anna v

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11843

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Retired experimental particle physicist

	25,899 reputation	bio	website		visits	member for	2 years, 4 months
11843 badges		location	Greece		seen	5 mins ago

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4h	revised	The Univere's mass-energy and uncertainty clarification
5h	revised	The Univere's mass-energy and uncertainty clarification
5h	comment	The Univere's mass-energy and uncertainty @BenCrowell by the way, you say " the OP has the inequality the right way around", but the OP is treating the inequality as an equality. It is OK to find the order of magnitude limits but it still is an inequality, setting a lower bound to the product.
5h	comment	The Univere's mass-energy and uncertainty @BenCrowell conservation of energy does not apply to General Relativity which is the state of the creation of the universe, which is when coherent quantum states could exist and one could talk of virtual creation.
5h	answered	Can a single molecule have a temperature?
6h	answered	The Univere's mass-energy and uncertainty
14h	comment	Magnitude of a photon? @twistor59 That is the probability for the photon to go through or be reflected. The individual photon is not split of course. It certainly is very sloppy terminology.
19h	comment	Magnitude of a photon? @OndřejČernotík a photon is an individual particle withe energy hnu and a spin (+/-1). It cannot be split. It can Compton scatter on an electron and change its frequency, be absorbed kicking an electron to a higher level, or pair produce in the field of a nucleus for high energy gammas. thats about all.
20h	comment	Magnitude of a photon? It does not make sense at all. One can split classical electromagnetic waves, not individual photons. There is nothing there to split. what is the book?
20h	comment	Magnitude of a photon? sounds wrong in my opinion. Missprint or something. A photon is one of the elementary particles, cannot be split, it has mass 0 and is only characterized by its energy/frequency and spin orientation (=/-1). en.wikipedia.org/wiki/Photon
21h	comment	Calculate energy from an reaction @DeerHunter and the other downvoter: why such hostility to a new user? You could ignore the question after all. kudos to Nivalth for taking the risk you perceived in the link.
21h	comment	Calculate energy from an reaction have you thought of energy conservation given the special relativity relation of mass with energy?
1d	answered	Non-isolated universe and arrow of space
1d	revised	Collision between a photon and an electron after edit of question
1d	answered	Collision between a photon and an electron
2d	comment	Quantum mechanics and everyday nature but @joshphysics accepting the existence of photons in a beam of light is a circular argument, because a photon is the quantum of light.
2d	comment	Best current bounds on nonconservation of momentum? handwaving, I would expect that the small error in mass of J/Psi mdelta(m)~pdelta(p) ; in Mev (c=1), 30000.01=30 so pdelta(p)~30MeV for momenta in the low GeV range where experiments are more accurate.
2d	comment	Best current bounds on nonconservation of momentum? All the masses in the particle data group listings are the result of many different experiments and are found by summing up in histograms the invariant masses of the sum of particles composing the resonances. m^2=E^2-p^2. The whole Standard Model would flop if energy and momentum are not conserved within the experimental errors.If one had the experimental data one could easily get the momentum errors typical of particle experiments. It is not easy to find these particularly at low energies, where the accuracies are higher so I cannot write it up in an answer.
May 21	answered	Convergence of Light on the Retina
May 21	comment	Probability distributions When you prescribe "random number" by definition it is the uniform distribution. The one that tells us that throwing a dice will come up with the face six 1/6th of the time.