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I'm a physics graduate student.


Feb
1
revised How long does an object experience motionlessness at the beginning of its descent?
edited title
Feb
1
comment Is thermodynamic reversibility a function of path?
@joshphysics good link. I updated the answer.
Feb
1
comment Is thermodynamic reversibility a function of path?
@Christoph Good point. I updated the answer.
Feb
1
revised Is thermodynamic reversibility a function of path?
added 266 characters in body
Feb
1
awarded  Disciplined
Jan
31
answered Is thermodynamic reversibility a function of path?
Jan
29
awarded  Popular Question
Jan
28
awarded  Good Answer
Jan
27
comment Why and how is the speed of light in vacuum constant, i.e., independent of reference frame?
@JerrySchirmer To be honest I was describing physics that was beyond me. I simply remembered reading this in Feynman's QED. Looking it up, on pp 89 it says "The major contribution occurs at the conventional speed of light... but there is also an amplitude for light to go faster (or slower) than the conventional speed of light. You found out that in the last lecture that light doesn't go only in straight lines; now, you find out that it doesn't go only at the speed of light!" Maybe I misunderstand just what this means, though. I don't know quantum field theory.
Jan
26
awarded  Nice Answer
Jan
19
asked Why doesn't a typical beam splitter cause a photon to decohere?
Jan
19
answered Noether Theorem and Energy conservation in classical mechanics
Jan
19
comment Noether Theorem and Energy conservation in classical mechanics
pppqqq Is correct. Your procedure begins by assuming that for a given trajectory, the value of the Lagrangian is constant. I.E., you throw a ball through the air and over the course of its flight kinetic-potential energy stays constant. This is wrong, so of course the result you get is wrong.
Jan
14
awarded  special-relativity
Jan
14
comment Solids: is energy expended in some fashion by, say, a table to keep the top from sinking down against gravity?
That is very difficult to calculate. All I am saying is that things decay. Old buildings fall down, old statues rust, etc. Presumably a table will decay a bit more quickly with gravity than without it. There is not necessarily a constant energy input required. It is just the case that some non-zero amount of energy is required over long times in order to counter the table's gradual decay.
Jan
13
revised Solids: is energy expended in some fashion by, say, a table to keep the top from sinking down against gravity?
deleted 2 characters in body
Jan
13
comment Solids: is energy expended in some fashion by, say, a table to keep the top from sinking down against gravity?
The energy of the table changes whenever its state changes. If the table breaks and collapses all at once, then that's how it happens. If it slowly sags with age, then that's how it happens. I don't understand the second question.
Jan
13
comment is action integral Lorentz invariant?
I'm not sure what the "first postulate" is, sorry. I'm saying that there is some $\mathbf{x}(\tau)$ which is the trajectory. It's a four-vector position as a function of proper time and is invariant. If you find it in two different frames, you'll get two different sets of coordinates describing the same $\mathbf{x}(\tau)$.
Jan
13
answered is action integral Lorentz invariant?
Jan
13
answered Solids: is energy expended in some fashion by, say, a table to keep the top from sinking down against gravity?