50,153 reputation
230107
bio website
location Greece
age 74
visits member for 3 years, 8 months
seen 41 mins ago

Retired experimental particle physicist.

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


4h
answered Did the Big Bang happen at a point?
4h
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/…
12h
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 .
1d
answered Observing a particle over a certain domain
1d
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
2d
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 .
2d
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.
2d
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 .
2d
answered Anti-neutrons, anti-quarks, isospin: What is observed and what is derived?
2d
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".
2d
revised Matter and antimatter differences?
positron instead of electron for decay of antineutron. otherwise charge and lepton number violated
2d
revised How can a particle in a medium ever travel faster than light?
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2d
answered How can a particle in a medium ever travel faster than light?
2d
revised How did Pauli and Fermi deduce the existence of the neutrino?
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Sep
20
comment How did Pauli and Fermi deduce the existence of the neutrino?
@JerrySchirmer The question is why they did not propose another electron, which the questioner supposes has small energy. This is not true .
Sep
20
answered How did Pauli and Fermi deduce the existence of the neutrino?
Sep
20
answered How do we know that space expanded with speed faster that a speed of light during big-bang inflation?
Sep
19
revised How are theories in physics validated against existing knowledge in practice?
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Sep
19
comment Armageddon prevention
@DavidHammen well, I would use then two or three jets to control rotations and give the desired momentum thrust. For rubble water? to freeze it together: land on night side, which is the side you would want to apply the thrust to. Of course it would require extremely intelligent robots. Maybe manned vehicles . Science fiction :).
Sep
19
comment Armageddon prevention
@DavidHammen you seem to have numbers "the energy needed to turn an impact into a miss exceeds the yearly energy consumption by all of humanity" Do you have a link? I am thinking in terms of changing the asteroid's orbit by sending a rocket with a robot device which will attach the rocket itself on the asteroid perpendicular to the orbit and keep kicking to change it. Not an explosion. Turn it into a rocket.