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237151
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location Greece
age 75
visits member for 4 years, 3 months
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Retired experimental particle physicist.

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


Dec
18
comment Physics the Why vs. How question?
continued: We have taken to the "Why" to "why D"
Dec
18
comment Physics the Why vs. How question?
@Ingo Sure, that is the process when then we gather data and are on the way of building up a mathematical theory. after a while we say that B happened because it was preceded by A. When we discover that A is always preceded by C and C is always preceded by D etc we are on the way to a mathematical theory which has formed our way of describing data in physics. Then we see that we know how B happens, it is because of D, and if we want B to happen we create the D situation because we have the causal path of how each causes the other. How gives the causal path which is the only thing we can do.
Dec
18
awarded  thermodynamics
Dec
17
comment Does a charged particle accelerating in a gravitational field radiate?
@innisfree Gravity at the moment knows nothing of quantum mechanics in a consistent framework. A charged particle necessarily is a quantum mechanical entity. We have to wait for the unified q uantum theory to be able to see what the weak equivalence principle will look in it. Till then semiclassical arguments have to hold, and it is an experimental fact that accelerating or decelerating charges emit radiation, and this energy will come from somewhere.
Dec
17
comment Physics the Why vs. How question?
@Ingo We can only really show how from the postulates and the axioms of our model for that particular physical phenomenon we can explain this phenomenon. Then one goes into "why these axioms and postulates", which are only answered with "because that is what fits the data".
Dec
17
answered Physics the Why vs. How question?
Dec
17
comment Do all massless particles (e.g. photon, graviton, gluon) necessarily have the same speed $c$?
@NickKidman All I am saying that there should be a connection with data . There could be an infinity of mathematical constructs, but can they model the data?
Dec
17
comment Do all massless particles (e.g. photon, graviton, gluon) necessarily have the same speed $c$?
@NickKidman I think the difference with your example lies in the quantum numbers . The virtual particles are not arbitrary functions, they carry the quantum number conservations and the pole/propagetor that represents them has the on mass shell value except that in the internal lines things go imaginary.
Dec
17
comment Do all massless particles (e.g. photon, graviton, gluon) necessarily have the same speed $c$?
@KevinDriscoll Well, when really kicked out of the nucleus gluons do make jets so their reality seems to me to be backed by experiment.cerncourier.com/cws/article/cern/29201
Dec
17
answered Do all massless particles (e.g. photon, graviton, gluon) necessarily have the same speed $c$?
Dec
16
revised Experiment dropping electrons into glass of protons
spelling
Dec
16
answered Experiment dropping electrons into glass of protons
Dec
16
comment Quantum mechanics potential barrier problem
Have a look at hyperphysics.phy-astr.gsu.edu/hbase/quantum/barr.html . The exponential decay is within the barrier. on the other side it is again a propagating wave with imposed continuity conditions on the boundary.Note it is a probability wave.
Dec
16
comment Can sand falling in a floating hourglass cause it to sink? (Follow up to hourglass question)
A variation in this video youtube.com/watch?v=kctdo6rQZbY
Dec
15
comment Why does Venus rotate the opposite direction as other planets?
I meant the probability of having the correct velocity to be captured into orbit is small , although I have not calculated it.
Dec
15
comment Why does Venus rotate the opposite direction as other planets?
Hi Ubuntu . Welcome. Your answer sounded like a question. We tend to be more like a class presentation here than a friendly discussion and it has been edited accordingly by the moderator. The answers are supposed to be graded for posterity :) by the up arrows. Now on the content, I think if one calculates the probability for such a large planet to be on its own and pass the sun and be captured the number would come out very small. There do exist rogue planets en.wikipedia.org/wiki/Rogue_planet but the universe is very large and probabilities of falling into orbit small.
Dec
15
awarded  Deputy
Dec
15
comment Why does Venus rotate the opposite direction as other planets?
@UbuntuSouthAfrica You have not interrupted anything, and it is an old discussion. A captured planet would need careful calculations as to the probability of finding itself and in such a size on the path of Sol.
Dec
15
answered Quantum barrier for photons
Dec
14
comment Do you regret being a Physicist?
I am pushing on 74 and fortunately at the time I was thinking of a university it was enough that one got a university degree, not many people did at that time, so there was no negative pressure. I knew I wanted to be a physicist from age 11 or 12 and even though at times other almost equal passions got my attention ( including having two children) I still found physics exciting, creative and good for the little grey (or white, since I am a woman) cells. It is trite, but true: follow your passion and you will not regret it.