Reputation
Next tag badge:
99/100 score
38/20 answers
Badges
3 60 209
Impact
~3.0m people reached

Nov
12
revised Can light gravitationally affect itself?
added link
Nov
12
comment Can light gravitationally affect itself?
Ray of light is a bad term. Rays are just geometrical tools pointing at the energy transfer direction of the electromagnetic wave. An electromagnetic wave is composed out of zillion of photons, at the underlying quantum mechanical level. The wedding of general relativity and quantum mechanics has not yet been decided upon. It is a frontier of research. The answer by Dirk is in the classical framework of general relativity. I think you should use "electromagnetic wave" to be precise classically.
Nov
12
answered What exactly are light waves?
Nov
12
comment Can electromagnetic fields be used to shield electromagnetic radiation?
to qualify my previous comment, a the photon level the interaction with a magnetic or electric field goes with higher loops in Feynman diagrams, which involve the coupling constant 1/137 at least to the power of -16 multiplying the interaction crossection, thus the interaction with the magnetic field will be very very weak
Nov
12
answered What is the entropy of a pure state?
Nov
12
comment Does the gravity affect voltage in a circuit?
As you say the effect is very very small. This is fun to know : home.web.cern.ch/about/updates/2012/06/… .. There was never a question that the beam was pulled by the moon :) .
Nov
11
comment Earth's and Moon's outgoing radiation
@DavidHammen of course for absorption, no for elastic scattering which reflection is . there variations must be smoother depending on the effective albedo/reflectivity of bulk matter. earthshine is radiation from the ground, which will have the discontinuities of the absorption spectra, and the reflected radiation from clouds snow water droplets etc, much smoother. In the violet region next to UV the variations are fairly smooth, imo
Nov
11
comment Earth's and Moon's outgoing radiation
@DavidHammen sure as far as penetration goes, but reflectivity is quoted as 35% eesc.columbia.edu/courses/ees/climate/lectures/radiation_hays
Nov
11
comment Earth's and Moon's outgoing radiation
@DavidHammen from the link in the comment above it is true that most of the ground level turns into infrared, but there is a lot that is reflected from the troposphere . Usually changes are smooth, the graph you show shows flatness. I think to within an order of magnitude it should be ok to extrapolate the curve. It depends what one aims to do with the number.
Nov
11
comment Earth's and Moon's outgoing radiation
5000 angstrom are 500 nanometers, that is why I am talking of estimate, since the plot ends at the beginning of ultra violet. Since the earth is more or less in equilibrium ( we are not boilint or freezing) with the incoming radiation, I would take the watts/m**2 from the first plot as in the correct ball park, one might check the percentage absorption of UV and correct further. earthobservatory.nasa.gov/Features/UVB/uvb_radiation3.php . some UV is completely reflected so the estimate from the original sun curve might not be off
Nov
11
answered Earth's and Moon's outgoing radiation
Nov
11
answered Why does the measurement of some observable $A$, the measured value is always an eigenvalue of the operator?
Nov
11
answered What is the experiment used to actually observe the position of the electron in the H atom?
Nov
11
comment Where is the fine-structure constant in this list?
Have you forgotten that coupling constants run? i.e. are functions of energy? the familiar ~ 1/137 becomes ~1/128 , as measured experimentally see www2.ph.ed.ac.uk/~rhorsley/SII09-10_mqft/lec16_2.pdf for example
Nov
10
answered Neutrinos and photons
Nov
9
comment Buoyancy Dilemma
yes, it is a method of measuring the density, grms per centimeter cube.
Nov
9
revised Electrostatics and two electric charges
added 1005 characters in body
Nov
9
comment Electrostatics and two electric charges
@Sofia ok, I will edit.
Nov
9
comment Buoyancy Dilemma
by definition of buoyant. Archemedes en.wikipedia.org/wiki/Archimedes discovered that the density of an object could be measured by the volume of water its submersion displaced. a first measurement of density without destructing the object. Then logic comes in that if the volume of water displaced has a larger weight than the object , the object floats.
Nov
9
comment Why does the Copenhagen interpretation assert randomness if this cannot be tested?
It is my opinion of course, formed by experience and reading. Have a look at this blog entry on the copenhagen interpretation motls.blogspot.gr/2011/05/… , which is much broader than your question.