50,058 reputation
230107
bio website
location Greece
age 74
visits member for 3 years, 8 months
seen 2 hours ago

Retired experimental particle physicist.

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


2h
answered Anti-neutrons, anti-quarks, isospin: What is observed and what is derived?
2h
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".
4h
revised Matter and antimatter differences?
positron instead of electron for decay of antineutron. otherwise charge and lepton number violated
6h
revised How can a particle in a medium ever travel faster than light?
deleted 6 characters in body
6h
answered How can a particle in a medium ever travel faster than light?
15h
revised How did Pauli and Fermi deduce the existence of the neutrino?
added 948 characters in body
18h
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 .
18h
answered How did Pauli and Fermi deduce the existence of the neutrino?
22h
answered How do we know that space expanded with speed faster that a speed of light during big-bang inflation?
1d
revised How are theories in physics validated against existing knowledge in practice?
added 2608 characters in body
1d
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 :).
2d
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.
2d
answered How are theories in physics validated against existing knowledge in practice?
2d
comment Is the Standard Model consistent (UV complete)?
I suppose with your first sentence you are implying that the consistent perturbative expansions are not all the possible perturbative expansions from the model: that a subspace is only covered by the consistent ones.Otherwise I cannot imaging how an expansion of a function would not represent the function if it is well behaved. ?
2d
comment Momentum of electron problem
You should be using relativistic kinematics, the total energy of the electron is not its kinetic energy only en.wikipedia.org/wiki/…
2d
comment Why do roads appear wet on hot days? I do not understand
No, the density fluctuations are there but the refraction index is such that the angles of total reflection ( which are essentially what one gets at interfaces) are larger than the angle from the vertical your eye subtends when you get closer.
2d
comment Is antimatter power theoretically possible?
There are no free floating positrons. They have been created as electron positron pairs at some point in their life line. Thus energy conservation says that you can never have "leftover power to spare" . The best you could have would be a technologically hard to create "battery", i.e. energy storage device.
2d
comment Why do roads appear wet on hot days? I do not understand
If the road were a mirror, you would see an image of the sky on the road. The density changes of air due to temperature changes refract the light coming form objects in such a way that an image appears as if there were a reflecting surface, like water on the road. It is a refractive interface that geometrically creates similar optical distortions.
2d
answered Why do roads appear wet on hot days? I do not understand
2d
answered What theory unifies the electroweak and the strong forces?