29,768 reputation
33994
bio website inspirehep.net/…
location Duchy of Grand Fenwick
age 43
visits member for 3 years, 5 months
seen 15 mins ago

Experimental nuclear and particle physicist. These days I'm teaching, but I've spent a lot of time on nucleon structure in fixed target electron scattering and neutrino oscillations using reactors and beam sources.


38m
comment Birds sitting on electricity wires:potential difference between their feets
Note that in AC lines (which includes some but not all "high tension" lines) the potential difference between two points that are "nearish" can be dominated by the oscillation of the signal rather than the ohmic attenuation. With 50 or 60 Hz signals and standard issue birds this is not an issue, but the bare statement was bothering me.
1h
comment What Did Nobelaureate Smoot Mean by “Modern Efforts to Find Violations of Special Relativity”
None that I have heard of, but that doesn't mean much ... there's lots of stuff going on that I don't hear about.
1h
revised What Did Nobelaureate Smoot Mean by “Modern Efforts to Find Violations of Special Relativity”
deleted 9 characters in body
1h
answered What Did Nobelaureate Smoot Mean by “Modern Efforts to Find Violations of Special Relativity”
2h
comment How come that an Infinite universe will collapse under gravity?
I can only guess why people are down voting this question, but I find it enormously unclear. I suspect that you have a big structure of interconnected ideas in your head and that this might make sense in the context of those thoughts, but no one in your audience is coming from that perspective. This is a common problem in technical writing especially where there is pressure to be concise.
4h
comment Why are sine/cosine always used to describe oscillations?
"So it is inevitable that, with these definitions of "stable equilibrium", the resulting vibrational pattern at small amplitudes will be sinusoidal. Always." Well, occasionally you get cases where $k=0$ and the first non-trivial term is the $g^{(3)}$ term (not $g^{(2)}$, because that makes your equilibrium unstable again), but these situations are few and far between.
4h
revised What causes the dimensions of a star increase when its hydrogen fuel is exhausted?
edited tags
4h
comment When a star turns into a red giant what stops its core contracting
Closely related: physics.stackexchange.com/q/91716
4h
comment How does the process of protein denaturatation work?
@Awesome Just for future reference--rather than input on this question--it is possible for questions to be on-topic on more than one Stack Exchange site. In particular there are substantial areas of overlap between physics and both chemistry and astronomy. In those the poster can put it where (s)he likes, but for new posters you might appraise them of the existence of the other site.
5h
comment How does nuclear war look like from space?
"If the Soviets in their psychotic ideological driven paranoia had actually pushed the button," It is worth noting that it was a soviet officer named Stanislav Petrov who didn't 'push the button' when doctrine called for him to do so. The fact that the system (and presumably the highest leadership) was screwed up does not imply that the people were as well.
5h
comment Why does a nuclear explosion have directionality?
I want to emphasize @DeerHunter's point here, that ring is a real effect, but it is not a property of the explosion itself; instead it is a property of the geometric relationship and interaction between the explosion and the ground.
8h
comment Angular momentum depends on origin?
@TadeusPrastowo These facts are implicit in the material usually presented in an introductory course, and lecturers often mention them in passing. Alas, very few students really notice. I suspect that most students are too busy learning the process and basics to take full advantage of this way of thinking. So leaving it unemphasized is another of the (many!) simplifying lies we tell in a first course.
9h
comment Is cosmic background radiation absolute
You should be very clear that an identifiable, agreed-upon base frame is in no way a "special" or "privileged" frame. Being able to pick a frame that every one (or at least every one for a long distance around) can agree upon does not break relativity.
9h
answered Can't virtual images be put on a screen?
10h
revised Can't virtual images be put on a screen?
edited tags
20h
comment How long would it take to get to Kepler 189f?
In any case the Earth-bound observers sees the ship experiencing slow time but crossing the full distance, while shipboard observers experiences normal time (the guys on Earth look slow to them) but cross the shortened distance. Both sets can agree on the elapsed time on the ship's clock but explain it in different ways.
1d
comment Why exactly are images formed by lenses/mirrors?
The place to start is to be very sure you understand what it is that you see in the first place ... that is what is it that happens when you look at an object that lets you "see" it at all. Once you've got that the answer follows from the geometry of reflection or refraction by properly shaped mirrors and lenses.
2d
comment Anchor of a boat
You weight anchor (remove it from the sea bed and bring it aboard) by hauling on the line, this moves the ship toward the anchor until the angle is sufficient for it to unhook, and eventually lift off the sea bed. In some places it is possible for anchors to become so wedged in rocks on the sea floor that they can not be recovered which is a disaster of medium proportions, and is thankfully rare. Drogues don't stop the ship, they simply reduce the degree to which you move relative the water you're in, thus reducing the hazard presented by not actively piloting the vessel.
2d
comment Breakout - physics when ball hits paddle?
This question appears to be off-topic because it is about the implementation of a video game. If you would like I can ask the mods on Game Development if they are interested in hosting this question. Just comment to that effect.
2d
answered What is the meaning behind the neutrino oscillation parameter?