35,921 reputation
350122
bio website inspirehep.net/…
location Duchy of Grand Fenwick
age 43
visits member for 4 years, 1 month
seen 1 hour 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.


Dec
10
reviewed Approve What's the difference between centre of mass & centre of gravity for massive bodies?
Dec
9
awarded  Nice Answer
Dec
9
awarded  Enlightened
Dec
9
awarded  Nice Answer
Dec
9
comment Does infinity really exist?
As usual you should define what it would mean for a mathematical concept to "actually exist". How would that be different from it's not actually existing?
Dec
9
answered What's the difference between centre of mass & centre of gravity for massive bodies?
Dec
7
comment From escape velocity to gravitational acceleration
Strictly speaking you also know need to know that the mass distribution is (a) spherically symmetric and (b) confined to smaller radii than your current position. Obviously that is reasonably true "at the surface of a planet", but I thought I'd throw it out there.
Dec
7
comment Has the speed of the higgs boson been measured yet?
Particle with non-zero mass can take on any speed below the speed of light (given sufficient energy). Particles with zero mass are the only ones that have a fixed speed and they all have the same speed: $c$.
Dec
6
comment If we increase the aperture of a telescope and decrease its magnification, can it be harmful to the eyes?
See also exocomics.com/352
Dec
6
comment Can matter be annihilated to form kinetic energy
Kinetic energy isn't a "stuff", it is a property of an object or system. I know, I know. We talk about energy using language that treats it as a thing, but you have to keep in mind that it is not something that you can isolate and say "Ta da! I have a beaker of energy!".
Dec
5
revised Relativistic centripetal force
Fix some idiot math miskaes pointed out in the comments.
Dec
4
comment What would happen if you put your hand in front of the 7 TeV beam at LHC?
@AndreHolzner Hmmm .. good call on the beam loss. Don't know why I didn't see that. It's going to drop the total energy considerably, though I don't think it changes the conclusion too much; less damage, but still significant and all the way through. Aside: the $10^{11}$ is protons in the ring, not per bunch (and it's a number I took from a commenter as I didn't know it). I suspect that it's gone up a bit since 2011.
Dec
4
comment Can the half-life of a free neutron be calculated or is it just empirical?
See my answer to Why is the (free) neutron lifetime so long?.
Dec
3
comment Does the mass of an electron change with its “energy state”?
@YoustayIgo The invariant mass of a particle or system is defined as the length of the energy-momentum four vector. As such it is a Lorentz scalar and is measured to be the same in any frame of reference. All Lorentz scalars (including the proper-time) have that property, so people who are serious about relativity lean heavily on them because they simply all kinds of computations. A large fraction of relativists only talk about invariant mass, eschewing as unnecessary, obsolete and confusing the notion of "relativistic mass"; which is not to say that this concept can't be defined and used.
Dec
3
comment What is the general definition of signal acceptance?
Some people lump selection into acceptance, some do not. The important thing is to make clear what each of the several multiplicative factors that go into your rate computation mean. Personally I think of them as separate: acceptance rules what potential events generate a signal in the detector and selection is a separate step in which you decide what signals to consider.
Dec
3
comment Introducing angular momentum for the first time to a class
@docscience Safer to have the student spun up with the books in close.
Dec
3
comment Introducing angular momentum for the first time to a class
Do a demonstration that can't be explained without it. This is science, after all. The simple "figure skater" spinning demo will do. A gyroscope demo can be more striking, but the former is easier to explain. I usually do both. Also racing wheels, the rolling versus sliding loop-de-loop problem.
Dec
3
answered What is the general definition of signal acceptance?
Dec
3
comment What is this simple mechanism called?
My (personal, not moderator-power) opinion is that this is not a physics questions. This mechanism is a perfectly ordinary piece of mechanical equipment. Asking about specialized lab equipment would be one thing, but what is there about this thing that makes Physics the right site for it?
Dec
3
comment Looking for the actual reason of refraction explained precisely without analogies
@TomášZato It's the magnetic susceptibility.