117,255 reputation
5183313
bio website ratsauce.co.uk
location Chester, United Kingdom
age 53
visits member for 3 years, 11 months
seen 7 mins 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.


Jun
16
comment Why didn't electroweak symmetry breaking happen earlier than it did?
@user50489: you can roll back the edit, though I would leave it as it is.
Jun
16
comment Why do all elements above $\require{mhchem}\ce{Fe}$ not decay to $\ce{Fe}$?
@Joseph: oops, that should be lower binding energy, i.e. less stable.
Jun
16
comment Time dilation at the Big Bang
@Anixx: the proper time to the Big Bang is the only time that makes physical sense.
Jun
16
comment How to get the accurate relativistic momentum form for photons?
possible duplicate of If photons have no mass, how can they have momentum?
Jun
16
comment Surely proper time expands like proper space?
@JohnEastmond: you derived that equation by requiring that $ds = 0$. It's not some general equation for calculating how comoving distance changes with time. It's an equation that tells you how comoving distance must change with time to keep the line element equal to zero.
Jun
16
comment Kinematics and Energy - Finding the work done in projectile motion
@Gummybears: if work is done on the projectile its energy must change. Is the energy of the projectile at the moment it is launched different to its energy at the moment it returns to the ground (ignoring air resistance)?
Jun
16
comment How does Passivation in Mercury-arc-valve cause “diode” behavior
Have you looked at the Wikipedia article?
Jun
16
comment Losing mass in space
@Gummybears: no, Theresa is correct. The chemical reactions that our metabolism uses convert chemical energy to heat, and that heat would presumably be radiated away from the spaceship. The spaceship mass would fall by $m = E/c^2$ where $E$ is the energy radiated away. However in the context of this question the mass lost is negligable.
Jun
16
comment Surely proper time expands like proper space?
@JohnEastmond: I'm not sure I see your point. The speed of light is invarient for a comoving observer so they can measure distance in light years and the distance they measure will be the proper distance (at least locally). The expansion just means the number of light years they measure to some other distant comoving observer increases with time (as the universe expands).
Jun
16
comment Surely proper time expands like proper space?
@JohnEastmond: no, because the speed of light in comoving coordinates is falling. The expansion in the proper distance balances this out and keeps the speed of light at $c$. The proper time doesn't need to change.
Jun
16
comment Mathematically possible vs physically probable outcomes
It depends on what you mean by normal circumstances. Anything with a non-zero probability will occur if you wait long enough.
Jun
15
comment Gravitational effect of charged masses held apart by a rod?
I'm pretty certain that the gravity is greater with the rod present, because the pressure in the rod appears on the leading diagonal in the stress energy tensor. However I don't know enough GR to make this quantitative.
Jun
15
comment Gravitational effect of charged masses held apart by a rod?
Can you clarify what you're asking? Are you asking us to calculate the spacetime curvature with and without the rod present? If so that's a formidable challenge. If you're just asking whether the electrostatic repulsion could be equal to the gravitational attraction then yes it can.
Jun
15
comment Reconciling “The Big Crunch” with the 2nd Law of Thermodynamics
Related, though not a duplicate: How does the evolution of a solar system not break the second law of thermodynamics?
Jun
15
comment Energy of an EM Wave and its temperature and amplitude
Indeed! For example you can't define the temperature for a single atom. Temperature is an emergent property of an ensemble.
Jun
15
comment How is the direction of Magnetic/Electric Lines of Force Known?
@EvilWarrior: I wouldn't say the fundamentals are unknown. The shape of the lines is predicted by Maxwell's equations. The direction isn't predicted because it isn't a fundamental property but just a human convention.
Jun
15
comment How is the direction of Magnetic/Electric Lines of Force Known?
Although there are no isolated magnetic monopoles we can make magnetic dipoles. The interaction of dipoles with the field is more complicated, but can (with some effort) be used to trace the field lines just as a monopole would. But we end up with the same problem as an electric field. Defining which way the field line goes is just a convention. We define the direction as from North to South, but we could equally define it as from South to North without changing any of the physics.
Jun
15
comment Can any gas be liquidified by lowering the temperature?
@Abolfazl: see the Wikipedia article on fermionic condensates. As Rob says, the fermions pair up and the pairs then form a condensate. This has been done with potassium atoms.
Jun
14
comment Experimental proof of the principle of superposition in QM
possible duplicate of How can they prove the superposition of particle states prior to measurement
Jun
14
comment How can I find the motion equations of the 2-dim harmonic oscillator?
Can you give us some idea of your background? Are you a mathematician - if you're considering solving equations of motion you're presumably happly with differential equations. Does this article on the 2D harmonic oscillator make any sense?