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seen Sep 4 at 18:03

Phd student


May
13
comment Is it pions or gluons that mediate the strong force between nucleons?
@Lubosh, belay that last request, I just found a 12page study into whether or not the pion model is appropriate to teach at a pre-University level. For anyone interested it's here: teachers.web.cern.ch/teachers/archiv/HST2002/feynman/…
May
13
comment How do you explain spinning tops to a nine year old?
+1 for the bicycle wheel suggestion. It's a great way to get the point across in a way that can really be seen, and felt. Careful not to catch your nose on the spinning tyre though! ;)
May
13
comment Help getting the distance an object has moved
not only was the question very close to being a "do my homework" type question anyway, clearly not permitted in the FAQ, but your answer has gone one step further and does it. Hence why I phrased my attempt more as a guide than complete calculation.
May
13
comment Maxiumum weight a buoy can float
@Georg - The volume of pressurized are is not meaningless; it has a mass associated with its volume and density. However, I was assuming the walls of the buoy were thin, and the air wasn't significantly pressurized (since this would have a detrimental effect on the buoyancy anyway.) Perhaps I could have stated this but I didn't want to overcomplicate a brief comment.
May
13
comment Maxiumum weight a buoy can float
Buoyancy is related to the weight of the volume of material displaced. In your case this means the max weight would be equal to $3943mm^3$ of water, minus the 0.8kg weight of the buoy..
May
13
revised On black holes, Hawking radiation and gravitational atoms
Typo
May
13
comment Is it pions or gluons that mediate the strong force between nucleons?
@Lubosh, agreed (with all the above). Any chance of seeing some of the beautiful mathematics that govern pion & gluon exchange, and the calculation behind knowing when one is more suitable than the other? .. For my benefit rather than my student ;) References/links are equally as welcome as transcribing the relevant buts on here. Clearly I can find the wiki page on QCD but there's no mention of the applicability of the pion vs gluon models..
May
13
comment Help getting the distance an object has moved
@Georg and @Qmechanic An unusual unit for distance. If that is indeed the case here, well .. fine.
May
13
comment Help getting the distance an object has moved
@Omega - Is there a typo in your unit for the speed? 14hm/min doesn't make any sense..
May
13
answered Help getting the distance an object has moved
May
12
revised Space-time hospitality
added 5 characters in body
May
12
comment Shape of Fan Blades
@Martin - Very interesting, thanks. I wonder whether the same principle work for a water pump? I suspect one would require near-lamina flow from the internal pump to holes but have no idea if this is feasible..
May
12
comment The meaning of action
This is a nice compliment to the others answers but I feel it necessary to point out that the book you cite (QFT Demystified) contains a huge number of errors and in many sections over-simplifies the theory. It should not be considered as a suitable introductory text to the subject, or even one that should be trusted.
May
10
revised Space-time hospitality
Typo
May
10
revised Space-time hospitality
deleted 3 characters in body
May
10
answered Space-time hospitality
May
10
comment Space-time hospitality
Whilst this question is hugely hypothetical (and could have been better worded) I see no harm in considering the requirement of gravity on the possibilty of life. Up-voting to conteract down-votes that I believe to be unfair.
May
10
comment Is it pions or gluons that mediate the strong force between nucleons?
@genneth, I completely agree, in general. The student in question however, is particularly inquisitive and specifically asked for an answer that was not 'dummed-down' due to it being too complex. One of my old Professors used to say "Simplify, simplify, but don't through the baby out the bathwater." I think in this instance, whether or not to settle on the pion model is equivalent to the baby sitting on the rim of the bath..
May
10
comment Is it pions or gluons that mediate the strong force between nucleons?
@Lubosh, Thanks. I read your answer with great interest (3 times!) Would I be correct to summerize that pion-exchange is merely a crude (non-renormalizable) approximation and it is closer to the truth to teach that it is instead just gluon exchange? (I say closer to the truth because I'm sure that if sea- and valence-quarks, and their associated PDFs, are properly taken into account the situation must be become significantly more complex.)
May
10
comment What happens if you try to freeze water in an water tight container
+1 for the great video link