2,140 reputation
1539
bio website none.seriously
location Switzerland
age 30
visits member for 3 years, 9 months
seen Aug 17 at 19:00

Physicist.


Aug
12
comment Finding the cosmological redshift of a galaxy in the expanding Universe
@user57074 You should ask that as a new question and not in a comment. But in short, the photon has the energy of the "observed" wavelength - when you change the inertial frame, energy is no longer "conserved" the way you'd expect it to be
Aug
11
comment What restores balance to a repulsive electric force on an electroscope?
it's not only about rendering costs, but also about the potential screwing up with the site's search function I'd guess. Anyway, please take no offence in my editing this out
Aug
11
revised What restores balance to a repulsive electric force on an electroscope?
fixed formatting
Aug
7
comment How to measure Entropy?
agreed, let's do this again sometime :D
Aug
7
accepted How to measure Entropy?
Aug
7
comment How to measure Entropy?
@Phonon sounds sadly reasonable :/ one'd have to describe entropy in terms of the standard model to get close to that I guess, and the usual observer-influences-system part of quantum physics destroys my hopes in said omnimeter...
Aug
7
comment How to measure Entropy?
@Phonon interesting analogy :) though ideally one would find a perturbation that yields the same equilibrium as before (what with non-interfering) and observe the evolution itself, no? interesting idea, I wonder if this allows for a sufficiently general device though. I'm still hoping for an entropy-meter...
Aug
7
comment How to measure Entropy?
@Phonon true, but isn't there some kind of boundary condition for entropy that allows one to have a well-defined system that upon contact with the system to be measured can somehow obtain its entropy (or rather, the difference to another point or system) just the way a classical voltmeter works?
Aug
7
comment How to measure Entropy?
Thanks for the input, too bad it ain't that simple... but that means in order to obtain a checkmark on this answer I'm afraid the original question, how to (generally) measure Entropy, needs to be answered. As @celtschk said, temperature is also not "directly" measured yet one does not need to make any assumptions on the system the temperature of which is measured, except for it coupling to the thermometer with little to no interference of course
Aug
2
comment How to measure Entropy?
@Phonon that's an interesting read there, thanks! concerning the vagueness, my question boils down to whether a device similar to a voltmeter or thermometer exists for entropy.
Aug
2
asked How to measure Entropy?
Jul
31
revised Why does $\mathcal L = -\frac14 F^{\mu\nu} F_{\mu\nu}$ imply Photons are massless?
linked to archive version
Jul
22
revised Analytic continuation of imaginary time Greens function in the time domain
improved formula typesetting
Jul
2
awarded  Curious
Jun
30
awarded  Notable Question
Mar
20
comment How would we tell antimatter galaxies apart?
@endolith Good question - I can't answer it though, maybe it's worth a new question here. From my limited understanding of cosmology I'd suspect that might reduce the amounts of dark matter and dark energy required to explain the universe, and maybe also inflation. But I'm really only speculating... This answer to my strongly related question gives some sources that may be helpful, but I didn't fully read them to be honest...
Mar
5
comment Is there something similar to Noether's theorem for discrete symmetries?
I'm afraid you're mixing up symmetry and conserved quantity here
Feb
27
comment Is there any way to annihilate matter without the use of anti-matter?
It's probably "cheating", but there probably exist virtual states where this happens. It's just not a finished process, i.e. while this contributes to some probabilities it won't be actually observable... Then again you could claim $p + e^- + \gamma \to n + \nu$ made the proton vanish without any anti-matter involved...
Feb
16
comment Is it fair to judge this speedskating race by only 3 thousands of a second?
"And it's a dead heat! They're checking the electron microscope. And the winner is...number 3, in a quantum finish." "No fair! You changed the outcome by measuring it."
Nov
6
accepted Are there models/simulations of antigravitational antimatter-galaxies?