77,426 reputation
178166
bio website ratsauce.co.uk
location Chester, United Kingdom
age 53
visits member for 3 years, 3 months
seen 10 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.


Apr
3
comment Could the universe be a series of Big Bangs?
Or I posted the same answer on this site here
Apr
3
comment Could the universe be a series of Big Bangs?
You might be interested in this pop-sci level description of the Big Bang that I posted on the SciFi Stack Exchange. Alternatively see this answer for a more rigorous discussion.
Apr
3
comment Could the universe be a series of Big Bangs?
The Big Bang wasn't an eruption of energy/mass E from a singularity O. Your question is predicated on the idea that the Big Bang was like an explosion happening at a point with everything flying away from that point. The Big Bang was completely different from this, so as it stands your question can't be usefully answered.
Apr
3
comment Recoil from a shotgun
@Aksakal: it's impossible to predict how far the chair would move. That will depend on the friction in the wheels and the surface that it's rolling on. Since I rather doubt the manufacturers provide this information you would have to determine the frictional loses in the chair by experiment.
Apr
3
comment Spinning theoretical object moving faster than the speed of light
I don't think the proposed question is a duplicate. This question is similar to the relativistic rotating disk and that's hard enough that I've never seen a really convincing analysis of it. The question isn't about signalling, as in the rigid rod. You could accelerate your spinning rod arbitrarily slowly to avoid problems with stresses propogating along the rod at finite speed.
Apr
3
comment Is gravitational force affected by intervening medium?
youtube.com/watch?v=-4_rceVPVSY
Apr
3
comment Which big bang theory has more assumptions?
See Is the law of conservation of energy still valid?. I can't speak for most physicists, but GR is not as hard as the popular myth suggests.
Apr
3
comment Pendulum (highschool)
@Mathbreaker: see my answer for the derivation of kecer's formula for $g$.
Apr
3
comment Pendulum (highschool)
What value of $g$ do you get using the simple formula? In general the more complex formula gives slightly higher value of $g$.
Apr
3
comment Which big bang theory has more assumptions?
@rowanman28: Energy is not conserved in GR because it does not respect time shift symmetry. This makes the first law of thermodynamics inapplicable. No-one knows what dark energy is. If it's a cosmological constant that can be interpreted either as a fluid with an unusual equation of state, or as a geometrical property of the universe and not energy at all. It depends which side of the = sign you put $\Lambda$. Dark energy was indeed a surprise to it's discoverers, but then so was special relativity back in 1905 and we all accept it now.
Apr
3
comment Is Dark Energy Pushing Us Or Pulling Us?
See for example Void or Dark Energy? and Local Void vs Dark Energy: Confrontation with WMAP and Type Ia Supernovae
Apr
3
comment Is Dark Energy Pushing Us Or Pulling Us?
See the question Qmechanic has linked. If our bit of the universe is below the average density this could account for the acceleration. However this requires us to be at the centre of the underdense region, which seems a bit of a coincidence. Also there is other evidence for dark energy.
Apr
3
comment Kinematics, why must the final velocity be 50km/hr?
To be fair it would be a great deal of work to put all the details in the question as it would require reproducing large parts of the paper.
Apr
2
comment Is the Hilbert-Felber model of repulsive gravity correct?
Aaah... I wonder if, in the rest frame of the distant observer, the object never passes the black hole but gets continually pushed along in front of it and therefore accelerated to the same speed. If so I'm not sure how you'd get off the train.
Apr
2
comment Is the Hilbert-Felber model of repulsive gravity correct?
@AndrewPalfreyman: yes, but after the black hole has passed, why isn't the effect reversed leaving the object displaced but stationary?
Apr
2
comment Centrifugal force when there is no friction
possible duplicate of Direction of friction on particle placed on a rotating turntable
Apr
2
comment Light and Prisms
However, your LCD screen and/or phone produce pretty convincing pictures using just RGB, so RGB reproduces enough colours to convince.
Apr
2
comment Light and Prisms
@jinawee: If the cone cells just responded to pure red, green and blue light then RGB would be able to produce every colour the eye could see. However the cone cells respond to a broad range of wavelengths (as shown in the graph in my answer) and their ranges overlap. That means there will be some combinations of cone cell response that cannot be expressed as a sum of the individual responses to just red, just green and just blue light, and hence there are some colours that can't be reproduced using RGB.
Apr
2
comment Centrifugal force when there is no friction
If there is no friction the coin will remain motionless where it is while the disk rotates underneath it.
Apr
2
comment Light and Prisms
The other one is probably CMY (or CMYK). RGB is additive mixing, like the screen on your phone, and CMY is subtractive, like your inkjet printer.