Relativists agree that a third observer can perceive light approaching objects
at speeds other than c.
What does relativity say about 'speeds of departure'?

If a photon leaves source at c relative to the source, what departing speed
does a third observer ascribe to it?

If two relatively moving sources emit photons in a particular direction, what
departing speeds does the third observer assign to them....wrt either source?
____________

No silly answers please.

HW.
www.users.bigpond.com/hewn/index.htm

Sometimes I feel like a complete failure.
The most useful thing I have ever done is prove Einstein wrong.

"Henri Wilson" H@.. wrote in message
...
Relativists agree that a third observer can perceive light approaching
objects
at speeds other than c.


It is purely a definitional thing.

What does relativity say about 'speeds of departure'?

If a photon leaves source at c relative to the source, what departing
speed
does a third observer ascribe to it?

The speed relative to the source obviously depends on the speed of the
source.


If two relatively moving sources emit photons in a particular direction,
what
departing speeds does the third observer assign to them....wrt either
source?


That depends on the speed of the sources - obviously.

Bill

____________

No silly answers please.

HW.
www.users.bigpond.com/hewn/index.htm

Sometimes I feel like a complete failure.
The most useful thing I have ever done is prove Einstein wrong.

"Henri Wilson" H@.. wrote in message ...
Relativists agree that a third observer can perceive light approaching objects
at speeds other than c.

With a few notable exceptions everyone in the world agrees
that a third party observer can perceive the distance between
light signals and/or objects to shrink or grow at time-rates
between 0 and 2c.
Usually this is called
- closing speed between... , or
- relative speed between... as seen by a third party.

What does relativity say about 'speeds of departure'?

One could decide to reseve "closing speed" for the time rate
of shrinking of the distance between light signals and/or objects,
and "opening speed" for the time rate of growing of the distance


If a photon

forget photons. Take light signals - photons are more complicated.

leaves source at c relative to the source, what departing speed
does a third observer ascribe to it?

As you well know, c+v or c-v, depending on the directions.


If two relatively moving sources emit photons in a particular direction, what
departing speeds does the third observer assign to them....wrt either source?

Everyone, including the third observer, would agree that
an observer riding with the source, measures every signal
to have speed c w.r.t. himself.
As ssen by the thitd party, depending on what you mean
with "a particular direction", the "closing" or "opening"
speeds between either source and either signal could be
c+v, c-v, c+u or c-u. Between the sources u+v or |u-v|.
Between the signals 0 or 2c.

____________

No silly answers please.

I'm sure you will find them utterly silly.
But that is your problem.

Dirk Vdm

On Wed, 14 Sep 2005 22:03:15 GMT, "Bill Hobba" wrote:


"Henri Wilson" H@.. wrote in message
.. .
Relativists agree that a third observer can perceive light approaching
objects
at speeds other than c.


It is purely a definitional thing.

What does relativity say about 'speeds of departure'?

If a photon leaves source at c relative to the source, what departing
speed
does a third observer ascribe to it?

The speed relative to the source obviously depends on the speed of the
source.


If two relatively moving sources emit photons in a particular direction,
what
departing speeds does the third observer assign to them....wrt either
source?


That depends on the speed of the sources - obviously.

Bill

Look folks!
Bill has finally taken up LET.



HW.
www.users.bigpond.com/hewn/index.htm

Sometimes I feel like a complete failure.
The most useful thing I have ever done is prove Einstein wrong.

On Wed, 14 Sep 2005 22:19:00 GMT, "Dirk Van de moortel"
wrote:


"Henri Wilson" H@.. wrote in message ...
Relativists agree that a third observer can perceive light approaching objects
at speeds other than c.

With a few notable exceptions everyone in the world agrees
that a third party observer can perceive the distance between
light signals and/or objects to shrink or grow at time-rates
between 0 and 2c.
Usually this is called
- closing speed between... , or
- relative speed between... as seen by a third party.

What does relativity say about 'speeds of departure'?

One could decide to reseve "closing speed" for the time rate
of shrinking of the distance between light signals and/or objects,
and "opening speed" for the time rate of growing of the distance


If a photon

forget photons. Take light signals - photons are more complicated.

leaves source at c relative to the source, what departing speed
does a third observer ascribe to it?

As you well know, c+v or c-v, depending on the directions.


If two relatively moving sources emit photons in a particular direction, what
departing speeds does the third observer assign to them....wrt either source?

Everyone, including the third observer, would agree that
an observer riding with the source, measures every signal
to have speed c w.r.t. himself.
As ssen by the thitd party, depending on what you mean
with "a particular direction", the "closing" or "opening"
speeds between either source and either signal could be
c+v, c-v, c+u or c-u. Between the sources u+v or |u-v|.
Between the signals 0 or 2c.

Thank you Dinky.

You have fully supported the notion that the BaT is the main cause of star
brightness variation.
You aren't totally useless after all!



HW.
www.users.bigpond.com/hewn/index.htm

Sometimes I feel like a complete failure.
The most useful thing I have ever done is prove Einstein wrong.

Henri Wilson wrote :
Thank you Dinky.

You have fully supported the notion that the BaT is the main cause of star
brightness variation.
You aren't totally useless after all!

You've just shown how illiterate you are in basic geometry, algebra
and physics (not speaking about common sense).

How do you feel now ?

In sci.physics.relativity, H@..(Henri Wilson)
H@
wrote
on Wed, 14 Sep 2005 21:43:32 GMT
:
Relativists agree that a third observer can perceive light approaching objects
at speeds other than c.
What does relativity say about 'speeds of departure'?

SR says all lightspeed is c. Ballistic theory says
lightspeed from a lamp *cannot* be c, unless the lamp's
temperature is at absolute zero.

[rest snipped]

--
#191,
It's still legal to go .sigless.

"YBM" wrote in message ...
Henri Wilson wrote :
Thank you Dinky.

You have fully supported the notion that the BaT is the main cause of star
brightness variation.
You aren't totally useless after all!

You've just shown how illiterate you are in basic geometry, algebra
and physics (not speaking about common sense).

How do you feel now ?

Most Village Idiots feel fine - whatever you throw at them.

Dirk Vdm

On Fri, 16 Sep 2005 04:00:11 GMT, The Ghost In The Machine
wrote:

In sci.physics.relativity, H@..(Henri Wilson)
H@
wrote
on Wed, 14 Sep 2005 21:43:32 GMT
:
Relativists agree that a third observer can perceive light approaching objects
at speeds other than c.
What does relativity say about 'speeds of departure'?

SR says all lightspeed is c. Ballistic theory says
lightspeed from a lamp *cannot* be c, unless the lamp's
temperature is at absolute zero.

You really do have a vivid imagination Ghost.
Have you ever thought of writing SciFi?


[rest snipped]


HW.
www.users.bigpond.com/hewn/index.htm

Sometimes I feel like a complete failure.
The most useful thing I have ever done is prove Einstein wrong.

On Fri, 16 Sep 2005 04:45:59 +0200, YBM wrote:

Henri Wilson wrote :
Thank you Dinky.

You have fully supported the notion that the BaT is the main cause of star
brightness variation.
You aren't totally useless after all!

You've just shown how illiterate you are in basic geometry, algebra
and physics (not speaking about common sense).

How do you feel now ?

Moron, your religion accepts 'closing speeds' that are not c.

Surely the same approach produces 'departing speeds' that are also not c.

Even Dinky seems to agree.





HW.
www.users.bigpond.com/hewn/index.htm

Sometimes I feel like a complete failure.
The most useful thing I have ever done is prove Einstein wrong.