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location Greece
age 74
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Retired experimental particle physicist.

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


Sep
24
comment Did the Big Bang happen at a point?
@JoeBlow No. Read the answer by John. The quantum picture joins smoothly with the classical picture and the quantum dimension is expected to make the origin,time=0, point fuzzy. You can gain an intuition by the surface of a balloon analogy. On the surface of a balloon two dimensional intelligent species would feel expansion and all points of their world receding from each other, but the third dimension would have no meaning within their world. In the beginning of their time all balloon points would extrapolate to that one point where the expansion started. All points were the beginning point
Sep
24
comment Parity of baryons. Why it is hard to find the parity determination of baryons?
Maybe you have not looked at en.wikipedia.org/wiki/List_of_baryons . slide 2 here www.physics.ohio-state.edu/~kass/P780_L6_sp03.ppt . baryons by convention have parity +
Sep
24
answered What will happen if two photons collide perpendicularly?
Sep
24
comment What will happen if two photons collide perpendicularly?
@BrandonEnright Photons interact with each other very weakly, with higher order terms so they cannot be considered in this framework. It is classical intererence patterns for coherent sources , digitalcommons.unl.edu/cgi/… spurious interference patterns for incoherent ones,
Sep
24
comment Experiment which shows that Newtons third law is not true for magnetic forces
From the link above "Feynman gives a simple example, two charge particles, one moving directly towards the other and the other one moving in some other random direction ." from this I would guess that if one set up two wires one in the x direction and the other in the y, with two independent dc circuits and started a dc current at the same time on both (with the correct direction) , only one of them would move. It would be interesting to try if you have the lab equipment. see relevant paragraph digitalcommons.unl.edu/cgi/…
Sep
24
comment Experiment which shows that Newtons third law is not true for magnetic forces
have a look also at this which clears up the situations of the "naive" violation of third law physics.stackexchange.com/questions/43269/…
Sep
24
comment Experiment which shows that Newtons third law is not true for magnetic forces
Have a look at this suggestion youtube.com/watch?v=PhfX51FpjwI. One could do the experiment and measure the velocities; simpler for same weight magnets measure distance traveled. This is a suggestion that will show it works for simple magnetic forces.
Sep
23
revised Is mass in particle physics classical or relativistic?
added 170 characters in body
Sep
23
comment Is mass in particle physics classical or relativistic?
@Ruslan we cannotavoid the fact that E=m*c^2 is the most known relativistic mass formula to the general public.
Sep
23
answered Is mass in particle physics classical or relativistic?
Sep
23
answered Did the Big Bang happen at a point?
Sep
23
comment How close can you get to lava before burning?
They do it for fun and games youtube.com/watch?v=BAdFvTo9874 huffingtonpost.com/2014/09/05/…
Sep
23
comment Why can't electrons fall into the nucleus?
@rmhleo Sure, "why" is answered with "how" the current theory explains things, until we hit the basic assumptions ( mathematics and postulates) that make up the theory. and so on for any new theory .
Sep
22
answered Observing a particle over a certain domain
Sep
22
comment Can two electrons get ever so close as to touch each other?
It is the inverse of the conundrum that generated the need for quantum mechanics, i.e. two opposite charges and their attraction. In this case the infinite energy is enough to save classical mechanics. In the opposite charges there would have been no atoms if not for QM
Sep
21
comment Can be this configuration used to faster than light communication?
I think the crux lies in that the observer in the frame of A, once he/she knows the A state, knows what the B state is, but cannot communicate it to the framework of the observers of B. How will the observer at B know that A has has been measured? even or odd seconds makes no difference. B observer cannot know about the collapse of A .
Sep
21
comment Anti-neutrons, anti-quarks, isospin: What is observed and what is derived?
I am saying that annihilation is a complex phenomenon that has been extensively studied and the theory fits the data to a t. The theory assumes that protons and neutrons are made up of quarks and antiprotons antineutrons of antiquarks , and it works.
Sep
21
comment Anti-neutrons, anti-quarks, isospin: What is observed and what is derived?
Pure energy has no meaning for antiproton proton annihilation. It goes mostly through the creation of pions which are pairs of quark antiquark.Neutron hitting antineutron annihilates the same as proton hitting antiproton from isospin symmetry. see links in lubos' answer. Only limits are given for antiroton proton to gamma , the crossection is so small journals.aps.org/pr/abstract/10.1103/PhysRev.184.1415 .
Sep
21
answered Anti-neutrons, anti-quarks, isospin: What is observed and what is derived?
Sep
21
comment What is entropy really?
You should take out the "really" from your title because entropy is really the macroscopic manifestation of the real fact that matter is not continuous but is discrete, made up of zillions of particles, and the "real" answer is the one of statistical mechanics, from which thermodynamics emerges macroscopically. Maybe "in classical thermodynamics" should replace your "really".