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location Greece
age 75
visits member for 4 years, 6 months
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Retired experimental particle physicist.

The picture is a fayum . It looks like aunts and cousins of mine :).


5h
comment where has the energy gone when the test charge turned away?
It is a way of adding up the mathematics. The test particle gets the energy (kinetic) or gives up the energy in a system where the charge/gravitational_mass is at rest.
7h
comment where has the energy gone when the test charge turned away?
in potential problems all the actions and reactions have to be taken into account. To remove something you supply energy, or to bring to a certain point, the field does not lose energy.
1d
comment Is there uncertainity of position of the perfectly homogenous radiating body?
@Probably The model is wrong used for photons, as photons are elementary particles with quantum mechanical attributes and the way the classical electromagnetic field that he is talking about is being built up by photons is complicated, zillions of photons contribute to the classical electromagnetic wave. The radiation of one photon is independent from any other so there will be no balance that he proposes. Due to the energy and momentum taken away by a single photon the center of mass of the body will move, and I have tried to estimate the dimensions of this motion using the HUP.
2d
comment Is there uncertainity of position of the perfectly homogenous radiating body?
They are not axioms, they are postulates. Axioms mean that from a few mathematical axioms all the theory can be derived. The postulates are not mathematical, they are statements that connect a coherent mathematical model to data. The HUP applies to everything , except h_bar is so small that it is always satisfied in classical situations where we can measure, within our errors. Only when single particles or coherent quantum mechanical states are involved (crystal) the HUP comes into play.
2d
comment Is there uncertainity of position of the perfectly homogenous radiating body?
continued: and can be described with a QM wavefunction.
2d
comment Is there uncertainity of position of the perfectly homogenous radiating body?
@Probably Physics does not have axioms. Axioms belong to mathematics. Physics uses mathematics and has postulates, which relate measurable quantities to the output of mathematical operations. Quantum mechanics is the regime of photons, there are no photons in classical physics. In classical physics one can postulate a body radiating classical electromagnetic radiation symmetrically and thus overall not moving. When one goes to a one photon at a time radiation then it is the quantum regime where the Heisenberg principle applies. Crystals are macroscopic manifestation of the underlying qm state
Jul
29
comment What is high energy physics?
@KyleKanos well, after xrays, which are atomic size values, the photons from MeV on are called gammas.
Jul
29
comment Is there uncertainity of position of the perfectly homogenous radiating body?
@Probably The crystal is not random. It is controlled by very precise quantum mechanical functions that give the probability for finding the atoms at specific locations. The Heisenberg uncertainty is an over all tool that reflects the intrinsic structure of the operator functions that are involved in the generation of the state function whose square gives the probabilities. A calculational tool, imo.
Jul
29
comment Can the uncertainty principle be redefined for different standard deviations?
@joshphysics Suppose you are looking at crystal structure, and you want the uncertainty in the location of an atom in that structure when probed by photons. The relevant length is the distance between centers ( d(X) ) and the relevant momentum is the momentum of the photon, )which ends up to d(lambda) ). Nothing to do with statistical standard deviation to get an answer to that.
Jul
28
comment Can the uncertainty principle be redefined for different standard deviations?
@ACuriousMind I think you are confusing necessary and sufficient. A standard deviation is sufficient to define an interval, but not necessary. The heisenberg uncertainty can be applied to a larger set than standard deviations.
Jul
28
comment Can the uncertainty principle be redefined for different standard deviations?
Actually it is not the statistical standard deviation in the uncertainty principle. It is about and interval delta(x) and an interval delta(p) which can be defined in any way the problem defines. An interval on the axis x and the axis p. hyperphysics.phy-astr.gsu.edu/hbase/uncer.html
Jul
28
comment What stops giant cruise ships toppling over in rough seas?
@CarlWitthoft read the link. These large cruiseships use stabilizers, which means with a power failure they are at the mercy of the winds.
Jul
27
comment What stops giant cruise ships toppling over in rough seas?
This blog is interesting onlyinamericablogging.blogspot.com/2012/01/…
Jul
27
comment Why is not the entropy of earth increasing?
you must justify your question, by a link at least: who says that the entropy of the earth is not increasing?
Jul
27
comment Do atoms behave like waves?
I think you should add the links, because after a while comments may disappear here, whereas answers are permanent
Jul
27
comment Do atoms behave like waves?
The virus will not be in two places at once. The probability of finding it will be different in the two places. Another tack: the probability of passing through slit 1 and the probability of passing through slit 2 have the wave nature. Nothing creepy. Try passing a basketball through a loop . A probability curve describes it. Each individual trial has a probability . It does not mean that the ball that passed the loop also hit the side.
Jul
27
comment Do atoms behave like waves?
correct, but one should add that the quantum effects, which is the wavelike nature of the probability of finding a particle, depend on the size of h_bar, which is a very small number. For large dimensions, masses and energies where we live and classical mechanics applies, it is effectively zero.
Jul
26
comment Why particles don't lose mass when they radiate
@xaxa The energy comes from the potential energy that the field supplies when an electron is accelerating or decelerating in it. When the electron is at rest because one has transformed to the rest system of the electron, the electromagnetic radiation is coming from the changes in the field which is also transformed to the rest system of the electron. For another pov look at this philpapers.org/rec/HARRFA
Jul
26
comment Electron as a standing wave and its stability
Yes, quantum mechanics developed because of the OBSERVED stability of the atoms/molecules and the OBSERVED spectra of transitions between energy levels. The Bohr theory had to postulate the stability. Schrodinger's equation for the hydrogen atom contains the stability from more general postulates. hyperphysics.phy-astr.gsu.edu/hbase/quantum/qm.html that could explain atomic spectra generally. An please note that the wave nature displayed at the particle level is a PROBABILITY WAVE. hyperphysics.phy-astr.gsu.edu/hbase/quantum/wvfun.html , NOT an energy or mass wave.
Jul
25
comment How does the Pluto-Charon orbital 'dance' affect Pluto's elliptical orbit around the Sun?
Maybe you should add a sentence to the effect that pluto itself is dancing around the orbit traversed by the center of mass, so Pluto's orbit is elliptical+/- the woble of the duo.