22,420 reputation
150115
bio website lightandmatter.com
location Fullerton, California
age
visits member for 3 years, 2 months
seen 1 hour ago

I teach physics at Fullerton College, a community college in Southern California. I have an undergrad degree in math and physics from Berkeley and a PhD in physics from Yale. Back when I was doing research, my field was experimental low-energy nuclear physics.


Sep
9
comment What is the composition of the universe's population of neutrinos?
@KyleKanos: In this context, does decoupling basically mean when the temperature got below the electroweak unification energy?
Sep
9
comment What is the composition of the universe's population of neutrinos?
@KyleKanos: From the title of the paper, sounds like "relic" is used to refer to the old, thermalized component...?
Sep
9
revised What is the composition of the universe's population of neutrinos?
added 119 characters in body
Sep
9
comment What is the composition of the universe's population of neutrinos?
@Héctor: I'm thinking that the answer would probably involve a combination of empirical knowledge and theoretical predictions.
Sep
9
asked What is the composition of the universe's population of neutrinos?
Sep
9
revised Conservation of angular momentum in Earth-Moon system
added 68 characters in body
Sep
9
comment Conservation of angular momentum in Earth-Moon system
@dmckee: Very interesting. Would love to learn more about this. Maybe it would make a good question of its own.
Sep
9
comment Conservation of angular momentum in Earth-Moon system
I just went ahead and did it, since we seem to be in agreement.
Sep
9
revised Conservation of angular momentum in Earth-Moon system
combine answers as proposed
Sep
9
comment Conservation of angular momentum in Earth-Moon system
How about if we just copy the beginning of my text into your answer, then delete my answer? Your diagram is nice and addresses the main point of the question.
Sep
9
comment How does a magnetic field cause objects to move?
Also if every reaction has an equal and opposite reaction, when two magnet move together (or away from each other) what is the opposite reaction? This is a question about Newton's third law in general, not about magnets. Newton's third law does not imply equilibrium, because the forces act on different objects.
Sep
8
comment Motivation for preservation of spacetime volume by Lorentz transformation?
related: physics.stackexchange.com/questions/133375/…
Sep
8
comment Physical/geometrical interpretaion of the determinant of a matrix
IMO this answer is misleading, for the reasons given in the final paragraphs of my answer.
Sep
8
answered Physical/geometrical interpretaion of the determinant of a matrix
Sep
8
comment Physical/geometrical interpretaion of the determinant of a matrix
related: physics.stackexchange.com/questions/75102/…
Sep
8
comment Theoretical Stability of “AB-matter”
@LoganR.Kearsley: I don't think that works, because the scale of the electron cloud would be $\sim 10^5$ times larger than the nuclear scale. That's why electrons don't stabilize real nuclei that are unstable with respect to fission.
Sep
8
answered Theoretical Stability of “AB-matter”
Sep
7
comment Is special relativity a special case of general relativity, qualitatively?
It should also be pointed out that this is one way of stating the equivalence principle: that spacetime is locally Minkowski, i.e., SR is always a valid local approximation to GR.
Sep
7
comment Is special relativity a special case of general relativity, qualitatively?
I don't think this is as good an answer as Red Act's. There is the issue mentioned parenthetically, which is that you can have vacuum spacetimes that are not Minkowski. In addition, one can write down metrics that don't look like the Minkowski metric, but are in fact the Minkowski metric written in different coordinates. Curvature is really the issue here. the Minkowski metric is the simplest and best known I don't think this works. I could write the Minkowski metric in coords that make it look complicated. The criterion is flatness, not simplicity.
Sep
7
comment When sliding down steep hill, is it safer to go down back or front against the hill?
There are certainly physics issues involved in this question, but as pointed out by David Hammen in a comment, there is not enough information in the question to formulate a model. If this were asked on outdoors.SE, I would have the same complaint: it's too vague to be answerable. Voting to close as not clear.