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[Sean Mirrsen]

I'm just using common sense. It's known that energy has mass. It's known that light transfers energy. Therefore light cannot have "no mass", even at rest, because it would mean it does not exist then. The wording of "no object posessing mass" may be true in regards to attaining lightspeed, because said object would fall apart and become an energy wave at lightspeed, but it's wrong to use it to determine the mass of such quirky stuff that are waveform-particles.

[mainiac]

Somebody help me here.

The short answer: because time and distance become dilated.

The long answer: We'd really like to know.  Why not get a PhD and move to Cern to help answer that question?

[mainiac]

I'm just using common sense. It's known that energy has mass. It's known that light transfers energy. Therefore light cannot have "no mass", even at rest, because it would mean it does not exist then. The wording of "no object posessing mass" may be true in regards to attaining lightspeed, because said object would fall apart and become an energy wave at lightspeed, but it's wrong to use it to determine the mass of such quirky stuff that are waveform-particles.

You aren't using common sense.  You are using "common sense."

Common sense is using what you know to be true to make obvious conclusions.

"Common sense" is using what you "know" to be true to make "obvious" conclusions.

[Sean Mirrsen]

Well, I know the two basic points to be true. I never studied particle physics but from the two facts I know to be true - that energy has mass and that light transfers energy - I derive that it is impossible for light to exist in a state where it would have no mass. If it gains its mass from relativistic speed, then it cannot exist at anything other than relativistic speed. Which is why I said that nothing can be created and posess a speed by virtue of existing. Light, to me, seems rather the opposite of that, existing (as a particle) by the virtue of posessing speed.

[mainiac]

Well, I know the two basic points to be true. I never studied particle physics but from the two facts I know to be true - that energy has mass and that light transfers energy-

Congrats.  You know something that up until now, we thought to be false.  You should publish a book.

(How many times, and with what degree of sarcasm, must I chide you for making unsound assumptions?)

[Psyco Jelly]

Well, I know the two basic points to be true. I never studied particle physics but from the two facts I know to be true - that energy has mass and that light transfers energy-

Congrats.  You know something that up until now, we thought to be false.  You should publish a book.

(How many times, and with what degree of sarcasm, must I chide you for making unsound assumptions?)

You forget about relativistic mass. Since matter is just a condensed form of energy, energy has utterly trivial mass. but there is still mass.

[mainiac]

Some energy has mass, yes.  But he was treating that as universally true.  Which it ain't.

[Psyco Jelly]

Well, the energy itself doesn't have mass, but the particle that carries that energy does. A photon is no exception. I guess you say that light itself doesn't have mass, but a photon does. It's really weird.

[mainiac]

Well, the energy itself doesn't have mass, but the particle that carries that energy does. A photon is no exception. I guess you say that light itself doesn't have mass, but a photon does. It's really weird.

This level of particle physics is above my paygrade.  But I know the level of relativistic physics we are discussing.  And for relativistic physics of this nature, we can safely treat light as being having zero mass.

[Sean Mirrsen]

In the words of John Tickle, "Here's one for you". There is a completely enclosed system. Inside it is a device holding a pebble of antimatter within a magnetic field, with a timer to release the field at a certain point. Will the total mass(any of the subtypes of it) of the system decrease when the annihilation happens?

What I think is that rest mass may decrease because unconfined energy will not effect the system, but relativistic mass must remain the same if no energy escapes, and if in the same system was a device that absorbed all existing forms of energy and converted them into matter, eventually the rest mass would also return to the original value.

[mainiac]

Your scientific methodology, in a word, sucks.  You observe a characteristic in one situation, then ASSUME it applies to another.  But you make absolutely no effort to see if the situations are the same.  Despite there being glaring differences.

At the start and end of your enclosed system, the masses will be the same.  However, when the annihilation first happens, releasing lots of light, the mass goes down a lot.

[Sean Mirrsen]

I think I said exactly that. Rest mass will decrease, because "energy pressure" will not affect it. But relativistic mass? The total energy released during the annihilation would equal, as per the conversion, the mass that was annihilated.

If you take the broadest meaning of mass, then a system cannot release energy without expending mass, in however miniscule quantities. Of course, direct conversion doesn't magically happen in a static object, so there aren't really ways to "measure" mass of energy, especially rest mass. You can't say that of a photon either, because it gains mass from relativistic speed, and does not exist as a particle if stopped.
------
Epilogue: Well alright, I've ran out of plausible clauses for this discussion. I don't really like educated scientists, because knowledge allows to defend a known point of view. I don't know, which is why I intend to find out through observation rather than scrupulous study of what others found out. Like I said, I consider this a positive ability.

[Ampersand]

You know, I've been thinking about it, and it shames me to admit, that I'm at loss as to why it is supposed to be so. After all, the thing that first comes to mind is the relativistic mass increase, that would need more and more force to accelerate it by the same factor. Yet, the mass increase is associated with the frame of reference that is moving, i.e. from the point of view of the ship, it's the planets that are moving. So it's the planets that should gain mass, not the spaceship, no? Somebody help me here.

If I recall correctly, this is exactly the sort of problem that Einstein confronted when he first began putting Relativity on paper. It's the twin paradox. One twin remains on earth while another leaves on a spacecraft that goes at relativistic velocities. To the point of view of either twin, it is the other that is accelerating away, and thus, the other that is undergoing time dilation effects.

The solution is simple. It is not relative motion between objects within space-time that matters, but motion relative to space-time itself that matters.

That is, the Earth remains more or less stationary relative to space-time, while the space craft is moving at a significant fraction of C relative to space-time.

[mainiac]

I intend to find out through observation rather than scrupulous study of what others found out. Like I said, I consider this a positive ability.

So, basically, you don't want to learn from others, and you are proud of this fact.

[Sean Mirrsen]

No, I don't want to take what others learned for a fact, and instead analyze and form my own theories. With nothing but observation, common sense and logic. Granted, I'd need a lab the size of our city to do any serious research, but I'm not yet aiming for serious.