367 reputation
18
bio website snowhare.com
location
age
visits member for 3 years, 2 months
seen Sep 22 '13 at 16:25

Jun
10
comment Could a coronal mass ejection be responsible for this?
The sensor probably does interface with grid power. A sensor has to connect to the equipment it is being used for so there is very probably an electrical connection and it is probably actually powered by the equipment it is connected to. Sensors usually aren't self powered.
Jan
30
comment Could an ultra-relativistic particle tunnel directly through a stellar mass black hole?
I'm not sure we aren't talking past each other. My question is about the quantum mechanical possibility of the particle quantum tunnelling 'past' the barrier posed by black hole without ever actually 'entering' it (ala the Klein Paradox). I'm happy either way - I just want a clear explanation of why it can or cannot.
Jan
29
comment Could an ultra-relativistic particle tunnel directly through a stellar mass black hole?
I'm not getting why the cross-sectional area of the horizon matters. We are talking about the probability of the particle tunnelling through a thin potential barrier. The size of the barrier in the directions perpendicular to the direction of motion would seem to be irrelevant. To put it another way - if I were to replace the black hole with a normal matter wall, how would that differ for the question of tunnelling a ultra-relativistic particle through it?
Oct
23
comment Why are photons released from high-voltage electricity through a near vacuum?
What actual example of photons being generated in a vacuum by high-voltage electricity are you thinking of?
Apr
14
comment Will a hole cut into a metal disk expand or shrink when the disc is heated?
Here is a way to think about it that makes the answer obvious. Replace 'cut a hole into with 'draw a circle on' and consider what happens to the drawn circle when the disc is heated.
Apr
10
comment Is there a named unit that, when divided by 32, gives meters per second?
It sounds like someone got a meters to feet conversion backwards. 10 meters is about 32.8 feet. Also, are you getting meters per second (velocity) or meters per second squared (acceleration)? 1 g is about 9.8 meters/(sec*sec) or 32.1 feet/(sec*sec). Another context where 32 shows up is in atmospheres of pressure. You get about 1 atmosphere of pressure for a water column 32 feet deep. Context would help a lot in guessing why 32 is showing up.
Apr
6
comment Why does a coin falls faster when it's flipping as well?
To extend on my remark about the difference in the fall distance of the center of mass: A difference of only 1.1 millimeters in the fall distance would change the fall time by 15 milliseconds. That is on the order of the thickness of a typical small coin.
Apr
6
comment Why does a coin falls faster when it's flipping as well?
You need to specify your experimental setup better. I can think of a few things that could be causing issues such as differences between the location and fall distances of the center of mass of the coin when dropped to make it flip vice dropped to not flip. You could be accidentally be effectively dropping the 'flipping' coin a shorter distance. You could also be having air flow effects caused by a nearby surface as the coin rotates. There are several possible sources of the difference, but they depend on your setup.
Apr
1
comment If you place a spring on a neodymium hard-drive magnet, it appears to vibrate in slow-motion. Why is that so?
Are you using a compact florescent light on your desk? If you are, you may be seeing a 'strobe' effect rather than a large physical change in the frequency. A small change in the oscillation frequency could produce a visual 'beat frequency' effect where it appears to vibrate much slower than the actual change in frequency would suggest.
Mar
29
comment How do levers amplify forces?
Here is a mental model that might help. Think of a series of balls connected in a straight line by very rigid springs floating in space with no external forces acting on it. When it is in its 'rest state' there are no stresses on it. Now give the ball at one end of the assembly a push at right angles from the line. When you do that the spring connecting it to the next ball bends a bit - transmitting the force to the next ball as it tries to straighten out the line. From there to the next ball, and so on.
Feb
27
comment Equivalence principle and radiation from falling particle
Here is a Java applet that helps visualize what happens when a charge accelerates. Play around with it and it will help.
Feb
26
comment Equivalence principle and radiation from falling particle
Don't think about it from an energetic argument. Think about it from the perspectives of what the time evolution of the electric field looks like in the co-moving frame of reference and then from the laboratory frame of reference.
Feb
25
comment Keeping air in a well
This is equivalent to constructing a shell around a planet at some arbitrary altitude. The pressure at the bottom of your hole will remain steady as long as the air pressure at the top is the same as the 'natural' pressure for that altitude.By which I mean if you start with some global specific (low) pressure at the top before you start digging, the pressure at the bottom of the hole will simply be the pressure you would get if the atmosphere was as much thicker as your hole is deep.
Feb
16
comment Why does a window become a mirror at night?
The adjustment of pupil size is only a small part of the story (it accounts for perhaps a factor of 10 in the overall sensitivity). The eye actually becomes more and less sensitive by a much larger factor via other mechanisms. It is more akin to turning up and down the gain of the retina itself.
Jan
30
comment What is the difference between a Rodin coil and a Rodin starship?
As Alexander said - it's a regular electromagnet. If you backtrack to find the background on Mr Rodin and his 'Rodin coil', you will find he is a classic case of a physics kook.
Jan
29
comment Why does electron-positron annihilation prefer to emit photons?
Yes..but that doesn't actually answer my question. In the low energy limit why are photon pairs preferred over gravitons or neutrinos?
Jul
5
comment maximum rotational speed
A nice explanation can be found on pages 16 and 17 of this article by M. Camernzind and A. Muller. In essence, it is the speed that the black hole frame drags. It can't exceed the speed of light at the event horizon or you would no longer have an event horizon.