77,296 reputation
178165
bio website ratsauce.co.uk
location Chester, United Kingdom
age 53
visits member for 3 years, 3 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.


Apr
8
comment Time taken in changing surface tension
The surface tension does not depend on the container. It is a property of the water/air interface. Can you post a link for the claim that surface tension is lower in a burbot. I tried Googling but all I found were articles about the fish burbot.
Apr
7
comment How a accelerated object sees another accelerated body in Special relativity?
The only way I know of to solve this would be to transform from the $a_1$ frame to an inertial frame then transform back to the $a_2$ frame. The equations you need are in John Baez's article on the Relativistic Rocket.
Apr
7
comment Frequency of touch, taste, and scent
This question appears to be off-topic because it is about human biology
Apr
6
comment Is there an analogue of a geodesic for the evolution of the electromagnetic field?
It's amazing what has been asked before :-)
Apr
6
comment Distance Between Two Photons Calculated in Different Inertial Frames
@Andrew: You're welcome :-) About 35 years ago my physics tutor instructed me most severely to always reach for the Lorentz transforms when solving problems in SP. I have spent the 35 years since passing this on :-)
Apr
6
comment Electric impluses inside nerve cells
@forsberg: electromagnetic waves certainly carry energy, but not charge.
Apr
6
comment CCD's and the photoelectric effect
Have you looked at the Charge generation section of the relevant Wikipedia article?
Apr
6
comment Electric impluses inside nerve cells
@forsberg: Electromagnetic waves do not carry any charge.
Apr
6
comment Where does the phase difference come from in a Josephson Junction?
@Anupam: $\sin\theta(t)$ is a perfectly standard way of specifying $\sin(\theta(t))$. We use this notation to save multiple brackets, just as we often write $\sin\theta$ instead of $\sin(\theta)$. If that is the reason for your downvote it is unjustified.
Apr
6
comment Where does the phase difference come from in a Josephson Junction?
@Anupam: why is it dimensionally incorrect? The dimensions seem fine to me. $\sin\theta$ is dimensionless and the dimensions of $I$ and $I_0$ obviously match.
Apr
6
comment Where does the phase difference come from in a Josephson Junction?
@Anupam: this seems a perfectly reasonable question. Why did you downvote it?
Apr
6
comment Order of magnitude
@GaurangTandon: you say we have to be precise, but the whole point is that with an order of magnitude estimate we aren't being precise. We're saying our estimate could be ten times too big or ten times too small. It seems odd to be quibbling about the difference between $3.16$ and $3.17$ when the real value could be as low as $0.31$ or as high as $31$.
Apr
6
comment Can we think of gravity as space itself moving?
@user43783: be cautious about thinking of spacetime as some kind of rubber foam that we can compress or stretch then have it spring back. Spacetime isn't a physical object, it's a manifold equipped with a metric, both of which are mathematical structures. It's really only our coordinate system that's flowing. Having said this, for a white hole the Gullstrand-Painleve radial coordinate would be flowing outwards, so this may well be the case for an evaporating BH. I'd have to sit down and think about it.
Apr
6
comment How does negative energy from Hawking Radiation cause a Black Hole to shrink?
Both virtual particles and antiparticles may have a negative energy or a positive energy. Any negative energy object absorbed by the black hole will cause it to shrink because it decreases the total energy, and therefore mass, of the black hole.
Apr
5
comment Matter vs. Antimatter shortly after Big Bang
One has to admire the extraordinary amount of effort you put into to writing your answers.
Apr
5
comment Dark energy and conservation of energy
@Christoph: I note the question you've linked contains contrary opinions from Phil Gibbs and Luboš Motl. They are both vastly better physicists than I will ever be, so how am I to judge who is right? The impression I get is that whether energy is conserved or not depends on exactly what you count as energy. You would have to concede there is no time shift symmetry, so we cannot simply shout Noether's theorem and wave our arms.
Apr
5
comment Dark energy and conservation of energy
This article by John Baez might be of interest as background reading.
Apr
5
comment How does negative energy from Hawking Radiation cause a Black Hole to shrink?
In GR all matter is treated as energy via Einstein's famous equation $e = mc^2$. GR makes no distinction between matter and energy - both create a gravitational field. Both matter and anti-matter have the same (positive) energy simply given by their mass. A negative energy particle is one that, in effect, has a negative mass, and of course adding a negative mass to a black hole will reduce its total mass. This is a gruesome oversimplification, but if you insist on using the particle-antip[article explanation of Hawking radiation this is basically what happens.
Apr
5
comment Dark energy and conservation of energy
See the link I've suggested. The FLRW metric that (we think) describes our universe is time dependant and this means energy is not conserved.
Apr
5
comment Dark energy and conservation of energy
possible duplicate of Conservation law of energy and Big Bang?