On Thursday, June 2, 2022 at 7:03:23 PM UTC-7, tjrob137 wrote:
> > A simple radar speed gun always just shows the rate of change of the
> > distance between gun and target.
>
> Whenever you mention distance, time, velocity, or speed, you MUST
> specify the coordinates relative to which it is measured. Here, of
> course, speed (aka rate of change of distance) is measured relative to
> the radar gun's inertial rest frame, along the line-of-sight of the
> radar beam.

Again, t\he relevant quantity here is not the target's speed in terms of some coordinate system, it is (as stated above) the rate of change of distance, which is not synonymous with speed. You can see this if you consider a car moving transversely at high speed in terms of your co-moving inertial coordinates. Pointing a speed gun at that car will not read it's speed in the gun's coordinate system, it will read essentially zero, because that is the rate of change of the distance at that moment. This is the extreme "cosine effect".

> I WAS careful: I said "along the line-of-sight of the radar beam".

Nope, the statement that you were witlessly trying to "correct" was not restricted to cases when the motions are all parallel to the beam, it is fully general, and subsumes not only the trivial 1-dimensional case, but all cases. Again, in every case, a simple radar speed gun always just shows the rate of change of the distance between gun and target.

> The equations used to convert the Doppler shift to a speed were derived
> using the inertial rest frame of the gun, and inherently reference that
> frame.

Again, the first order Doppler effect used in radar speed guns can be worked out in terms of either the gun's or the target's (or the ground's, etc.) co-moving inertial coordinates; they all give the same first order result, which is all a speed gun can detect.

> [The gun] is CLEARLY making a measurement relative to
> its own (instantaneously co-moving) (locally) inertial rest frame.

The gun is just evaluating the ratio of the frequencies of the emitted and returning signals, and from this it infers the rate of change of the optical path length. That is all it is doing. No distance measurements, so simultaneity stipulations, etc. Again, the sentence you were pompously trying to correct is "A simple radar speed gun always just shows the rate of change of the distance between gun and target." If all you're saying is the self-evident fact that spatial distances and temporal intervals are expressed in terms of coordinate systems, well duh. The point is that, in this context, whether we use the inertial coordinates of the gun or the target or the road makes no appreciable difference to the operation of the device. This is essential to dispel Ed's misconceptions (and apparently yours).

> THE RADAR GUN CANNOT -- it can only use its own (instantaneously
> co-moving) (locally) inertial rest frame. Because that is how it is
> constructed.

That's insane. Again, all the radar gun is doing is measuring the ratio of two frequencies. If you are pointing out that the gun is constructed to be at rest relative to itself, well, duh.

pat dolan wrote:
> Can there ever be a coordinate system in which the speed of an object is greater than c?

Of course. Coordinate systems in which the speed of material objects exceed the standard numerical value c are quite trivial to construct. Indeed, coordinate system in which the speed of light is everywhere c in all directions (locally) are actually quite specialized.

On Thursday, June 2, 2022 at 1:05:29 PM UTC-4, whodat wrote:
> On 6/2/2022 9:56 AM, Ken Seto wrote:
> > On Wednesday, June 1, 2022 at 11:43:28 AM UTC-4, Richard Hachel wrote:
> >> Le 01/06/2022 à 16:51, Ken Seto a écrit :
> >>
> >>> in terms of absolute time.
> >> Absolute time does not exist.
> >> Absolute simultaneity does not exist.
> > t.
> > Assertions are not valid argument.ust made an assertion instead.
> While you're right, Ken, there's much more to the statements he's made
> than meets the eye. What sort of valid arguments can be made that
> something does not exist? This is not a trick question.
are an assertion that absolute time
I presented my argument why absolute time exists. He should present his argument why absolute time doesn't exist......but instead he just made an assertion that absolute time doesn't exist.

> >> Even worse, and this is where we have to pull out the tissues, the notion
> >> of an “absolute present time plan” is fake news.
> >>
> >> Fake news taught by hundreds of relativist theorists who think they
> >> figured out they were smart, and who aren't smart at all. Arrogant towards
> >> the "cranks" yes.
> >>
> >> But smart, no.
> >>
> >>
> >> R.H.

On Thursday, June 2, 2022 at 3:55:13 PM UTC-4, tjrob137 wrote:
> On 6/2/22 9:20 AM, Ed Lake wrote:
> > The gun emits photons that represent the LOCATION of the gun RELATIVE
> > TO THE GROUND.
> NONSENSE! The radar gun "knows" NOTHING AT ALL about the ground. The
> radar gun inherently measures speed relative to the inertial frame in
> which it is at rest. That is the ONLY frame that it "knows" anything about.
>
> [We are discussing a simple, single-beam radar gun.]
> > And because it is STATIONARY relative to the ground, the gun emits
> > photons that oscillate at a frequency that matches the frequency that
> > would be emitted by a gun actually ON the ground.
> The photons don't oscillate. But for this physical situation the radar
> wave emitted by the gun is indeed the same frequency of a similar gun
> resting on the ground (measured in the inertial frame of the ground).
>
The gun emits light at certain frequency F1 and the receiver receives frequency F2 The speed of the receiver is calculated as follows:;
Receiver speed wrt the gun = wavelength at the gun (F1-F2)
Conversely we can say that:
Speed of the gun wrt the receiver = wavelength at the gun(F2-F1)
>
> > The photons travel at c to the Camaro. The Camaro is moving at speed v.
> > The photons, therefore, hit the Camaro at c+v (the "closing speed").
> That is an unusual way to think of this, because "closing speed" is a
> purely mathematical artifact with no physical meaning (e.g. there is no
> possible way to measure it, one can only calculate it by subtracting two
> measurable speeds).
>
> [Let me ignore the effect of the air, which is
> negligible here.]
>
> Relative to the inertial rest frame of the Camaro, the incoming radar
> wave moves with speed c, as does the reflected wave. But since the
> Camaro is moving relative to the source of the incoming radar wave, in
> the Camaro rest frame the incoming wave has a higher frequency than it
> has in the radar gun's frame (Doppler shift); in the Camaro frame the
> incoming and reflected radar waves have the same frequency. But in the
> radar gun's frame the reflected wave has a higher frequency than the
> gun's emitted wave (also Doppler shift), and that difference is used by
> the gun to determine the Camaro's speed RELATIVE TO THE GUN'S REST FRAME.
>
> > Atoms
> > in some reflective surface on the car ABSORB the photons [...]
>
> No, they don't. The wave is REFLECTED, not absorbed. Light reflecting
> from a metallic mirror does not involve absorption -- internet articles
> that claim so are WRONG. See my initial post in the thread "What Happens
> When Light is Reflected?" -- the light is reflected by the conduction
> electrons, not the atoms.
>
> Tom Roberts

On Thursday, 2 June 2022 at 22:35:56 UTC+2, tjrob137 wrote:
> On 6/2/22 2:10 PM, Al Coe wrote:
> > On Tuesday, May 31, 2022 at 1:43:57 PM UTC-7, det...@outlook.com
> > wrote:
> >> Most radar guns have the capability of measuring their own speeds.
> >>
> >
> > A simple radar speed gun always just shows the rate of change of the
> > distance between gun and target.
> Whenever you mention distance, time, velocity, or speed, you MUST
> specify the coordinates relative to which it is measured.

Or, at least, in the world of Tom's delusions everyone does.

On Thursday, June 2, 2022 at 10:07:33 PM UTC-4, patdolan wrote:

>
> Can there ever be a coordinate system in which the speed of an object is greater than c?

Yes. But not for an inertial frame.

On Friday, 3 June 2022 at 15:04:38 UTC+2, rotchm wrote:
> On Thursday, June 2, 2022 at 10:07:33 PM UTC-4, patdolan wrote:
>
> >
> > Can there ever be a coordinate system in which the speed of an object is greater than c?
> Yes. But not for an inertial frame.

Impossible for incompetent amateurs only.

On Thursday, June 2, 2022 at 2:11:00 PM UTC-5, Al Coe wrote:
> On Tuesday, May 31, 2022 at 1:43:57 PM UTC-7, wrote:
> > Most radar guns have the capability of measuring their own speeds.
> A simple radar speed gun always just shows the rate of change of the distance between gun and target. A "moving radar" device determines the speed of the gun relative to the ground by measuring the rate of change of the distance between the gun and some object(s) at rest on the ground. There is nothing magical or mysterious about this.

You are talking about LIDAR guns, not radar guns. Lidar works by
sending a burst of photons to a target and then measuring how long
it takes for a signal to return. That gives the first distance. Then a
fraction of a second later the gun does it again. That gives the second
distance. The gun then computes the distance the target traveled
between the two measurements. Knowing the speed of light, the gun
can then compute the target's speed.

Lidar guns MUST be used while stationary. Most police departments
are phasing out hand-held radar guns and are replacing them with lidar
guns. They still use vehicle mounted radar guns, however.

Ed

On Thursday, June 2, 2022 at 2:55:13 PM UTC-5, tjrob137 wrote:
> On 6/2/22 9:20 AM, Ed Lake wrote:
> > The gun emits photons that represent the LOCATION of the gun RELATIVE
> > TO THE GROUND.
> NONSENSE! The radar gun "knows" NOTHING AT ALL about the ground. The
> radar gun inherently measures speed relative to the inertial frame in
> which it is at rest. That is the ONLY frame that it "knows" anything about.

Okay, but that "inertial frame" is the ground.

>
> [We are discussing a simple, single-beam radar gun.]
> > And because it is STATIONARY relative to the ground, the gun emits
> > photons that oscillate at a frequency that matches the frequency that
> > would be emitted by a gun actually ON the ground.
> The photons don't oscillate. But for this physical situation the radar
> wave emitted by the gun is indeed the same frequency of a similar gun
> resting on the ground (measured in the inertial frame of the ground).

Photons do indeed oscillate. Simple experiments will show that a radar
gun does NOT emit waves. The oscillations are of the electric and magnetic
fields of the photon. Those oscillations have wave-like properties.

> > The photons travel at c to the Camaro. The Camaro is moving at speed v.
> > The photons, therefore, hit the Camaro at c+v (the "closing speed").
> That is an unusual way to think of this, because "closing speed" is a
> purely mathematical artifact with no physical meaning (e.g. there is no
> possible way to measure it, one can only calculate it by subtracting two
> measurable speeds).

Nope. Radar guns measure differences in oscillation frequencies as
I explained in my previous post.

>
> [Let me ignore the effect of the air, which is
> negligible here.]
>
> Relative to the inertial rest frame of the Camaro, the incoming radar
> wave moves with speed c, as does the reflected wave. But since the
> Camaro is moving relative to the source of the incoming radar wave, in
> the Camaro rest frame the incoming wave has a higher frequency than it
> has in the radar gun's frame (Doppler shift); in the Camaro frame the
> incoming and reflected radar waves have the same frequency. But in the
> radar gun's frame the reflected wave has a higher frequency than the
> gun's emitted wave (also Doppler shift), and that difference is used by
> the gun to determine the Camaro's speed RELATIVE TO THE GUN'S REST FRAME.

Yes, that is how radar guns are often described as working. But it is IDIOTICALLY
WRONG. It assumes that the return wave will reflect off just one part of the car.
In reality, the wave would reflect off the bumper, then off the front of the car, off
the windshield, and meanwhile waves are also bouncing off the ground, off of
street signs, etc. There would be dozens of INTERMINGLED waves returning to
the gun. The gun would have to way of separating one wave from another.

With oscillating photons, every returning photon from the car oscillates at the
same rate. And every photon returning from stationary objects oscillates at a
different rate. So, the gun can easily measure the target's speed correctly.

>
> > Atoms
> > in some reflective surface on the car ABSORB the photons [...]
>
> No, they don't. The wave is REFLECTED, not absorbed. Light reflecting
> from a metallic mirror does not involve absorption -- internet articles
> that claim so are WRONG. See my initial post in the thread "What Happens
> When Light is Reflected?" -- the light is reflected by the conduction
> electrons, not the atoms.

Totally WRONG. as usual. Photons are exchanges of energy moving from
one atom to another. An atom is heated and emits a photon to get rid of
that excess energy. The photon travels to a reflective surface on the target
vehicle where it is absorbed by an atom. That atom cannot hold the extra
energy, so it emits a NEW photon back in the direction from which the original
photon came. The radar gun receives that photon and compares its oscillation
frequency to the oscillation frequency of the photon it emitted and that gives
the gun the speed of the target.

I provided a NASA description of how a radar gun can use a single photon to
measure the speed of a target. Here it is again;
https://www.grc.nasa.gov/www/k-12/Numbers/Math/Mathematical_Thinking/how_do_police_radars.htm

The idea that radar guns emit "waves" is just plain STUPID and can be disproved
in many ways.

The idea that photons cannot oscillate is disproved by radar guns. Your problem
may be the terminology. Technically, photons do not oscillate, they have electric
and magnetic fields which oscillate. But since a photon consists entirely of an
oscillating electric field and an oscillating magnetic field, it is not incorrect to say
that a photon oscillates.

I have a radar gun. I've extensively experimented with them and researched them.

If I point my radar gun at the blade tips of a rotating fan, the gun shows 41 mph.
If I point the gun at the middle of the fan blades, the gun shows about 30 mph.
If I point the gun at the base of the fan blades, the gun shows about 22 mph.

How can that be done with waves?

The operator's manual for my TS-3 radar gun says that the "beam width" is 12 degrees.
How can you have a beam width of 12 degrees if a gun emits waves?

Ed

On 6/2/22 9:07 PM, patdolan wrote:
> Can there ever be a coordinate system in which the speed of an object is greater than c?

Sure. For instance, relative to rotating coordinates, objects
sufficiently far away will have coordinate speeds > c.

The limit of c in SR applies only to speeds relative to inertial frames.

Tom Roberts

On Friday, June 3, 2022 at 9:49:03 AM UTC-5, Ed Lake wrote:

My previous post contains some key questions. I'll ask them again here:

If I point my radar gun at the blade tips of a rotating fan, the gun shows 41 mph.
If I point the gun at the middle of the fan blades, the gun shows about 30 mph.
If I point the gun at the base of the fan blades, the gun shows about 22 mph.

How can that be done with waves?

The operator's manual for my TS-3 radar gun says that the "beam width" is 12 degrees.
How can you have a beam width of 12 degrees if a gun emits waves?

Ed

On 6/2/22 9:47 PM, Al Coe wrote:
> the first order Doppler effect used in radar speed guns can be
> worked out in terms of either the gun's or the target's (or the
> ground's, etc.) co-moving inertial coordinates; they all give the
> same first order result, which is all a speed gun can detect.

You confuse what an analyst can calculate with what a radar gun actually
does. Radar guns measure speed [#] relative to their (instantaneously
co-moving) (locally) inertial rest frame.

[#] Projected onto the line-of-sight of their beam.

You keep obfuscating and diverting, in an attempt to avoid admitting you
forgot one of the primary lessons of modern physics:

Whenever you mention distance, time, velocity, or speed,
you MUST specify the coordinates relative to which it is
measured.

Tom Roberts

On Friday, June 3, 2022 at 7:08:41 AM UTC-7, det...@outlook.com wrote:
> > A simple radar speed gun always just shows the rate of change of the distance between gun and target. A "moving radar" device determines the speed of the gun relative to the ground by measuring the rate of change of the distance between the gun and some object(s) at rest on the ground. There is nothing magical or mysterious about this.
>
> You are talking about LIDAR guns, not radar guns.

Nope, I'm talking about radar speed guns (although the same statement applies to LIDAR speed guns). Again, a simple speed gun reads the rate of change of the distance between gun and target. If you think this is not true, go ahead and describe a situation in which you believe a simple radar speed gun reads something other than the rate of change of the distance between gun and target.

On Friday, June 3, 2022 at 8:43:52 AM UTC-7, tjrob137 wrote:
> On 6/2/22 9:47 PM, Al Coe wrote:
> > the first order Doppler effect used in radar speed guns can be
> > worked out in terms of either the gun's or the target's (or the
> > ground's, etc.) co-moving inertial coordinates; they all give the
> > same first order result, which is all a speed gun can detect.
> You confuse what an analyst can calculate with what a radar gun actually
> does.

Nope. As explained above, what a radar gun actually does is simply measure the ratio of the transmitted and returned signals, and from this it infers the rate of change of the optical path length. That's all.

> [#] Projected onto the line-of-sight of their beam.

Again, the statement is fully general, not restricted to 1-dimensional cases. And your misconception about the dependence of choice of gun's or target's frame has already been explained.

On 6/3/22 9:49 AM, Ed Lake wrote:
> On Thursday, June 2, 2022 at 2:55:13 PM UTC-5, tjrob137 wrote:
>> On 6/2/22 9:20 AM, Ed Lake wrote:
>>> The gun emits photons that represent the LOCATION of the gun RELATIVE
>>> TO THE GROUND.
>> NONSENSE! The radar gun "knows" NOTHING AT ALL about the ground. The
>> radar gun inherently measures speed relative to the inertial frame in
>> which it is at rest. That is the ONLY frame that it "knows" anything about.
>
> Okay, but that "inertial frame" is the ground.

NOT AT ALL. The radar gun "knows" NOTHING AT ALL about the ground.
Repeating falsehoods does not make them true. The radar gun inherently
measures speed relative to the inertial frame in which it is at rest.

> [... confusion about how radar guns actually work]
The operator of the radar gun must ensure that the reflected waves come
from the target vehicle, and not extraneous reflectors. The gun displays
the speed corresponding to the largest Doppler shift within its beam,
which combined with the operator's aiming of the beam automatically does
the separation you claim cannot be done.
> With oscillating photons, every returning photon from the car oscillates at the
> same rate. And every photon returning from stationary objects oscillates at a
> different rate. So, the gun can easily measure the target's speed correctly.

Replace your incorrect "photon" with "radar wave", and this is correct.

> If I point my radar gun at the blade tips of a rotating fan, the gun shows 41 mph.
> If I point the gun at the middle of the fan blades, the gun shows about 30 mph.
> If I point the gun at the base of the fan blades, the gun shows about 22 mph.
>
> How can that be done with waves?

In the obvious way: the wave emitted by the gun has a rather narrow
divergence, so you can point it accurately at a target.

> The operator's manual for my TS-3 radar gun says that the "beam width" is 12 degrees.
> How can you have a beam width of 12 degrees if a gun emits waves?

By limiting the beam divergence. It is straightforward microwave
engineering to design a radar antenna that emits a beam with such a
narrow divergence. Such design tools model the radar beam as a wave, not
photons. You merely display your personal ignorance.

Tom Roberts

On Friday, June 3, 2022 at 10:44:23 AM UTC-5, Al Coe wrote:
> On Friday, June 3, 2022 at 7:08:41 AM UTC-7, wrote:
> > > A simple radar speed gun always just shows the rate of change of the distance between gun and target. A "moving radar" device determines the speed of the gun relative to the ground by measuring the rate of change of the distance between the gun and some object(s) at rest on the ground. There is nothing magical or mysterious about this.
> >
> > You are talking about LIDAR guns, not radar guns.
> Nope, I'm talking about radar speed guns (although the same statement applies to LIDAR speed guns). Again, a simple speed gun reads the rate of change of the distance between gun and target. If you think this is not true, go ahead and describe a situation in which you believe a simple radar speed gun reads something other than the rate of change of the distance between gun and target.

Radar guns detect the difference in photon oscillation frequencies between
the photons it emits and the photons that are returned. The difference is
called the "beat frequency." There's a calculator for beat frequencies at
this link: http://hyperphysics.phy-astr.gsu.edu/hbase/Sound/radar.html#c4

Unfortunately, the illustration shows waves instead of photons.

I neglected to mention in my previous comment that Lidar guns emit LASER
light. So, they can be more accurately pointed at a target. A typical RADAR
gun has a beam width of 12 degrees, so it is more difficult to pinpoint a target.

Lidar is used to measure distances. You can fly over some landscape with
lidar pointed at the ground and measure the distances to hills and valleys,
giving you a 3D picture of the ground.

Police Lidar guns have a "gun sight" that you look through to make sure
you are pointing at the right target. When you pull the trigger, it does a
distance measurement to the target, then about 1/10th of a second later
it does another measurement. Knowing the speed of light, the gun then
calculates the target's speed by dividing the difference in distance by
the time between measurements.

Here's a video that explains how lidar guns work: https://www.youtube.com/watch?v=9t5CZ5kFdmQ

Ed

On Friday, June 3, 2022 at 10:52:05 AM UTC-5, tjrob137 wrote:
> On 6/3/22 9:49 AM, Ed Lake wrote:
> > On Thursday, June 2, 2022 at 2:55:13 PM UTC-5, tjrob137 wrote:
> >> On 6/2/22 9:20 AM, Ed Lake wrote:
> >>> The gun emits photons that represent the LOCATION of the gun RELATIVE
> >>> TO THE GROUND.
> >> NONSENSE! The radar gun "knows" NOTHING AT ALL about the ground. The
> >> radar gun inherently measures speed relative to the inertial frame in
> >> which it is at rest. That is the ONLY frame that it "knows" anything about.
> >
> > Okay, but that "inertial frame" is the ground.
> NOT AT ALL. The radar gun "knows" NOTHING AT ALL about the ground.
> Repeating falsehoods does not make them true. The radar gun inherently
> measures speed relative to the inertial frame in which it is at rest.

According to Relativity, time ticks at a given rate on the surface of the
earth. That rate incorporates the fact that the earth is spinning on it axis,
it is orbiting the sun, and the sun is orbiting the center of the Milky Way
galaxy, etc. And that rate also determines the properties of atoms at
that location, their mass, frequencies, etc. Altitude also affects the
properties of those atoms. It is considered an "inertial frame," even
though it is not moving in a straight line.

A "stationary" radar gun at that point on the surface of the earth will have
atoms that reflect that location's speed and and gravity.

Atoms in a MOVING object will have slightly different properties. The
difference is directly rated to the difference in speed between the moving
object and the "stationary" object. (In reality, it is a difference in speed
between two different moving objects. We just consider the earth to be
"stationary," since we are measuring speeds relative to the earth.)

> > [... confusion about how radar guns actually work]
> The operator of the radar gun must ensure that the reflected waves come
> from the target vehicle, and not extraneous reflectors. The gun displays
> the speed corresponding to the largest Doppler shift within its beam,
> which combined with the operator's aiming of the beam automatically does
> the separation you claim cannot be done.

Right. It cannot be done because the "beam" width is 12 degrees. That means
that at 500 feet, the "beam" will be 105 feet wide. At 200 feet it will be 42 feet
wide. If the gun is pointed at an oncoming truck, the front of the truck will be
about 10 feet in front of the trailer. Both will reflect "waves." And there is no way
to separate waves from the tractor and waves from the trailer. If you can't
tell one wave from another, you cannot use waves to measure speeds.

> > With oscillating photons, every returning photon from the car oscillates at the
> > same rate. And every photon returning from stationary objects oscillates at a
> > different rate. So, the gun can easily measure the target's speed correctly.
> Replace your incorrect "photon" with "radar wave", and this is correct.
> > If I point my radar gun at the blade tips of a rotating fan, the gun shows 41 mph.
> > If I point the gun at the middle of the fan blades, the gun shows about 30 mph.
> > If I point the gun at the base of the fan blades, the gun shows about 22 mph.
> >
> > How can that be done with waves?
> In the obvious way: the wave emitted by the gun has a rather narrow
> divergence, so you can point it accurately at a target.

A BEAM has a divergence. A BEAM of photons has a divergence.
What is a "beam of waves"? How can it have a divergence if the
primary property of a wave is to spread out IN ALL DIRECTIONS from the
source? Can you have sound waves that are confined into a narrow beam?
NO! So, how are light waves different from sound waves?
> > The operator's manual for my TS-3 radar gun says that the "beam width" is 12 degrees.
> > How can you have a beam width of 12 degrees if a gun emits waves?
> By limiting the beam divergence. It is straightforward microwave
> engineering to design a radar antenna that emits a beam with such a
> narrow divergence. Such design tools model the radar beam as a wave, not
> photons. You merely display your personal ignorance.

No, you display your ignorance in not knowing the difference between a BEAM
and a WAVE. You can easily focus PHOTONS into a beam. You cannot focus
sound waves into a beam. So, how do you focus light waves into a beam?

Ed

What day is it, is it Friday already? Boy, i don't know where time
goes...

--
The Starmaker -- To question the unquestionable, ask the unaskable,
to think the unthinkable, mention the unmentionable, say the unsayable,
and challenge
the unchallengeable.

> On 6/2/22 9:07 PM, patdolan wrote:
> > Can there ever be a coordinate system in which the speed of an object is greater than c?
>

In order for there to be a coordinate system in which the speed of an
object is greater than c,

i would have to make some 'changes at the knob'.

There are knobs on the machine, and by making an adjustment to the knobs
i can increase
the speed of c.

What speed do you want it at???? 33, 45 or 78?

Keep in mind, any changes i make means i have to adjust some of the
other knobs on the machine...

and then you'll still going to ask the same question

Can there ever be a coordinate system in which the speed of an object is
greater than c?

Come on, I got it right this time, what is the problem with the c now?

You have no idea what it took me to get all these knobs adjusted...just
right.

--
The Starmaker -- To question the unquestionable, ask the unaskable,
to think the unthinkable, mention the unmentionable, say the unsayable,
and challenge
the unchallengeable.

On Friday, June 3, 2022 at 9:06:54 AM UTC-7, det...@outlook.com wrote:
> > > > A simple radar speed gun always just shows the rate of change of the distance between gun and target. A "moving radar" device determines the speed of the gun relative to the ground by measuring the rate of change of the distance between the gun and some object(s) at rest on the ground. There is nothing magical or mysterious about this.
> > >
> > > You are talking about LIDAR guns, not radar guns.
> >
> > Nope, I'm talking about radar speed guns (although the same statement applies to LIDAR speed guns). Again, a simple speed gun reads the rate of change of the distance between gun and target. If you think this is not true, go ahead and describe a situation in which you believe a simple radar speed gun reads something other than the rate of change of the distance between gun and target.
>
> Radar guns...

I guess you missed my question, so I ask again: Please describe the circumstances in which you believe that the reading on a simple radar speed gun does *not* equal the rate of change of the distance between gun and target.

On June 3, det...@outlook.com wrote:
> you display your ignorance in not knowing the difference between a BEAM
> and a WAVE. You can easily focus PHOTONS into a beam.
> You cannot focus sound waves into a beam. So, how do you focus light waves
> into a beam?

Right.
Message these guys, let them know you're onto their fraud -

https://www.fierceelectronics.com/components/choosing-ultrasonic-sensor-for-proximity-or-distance-measurement-part-2-optimizing

--
Rich

On June 3, det...@outlook.com wrote:
> Police Lidar guns have a "gun sight" that you look through to make sure
> you are pointing at the right target. When you pull the trigger, it does a
> distance measurement to the target, then about 1/10th of a second later
> it does another measurement.
> Knowing the speed of light, the gun then calculates the target's speed by
> dividing the difference in distance by the time between measurements.

Big hole in your analysis, Ed -

The speed of light emitted by the gun is known. But the light speed
reflected from the target is c + v, remember?

And v is UNKNOWN, that's the point! Hence the gun cannot calculate
the target's speed.

I'm surprised that an uberlogician like yourself would err this way -

--
Rich

On June 2, det...@outlook.com wrote:
> > >>> I was just trying to debunk the idea that all motion is relative, and if
> > >>> A is moving at 100 kps relative to B, then B is also moving at 100 kps
> > >>> relative to A. That is nonsense. We know who is moving faster because
> > >>> one of them had to ACCELERATE to get to the higher speed.
>
>> >> A Camaro travels east on Route 80, at 90 mph, approaching exit 60.
>> >> A police radar trap sits at that point.
>> >> The car is actually moving, because he had to accelerate. The police car
>> >> is obviously stationary.
>> >> Now the trick: the police car is atop a very long flatbed train, zooming
>> >> eastbound at 90 mph. It's driving westward (opposite) the train,
>> >> 90 mph. Hence the cop is STATIONARY, relative to exit 60.
>> >> Now look at the police car vs. Camaro. If relative motion is bunk, which
>> >> is REALLY moving, and which is stationary?
>
>>> If I understand you correctly, the police car is technically "stationary" since
>>> it is not moving relative to the earth, and the Camaro is moving at 90 mph.
>
>> Correct.
>> To precise, police car's speed is irrelevant, only the speed
>> of the radar gun matters.
>
>>> A radar gun in the police car would definitely measure the speed of the
>>> Camaro to be 90 mph.
>
>> i) Camaro zooms east at 90 mph. Cop is parked, obviously stationary.
>> ii) Camaro, same as case (i). But the cop is driving westward at 90 mph.
>
> No, the cop is racing to remain "stationary." His radar gun doesn't "know"
> about the train or how the cop car is moving aboard the train. All the gun
> "knows" is that it is "stationary" relative to the ground.
>
>> In (ii), they are moving the same speed THROUGH SPACE,
>> in opposite directions. In fact, we can ignore the earth completely!
>> What's pertinent is their speed through space. They accelerated
>> identically, to the same speed. Therefore their closing speed must be 180.
>
> The closing speed for the train and the Camaro is 180,

No, train and Camaro move in sync, eastbound, no relative motion.

> but the cop car is moving at 90 mph aboard the train, so the closing speed between the
> cop car and the Camaro is 90 mph.
> The gun emits photons that represent the LOCATION of the gun RELATIVE
> TO THE GROUND. If the gun was moving, then the photons would oscillate
> at a higher frequency that represents the guns' motion relative to the ground.
> In your thought experiment, the cop car is STATIONARY relative to the
> ground. That is all the gun knows.
> And because it is STATIONARY relative to the ground, the gun emits
> photons that oscillate at a frequency that matches the frequency that
> would be emitted by a gun actually ON the ground.

You're fixated on the ground.

Let's remove the earth. Camaro, train, and cop car are all rocketing
through empty space, same speeds as above. Now, what's stationary
relative to what? Does the radar gun suffer a nervous breakdown, when
it loses contact with earth?

--
Rich

On Friday, June 3, 2022 at 1:40:19 PM UTC-5, Al Coe wrote:
> On Friday, June 3, 2022 at 9:06:54 AM UTC-7, wrote:
> > > > > A simple radar speed gun always just shows the rate of change of the distance between gun and target. A "moving radar" device determines the speed of the gun relative to the ground by measuring the rate of change of the distance between the gun and some object(s) at rest on the ground. There is nothing magical or mysterious about this.
> > > >
> > > > You are talking about LIDAR guns, not radar guns.
> > >
> > > Nope, I'm talking about radar speed guns (although the same statement applies to LIDAR speed guns). Again, a simple speed gun reads the rate of change of the distance between gun and target. If you think this is not true, go ahead and describe a situation in which you believe a simple radar speed gun reads something other than the rate of change of the distance between gun and target.
> >
> > Radar guns...
>
> I guess you missed my question, so I ask again: Please describe the circumstances in which you believe that the reading on a simple radar speed gun does *not* equal the rate of change of the distance between gun and target.

Your question makes no sense. A radar gun does NOT measure the rate of
change of distance between gun and target. It measures the frequency difference
between the photons it emits and the photons it receives back. That frequency
difference results from the difference in SPEEDS between the gun and the target.

HOWEVER, IN THEORY the 70 mph reading on the radar gun can be mathematically
converted into a difference in distances. The gun will show 70 mph if the target
is 100 feet from the gun or 500 feet from the gun, but mathematically if it is
traveling at 70 mph, so you should be able to compute what distance it traveled
DURING ANY SHORT PERIOD OF TIME. There is just no way to relate that period
of time to a distance between the gun and the target, since you do not know the
time between measurements. The gun does not measure that.

Ed

On Friday, June 3, 2022 at 1:59:25 PM UTC-5, RichD wrote:
> On June 3, wrote:
> > you display your ignorance in not knowing the difference between a BEAM
> > and a WAVE. You can easily focus PHOTONS into a beam.
> > You cannot focus sound waves into a beam. So, how do you focus light waves
> > into a beam?
> Right.
> Message these guys, let them know you're onto their fraud -
>
> https://www.fierceelectronics.com/components/choosing-ultrasonic-sensor-for-proximity-or-distance-measurement-part-2-optimizing

That article is about transducers. Transducers convert one form of energy into
another. So, if you focus sound waves into a "beam," there is no "beam," there are
just lower amplitudes of sound the farther you are from the focus point "beam."

Transducers seem very different from how sound works normally..

Ed

El viernes, 3 de junio de 2022 a las 12:59:22 UTC-4, det...@outlook.com escribió:
> On Friday, June 3, 2022 at 10:52:05 AM UTC-5, tjrob137 wrote:
> > On 6/3/22 9:49 AM, Ed Lake wrote:

> > The operator of the radar gun must ensure that the reflected waves come
> > from the target vehicle, and not extraneous reflectors. The gun displays
> > the speed corresponding to the largest Doppler shift within its beam,
> > which combined with the operator's aiming of the beam automatically does
> > the separation you claim cannot be done.

> Right. It cannot be done because the "beam" width is 12 degrees. That means
> that at 500 feet, the "beam" will be 105 feet wide. At 200 feet it will be 42 feet
> wide. If the gun is pointed at an oncoming truck, the front of the truck will be
> about 10 feet in front of the trailer. Both will reflect "waves." And there is no way
> to separate waves from the tractor and waves from the trailer. If you can't
> tell one wave from another, you cannot use waves to measure speeds.

The radar detector receives all of those reflected signals and they vary in strength. Therefore, the radar detector will receive some small signals at low frequency (from static objects like poles or houses) and strong signals at the frequency of the moving vehicle. No radar looks to separate waves from the tractor from waves from the trailer (that is pure nonsense).

> > > How can that be done with waves?
> > In the obvious way: the wave emitted by the gun has a rather narrow
> > divergence, so you can point it accurately at a target.

> A BEAM has a divergence. A BEAM of photons has a divergence.
> What is a "beam of waves"? How can it have a divergence if the
> primary property of a wave is to spread out IN ALL DIRECTIONS from the
> source? Can you have sound waves that are confined into a narrow beam?
> NO! So, how are light waves different from sound waves?

There are in every radar gun things called antennas. The radar gun transmitter/receiver antenna has a narrow directivity (of 12 degrees intead of 360 degrees).

> > > The operator's manual for my TS-3 radar gun says that the "beam width" is 12 degrees.
> > > How can you have a beam width of 12 degrees if a gun emits waves?
> > By limiting the beam divergence. It is straightforward microwave
> > engineering to design a radar antenna that emits a beam with such a
> > narrow divergence. Such design tools model the radar beam as a wave, not
> > photons. You merely display your personal ignorance.

> No, you display your ignorance in not knowing the difference between a BEAM
> and a WAVE. You can easily focus PHOTONS into a beam. You cannot focus
> sound waves into a beam. So, how do you focus light waves into a beam?
>
Nonsense. Read, for instance, https://en.wikipedia.org/wiki/Sonic_weapon