gravitional forces now rule as the once star is now a black hole. Speed of light does not matter as it become part of the singularity. Even light can not escape this.

    DBCassidy
     
  6. fuzzy1

    fuzzy1 Senior Member

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    If the sun were massive enough to do this (it isn't), the increase in gravity would be limited to what is now the star's interior. The black hole itself, out to its event horizon, would occupy only a very very small portion of the current stellar core.

    If the entire stellar mass ended up in the hole, its mass would be identical to the star from which is was born. Objects in orbit around it would feel no change in gravity. But supernovas eject their outer layers and a lot of energy, a considerable portion of their total mass, so the remaining black hole has less mass than the original star. Objects in orbit that are not fully ablated by the expelled hot gas would feel less gravity after the gas layers pass. Objects at Pluto's distance are likely to escape the weaker gravity.
     
  7. austingreen

    austingreen Senior Member

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    I was only trying to answer hills thought experiment about the sun disappearing I would not follow it to the sun exploding in a symmetrical fashion, I'm not sure how you do that, but if that is your thought experiment, once the sun stops being very small compared to the distance to pluto then you can no longer just treat it as a single point at the center of gravity, but must do a summation of the gravitation of its parts. That is most easily done by approximation of an enlarging hollow sphere, and integrating the gravitational pull, but this gets very difficult with pluto's eccentric orbit and gravitation slowing the increase of sphere size.

    What is likely to actually happen is the sun in about 5 billion years will become a red giant and engulf the earth. This will still be very small compared to the distance to pluto, so pluto will only feel the slightly smaller mass as nuclear fuel is used up. After hundreds of millions of years the fuel will start running low and the sun will become a white dwarf. In this process that IIRC takes tens of thousands of years, solar winds going millions of mph will throw off material leaving a white hot core. This material will form a planetary nebula much more distant from the sun than pluto is now. Someone else can do the calculations whether pluto just increases its orbit, or becomes part of this nebula much further out.
     
  8. dbcassidy

    dbcassidy Toyota Hybrid Nation, 8 Million Strong

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    If you traveled to the event horizon, you would not be able to report your finding. the gravitional forces exerted upon you would be unimagineable. Your would now become part of the singularity.

    DBCassidy
     
  9. FL_Prius_Driver

    FL_Prius_Driver Senior Member

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    Advance Physics trivia. There are two event horizons for a black hole.
     
  10. fuzzy1

    fuzzy1 Senior Member

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    Pluto gets only barely closer than 3,000,000,000 miles from the sun.

    The sun's surface is currently about 430,000 miles away from its center. If the sun were simply compressed into a black hole, the singularity would be located at the same point as the center of mass is now, and the event horizon would be only about 2 miles out, far far below the current solar surface.

    Converting the sun to a black hole would have no gravitational impact on Pluto. The blast wave that accompanies common black hole formation is another matter.