103,729 reputation
4151274
bio website ratsauce.co.uk
location Chester, United Kingdom
age 53
visits member for 3 years, 8 months
seen 1 min 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.


Sep
7
comment Do we weigh less in the morning?
possible duplicate of Are we slightly lighter during the day and slightly heavier at night, owing to the force of the Sun's gravity?
Sep
7
comment Special Relativity, 2nd Postulate — Why?
The question I've linked shows how the second postulate can be regarded as a consequence of the invariance of the line element. Of course you may consider this to be replacing one unintuitive assumption with a different unintuitive assumption - welcome to relativity :-)
Sep
7
comment Riemann curvature tensor notation in Wald
Re (2): indicies are raised and lowered by multiplying by the metric, so $R_{abcd} = R_{abc}^{\quad e} g_{de}$. See 3.2.19 on page 39.
Sep
7
comment Special Relativity, 2nd Postulate — Why?
possible duplicate of Special Relativity Second Postulate
Sep
7
comment Riemann curvature tensor notation in Wald
See the top of page 26 where he explains what the square brackets mean.
Sep
7
comment Perceiving travel speeds from different view points
@HarryDavid: see this question
Sep
7
comment Does someone falling into a black hole see the end of the universe?
@Inverse: I think my illustration of the path is a bit off and it should look more like my answer to this question
Sep
7
comment Space curvature based on net energy = 0
@gwho: no. See this Wikipedia article for what equation of state means.
Sep
6
comment Paradox while Cooling & Heating in Air?
possible duplicate of After what speed air friction starts to heat up an object?
Sep
6
comment Atomic Brownian Motion
Atomic Brownian motion is something of an oxymoron. Can you be clearer about exactly what type of motion you are considering. For example are you thinking about atomic motions in a crystal lattice? An isolated atom has no internal motion - its eigenfunctions are solutions of the time independant Schrodinger equation.
Sep
6
comment Gravity and electromagnetism
@user34793: did you mistype that last comment?
Sep
6
comment Why do skidding wheels have less traction than non skidding wheels?
Jack, I've linked a question that is basically the same as yours. The friction for a skidding wheel is given by the dynamic friction coefficient and for a non-skidding wheel by the static friction coefficient. Experimentally we observe that dynamic friction is lower than static friction, but why this should be is a somewhat vexed question. The answers to the question I've linked discuss some of the current theories.
Sep
6
comment Gravity and electromagnetism
@user34793: What is a halogram? If you meant a hologram then this is an interference phenomenon and does not require light to be travelling in a curved trajectory.
Sep
6
comment How does a knife cut things at the atomic level?
This is really a duplicate of What happens when we cut objects?, but lemon's answer is so much better than any of the answers to the previous question that I'm reluctant to vote to close.
Sep
6
comment How much has the Milky Way moved since it's forming?
@kutschkem: that's been asked! See Assuming that the Cosmological Principle is correct, does this imply that the universe possess an empirically privileged reference frame?
Sep
6
comment Gravity and electromagnetism
The phrase wave nature of curved light of curved light doesn't really make sense. It's one of the fundamental principles of GR that spacetiem is always locally flat. At any spacetime point light propagates locally just as it does in Minkowski spacetime. Indeed, light always travels in a straight line. The trajectory may look curved to external observers but it doesn't look curved to the light.
Sep
6
comment Are Stars getting 'Less Massive?
@NickI: yes, but the amount of radiation the star produces changes during its lifetime.
Sep
6
comment Gravity and electromagnetism
Your scenario 2 is too vague for me to comment. You'll need to be a bit more specific about what calculations you're proposing.
Sep
6
comment Space curvature based on net energy = 0
@gwho: The zero energy is potential energy + energy of matter/dark energy as give by $mc^2$. The energy of all the matter/energy is positive as you say, and the gravitational potential energy is negative, so the two cancel and sum to zero (although as I mentioned in the answer this is a contentious issue).
Sep
6
comment Is there a strong evidence of antineutron existance?
@HolgerFiedler: I've extended my answer a bit - see if that makes things clearer. If you want to ask about charge exchange reactions this is probably a separate question.