Radio waves faster than light
 

"Jim Lux" napisal w wiadomosci
...
Szczepan Bialek wrote:


For me will be enough your steatment if speed of light and radio waves
were measured in different regions of the Solar System.
Katz: http://ipnpr.jpl.nasa.gov/progress_report/42-65/65I.PDF
wrote that the electron temperatures are from 10^4 to 10^6. Look at Fig
2. Place the Mars instead a spacecraft. Between (a) and (c) should be
some differences.


Are you asking if the calculations in Katz's paper for the two paths have
been experimentally verified? I don't know..

They were verified because there is a radio transmitter on the Mars. We do
not know the results.
S*

Radio waves faster than light
 

On Thu, 17 Mar 2011 17:19:09 -0700, Jim Lux
wrote:

Certainly he predicts that the temporal dispersion is going to be 0.1ps
for near IR, which is, shall we say, challenging to measure.

Why?

measuring things to tenths of a picosecond, repeatably, can be tricky..
That's like measuring the phase difference between two 10 GHz signals
to 0.3 degrees. Or, another way to look at it is 1 picolightsecond is
about a third of a millimeter.

A third of a millimeter is no big deal and for an optical (or
sub-optical) signal - trivial. Perhaps, when stated in terms of two
10 GHz signals, "near IR" is being vastly over stated.

You're looking at
a) figuring out how to generate two signals at near IR that has a
frequency offset that can be accurately controlled.

Controlled? This is dreaming in technicolor (or near IR color) if the
source is celestial.

I thought the discussion was about dispersion, the characteristic of
the medium, not sources.

Probably some sort
of heterodyne mixing scheme would be easiest.

Heterodyning is extremely commonplace and accurate - why would it be
pondered as an alternative method?

b) sending those two signals over the optical path through
interplanetary space.

This blurs my understanding of celestial where two signals is a
poverty of what is available from ANY celestial source.

c) recovering the signals,

If there is a problem of recovery, it seems it is more a practical
matter of source selection. Given the billions of celestial sources
available, I don't understand the problem.

measuring the propagation time variation
(say, by looking at the phase difference between the modulation
signals), and then removing atmospheric effects.

Why worry about the atmosphere when you can get above it?

d) it's probably going to be a pretty weak signal, so you'll need to
average. That means your measurement system has to be picosecond stable
over the averaging interval.

OK, so I am lost. This laundry list of difficulties seems to be
prepared to anticipate failure.

Name the near IR source and defend its choice in light (no pun) of
these intractable difficulties.

None of those steps are particularly simple or easy.

I've worked on systems to measure the (microwave) distance to Jupiter
and back with an accuracy of around 1 part in 1E15 at 32 GHz,

32 GHz is what photonics would call far-far IR at roughly 3 to 4
orders of magnitude distant from "near IR."

integrating over 1000 seconds. That's tenths of a picosecond out of 1000
seconds. It's challenging.

No doubt - like trying to push a peanut up Pike's Peak with your nose.
That too has been done with challenge in mind.

How did this slip from "near IR" to 32 GHz?

73's
Richard Clark, KB7QHC

Radio waves faster than light
 

On 3/18/2011 1:16 PM, Richard Clark wrote:

How did this slip from "near IR" to 32 GHz?

Hello Richard!

I'm back, and I see the old neighborhood hasn't changed much, although I
haven't seen anything from Art - hopefully the chap hasn't had a bed turn.

Here is a question or two for those who have some doubt as to the speed
of light.

A probe recently inserted itself into orbit around Mercury. How does
some presumed superluminal velocity affect the insertion?

The idea that "we" have a transmitter on Mars notwithstanding, Jupiter
has been transmitting RF for a long time. There are enough other
spacecraft running around in our solar system, and certainly if radio
waves traveled at some other velocity than what we thought they did, it
would mean a strange and useless conspiracy to hide that fact.

Cue up the twilight zone music and grab your aluminum foil hats everyone.

- 73 de Mike N3LI -

Radio waves faster than light
 

"Mike Coslo" napisal w wiadomosci
...
On 3/18/2011 1:16 PM, Richard Clark wrote:

How did this slip from "near IR" to 32 GHz?

Hello Richard!

I'm back, and I see the old neighborhood hasn't changed much, although I
haven't seen anything from Art - hopefully the chap hasn't had a bed turn.

Here is a question or two for those who have some doubt as to the speed of
light.

A probe recently inserted itself into orbit around Mercury. How does some
presumed superluminal velocity affect the insertion?

The idea that "we" have a transmitter on Mars notwithstanding, Jupiter
has been transmitting RF for a long time. There are enough other
spacecraft running around in our solar system, and certainly if radio
waves traveled at some other velocity than what we thought they did,

Not we but you.

it would mean a strange and useless conspiracy to hide that fact.

Somebody wrote that the data from the Mars are available. But it is not easy
to find them.
S*

Radio waves faster than light
 

Szczepan Bialek wrote:

Somebody wrote that the data from the Mars are available. But it is not easy
to find them.
S*

Since data from Mars is less than 150 years ago I doubt you would read it
and I know you wouldn't understand it if you did.


--
Jim Pennino

Remove .spam.sux to reply.

Radio waves faster than light
 

On Sat, 19 Mar 2011 07:51:45 -0500, Mike Coslo wrote:

On 3/18/2011 1:16 PM, Richard Clark wrote:

How did this slip from "near IR" to 32 GHz?

Hello Richard!

Hello Mike,

Welcome back to the Land of Odds.

The idea that "we" have a transmitter on Mars notwithstanding, Jupiter
has been transmitting RF for a long time.

Jupiter was one of my first DX goals back in the early 60s. However,
to expand upon your offering (I was wondering when anyone would
mention these sources), Earth, too, is a natural RF source (to
distinguish from the unnatural - such as stations carrying Fox Noise).

Quoting Wikipedia on Jupiter (nothing much said of the other planets
other than Earth):
"The intensity of Jovian radio emissions usually varies smoothly with
time; however, Jupiter periodically emits short and powerful bursts (S
bursts), which can outshine all other components. The total emitted
power of the DAM component is about 100 GW, while the power of all
other HOM/KOM components is about 10 GW. In comparison, the total
power of Earth's radio emissions is about 0.1 GW."

("emissions in the range 3 to 40 MHz are referred to as the decametric
radiation or DAM")

This decametric radiation would put us (returning to my quoted
question above) another several orders of magnitude beneath "near IR"
and into the "frigid IR" (a distinct irony with temperatures hovering
in the hundredths of a degree K).

73's
Richard Clark, KB7QHC

Radio waves faster than light
 

On Mar 18, 11:16*am, Richard Clark wrote:
On Thu, 17 Mar 2011 17:19:09 -0700, Jim Lux
wrote:

Certainly he predicts that the temporal dispersion is going to be 0.1ps
for near IR, which is, shall we say, challenging to measure.

Why?
measuring things to tenths of a picosecond, repeatably, can be tricky..
* That's like measuring the phase difference between two 10 GHz signals
to *0.3 degrees. Or, another way to look at it is 1 picolightsecond is
about *a third of a millimeter.

A third of a millimeter is no big deal and for an optical (or
sub-optical) signal - trivial. *Perhaps, when stated in terms of two
10 GHz signals, "near IR" is being vastly over stated.

The reference to 10 GHz was to try and relate the problem at Near IR
to something more familiar (since I suspect that most r.r.a.a are more
familiar with RF than light) (since speed of *light* was being
discussed, and the reference cited referred to optical communications
at Near IR)




You're looking at
a) figuring out how to generate two signals at near IR that has a
frequency offset that can be accurately controlled. *

Controlled? *This is dreaming in technicolor (or near IR color) if the
source is celestial.

The figures in the referenced paper showed a manmade source,
presumably with some sort of source which could be designed to make
measuring dispersion easier.



I thought the discussion was about dispersion, the characteristic of
the medium, not sources.

Precisely.. but if you're going to measure dispersion, you've got to
have a way to do it, and sending out two signals that are coherent
with each other at a known offset seems to be a fairly straightforward
approach.


Probably some sort
of heterodyne mixing scheme would be easiest.

Heterodyning is extremely commonplace and accurate - why would it be
pondered as an alternative method?

For optical signals, there could be other ways to generate multiple
signals at different frequencies that are coherent with each other. I
don't know enough about optical measurement techniques. I *do* know
that you can modulate near IR with RF signals using a variety of
techniques.



b) sending those two signals over the optical path through
interplanetary space.

This blurs my understanding of celestial where two signals is a
poverty of what is available from ANY celestial source.


Back to the figure reference.
And, of course, getting coherent signals from a celestial source might
be a challenge. I don't know.. maybe some sort of clever correlation
technique in an interferometer would do. Not really my field.
c) recovering the signals,

If there is a problem of recovery, it seems it is more a practical
matter of source selection. *Given the billions of celestial sources
available, I don't understand the problem.

Precision detection of a man made signal from across the solar system
is a challenge.



measuring the propagation time variation
(say, by looking at the phase difference between the modulation
signals), and then removing atmospheric effects.

Why worry about the atmosphere when you can get above it?

Indeed. That would make things easier, and is something that people
want to do. But so far, we're stuck with just sending the transmitter
out there.



d) it's probably going to be a pretty weak signal, so you'll need to
average. That means your measurement system has to be picosecond stable
over the averaging interval.

OK, so I am lost. *This laundry list of difficulties seems to be
prepared to anticipate failure.


Not so much failure, but that the original question asked for
experimental data to confirm a fairly well understood effect. My
point is to show that collecting that experimental data is non-
trivial, and not something that you can just rig up in your backyard
with baling wire and sealing wax.


Name the near IR source and defend its choice in light (no pun) of
these intractable difficulties.

There has been more than one optical comm experiment from deep space.


None of those steps are particularly simple or easy.

I've worked on systems to measure the (microwave) distance to Jupiter
and back with an accuracy of around 1 part in 1E15 at 32 GHz,

32 GHz is what photonics would call far-far IR at roughly 3 to 4
orders of magnitude distant from "near IR."

integrating over 1000 seconds. That's tenths of a picosecond out of 1000
seconds. It's challenging.

No doubt - like trying to push a peanut up Pike's Peak with your nose.
That too has been done with challenge in mind.

Well.. yes, it *is* hard, but if you want to know the internal
structure of another planet, it does take some work.




How did this slip from "near IR" to 32 GHz?


The example of 32 GHz is to illustrate that I am not just speculating
about the difficulties of doing it at IR. I have personal knowledge
of how hard it is at 32GHz, and I'm pretty sure it's harder at Near
IR.

So someone on a listserv or usenet group who's looking for a "hey I
did the experiment yesterday, and sure enough, dispersive media have
dispersion" isn't going to get it. Nor are they likely to find the
results of someone who might have done it for real without digging a
bit.

Radio waves faster than light
 

On Mar 19, 12:07*pm, Richard Clark wrote:
On Sat, 19 Mar 2011 07:51:45 -0500, Mike Coslo wrote:
On 3/18/2011 1:16 PM, Richard Clark wrote:

How did this slip from "near IR" to 32 GHz?

Hello Richard!

Hello Mike,

Welcome back to the Land of Odds.

The idea that "we" have a transmitter on *Mars notwithstanding, Jupiter
has been transmitting RF for a long time.

"The intensity of Jovian radio emissions usually varies smoothly with
time; however, Jupiter periodically emits short and powerful bursts (S

It would be difficult to make measurements of dispersive propagation
in the interplanetary media using the natural emissions of Jupiter,
since you don't have knowledge of the relative phases/timing of the
emissions at different frequencies, so you have nothing to compare
against on earth.

If you had two receivers in space separated by some distance along a
line from Jupiter, maybe you could do it. If they're on earth, I
think the ionospheric variation would dominate your measurement.

That said, at least you can get a big frequency ratio so the 1/f1^2-1/
f2^2 term would be large.

Maybe the folks building LOFAR have some clever ideas on compensating
for the ionosphere and they will be able to use Jupiter as a source
for this sort of measurement (if they're interested.... I suspect
they're not..)

Radio waves faster than light
 

On Sat, 19 Mar 2011 18:36:11 -0700 (PDT), Jim Lux
wrote:

It would be difficult to make measurements of dispersive propagation
in the interplanetary media using the natural emissions of Jupiter,
since you don't have knowledge of the relative phases/timing of the
emissions at different frequencies, so you have nothing to compare
against on earth.

Hi Jim,

We would first have to agree what "dispersion" means.

If it conforms to optical dispersion (this having started, at least
for me, in the near IR, which is optical as far as I am concerned),
then the wide bandwidth (offering us with many time coherent sources)
through a frequency dependent media would present different phase
shifts which could then be cross-correlated. Modal dispersion might
present a problem because even though Jupiter is far away, it still
presents a significant arc of span across space (i.e. not even close
to being a point source).

73's
Richard Clark, KB7QHC

Radio waves faster than light
 

On Sat, 19 Mar 2011 18:29:43 -0700 (PDT), Jim Lux
wrote:

How did this slip from "near IR" to 32 GHz?


The example of 32 GHz is to illustrate that I am not just speculating
about the difficulties of doing it at IR. I have personal knowledge
of how hard it is at 32GHz, and I'm pretty sure it's harder at Near
IR.

Hi Jim,

The display and measure of Newton's rings is exceedingly trivial for
optical time/phase/freq/distance differences far shorter in shift (nm
to um) than what is being described here (in mm).

73's
Richard Clark, KB7QHC