De Sitter double star experiment:

http://en.wikipedia.org/wiki/De_Sitt...tar_experiment

A star in a binary star system is moving towards the earth at 'v' and
emits a photon towards the earth.

How can a photon of light be traveling at c+v towards the earth while
the star that emitted the photon is now moving away from the earth at
the same time the photon is traveling away from the star at 'c' in the
star rest frame?

On Jul 1, 5:32*am, mpc755 wrote:
De Sitter double star experiment:

http://en.wikipedia.org/wiki/De_Sitt...tar_experiment

A star in a binary star system is moving towards the earth at 'v' and
emits a photon towards the earth.

How can a photon of light be traveling at c+v towards the earth while
the star that emitted the photon is now moving away from the earth at
the same time the photon is traveling away from the star at 'c' in the
star rest frame?

What makes you think it does?

Read the results of the experiment.

On Jul 1, 9:41 am, Eric Gisse wrote:
On Jul 1, 5:32 am, mpc755 wrote:

De Sitter double star experiment:

http://en.wikipedia.org/wiki/De_Sitt...tar_experiment

A star in a binary star system is moving towards the earth at 'v' and
emits a photon towards the earth.

How can a photon of light be traveling at c+v towards the earth while
the star that emitted the photon is now moving away from the earth at
the same time the photon is traveling away from the star at 'c' in the
star rest frame?

What makes you think it does?

Read the results of the experiment.

I don't think it does. I'm asking why is it assumed to be so.

http://en.wikipedia.org/wiki/De_Sitt...tar_experiment

"For an object moving directly towards (or away from) the observer at
v metres per second, this light would then be expected to still be
travelling at (c + v) ( or (c - v) ) metres per second by the time it
reached us."

http://en.wikipedia.org/wiki/Emission_theory

"The simplest form of emission theory says that radiating objects
throw off light with a speed of "c" relative to their own state of
motion, and (unless we have reason to believe that the light changes
speed in flight), we then expect light to be moving towards us with a
speed that is offset by the speed of the distant emitter (c ± v) )."

Either the photon is traveling at c+v when it reaches the earth, or it
is traveling at 'c' as it propagates away from the star in the star
rest frame, but not both.

I say the photon propagates away from the star at 'c'.

On Jul 1, 9:51*am, mpc755 wrote:
On Jul 1, 9:41 am, Eric Gisse wrote:





On Jul 1, 5:32 am, mpc755 wrote:

De Sitter double star experiment:

http://en.wikipedia.org/wiki/De_Sitt...tar_experiment

A star in a binary star system is moving towards the earth at 'v' and
emits a photon towards the earth.

How can a photon of light be traveling at c+v towards the earth while
the star that emitted the photon is now moving away from the earth at
the same time the photon is traveling away from the star at 'c' in the
star rest frame?

What makes you think it does?

Read the results of the experiment.

I don't think it does. I'm asking why is it assumed to be so.

http://en.wikipedia.org/wiki/De_Sitt...tar_experiment

"For an object moving directly towards (or away from) the observer at
v metres per second, this light would then be expected to still be
travelling at (c + v) ( or (c - v) ) metres per second by the time it
reached us."

http://en.wikipedia.org/wiki/Emission_theory

"The simplest form of emission theory says that radiating objects
throw off light with a speed of "c" relative to their own state of
motion, and (unless we have reason to believe that the light changes
speed in flight), we then expect light to be moving towards us with a
speed that is offset by the speed of the distant emitter (c ± v) )."

Either the photon is traveling at c+v when it reaches the earth, or it
is traveling at 'c' as it propagates away from the star in the star
rest frame, but not both.

I say the photon propagates away from the star at 'c'.- Hide quoted text -

- Show quoted text -

A jet fighter flies at the velocity u and has a gun that fires bullets
at the velocity of w.

When sitting on the ground the fighter's velocity is 0 and when it
fires at a target and the bullets hit the target at the velocity of v=
(0+w).

When flying toward the target at the velocity of u the bullet hits at
v=(u+w).

When flying away and shooting back at the target the bullet hits at v=
(u-w).

In emitter theory the bullet has the velocity c so the target is hit
by light traveling at (u+c). Since u is the velocity of the plane we
would write it (v+c). And since it doesn't matter which order we add
things we can swap it around to the more common (c+v).

On Jul 1, 11:21*am, Bruce Richmond wrote:
On Jul 1, 9:51*am, mpc755 wrote:



On Jul 1, 9:41 am, Eric Gisse wrote:

On Jul 1, 5:32 am, mpc755 wrote:

De Sitter double star experiment:

http://en.wikipedia.org/wiki/De_Sitt...tar_experiment

A star in a binary star system is moving towards the earth at 'v' and
emits a photon towards the earth.

How can a photon of light be traveling at c+v towards the earth while
the star that emitted the photon is now moving away from the earth at
the same time the photon is traveling away from the star at 'c' in the
star rest frame?

What makes you think it does?

Read the results of the experiment.

I don't think it does. I'm asking why is it assumed to be so.

http://en.wikipedia.org/wiki/De_Sitt...tar_experiment

"For an object moving directly towards (or away from) the observer at
v metres per second, this light would then be expected to still be
travelling at (c + v) ( or (c - v) ) metres per second by the time it
reached us."

http://en.wikipedia.org/wiki/Emission_theory

"The simplest form of emission theory says that radiating objects
throw off light with a speed of "c" relative to their own state of
motion, and (unless we have reason to believe that the light changes
speed in flight), we then expect light to be moving towards us with a
speed that is offset by the speed of the distant emitter (c ± v) )."

Either the photon is traveling at c+v when it reaches the earth, or it
is traveling at 'c' as it propagates away from the star in the star
rest frame, but not both.

I say the photon propagates away from the star at 'c'.- Hide quoted text -

- Show quoted text -

A jet fighter flies at the velocity u and has a gun that fires bullets
at the velocity of w.

When sitting on the ground the fighter's velocity is 0 and when it
fires at a target and the bullets hit the target at the velocity of v=
(0+w).

When flying toward the target at the velocity of u the bullet hits at
v=(u+w).

When flying away and shooting back at the target the bullet hits at v=
(u-w).

In emitter theory the bullet has the velocity c so the target is hit
by light traveling at (u+c). *Since u is the velocity of the plane we
would write it (v+c). *And since it doesn't matter which order we add
things we can swap it around to the more common (c+v).

So, you're saying a photon of light does not propagate away from the
star at 'c' in the star rest frame.

I'm saying it does. Even in emitter theory.

On Jul 1, 11:25*am, mpc755 wrote:
On Jul 1, 11:21*am, Bruce Richmond wrote:



On Jul 1, 9:51*am, mpc755 wrote:

On Jul 1, 9:41 am, Eric Gisse wrote:

On Jul 1, 5:32 am, mpc755 wrote:

De Sitter double star experiment:

http://en.wikipedia.org/wiki/De_Sitt...tar_experiment

A star in a binary star system is moving towards the earth at 'v' and
emits a photon towards the earth.

How can a photon of light be traveling at c+v towards the earth while
the star that emitted the photon is now moving away from the earth at
the same time the photon is traveling away from the star at 'c' in the
star rest frame?

What makes you think it does?

Read the results of the experiment.

I don't think it does. I'm asking why is it assumed to be so.

http://en.wikipedia.org/wiki/De_Sitt...tar_experiment

"For an object moving directly towards (or away from) the observer at
v metres per second, this light would then be expected to still be
travelling at (c + v) ( or (c - v) ) metres per second by the time it
reached us."

http://en.wikipedia.org/wiki/Emission_theory

"The simplest form of emission theory says that radiating objects
throw off light with a speed of "c" relative to their own state of
motion, and (unless we have reason to believe that the light changes
speed in flight), we then expect light to be moving towards us with a
speed that is offset by the speed of the distant emitter (c ± v) )."

Either the photon is traveling at c+v when it reaches the earth, or it
is traveling at 'c' as it propagates away from the star in the star
rest frame, but not both.

I say the photon propagates away from the star at 'c'.- Hide quoted text -

- Show quoted text -

A jet fighter flies at the velocity u and has a gun that fires bullets
at the velocity of w.

When sitting on the ground the fighter's velocity is 0 and when it
fires at a target and the bullets hit the target at the velocity of v=
(0+w).

When flying toward the target at the velocity of u the bullet hits at
v=(u+w).

When flying away and shooting back at the target the bullet hits at v=
(u-w).

In emitter theory the bullet has the velocity c so the target is hit
by light traveling at (u+c). *Since u is the velocity of the plane we
would write it (v+c). *And since it doesn't matter which order we add
things we can swap it around to the more common (c+v).

So, you're saying a photon of light does not propagate away from the
star at 'c' in the star rest frame.

I'm saying it does. Even in emitter theory.

And the reason you are saying light does not propagate away from the
star at 'c' in the star rest frame in emitter theory is the
following...

When the star, of a binary star pair, is traveling towards the earth
it emits a photon towards the earth at what you consider to be c+v.

As the star continues to orbit around its pair, it will eventually be
traveling away from the earth at velocity 'w'.

At this time, in the earth's rest frame, the photon will be traveling
away from the star at 'c+v+w'.

At this time, it does not seem possible for the photon to also be
propagating away from the star at 'c' in the star's rest frame.

"mpc755" wrote in message
...

De Sitter double star experiment:

http://en.wikipedia.org/wiki/De_Sitt...tar_experiment

A star in a binary star system is moving towards the earth at 'v' and
emits a photon towards the earth.

How can a photon of light be traveling at c+v towards the earth while
the star that emitted the photon is now moving away from the earth at
the same time the photon is traveling away from the star at 'c' in the
star rest frame?

As you say, at the time of emission the star is moving towards the earth at
velocity v, so the emission theory would have the light arriving with speed
c+v in the earth's rest frame.

Are you unsure because the star may now be moving away from the earth? The
speed of light is only c relative to the star rest frame /at the time of
emission/ - once emitted, there is no connection between the star and the
light to make it slow down or speed up as the star's velocity varies over
its orbit.

On Jul 1, 12:14*pm, "OG" wrote:
"mpc755" wrote in message

...



De Sitter double star experiment:

http://en.wikipedia.org/wiki/De_Sitt...tar_experiment

A star in a binary star system is moving towards the earth at 'v' and
emits a photon towards the earth.

How can a photon of light be traveling at c+v towards the earth while
the star that emitted the photon is now moving away from the earth at
the same time the photon is traveling away from the star at 'c' in the
star rest frame?

As you say, at the time of emission the star is moving towards the earth at
velocity v, so the emission theory would have the light arriving with speed
c+v in the earth's rest frame.

Are you unsure because the star may now be moving away from the earth? The
speed of light is only c relative to the star rest frame /at the time of
emission/ - once emitted, there is no connection between the star and the
light to make it slow down or speed up as the star's velocity varies over
its orbit.

That's what I am saying I disagree with. I'm saying, in the star's
rest frame, that the light propagates away from the star at 'c'.

In the star's rest frame, the star is stationary, and there is no
reason why the photon does not continue to propagate away from the
star at 'c' forever.

In the star's rest frame, the star's velocity never changes. It is
always zero.

mpc755 wrote:
On Jul 1, 12:14 pm, "OG" wrote:
"mpc755" wrote in message

...



De Sitter double star experiment:
http://en.wikipedia.org/wiki/De_Sitt...tar_experiment
A star in a binary star system is moving towards the earth at 'v' and
emits a photon towards the earth.
How can a photon of light be traveling at c+v towards the earth while
the star that emitted the photon is now moving away from the earth at
the same time the photon is traveling away from the star at 'c' in the
star rest frame?
As you say, at the time of emission the star is moving towards the earth at
velocity v, so the emission theory would have the light arriving with speed
c+v in the earth's rest frame.

Are you unsure because the star may now be moving away from the earth? The
speed of light is only c relative to the star rest frame /at the time of
emission/ - once emitted, there is no connection between the star and the
light to make it slow down or speed up as the star's velocity varies over
its orbit.

That's what I am saying I disagree with. I'm saying, in the star's
rest frame, that the light propagates away from the star at 'c'.

In the star's rest frame, the star is stationary, and there is no
reason why the photon does not continue to propagate away from the
star at 'c' forever.

In the star's rest frame, the star's velocity never changes. It is
always zero.

Well yes, I suppose you could say that; but the rest of the universe
moves relative to the star.

Emission theory would have the light comoving with the rest of the
universe rather than comoving with the emitting star.

On Jul 1, 12:52*pm, OG wrote:
mpc755 wrote:
On Jul 1, 12:14 pm, "OG" wrote:
"mpc755" wrote in message

....

De Sitter double star experiment:
http://en.wikipedia.org/wiki/De_Sitt...tar_experiment
A star in a binary star system is moving towards the earth at 'v' and
emits a photon towards the earth.
How can a photon of light be traveling at c+v towards the earth while
the star that emitted the photon is now moving away from the earth at
the same time the photon is traveling away from the star at 'c' in the
star rest frame?
As you say, at the time of emission the star is moving towards the earth at
velocity v, so the emission theory would have the light arriving with speed
c+v in the earth's rest frame.

Are you unsure because the star may now be moving away from the earth? The
speed of light is only c relative to the star rest frame /at the time of
emission/ - once emitted, there is no connection between the star and the
light to make it slow down or speed up as the star's velocity varies over
its orbit.

That's what I am saying I disagree with. I'm saying, in the star's
rest frame, that the light propagates away from the star at 'c'.

In the star's rest frame, the star is stationary, and there is no
reason why the photon does not continue to propagate away from the
star at 'c' forever.

In the star's rest frame, the star's velocity never changes. It is
always zero.

Well yes, I suppose you could say that; but the rest of the universe
moves relative to the star.

Emission theory would have the light comoving with the rest of the
universe rather than comoving with the emitting star.

In terms of the emission of light, the rest of the universe is moving
relative to the star.