77,451 reputation
178166
bio website ratsauce.co.uk
location Chester, United Kingdom
age 53
visits member for 3 years, 3 months
seen 8 hours 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.


Nov
19
comment Why less temperature at high altitude
@richard: heat transport in air requires convection, i.e. physical movement of the air, because heat radiation and absorption is very inefficient. However when you move air upwards it expands and cools, while if you move air downwards it compresses and heats. So the temperature gradient is inevitable. If air could transfer heat by radiation and absorption this would reduce the thermal gradient, but it can't.
Nov
19
comment What is the use of this formula 1 Tesla = 1 Newton/Ampere/Meter?
@XCIX: I'm not sure what you're asking.
Nov
19
comment Fermion boundary conditions at finite temperature
This paper (caution PDF) explains the need to anti-periodic boundary conditions in appendix A.
Nov
19
comment Why less temperature at high altitude
@richard: do you mean different heights, or different areas e.g. different countries?
Nov
19
comment Some doubts about photons
... you can convert photons to electrons and vice versa. This is known as pair production. But I agree with Carl that this is a conceptually exceedingly hard subject so be cautious about getting carried away with the very brief description I've given here.
Nov
19
comment Some doubts about photons
@physics: yes, every fundamental particle has it's own field. There isn't really a proton field because a proton is made from three quarks, but there is a quark field. All these quantum fields exist everywhere including the vacuum. In fact we've demonstrated this by measuring a consequence of these fields called the Casimir effect. You can create virtual electrons in a vacuum from nothing, but you can't create real electrons from nothing as that would violate conservation of energy. However ...
Nov
19
comment Some doubts about photons
@user34185: you're asking me to explain quantum field theory, and that would take a large book not a few comments! The photon field, like all quantum fields, is a continuous field that exists everywhere. It's discrete in the sense that energy is transferred to or from it in chunks (i.e. photons) but of course a photon can have any energy so the chunk can be any size. There is a fairly detailed discussion on Wikipedia, or Matt Strassler's blog has lots of articles on QFT.
Nov
19
answered Understanding the time dilation calculation in Brian Cox's Doctor Who lecture
Nov
19
comment Is there a matching material interior for the Kerr solution of Einstein's equations?
According to Wikipedia no solution to the matching is known.
Nov
19
answered Some doubts about photons
Nov
19
reviewed Close What “time” is it for or on Voyager 1? If you could be “still” in the Universe who fast would time be?
Nov
19
reviewed Close Creating a 2d magnet simulator
Nov
19
reviewed Approve suggested edit on Thermal exfoliation of graphite oxide
Nov
19
answered Angular Displacement
Nov
19
comment Does the pilot of a rocket ship experience an asymptotic approach to the speed of light?
But the pilot measures the distance moved as less than 4 lyrs, hence they don't measure their velocity as 4 lyrs/sec.
Nov
19
comment Does the pilot of a rocket ship experience an asymptotic approach to the speed of light?
@SuzanCioc: no, this is the velocity of the rest of the universe measured by the pilot of the rocket (the pilot thinks they are stationary). The velocity of the pilot measured by the stationary observer is given by $v = at/\sqrt{1 + (at/c)^2}$.
Nov
19
revised Does the pilot of a rocket ship experience an asymptotic approach to the speed of light?
Add footnote
Nov
19
comment Does the pilot of a rocket ship experience an asymptotic approach to the speed of light?
Can you show the calculations to support this conclusion?
Nov
19
answered Does the pilot of a rocket ship experience an asymptotic approach to the speed of light?
Nov
18
comment Problem with (grad school) physics education?
@YungHummmma In industry, which is where I worked, you almost never use e.g. an SEM yourself. There is a technician paid to run it and who is much better at than you will ever be. Likewise NMR, FTIR, and so on. The no. 1 skill is understanding what you're trying to achieve and what exactly the experiment you're planning is likely to tell you.