41,509 reputation
356134
bio website inspirehep.net/…
location Duchy of Grand Fenwick
age 44
visits member for 4 years, 8 months
seen 30 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.

Been reading Zemansky & Dittman's book on thermodynamics recently. Quote: ``The concept of temperature is rich in interpretations and levels of abstraction.'' Nice.


24m
comment Barrel length, not PSI, determines acceleration?
I didn't say anything about opinion, I say the analysis is simple and qualitative. There is a big difference. I like Mythbusters and use some clips from the show in my General Education classes. A quantitative analysis would tell you the functional dependence of muzzle velocity on both parameters. Then you would see several important things, like neglecting barrel friction is only viable for high-pressure systems (essentially all modern firearms), but the point is that you would be able to talk about how much change in pressure equates to how much change in length for a particular firearm.
1h
comment Barrel length, not PSI, determines acceleration?
Mythbusters is a entertaining show, and I'm all for anything that demonstrates the value of the empirical method to all and sundry, but ... the level of analysis they bring to their problems is suited to the general audience at which they target the show. The analysis is rudimentary and purely qualitative. Don't read too much into it.
1h
comment What is the simplest possible experiment that proves that there are atoms?
Arivero, what you propose here is essentially to find the law of definite proportion. You also want the laws of multiple and reciprocal proportions to complete the stochiometric picture. This was done by the mid 1800s, but it wasn't considered completely convincing at the time for exactly the reasons the @DanielSank points out. It's finished when combined with evidence of discrete little mass lumps existing below the microscopic scale.
5h
comment Can you tell your absolute speed in space?
Once again, there is nothing privileged about the frame of the CMB. It's not special in any fundamental way. Saying it is "as absolute as it gets" is another way of say that it is not absolute at all.
5h
comment What is the simplest possible experiment that proves that there are atoms?
Stochiometry was historically one of two pillars of argument (along with the Brownian motion calculation/observation agreement) that together brought people around. Crystalography came decades after the atomic hypothesis was accepted as fact.
5h
comment How would one get the particle beam in Stern Gerlach experiment
Didn't the original experiment use a thermal source (furnace) and a collimator? Indeed, the Wikipedia article shows exactly that in the image at the top of the page.
5h
comment What is the simplest possible experiment that proves that there are atoms?
Again, this is a way to gain data about atoms on the assumption that they exist, but it doesn't show that they exist.
5h
comment What is the simplest possible experiment that proves that there are atoms?
This gives you data about the size of the molecules assuming that they are there. It isn't clear evidence that matter comes in that form in the first place.
11h
comment Do we regularly measure and update our physical constants (By using the LHC)?
The automatic duplicate suggester is not particularly good. Nor are those obviously duplicates in my mind, they just touch and similar issues and might help you to see the bigger picture.
11h
answered Is circular masking a laser beam an acceptable way to get the beam diameter you require?
11h
revised Is circular masking a laser beam an acceptable way to get the beam diameter you require?
edited tags
11h
comment Can you tell your absolute speed in space?
"so your saying with the same amount of energy i could attain light speed?" No. Because the velocity that you add relative some other object does not compose by plain arithmetical addition, but by the relativistic composition rule. Understand that to occupants of the ship it is the rest of the universe whose energy is increasing without bound, not their own.
11h
comment Can you tell your absolute speed in space?
Watching the universe from the point of view of a arbitrarily fueled rocket is one of the reasons that "as one approaches light speed more energy is required to accelerate faster" is a sub-optimal way to talk about relativity. In the rockets frame it is the rest of the universe that is (a) getting harder to add speed to even thought the rocket experiences exactly the same acceleration it would have when at relative rest and (b) that effect is asymmetric over finite velocity changes. The whole business is better understood in terms of velocity composition.
11h
comment Do we regularly measure and update our physical constants (By using the LHC)?
Related: physics.stackexchange.com/questions/2725/… physics.stackexchange.com/questions/21721/… and also my answer to physics.stackexchange.com/questions/171790/…
13h
comment Do all the conservation laws of Physics take no time to propagate?
It is worth noting that the way we treat collisions in an introductory course---as a black boxes which happen on very short time scales and the details of which are ignored---misses exactly those features of real collisions that "transmit" the conserved quantities in finite time. That could lead to the impression the momentum leaps instantly from one extended object to another, but this is not a feature of proper understanding of what is happening in even very simple collisions.
1d
comment Modelling discrete spacetime
Conservation of angular momentum poses a very serious problem for attempts to discretize space. Viewed as a Noetherian conserved current, there is a requirement that the underlying space be invariant on arbitrary rotations. Indeed, working around these issues has been a major challenge for lattice computations.
1d
comment Why can't people just pump water from ground and flood deserts to make them habitable?
The phrase "dry hole" is rather important here.
2d
comment Fermi Level difference effect on thermionic emission in an open-circuit
Could you be clear about the way this differs from the question you asked earlier? They look superficially s very much the same. Generally you are expected to edit questions, not re-post when you need to clarify.
2d
comment Does wax go through a sharp phase transition when it melts?
Part of your problem may be the phrase "true phase transition". You won't find that phrase in Callen or any other serious text on the subject. Instead they will subscribe to one or more of the usual classification schemes. You are describing a "first order" phase transition, but there are other kinds.
2d
comment Why couldn't a space elvator's cable be tapered?
Every design beyond school-boy fantasies involves a tapering cable. Many also involve a tapering building from the surface too, thought that turns out to be a fairly minor gain.