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242159
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location Greece
age 75
visits member for 4 years, 4 months
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Retired experimental particle physicist.

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


Jan
30
comment Why do surfaces act like barriers for electrons?
A potential is what is giving the F force in your question above. Forces arise because of potentials.
Jan
30
answered Why do surfaces act like barriers for electrons?
Jan
29
comment Why does a floating balloon in an accelerated train moves forward but the pendulum moves backward?
look at this video youtube.com/watch?v=EYRuHSfR4R8 here acceleration is radial also youtube.com/watch?v=XXpURFYgR2E . The link of Christoff explains it. A matter of buoyancy. rule of thumb what floats up in air follows the balloon track, what sinks follows the pendulum.
Jan
29
reviewed Close Determining of Fracture Toughness without fatigue pre cracking, is it possible?
Jan
29
awarded  Custodian
Jan
29
reviewed Leave Open Given Velocity formula and told to find acceleration, I need help please.
Jan
28
comment Why does charge accumulate at points?
V could be the tip of a lightning rod
Jan
28
comment Could sphaleron-induced proton decay also cause vacuum decay?
@Dilaton en.wikipedia.org/wiki/Sphaleron
Jan
28
answered How can electrostatic forces provide lift to the gossamer spider?
Jan
27
comment Can a small change in the Earth temperature give rise to large-scale climate changes?
all I am saying is that the holocene has a flattish top sliding down of 10000 years. The other warm periods look like needles going fast downhill.
Jan
27
comment Can a small change in the Earth temperature give rise to large-scale climate changes?
My eyeball of the ice core temperatures records tells me that we are long overdue to a fall into the next ice age. The Holocene is exceptionally persistent at high values, fortunately. en.wikipedia.org/wiki/File:Vostok_Petit_data.svg . burn burn against the falling of the ice ( to paraphrase Dylan Thomas: rage rage against the dying of the light) endjoke/
Jan
27
answered Application of $E = mc^2$
Jan
26
comment Why does black get heated the most?
it is white that reflects all colors
Jan
26
comment Why positronium can annihilate in vacuum?
also a sum of frequencies will not be a frequency. a sum of photons has invariant mass .
Jan
26
comment Why positronium can annihilate in vacuum?
I think the confusion comes from your hW . E/c for a complex system of particles is not hW/c .
Jan
26
comment Why positronium can annihilate in vacuum?
It is pair production by Xrays that needs an interaction with a field in order to conserve momentum in the cms. hyperphysics.phy-astr.gsu.edu/hbase/relativ/releng.html#c4
Jan
26
comment Why positronium can annihilate in vacuum?
momentum is a vector and the second formula ignores the masses of the e an p too.
Jan
26
comment Hawking radiation and entropy
The law of constant or increasing entropy holds for closed systems.
Jan
26
comment Measuring background radiation
They are part of the "natural radiation" ( look at the link) to which biological organisms have adjusted during their evolution. It is excess over the background radiation that is harmful. Muons only ionize, alpha and and neutrons because they can interact strongly can do much more damage .
Jan
26
comment How energy conservation is not violated here?
internal energy is stored from the food we eat to be expended as we live and move.