Autumn_Man

But proper mass is also a misleading name.

Only to people who don't know what the term proper means. In this context the term proper means intrinsic. Proper mass is defined as the m in E^2 - (pc)^2 = m^2c^4. Until students learn what the terms mean who cares what mistakes they make. Mistakes are cleared up when the student learns the physics. Bad students believe all sorts of weird things

This is the reason why we use "invariant mass" or simply "mass" to refer to m.

"we" is what is found in the literature and "we" understand and use the term proper mass or rest mass too when that is the subject

From the point of view of particle, i.c., particle basis, light mass is zero.

 

But, from the point of view of light, the mass is only very short period physical property.

So, when light collide with photoelectric device surface, or similar situation, light mass is not zero and has particle property.

And, the other situation, light mass is zero and wave property.

On the particle point of view the relativistic mass of a photon is finite and has the value m = p/c = E/c²at all times. The proper mass or a photon is zero at all times.

When it comes to the invariant mass of disordered radiation there is a zero-momentum frame of the radiation and when there is energy and a zero momentum frame the invariant mass of that radiation is not zero. Tjhe invariant mass of a system of particles is defined the same way as proper mass is only with E replaced by the sum of all energies of the particles and p replaced by the sum of all 3-momentun of the particles.

That means that for a system of two photons moving parallel to each other in the same direction the invariant mass is zero. If the photons are moving in the oppsite direction of each other then the invariant mass of the two photons is non-zero

Until you realize that the proper mass of a photon is always zero and the relativistic mass of a photo is never zero people are going to run you around in circles.

I hate to be the one to tell all of you that the Earth isn't round. It's spherical.

There could not be a worse offense to the very reason for our protected freedom of speech, than this kind of censorship. This kind of censorship is exactly what is raising alarm across the nation, in discussions shows, and has focused me on concerns about morality, social change and politics. The censorship is being done by those who do not know the subjects and occasionally by those who do not even carefully read what a discussion is about. This is called "reactionary". It is not equal to critical thinking and reasoning. If nothing else, I hope you all take a good look at the censorship and question if this where you want to take us?

You're confusing freedom of speech as it pertains to our constitutional rights and as it pertains to our private lives. It doesn't hold in all wallks of life either. Freedom of speech is not absolute in the US. In particular you don't have freedom of speech when it comes to libel, slander, obscenity, copyright violation and incitement to commit a crime. You also can't go into a private organization and start preaching whatever is on your mind. In this case you can't go to a private discussion forum such as this and not follow the rules the've established to keep order to the place. You can't go into a Protestant Church or a Jewish temple and preach the Koran. In that sense you can't go to a private dicussion forum and place trhread containing pseudoscience in a place meant for mainstream physics either.

[math] E=mc^2 + pc[/math] from [math] E^2 = m^2c^4 + p^2c^2[/math] by finding the square root of both sides of the equation.

so [math] m=E/(c^2+pc) [/math]

 

Since the photon exists only at the speed of light it is as improper to find the "rest" mass as it is to find your personal mass at c......

Both are meaningless. The only mass for a photon that has any meaning is the relativistic mass.

 

Paul

A better term than rest mass is proper mass. It has no conotations about being measured in a rest frame. It's an intrinsic property of a particle and can be calculated using energy ann momentm by the relation (letting m = proper mass) E^2 - (pc)^2 = m^2 c^4. Solve for m and you have the proper mass of any particle as determined from any frame of reference.

We all agree that light has momentum. (m for notation sake only - Mass will use M)

We all agree that it has a velocity of C.

The mass of an object is the momentum divided by its velocity. ...

Without assuming a mass what is the momentum of a photon?

It depends on what terms you wish to express the momentum in. As you said above, m = p/v therefore p = mv where m is the relativistic mass of the body, not its rest mass.

now for the sake of measuring the very small let us use a scale that that multiplies the number (not the actual momentum just the number used to define it) by 1000000. We can call this scale nx's and note that a proton would have many millions of nx units as its mass.

 

so, take the momentum of a photon, multiply by 1000000 and divide by C.

What number do you end up with?

Sorry but I don't understand all that. Can you be clearer?

This is an assumption made about untested data. No one has determined the properties of the Higgs Boson or the higgs field. No one knows what effects the field may or may not have - it is all conjecture.

 

Paul

The problem here is that you're confusing rest mass with relativistic mass.

How does that jibe with [math]E^2 = p^2c^2 + m^2c^4[/math]? I get zero.

The problem is obvious, isn't it? He's talking about relativistic mass and you're talking about rest mass. The rest mass of a photon is zero and its relativistic mass is E/c²

Can somebody explain to me why the universe is expanding?

I think that the Big-Bang started the whole process by sending out a huge amount of energy at an event billions of years ago. It used to be believed that it was the momentum of the explosion that is carrying matter away but lately astrophysicists and cosmologists have discovered that the expansion is occuring at an accelerating rate. That can be due to various reasons such as the presense of a positive cosmological constant (which is more of an description than an explanation). Another reason would be negative pressure. Such sources act as negative active gravitational mass and is thought of as gravitational repulsion.

I have seen how very useful the principle of least action is, but don't really understand why the integral of the Lagrangian with respect to time is minimized. It seems to say the most efficient way to get from A to B is via a "path" that brings kinetic energy closest to potential energy. (Yes?) If so, then why is that most efficient?

 

Thanks for any insights.

The name Principle of Least Action is a misnomer. Its more accurate to refer to it as the Principle of Stationary Action since all that is required is that the first variation vanish.

Think of the analogy with normal functions. We consider here functions that are defined and continuous on open intervals. If the first derivative of a function is zero at a point then there is either a maximum, minimum or extremum at that point. If the second derivative of the function at that same point is positive then the function is a minimum at that point. If its positive then it’s a maximum and if its zero then its an extremal at that point.