Re: Basic Relativity Question from a Beginner

On May 29, 6:48 am, Albertito <albertito1...@xxxxxxxxx> wrote:
On May 29, 12:10 pm, "Dirk Van de moortel" <dirkvandemoor...@ThankS-NO-



SperM.hotmail.com> wrote:
ken.ger...@xxxxxxxxx <ken.ger...@xxxxxxxxx> wrote in message

  5efb11cf-479c-4b25-99c7-12e1fa82a...@xxxxxxxxxxxxxxxxxxxxxxxxxxx

My friend and I need a little help with a thought experiment. Any
input is appreciated.

Situation:
My friend and I each start at point A. At the same instant, we start
traveling at 60% the speed of light. He in one direction; me in the
exact opposite direction. After a certain amount of time, he shines a
flashlight back in the direction of our starting point (and me).

Questions:
Can I see the flashlight?

Yes.
Well... sort of. See below.

If so, what color is it?

:-)
See below.

What is our relative velocity to each other?

That would be
    ( 0.6 + 0.6 ) / ( 1 + 0.36 ) percent of light speed ==> 88%

The wavelength of the light you friend shone, divided by
    sqrt( (1 - 0.88 )( 1 + 0.88 ) ) = 0.064
So if he shone a blue laser with wavelenght 473 nm, you will
get a signal with wavelength 7400 nm, which is somewhere in
the infrared.
So you won't really *see* it after all :-)

Dirk Vdm

Dear Ken and friend, both of you are moving at
60% the speed of light in opposite directions wrt
the starting point, that's not good for two good
friends, is it?

Anyway, your relative speed is v = 60% + 60% = 120%
percent of light speed.

For the OP, this is an example of the crap you will find on UseNet.
Asking questions here comes with the burden of having to sort out the
gold from the crap.

The wavelength of the light you
friend shone, divided by Exp(-1.2) = 0.301. So if he shone
a blue laser with wavelenght 473 nm, you will get a signal
with wavelength 1570 nm, which is somewhere in the infrared.
So you won't really *see* it after all :-)

.

Relevant Pages

  • Re: Basic Relativity Question from a Beginner
    ... My friend and I each start at point A. At the same instant, ... exact opposite direction. ... So if he shone a blue laser with wavelenght 473 nm, ...
    (sci.physics.relativity)
  • Re: Basic Relativity Question from a Beginner
    ... My friend and I each start at point A. At the same instant, ... exact opposite direction. ... So if he shone a blue laser with wavelenght 473 nm, ... the necessity to demonstrate that your nonsense is nonsense. ...
    (sci.physics.relativity)
  • Re: Basic Relativity Question from a Beginner
    ... My friend and I each start at point A. At the same instant, ... exact opposite direction. ... So if he shone a blue laser with wavelenght 473 nm, ... the necessity to demonstrate that your nonsense is nonsense. ...
    (sci.physics.relativity)
  • Re: Basic Relativity Question from a Beginner
    ... My friend and I each start at point A. At the same instant, ... exact opposite direction. ... So if he shone a blue laser with wavelenght 473 nm, ... the necessity to demonstrate that your nonsense is nonsense. ...
    (sci.physics.relativity)
  • Re: Basic Relativity Question from a Beginner
    ... My friend and I each start at point A. At the same instant, ... So if he shone a blue laser with wavelenght 473 nm, ... the necessity to demonstrate that your nonsense is nonsense. ... Your velocity addition formula has *certainly* been ...
    (sci.physics.relativity)