92,175 reputation
3117220
bio website ratsauce.co.uk
location Chester, United Kingdom
age 53
visits member for 3 years, 6 months
seen 4 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.


Mar
25
comment Have I calculated the air flow of this fan correctly?
@user95786: Yes, that's the way I would do it. You have two variables: (1) the size/shape of the fan and (2) the revolution speed i.e. the gearing you use. I suspect Lemond established the best values for these by experiment.
Mar
25
reviewed Approve suggested edit on Does nonlocal theory violate causality?
Mar
24
answered Deriving group velocity formula
Mar
24
revised Have I calculated the air flow of this fan correctly?
added 16 characters in body
Mar
24
answered Have I calculated the air flow of this fan correctly?
Mar
24
comment Can relativistic momentum (photons) be used as propulsion for 'free' after the initial generation?
@Ehryk: If the two mirrors are fixed in position, e.g. fastened to each other in a rigid frame, then the light wouldn't red shift because no energy is being transferred to the mirrors. In your question the red shift occurs because the mirrors aren't fixed in place so the light can transfer energy to them by pushing them apart.
Mar
24
comment Can relativistic momentum (photons) be used as propulsion for 'free' after the initial generation?
@webb: I think the point is that the two mirrors are not connected, so they push each other apart.
Mar
24
answered Can relativistic momentum (photons) be used as propulsion for 'free' after the initial generation?
Mar
24
comment If nothing can travel faster than the speed of light, how can there be parts of the universe we can't see?
Have a look at my answer to Whats left at the center of the Universe after Big bang? for some background info.
Mar
24
comment If nothing can travel faster than the speed of light, how can there be parts of the universe we can't see?
possible duplicate of Can space expand with unlimited speed?
Mar
24
comment If nothing can travel faster than the speed of light, how can there be parts of the universe we can't see?
We didn't originate from a single infinitely dense point in space time in the Big Bang. This is a common misconception. Search this forum for flrw metric for many, many related questions.
Mar
24
comment Atmospheric heating and the reduction in viscosity
The viscosity of (an ideal) gas does indeed increase with temperature.
Mar
24
revised Atmospheric heating and the reduction in viscosity
Typo?
Mar
24
comment Free fall from space
8th grade is around age 14 isn't it? I couldn't have solved the differential equation describing this motion until around age 18. Good luck, but I suspect your ambition is running away with you.
Mar
24
comment Is every electromagnetic radiation considered “light”?
BTW an electrical circuit is unlikely to be operable at visible light frequencies because those frequencies are higher than the plasma frequencies of (most?) metals. However, in principle an electrical circuit running at visible light frequencies would indeed emit EM radiation that you could see.
Mar
24
comment Free fall from space
The trouble is the explanation needs to describe how you set up a differential equation to describe the motion of the particle, and how you solve the equation. This isn't as hard as it sounds - in the UK you do it in the last two years at school (age 17-18) and in more detail in the first year of a univversity physics degree. However to understand it requires a fair bit of maths background. To try and explain it here would be a long answer, and probably an unsuccessful one.
Mar
24
comment Is every electromagnetic radiation considered “light”?
See this question. The term light is normally used for EM radiation of a wavelength between 400 and 700nm. The only difference between light and other EM radiation is what our eyes are sensitive to.
Mar
24
comment Free fall from space
@ZilbermanRafael: the derivation is given in an answer to this question. It's hard going though.
Mar
24
comment Free fall from space
The working you've shown is correct, but it assumes the gravitational acceleration is constant. However 500km is far enough for the gravitational acceleration to change quite a bit so the fall time is longer than your calculation. The complicated equation in the Wiki article takes this into account. BTW using the full equaiton I get 340 seconds for the fall time.
Mar
24
comment Free fall from space
There is a related question here and the derivation of the equation is given in an answer to this question. However you may find this heavy going.