95,393 reputation
3129237
bio website ratsauce.co.uk
location Chester, United Kingdom
age 53
visits member for 3 years, 6 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.


2h
comment Cooling down a container in outer space
@kutschkem: oops! Thanks :-)
3h
comment What is the difference between a low vs. high entropy plasma just after and before a singularity occurs?
No-one knows. The question about why the entropy was so low just after the Big Bang is still an open one and there is no widely accepted mechanism to explain it.
3h
comment Does expanding space cost energy?
There are endless arguments about whether energy is or isn't conserved in the expansion due to dark energy. One view is that it isn't because the amount of dark energy increases with time as the universe expands. An opposing view is that this increase is balanced out by the energy of the gravitational field and overall energy really is conserved. See this article by Luboš Motl and this article by Phil Gibbs for opposing views
4h
comment Does expanding space cost energy?
I've suggested a duplicate because your question boils down to whether energy is conserved during inflation, and the duplicate question addresses this issue. Generally energy is not conserved in GR because by Noether's theorem energy conservation implies time shift symmetry, and this is violated during inflation and indeed during the current phase of accelerated expansion due to dark energy. If you search for energy conservation relativity you'll find many related questions.
4h
comment Does expanding space cost energy?
possible duplicate of Energy conservation in General Relativity
20h
comment Is there a substance that doesn't reflect OR absorb light from the visible light spectrum?
@VianEsterhuizen: I've updated my answer to respond to your edit. See what you think.
1d
comment Please explain these equations relating to Newtonian gravity
Why the downvote? What I've written can be verified by just Googling Newton's moon test. There's nothing controversial about it.
1d
comment Single slit diffraction pattern in 2D
@user154734: yes. Fraunhofer diffraction is just the limit in which the size of the aperture is small compared to the distance between the aperture and the screen showing the diffraction pattern.
1d
comment How do you calculate the power needed to keep something stationary?
I've posted a link to a duplicate for your first question. The second question needs to be asked separately as a different question.
1d
comment Physical reason why (hot) objects glow?
possible duplicate of What are the various physical mechanisms for energy transfer to the photon during blackbody emission?
1d
comment Where does energy go when performing a useless effort?
@ticster: yes, the wall is attached to the Earth, and the rocket is in principle moving the Earth slightly. However to include that in the answer seemed unnecessarily pedantic.
2d
comment A vehicle moves from rest to a certain distance. Would the distance time graph always be curved?
You say For example, a car moving from rest to 100m, with a constant velocity of 10m/s, but the car cannot both start at rest (i.e. velocity = 0) and have a constant velocity of 10m/s. If the velocity was initially 0 then changed to 10 it wasn't constant.
2d
comment How is voltage generated due to difference in temperature in a thermocouple?
possible duplicate of Thermo-Emf variation with temperature
2d
comment Does the universe have an edge/boundary/barrier? If yes, what is at the edge?
possible duplicate of Shape of the universe?
2d
comment Do the standard cosmology models spontaneously break Lorentz symmetry?
Related: Is the CMB rest frame special? where does it come from? and Assuming that the Cosmological Principle is correct, does this imply that the universe possess an empirically privileged reference frame?
2d
comment Wave packets and amplitude
@DrEntropy: indeed.
Jul
26
comment What reflects/scatters sunlight most?
See Why does the refractive index depend on wavelength? for some background on the link between optical absorption and refractive index. Yes, they are connected, but not in any simple way.
Jul
26
comment What reflects/scatters sunlight most?
That's a big question because absorption is determined by the band structure of the solid and also its defect states, while reflectivity is determined by the refractive index, which is in turn determined by the electronic structure. You're asking us to write you a several thousand word essay.
Jul
26
comment What reflects/scatters sunlight most?
It isn't clear what you're asking. Are you asking for the best known reflector of light with the solar spectrum?
Jul
26
comment Why does light travel at the same speed when measured by a moving observer?
See Relativistic addition of velocities of spaceships or search the site for relativistic velocity addition for (many) more relevant articles. If you use the relativistic addition formula to try to add (or subtract) any velocity to $c$ the result is always $c$.