19,162 reputation
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bio website lightandmatter.com
location Fullerton, California
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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.


Jul
25
answered How does the nature of nuclear force change between attractive or repulsive based on distance?
Jul
25
comment How does the nature of nuclear force change between attractive or repulsive based on distance?
I don't think this explanation really works, mainly because it treats the strong interaction between nucleons as fundamental, whereas in fact it's a residual interaction. For comparison, useful models of the residual electrical interaction between atoms usually have both an attractive and a repulsive part, and this argument clearly doesn't give the right answer for that situation.
Jul
25
comment How does the nature of nuclear force change between attractive or repulsive based on distance?
Most of the material in this answer is irrelevant to the question. The claim that the strong nuclear force is always attractive is an oversimplification.
Jul
24
comment Electric field generated by a point charge moving at the speed of light
The homework question asks about a limit, whereas the title of the question refers to a charge moving at c. These are two different things. It's not possible for a charge to move at exactly c. All charged particles have mass, and massive particles can't move at c.
Jul
22
awarded  Revival
Jul
22
awarded  Necromancer
Jul
20
comment Why “light cones” have different shapes near black holes?
This isn't quite right. It's true that Einstein originally thought about GR as a generalization of SR to accelerated frames of reference, but that doesn't actually work out well and isn't how relativists today think about it. In flat spacetime this would be drawn as a light cone with a 45 degree opening angle. Even in curved spacetime, it's possible to draw all your light cones with a 45-degree angle. This is what we do in a Penrose diagram.
Jul
20
answered Why “light cones” have different shapes near black holes?
Jul
19
awarded  Yearling
Jul
15
revised Why doesn't matter pass right through other matter if atoms are 99.999% empty space?
added 492 characters in body
Jul
15
answered Why doesn't matter pass right through other matter if atoms are 99.999% empty space?
Jul
9
awarded  Popular Question
Jul
2
awarded  Inquisitive
Jul
2
awarded  Curious
Jun
25
revised Metric expansion of space and Newton's second law
added 439 characters in body
Jun
25
answered Metric expansion of space and Newton's second law
Jun
23
awarded  Necromancer
Jun
20
awarded  Necromancer
Jun
16
awarded  Revival
Jun
15
answered Is the graviton hypothetical?