811. Mode of Propagation. - Only three methods are known by which energy may be transmitted from one point of space to another.

First, by the movement as a whole of some medium reaching from one point to the other, as in the case of ropes, belts, or shafting.

Second, by projectiles, as in the case of a shot from a gun or a ball thrown.

Third, by waves, as in case of sound or water waves.

The velocity with which a projectile travels depends on the initial impulse.  If light is communicated by means of particles shot out from the luminous body we should expect to find the velocity depending on the source and that particles emanating from the sun would have a different velocity from those from an electric light.

On the other hand, the velocity of a wave depends only on its wave length and the nature of the wave (whether compressional or transverse, etc.) and the properties of the medium of which it is a disturbance.  Sound waves from fiddle, pipe, or drum advance with the same speed through air. If light is a wave motion we may expect to find light waves, whatever their source, traveling with the same velocity through space, and this is precisely what experiment shows to be the case. This consideration therefore points to its being a wave motion.

811. Mode of Propagation. - Only four methods are known by which energy may be transmitted from one point of space to another.

First, by the movement as a whole of some medium reaching from one point to the other, as in the case of ropes, belts, or shafting.

Second, by projectiles, as in the case of a shot from a gun or a ball thrown.

Third, by undulation of a medium, as in case of sound or water waves.

Fourth, by emission, as in the case of light photons and other forms of electromagnetic energy.

The gravitational redshift happens when light tries to escape from a gravitational field. This is actually a phenomenon that you can explain using ordinary newtonian physics. Thanks to Einstein's famous E= m c squared, and Planck's equally famous law relating the energy of light to its frequency, E = h x frequency, we can see that as a particle of light (photon) moves out of a gravitational field, it must loose energy working against the gravitational field. Since photons always travel at the speed of light, the only place where this energy loss can show up is in a change of frequency. The frequency of the photon must decrease so that the energy carries by the photon is lower, and this corresponds to a 'red shift' to longer wavelengths. This phenomenon has been confirmed in laboratory experiments carried out by Pound and Rebka at Harvard University over 30 years ago. It's not a theory, its real.

Next, Einstein calculated how gravity would affect the frequency of a light beam. If a rocket is launched from the earth and sent into outer space, the gravity of the earth acts like a drag, pulling the rocket back. Energy is therefore lost as the rocket struggles against the pull of gravity. Similarly, Einstein reasoned that if light were emitted from the sun, then gravity would also act as a drag on the light beam, making it lose energy. The light beam will not change in velocity, but the frequency of the wave will drop as it loses energy struggling against the sun’s gravity. Thus, yellow light from the sun will decrease in frequency and become redder as the light beam leaves the sun’s gravitational pull. Gravitational red shift, however, is an extremely small effect, and Einstein had no illusion that it would be tested in the laboratory any time soon. (In fact it would take four more decades before gravitational red shift could be seen in the laboratory.)

In an era of atomic clocks, lasers, and supercomputers, scientists are mounting the kind of high-precision tests of general relativity that Einstein could only dream about. In 1959, for example, Robert V. Pound and G. A. Rebka of Harvard finally confirmed Einstein’s prediction of gravitational red shift in the laboratory, that is, that clocks beat at different rates in a gravitational field. They took radioactive cobalt and shot radiation from the basement of Lyman Laboratory at Harvard to the roof, 74 feet above. Using an extremely fine measuring device (which used the Mossbauer effect), they showed that photons lost energy (hence were reduced in frequency) as they made the journey to the top of the laboratory.

The Gravity Probe A payload was launched in 1976 from the NASA-Wallops Flight Center in Virginia. It followed an elliptical flight trajectory over the Atlantic, attaining an altitude of 10,000km (6,200 miles) above the Earth before crashing into the Atlantic Ocean. During this short trip, GP-A transmitted accurate measurements of slight changes in the clock's rate in lower gravity, and provided the best test of this portion of Einstein's theories that has been performed to date.

At the peak height of 10,000 km the clock should run 4.5 parts in 10¹⁰ faster than on the Earth's surface according to general relativity. The MASER clock's accuracy was reported to be 1 part in 10^-15. The observed effects matched the prediction to an accuracy of about 70 parts per million.

Light changes speeds	Light emitted at different speeds

The Pound–Rebka experiment is a well known experiment to test Albert Einstein's theory of general relativity. It was proposed by Robert Pound and his graduate student Glen A. Rebka Jr. in 1959,^[1] and was the last of the classical tests of general relativity to be verified (in the same year). It is a gravitational redshift experiment, which measures the redshift of light moving in a gravitational field, or, equivalently, a test of the general relativity prediction that clocks should run at different rates at different places in a gravitational field. It is considered to be the experiment that ushered in an era of precision tests of general relativity. 

The gravitational redshift of a light wave as it moves upwards against a gravitational field (produced by the yellow star below).

Robert Pound and Glen Rebka performed their historic experiments here at Harvard in the Jefferson Physical Laboratory. They were able to demonstrate that the frequency of gamma radiation measured at its source (on the building's roof) differed from the frequency measured in the basement. The incredibly small shift (about 1 part in a million billion) showed that clocks run slower in the basement than the roof because, being closer to the Earth, the gravitational field, and hence the space-time curvature, is larger there. The faster clock on the roof would read a lower frequency of gamma radiation and thus the wavelength would be longer, or red-shifted.

Photons are excess energy moving from atom to atom until they are observed or consumed. 

Photons are excess electromagnetic energy moving from atom to atom until they are transformed into a different form of energy. 

o

Photons are the smallest measure of light, and no, they don't have mass. So that's easy, right? Light is composed of photons, which have no mass, so therefore light has no mass and can't weigh anything.

Not so fast. Because photons have energy -- and, as Einstein taught us, energy is equal to the mass of a body, multiplied by the speed of light squared. How can photons have energy if they have no mass?

Does light have mass?  The short answer is "no", but it is a qualified "no" because there are odd ways of interpreting the question which could justify the answer "yes".

Light is composed of photons, so we could ask if the photon has mass.  The answer is then definitely "no": the photon is a massless particle.  According to theory it has energy and momentum but no mass, and this is confirmed by experiment to within strict limits.  Even before it was known that light is composed of photons, it was known that light carries momentum and will exert pressure on a surface.  This is not evidence that it has mass since momentum can exist without mass. 

Well if you read a textbook, you will find out that light can be thought of as being made up of particles called photons. These photons have no mass! So there is the simple answer, light has no mass and no weight. This is a lot like knowing the name of the bird, you know that light has no mass and no weight, but you don't know how light behaves.

Well it turns out that even though light has no mass, it is attracted by gravity. This effect is so small that we are not aware of it in ordinary light, but astronomers must keep this in mind, because there are certain situations when this effect will be observable. Now in order to see this effect, you need a large body with a lot of mass which will bend the path of light due to its gravity. One example of a big body is the Sun, but since the Sun gives off so much light itself, it is often difficult to see this. It turns out that during a total eclipse of the Sun, scientists can see the effect of the Sun's gravity bending starlight from distant stars. Incidentally, this effect was first predicted by Einstein, but scientists had to wait several months for the next eclipse to see if he was right. (He was, of course, correct.)

Light does not have mass, and therefore there is nothing for the force of gravity to pull on, so light doesn't have weight either.  However, light does have energy.

If you find it hard to understand quantum physics, theory of relativity, dark matter & dark energy, Unruh effect, standard model e.t.c...just know that...

That is a VERY IGNORANT thing for Mr. Tyson to say. It basically tells people that they shouldn't TRY to make sense of the universe. It also echoes what some university physics professors teach when they tell their students that physics doesn't have to be logical. They are just telling their students to BELIEVE what they are being told and don't ask questions!

I'll ask questions until I find answers that are logical and make sense. And if those answers do not fit with what Mr. Tyson or physics textbooks say, then I'll ask more questions and do research to find out which is correct.

that is what Einstein said. He cannot accept anything that to him is not logical. Therefore he never accepted Quantum Theory even though he had mathematically proven it he disregarded it. Who really knows?? They say you can mathematically prove almost anything but maybe our math is not the end it all.

Ed Lake, No No!!! You have to hear it in the right context!!

Mr Tyson was talking about things like quantum mechanics and the "bizarre things that molecules do"...Some of the things we find to be true about the universe are FRIGGIN BIZARRE and make NO sense whatsoever...he was saying that the nature of the universe is under no obligation to make sense!

He wasn't trying to say we shouldn't try to make sense of it.

Yes, Quantum Mechanics is a problem in that it argues things which defy logic and common sense. To me (and Einstein), that means QM cannot be trusted to be true. And, as Mike Noreika stated, "They say you can mathematically prove almost anything." I agree. Solving science problems with math tends to begin with an answer and then they develop equations that produce that answer.

Until I see solid proof to the contrary, I think the universe makes perfect sense and is entirely logical. And if there is something that SEEMS illogical or contrary to common sense, then it is a near certainty that there is something about it that we just do not yet fully understand.

well then...you never asked the universe to make sense and Mr Tyson wasnt talking about you

August 2, 2018 - I've been trying to organize the digitized books about physics I have in my computer.  I seem to have at least 400 different books scattered through a library of 1,031 items, more than half of which are scientific articles.  I keep track of everything on a computerized spreadsheet, but I haven't been making any detailed notes about what is contained in each book.  Below is a list of just 15 books (the spreadsheet also contains the file name, a ranking, the document type, the number of pages, whether it is digitally searchable or not, and a space for a brief note):



The only note I made about the book by Carl Ramirez was "Very heavy in mathematics, but might contain something worthwhile."  The notes also say that a couple others seem to be self-published, so they wouldn't make good references.

One book I browsed through this morning was the 3rd edition of "Physics for Scientists and Engineers - With Modern Physics" by Paul M Fishbane, Stephen Gasiorowicz and Stephen T Thornton (one of two books I have with that exact title).  When I read the underlined sentences below, I had to stop to make an image of them:

 

To me, the underlined sentences illustrate the insanity of what is being taught in many colleges today.  They say the particle theory of light cannot explain certain observations, so the book is going to promote the wave theory of light, which can explain those observations.   What is not mentioned is that the wave theory of light cannot explain other observations, primarily that light definitely consists of particles, not waves.  As Richard Feynman put it on page 14 of his book "QED: The Strange Theory of Light and Matter":

Newton thought that light was made up of particles—he called them “corpuscles”—and he was right (but the reasoning that he used to come to that decision was erroneous). We know that light is made of particles because we can take a very sensitive instrument that makes clicks when light shines on it, and if the light gets dimmer, the clicks remain just as loud—there are just fewer of them. Thus light is something like raindrops—each little lump of light is called a photon - and if the light is all one color, all the “raindrops” are the same size.

I want to emphasize that light comes in this form—particles. It is very important to know that light behaves like particles, especially for those of you who have gone to school, where you were probably told something about light behaving like waves. I’m telling you the way it does behave—like particles.

 

“What actually happens on a microscopic level is that the incoming photon is absorbed by the electrons of the mirror, which are set into oscillation by the photon’s oscillating electric field. The result is, for some materials (shiny ones), that the electrons’ oscillation creates a new photon that moves away from the mirror in the opposite direction. The incoming and outgoing photons are free and move at speed c, but they are not the same photon…”[

Also, in the radar gun circuitry, it is NEITHER photon nor waves. It is
electrical signals going from some sort of antenna likely in a waveguide, down a copper circuit trace here, an IC package lead, a
transistor gate etc. Here we have a signal from the continuous wave signal generator at 23 GHz to the transmitter circuit. The receive circuit amplifying a weak Doppler shifted signal, this plus a small amount from the CW oscillator are combined in a mixer circuit and lowpass filter and now we have a much lower frequency which is the difference between the transmitter frequency and the (Doppler shifted) received frequency from the radar target. This frequency can be directly displayed as a speed by (virtually) multiplying it by a constant. Again, inside the gun there are NO photons involved, no waves, it is all electronic signals.

If you drop a hammer in a well, it falls down into the well, it doesn't fall up from the bottom of the well to the Earth's surface. ... Things fall in the direction of where time runs slower... that's WHY things fall.  If you don't understand this, you don't understand the first thing about general relativity.

In classical mechanics, the gravitational potential at a location is equal to the work (energy transferred) per unit mass that would be needed to move the object from a fixed reference location to the location of the object.  It is analogous to the electric potential with mass playing the role of charge. The reference location, where the potential is zero, is by convention infinitely far away from any mass, resulting in a negative potential at any finite distance.

   

A Lagrange point is a location in space where the combined gravitational forces of two large bodies, such as Earth and the sun or Earth and the moon, equal the centrifugal force felt by a much smaller third body. The interaction of the forces creates a point of equilibrium where a spacecraft may be "parked" to make observations.

General relativity is a *local* field theory.  There is no spooky action at a distance.  Objects do not sense the direction of the lowest clock rate anywhere in the universe, they merely sense the *local* direction of reducing clock rates, and move in that direction.

   

#10.  Singularities are real.

#9.  The Big Bang didn't occur at  any spot, it happened everywhere.

There is a theorem, famous among cosmologists, showing that an inflationary state is past-timelike-incomplete. What this means, explicitly, is that if you have any particles that exist in an inflating Universe, they will eventually meet if you extrapolate back in time. This doesn't, however, mean that there must have been a singularity, but rather that inflation doesn't describe everything that occurred in the history of the Universe, like its birth. We also know, for example, that inflation cannot arise from a singular state, because an inflating region must always begin from a finite size.

#2. Scientists routinely LIE to the public.

The mathematicians point of view makes no sense unless you inexplicably believe the universe operates like a mathematical equation and there is no such thing as "cause and effect."

It appears that, to mathematicians, cause and effect are alien concepts.  Time Dilation is just an "illusion."

How can any scientist ignore cause and effect?   Answer: a scientist can't, but a mathematician can. 

Their beliefs are INSANE in any world where cause and effect are an important part of science. And their Prophet, Neils Bohr, didn't believe that cause and effect could explain the universe the way mathematics can.

In reality (and in SCIENCE), of course, HOW the clocks got to be moving is the key to everything.  But science is very much about CAUSE and EFFECT, which the mathematicians consider to be meaningless, worthless and just part of some philosophy.

If you CAUSE one of the clocks to move, you KNOW that that clock is moving and the other is still stationary.  And you know the "relative" speed is actually one clock's speed away from the other.  Therefore the clock that is moving will experience Time Dilation and the clock that is stationary will not.  It's as simple as that.  Yet, it seems incomprehensible to mathematicians. They can only view situation A and situation B, they cannot think about how one situation developed into the other. 

I was rather surprised to see this absurd belief stated so emphatically by mathematician physicists.  They equate understanding "cause and effect" to asking why 2 plus 2 equals 4.  They claim it is philosophy, not physics.  Cause and effect is all about why things happen.  The mathematician physicists do not care why things happen.  In one argument I was told that once the mathematical model is found, "cause & effect" becomes obsolete.  We understood this 2000 yrs ago!"

#3. "Cause and effect" has no meaning in science.

Consider two rows of clocks in relative motion, such as one row of clocks sitting along an embankment and another row of clocks on a moving train. (Each row of clocks has been synchronized using the usual physical processes in its frame.) We find that the readings on each clock on the train advance at a slower rate than the readings on the successive clocks on the embankment as it passes them, BUT we also find that the readings of each clock on the embankment advance at a slower rate than the readings on the successive clocks on the train as they pass it. So, which clocks are running faster? 

The crucial fact is this: When compared with the clocks on the embankment, the clocks on the train are not just ticking at a slower rate, their values are offset from each other by different amounts. When the clock at the middle of the train reads 12:00, the clock at the front of the train reads (say) 11:59 and the clock at the back of the train reads 12:01. (The clocks in between are all offset in proportion to their distance from the center).

It's standard in introductory texts. See for example Figure 2.4 in Rindler's "Essential Relativity".

There is a free copy of that book on-line, so I looked it up.  It's on page 40.  Below is a screen-capture of that page:

--------------------- start screen capture of page 40 -------------------

------------------------ end screen capture of  page 40 ----------

It's a bizarre theory that between any two reference frames (S and S') there will be another reference frame

July 19, 2018 - This morning I awoke thinking once again about radar guns.  There is still something about them that bothers me.  I can describe the problem by explaining the two situations as shown in the illustration below:



In Situation A, the speeder is moving eastward at 100 miles per hour from the point of view of the Police officer.  The officer's radar gun emits photons which oscillate at a specific frequency and which travel at the speed of light (c or 299,792,458 meters per second) toward the speeding car.

The global positioning system (GPS), while mentioned, is not properly credited for its importance in the worldwide distribution of accurate time. GPS has now become the dominant means to obtain time, even in ways of which the ultimate user is unaware. Its success and easy availability in providing time even threaten the development of new, more expensive clocks.

But the most significant development in time transfer since the 1980s has been the growth of two satellite navigation systems, GPS and GLONASS. GPS is a network of 24 Navstar satellites operated by the US Department of Defense. GLONASS (Global Navigation Satellite System) is a similar array of satellites operated by the Russian military.

The Russian system, GLONASS, is taking longer to gain acceptance and suffers from reliability problems. Like GPS, the constellation is supposed to have 24 operational satellites, but many have failed and by the spring of 2000 only ten were working.

Development of GLONASS began in the Soviet Union in 1976. Beginning on 12 October 1982, numerous rocket launches added satellites to the system until the constellation was completed in 1995. After a decline in capacity during the late 1990s, in 2001, under Vladimir Putin's presidency, the restoration of the system was made a top government priority and funding was substantially increased. GLONASS is the most expensive program of the Russian Federal Space Agency, consuming a third of its budget in 2010.

By 2010, GLONASS had achieved 100% coverage of Russia's territory and in October 2011, the full orbital constellation of 24 satellites was restored, enabling full global coverage.

In terms of positional accuracy GPS is slightly better than GLONASS overall, but due to the different positioning of the GLONASS satellites, GLONASS has better accuracy at high latitudes (far north or south).

If the two systems are stationary relative to one another and the space between them is flat (i.e. we neglect gravitational fields) then the photon emitted by the emitter can be absorbed by the electron in the receiver. However, if the two systems are in a gravitational field then the photon may undergo gravitational redshift as it travels from the first system to the second, causing the photon frequency observed by the receiver to be different to the frequency observed by the emitter when it was originally emitted. Another possible source of redshift is the Doppler effect: if the two systems are not stationary relative to one another then the photon frequency will be modified by the relative speed between them.

In the Pound-Rebka experiment, the emitter was placed at the top of tower with the receiver at the bottom. General relativity predicts that the gravitational field of the Earth will cause a photon emitted downwards (towards the Earth) to be blueshifted (i.e. its frequency will increase)

are specified by their manufacturer to operate only under accelerations less than 2 g.

the mechanical structure might not remain stable.")

Something else happened yesterday while I was arguing about the centrifuge time dilation experiment mentioned in my Analyzing the "Twin Paradox" paper.  I then had to create the illustration below to help explain my thoughts to myself.
 
The argument was about how time dilation works in the centrifuge situation.  Unlike the Hafele-Keating experiments, the spin of the earth plays no role in this experiment.  Even though it might seem otherwise, both clocks move around the Earth's axis together.  The stationary clock (x1) in the control room and the moving clock (x2) on the centrifuge are mathematically stationary relative to one another.  Part of the time the x2 clock is moving sideways to the left (A) relative to the x1 clock.  Part of the time the x2 clock is moving sideways to the right (C) relative to the x1 clock.  Part of the time the x2 clock is moving away (B) from the x1 clock.  And part of the time the x2 clock is moving toward (D) the x1 clock.   All relative movement is balanced out.  It is just as if the two clocks were both stationary relative to one another (for purposes of location).  

However, relative to the speed of light (which is where time dilation occurs) the centrifuge clock (x2) is moving significantly faster than the control clock (x1).  The fact that the movement is in a circle makes no difference.

For some reason, people keep wanting to measure time dilation between x2 and some point midway between x2 and the center of the spinning centrifuge.  I think it may be because that is how they model their mathematical equations.  They have no standard model equations that compare a point on the centrifuge to a point outside of the centrifuge room.

It is all very interesting, and sometimes I am getting defenders who explain things the way I explain them.  And they also criticize Tom Roberts for arguing the same nonsense about "signals" over and over and over, even though he has been proved wrong again and again and again. 

Also, the feedback I am getting about the centrifuge time dilation experiment on Facebook's Astrophysics and Physics group has all been positive.   It has mostly just been people clicking on "like" or "love," but there has occasionally been an intelligent question for me to answer.

Unfortunately, the article you posted to sci.physics.research is inappropriate for the newsgroup because its statements about special
relativity are simply wrong.  What Steve Carlip wrote,

SR says that in Alice's rest frame, Bob's
clock appears to tick slower than Alice's, and in Bob's rest frame, Alice's clock appears to tick slower than Bob's.  *You* don't get to decide which clock is "really" slower, unless you want to claim that your reference frame is better than anyone else's.

is correct.

[[Mod. note -- As Tom Roberts (& others) have pointed out, in order
to directly compare clocks A and B, A and B must be colocated for
the duration of the comparison, i.e., they must be at the same
position and (be observed by *all* observers to be) moving at the
same velocity.

If these conditions don't hold, then we can't directly compare A
and B.  We may be able to compare (say) A to signals broadcast by
B, but that's a rather different sort of (indirect) comparison.
-- jt]]

Your posting is inappropriate for sci.physics.research since it doesn't contain any scientific arguments. BTW, the language of science, particularly physics, in fact is math, at least it's the only language adequate to formulate what physics is about.      

Albert Einstein’s been having quite a few weeks! First his “imaginary elevator” thought experiment was confirmed with unprecedented precision, then his theory of relativity was shown to create gravitational lenses as expected even in other galaxies. And today, we learn that a central tenet of relativity still holds even at gravitational extremes. It’s no annus mirabilis, but it ain’t bad.

Today’s news, which appears in the journal Nature, concerns the equivalence principal, which roughly says that falling objects should all fall the same way. It sounds obvious put that way, of course, but the idea that heavier objects should fall at the same rate as lighter objects (discounting air resistance) still surprises people. The idea is that gravity accelerates heavier objects faster, sure, but because they’re more massive it’s harder for them to accelerate, so the two effects cancel out.

Let us assume that two portions of matter encounter each other a first time, separate, and then meet again. We are able to state that observers attached to one and to the other respectively during the separation will not have made the same evaluation of the duration of this separation and will not have aged to the same extent as each other, it follows from what has been said above that the ones that will have aged the least will be those whose motion during the separation has been farthest from being uniform, or who have undergone most accelerations.

In this observation there lies the means, for any one of us willing to devote two years of his life to it, of knowing what will have become of the Earth in two hundred years, of exploring the future of the Earth by taking a forward leap into its lifetime that will last two centuries for the Earth and two years for him, although it would have to be without any hope of returning or any possibility of becoming back to inform us of the result of his journey, since any attempt to do this could only carry him farther and farther forward.

To do this, our traveler would need only to agree to being shut up inside a projectile that the Earth would launch at a velocity sufficiently close to that of light, but still less than it, which is physically possible, arranging for an encounter with, say, a star to take place at the end of one year in the lifetime of the traveler and to send him back towards the Earth at the same velocity. Having returned to Earth two years older, he will emerge from his ark to find that our globe has aged two hundred years, provided that his velocity has remained within the range of only one part in twenty thousand less than the velocity of light. The most reliably established experimental facts of physics enable us to state that this is indeed what would happen.

We discuss a rather surprising version of the twin paradox in which (contrary to the familiar classical version) the twin who accelerates is older on the reunion than his never accelerating brother.

    

 

The human centrifuge shown above is located at NASA's Ames Research Center in Mountain View, California.  According to their web site, it can carry a payload of 1,200 pounds, and it can