117,067 reputation
5183312
bio website ratsauce.co.uk
location Chester, United Kingdom
age 53
visits member for 3 years, 11 months
seen 2 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.


Dec
7
comment Relation of gravitational pull with no air friction
possible duplicate of Why objects of different masses accelerate at the same speed under gravity
Dec
7
comment In the wet medium of an ocean, how does a hard shell form?
This question appears to be off-topic because it belongs on the Chemistry SE.
Dec
7
comment Has the speed of the higgs boson been measured yet?
@Jitter: why do you think the Higgs boson would behave differently to any other massive particle?
Dec
7
comment Ratios of produced gases in water electrolysis
This question appears to be off-topic because it belongs on the Chemistry Stack Exchange.
Dec
7
comment Ratios of produced gases in water electrolysis
Yes, it's entirely plausible that the oxygen is being converted to aluminium oxide. For electrochemical measurements we normally go to some lengths to avoid such reactions e.g. by using an inert metal such as platinum for the electrodes. BTW this really belongs on the Chemistry SE.
Dec
7
comment Question from Griffiths (EM): Synchronized clocks
@quarkleptonboson: the way the time dilation and length contraction are derived in introductory texts is actively misleading. See this question for a far better way to understand what is going on.
Dec
7
comment Typical energy of a solar flare
This isn't my area, so I won't risk a full answer, but the intensity of the $H_\alpha$ radiation is correlated to the temperature so a brightening means the area you're looking at is hotter. This correlates with flares simply because the flares are hotter - much, much hotter :-).
Dec
7
comment Why do these two derivations of the formula for impulse contradict?
@user2985684: you start with $p = mst^{-1}$ and you differentiate with respect to $t$ to get $dp = -mst^{-2}dt$. However this is wrong because the distance $s$ is a function of time, $s= vt$, and you're treating it as a constant when you differentiate.
Dec
7
comment Why do these two derivations of the formula for impulse contradict?
I can see why site members might downvote this question, but I urge you to consider that messing around with equations out of curiousity is how many of us got started in physics.
Dec
7
comment Why is $M\frac{dv}{dt} = v_{rel} .\frac{dm}{dt}$ correct and $(M - dm)\frac{dv}{dt} = v_{rel} .\frac{dm}{dt}$ wrong?
@user36790: it's hard to comment without seeing exactly what your book says. It's certainly true that to calculate the trajetories of rockets you need to account for the changing mass. The Wikipedia article on the Tsiolkovsky equation is a good place to start looking at this.
Dec
6
comment Did the Big Bang happen at a point?
Your argument appears to have no connection to general relativity.
Dec
6
comment Did the Big Bang happen at a point?
I'm not sure I follow you. Are you arguing that the Big Bang did happen at a point?
Dec
6
comment Why is $M\frac{dv}{dt} = v_{rel} .\frac{dm}{dt}$ correct and $(M - dm)\frac{dv}{dt} = v_{rel} .\frac{dm}{dt}$ wrong?
@user36790: the equation gives the force, which by definition is simply the product of mass and acceleration, $Ma$. If you were calculating the motion of a rocket you would need to take into account the fact that $M$, and therefore $a$, would both be functions of time. This makes the equation of motion more complicated, but it's still just a differential equation.
Dec
6
comment Why are atoms empty so much?
I have to say I think this is a misleading analogy. Planets aren't delocalised while electrons are. You risk leading the OP down a path to increased misunderstanding.
Dec
6
comment Why are atoms empty so much?
But 99% of an atom isn't empty. As ACuriousMind says it's filled with (at least one) delocalised electron.
Dec
6
comment Did the Big Bang happen at a point?
But the Big Bang did happen at a specific point in time. In the coordinates used in the FLRW metric the Big bang happened at $t = 0$. It's just that it happened everywhere at $t = 0$.
Dec
6
comment Why does gravitational singularity break the laws of physics?
@MBN: Well yes, you can create spacetimes with incomplete geodesics by tinkering with the global topology. This seems outside the scope of my answer though.
Dec
6
comment Using Special Relativity in Uniform Circular Motion
See also my answer to Is gravitational time dilation different from other forms of time dilation?
Dec
6
comment Can a strained diamond actually become conductive?
If I understand the article correctly this is a calculated band structure. There is no way to achieve this effect in diamond because it would fracture long before the C-C distance became large enough to merge the bands.
Dec
6
comment From which dimensionful constants does proton mass arise?
There's a nice overview here (400KB PDF).