130,252 reputation
8216356
bio website ratsauce.co.uk
location Chester, United Kingdom
age 54
visits member for 4 years, 2 months
seen 1 hour ago

Semi retired old time computer nerd who started programming on a Commodore Pet.

Since I'm also active in the Physics forum I should add that I started as a theoretical chemist, moved into solid state photochemistry and finally worked in industry as a colloid scientist. I only became a full time computer nerd in 1997.


Mar
14
comment In theory, could gravitational waves be used to make a “gravity laser”?
I have the same criticism of this that I have of Jerry's answer.
Mar
14
comment In theory, could gravitational waves be used to make a “gravity laser”?
I'm not sure this true because lasers don't have to rely on a population inversion of an excited state. Couldn't we build the equivalent of a free electron laser? A free mass quadrupole laser perhaps?
Mar
13
comment Is the center of the universe in another dimension?
The universe doesn't have a centre and the Big Bang didn't happen at a point.
Mar
12
comment Where do we get the terms involving $\Phi$ in parentheses come from in the static weak field metric?
I was tempted to copy it and claim it was my own work, but it seemed like too much trouble :-)
Mar
12
comment Production of electric field
@SHYAMANANDANINGOMBAM: it's a common shorthand to say a varying magnetic field produces an electric field, and we're probably all guilty of saying this at some time. However it is a misrepresentation of the real physics.
Mar
12
comment Where do we get the terms involving $\Phi$ in parentheses come from in the static weak field metric?
Hi Stan, there is a derivation in this article.
Mar
9
comment What would happen after the big crunch?
@user13068: the spacing between spacetime points at the Big Crunch is no defined because the metric is singular (or as MBN says, more precisely the Big Crunch isn't part of spacetime). However as we approach the Big Crunch the spacing between any pair of spacetime points tends to zero.
Mar
9
comment What would happen after the big crunch?
@user13068: the answers to Did the Big Bang happen at a point? explain why the Big Bang didn't happen at a point. The same arguments explain why the Big Crunch doesn't happen at a point.
Mar
9
comment What would happen after the big crunch?
I didn't downvote, but it is a rather trivial summary of a very complicated problem. Classically there is no aftermath to the Big Crunch because the metric is singular there. The possible post Big Crunch scenarios are based on speculative quantum gravity ideas. You should also make it clear a Big Crunch is impossible unless dark energy radically changes its equation of state in the future.
Mar
8
comment Is the universe 5 dimensional space-time or 4?
Gede, your question is basically a duplicate of Universe being flat and why we can't see or access the space “behind” our universe plane?. My answer to that question explains why there isn't a fourth dimension that space curves into. However I'm not going to flag your question as a duplicate unless you agree as if I do it will close this question.
Mar
8
comment Is the link between shadows a refraction of the light?
possible duplicate of Very strange shadow phenomenon
Mar
8
comment Who discovered that Helium had some effects on your voice?
I'm voting to close this question as off-topic because it is not about physics
Mar
8
comment can a wave on rope placed away from gravity go on forever?
@SCK: a body moving in a straight line at constant velocity doesn't have a time dependant quadropole moment so it won't radiate gravitational waves. See the definition of quadrupole moment.
Mar
8
comment can a wave on rope placed away from gravity go on forever?
@SCK: in principle any distribution of matter that has a time dependant quadrupole moment will radiate gravitational waves. In practice this radiation is vanishingly small in everyday life.
Mar
7
comment Why isn't in counting the no. of degrees of freedom, rotation about the axis running down the length of the molecule counted?
@garyp: we do consider rotational energy of the electron in the hydrogen atom. The $p$, $d$, $f$, etc are effectively the rotational excitations. We don't normally consider rotation of the proton because it's too small. Having said that, I bet there are excited states of the proton with angular momentum.
Mar
7
comment Why isn't in counting the no. of degrees of freedom, rotation about the axis running down the length of the molecule counted?
@garyp: any object rotating about an axis has rotational kinetic energy, and that energy is quantised. This does not rely on any assumptions about the object's shape or symmetry. However it's certainly true that it would be hard to excite rotational energy levels of an axially symmetric object because the symmetry means there's no way to apply a torque.
Mar
7
comment Why isn't in counting the no. of degrees of freedom, rotation about the axis running down the length of the molecule counted?
I just Googled it. Many decades ago, as an undergraduate, I solved the Schrodinger equation to calculate it but I have long since forgotten the details.
Mar
7
comment Is the strength of a muscle proportional to its cross-sectional area?
That article is concerned with the mechanics of jumping, and lots of effects are considered. I don't think it questions the basic principle that if you consider an isolated muscle the force it can produce is roughly proportional to its area.
Mar
7
comment Is the strength of a muscle proportional to its cross-sectional area?
I don't think this is a physics question - at best it's biophysics. I don't think anyone is claiming muscle strength is exactly proportional to area. The point is that when looking at scaling it is closer to a quadratic dependance than it is to a linear or cubic dependance.
Mar
7
comment Diffraction from a single slit experiment and Heisenberg's uncertainty principle
Hi, your question doesn't make sense as it stands (language issue?). Can you have a go at editing it to make it clearer what you are asking? Is the question Difference Between Fraunhofer and Fresnel Diffraction any help?