Re: A89: What's Wrong?


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Re: A89: What's Wrong?




You answered your own question.  It can reach the
speed of light because it has no mass (and therefore
must always be at the speed of light, since any
amount of energy would accelerate it to the speed
of light and thermodynamics states it must have
energy).  Though Newton says light would be
unaffected by gravity since it's proportional to it's
mass, Einstein demonstrated that massive objects
bend space, affecting ALL particles, regardless of
mass.  When a planet orbits a star, the planet and
star are actually orbiting each other (usually favoring
the star since it has a much larger mass).  This is
easy to see when there are two stars in a system,
since they orbit each other so equally.  However,
light does not have mass and therefore does not
affect other objects.  So light can orbit a star (this
would be the event horizon of a black hole), but the
star will never be pulled to orbit light.

In a message dated 1/8/01 11:07:05 PM US Mountain Standard Time, 
goodsell@bridgernet.com writes:

> True, and as the mass increases, the amount of energy required to accelerate
>  the object also increases, therefore it takes an infinite amount of energy
>  to get something to go the speed of light. I admit that I don't understand
>  this stuff in the slightest, I'm just restating something I read (and 
didn't
>  understand) in Stephen Hawking's book "A Brief History of Time". The thing
>  that throws me off is the question of why light itself doesn't have 
infinite
>  mass. One can argue that light doesn't have mass to begin with, therefore
>  when you multiply its mass by infinity, you still have 0. But it is known
>  (and predicted by Einstein's general theory of relativity) that light is
>  affected by massive objects. Hawking mentions briefly that objects travel 
in
>  straight lines through space-time, but these lines appear as geodesics in
>  out 3 dimensional perception (due to the warping of space-time that occurs
>  around massive objects), which is the foundation of gravity (or something
>  like that). Light travels in geodesics as well, so at first that seems to
>  explain it... But it seems to assume that only one body is warping
>  space-time. If the mass of the light passing by a star has no effect, then
>  how is it different for a planet? Wouldn't the planet's mass have no 
effect?
>  Obviously it does. So light still seems to be an exception to the rule. Am 
I
>  the only one who is confused by this?