Physics

I noticed today as I was drifting around my pool on a floating raft that i was leaving traces of shadows on the bottom. The shadows seemed to swirl around on the bottom every bit as dark as my shadow on the bottom, these swirling shadows would get bigger break up go into orbit around a bigger shadow, grow bigger break up and merge. Some of them lasted 3 minutes after they formed. You could only see them well at high noon. I was amazed at how much they resembled pictures of deep space where nebula and galaxies swirled around each other. I found that the best shadows were made with the least effort. Moving fast seemed to break up the effect but very gently moving caused the…

Currently we believe that light travels at C which is constant and nothing can exceed it, so I thought of something that also relates to the expanding universe. Would it not make more sense to say that light travels at maximum speed and that the universe has a speed limit, thus light travels at the speed limit which is C? It would mean that as the universe continues to expand at an increasing rate, it would eventually expand at the speed of light and not go any faster. This would be the reason for the universe to have a speed limit because if one were to travel past the speed of light it would mean that one would eventually outspeed the rate of the universe's …

I'm having some trouble with a pretty basic question and I'm not sure what I'm missing that will correct my thinking. If I have two electrons in a vacuum and they are set at arbitrary origins at a correspondingly arbitrary fixed distance between them with initial velocity 0 how do I find time as a function of distance? I'm looking at this like this: [math]a® = k_{e} \frac{q^{2}}{m \cdot r^{2}}[/math] where a is acceleration, r is the distance between the two electrons, [math] k_{e} [/math] is the Coulomb Constant, m is two times the electron mass and q is the charge on one electron. It is all well and fine to plot acceleration as a function of distance bu…

Can we be sure that decay times are constant? Particle decay is clearly some statistical process. Generally speaking, particles are some stable solutions of some physics (like a field theory) - they are some local/global energy minimums for given constrains like spin or charge. So from energetic point of view, particle decay should be getting out of some local energy minimum by crossing some energy barrier and finally reaching some lower energy minimum - just like in thermodynamics (?) Energy required to cross such energy barrier usually comes from thermal noise - in case of particle decay there would be required some temperature of vacuum ... Generally th…

This provides a comprehensive collection of links to audio/video courses and lectures in physics from education institutions. http://www.infocobuild.com/education/audio-video-courses/physics/physics.html The courses and lectures cover various subjects in physics such as classical physics, quantum physics, special relativity and scientific computing.

... and if it doesn't have a direction, then how do you describe the difference between the pressure on one side of a surface and the pressure on the other side? (ie. Let's say there was a force imbalance from one side of the surface to the other... does that mean the pressure has a direction?)

I always thought that thermodynamics/statistical physics is effective theory – statistical result of some fundamental physics below, but recently there became popular theories starting from ‘entropic force’ as fundamental (basing on holographic scenarios, like in http://arxiv.org/abs/1001.0785 ). I was taught that to introduce effective local thermodynamical parameters to given concrete situation, for each point we average inside some ball around it to get for example local entropy or temperature. For a simple mathematician like me it sounds like a nonsense – in fundamental theory describing evolution of everything there should be one concrete history of our universe – …

I often hear about how driving more slowly is supposed to save on fuel emissions. Are those who say so referring to "less fuel use per unit of time on the road" or do they mean over time as well? If so, why?

Hello, I'm looking for articles and documents for electronic circuits under a free license (eg Creative Commons) to translate it into French and post it on my site http://www.zonetronik.com Thank you in advance

Let's say you had a container from which matter could not enter or leave, but energy could enter or leave easily by conduction. This container is filled with warm, humid (but not saturated) air and then its temperature is lowered to far below the dewpoint without being opened. Would the drop in temperature cause condensation, or would the drop in pressure prevent it? Which factor would outweight the other, if either?

Hello everyone, In electrophoresis the least dense one moved less (other factors been the same for every particle). I'm assuming this is due to higher volume and more resistance but, doesn't electrophoresis measure kinetic friction, so the one with lowest density should move further. What kind of resistance does electrophoresis refer to. Thanks

So I hear that maglev trains are able to go up to hundreds of kilometres an hour. How quickly would they tend to approach such speeds, given the forces acting on the passengers due to acceleration? Would strong force over short time interval, or weak force over long time interval, be the preferred approach? Also, if they were about to round a turn at hundreds of kilometres an hour, would they slow down first, and if so for how long?

I'm reading about nuclear waste. Supposedly, it can be dangerous because it gives off ionizing radiation. Is there any way to put those emissions to work? Otherwise, is there a way to drain them from the source of emission at a faster rate? Could a current technology that relates to ionizing radiation be adapted to soak the emissions and/or divert them?

Hi, I am taking part in a science competition in which I must design a device that can measure time. I must measure 5 different lengths of time that range from anywhere from 10 to 300 seconds. The catch is that I am not allowed to use any electricity. I have a few ideas that I'd like to get some opinions on: The first is to set up a pressure-activated piston that would launch a ball onto a platform that would return the ball back onto the piston. I would record the amount of time it took for the ball to be launched each time, and simply count the number of times the ball is launched during the competition. The other idea is to build a series of alternating J s…

This is a big ramble fest I had with myself considering Loop Quantum gravity and M-Theory and I was wondering if anyone can either clarify my thoughts or clearly explain to me the difference on why they can't work together... here is my picture of my large conversation with myself on facebook and I doubt anyone on facebook has the IQ to solve this and the picture is in the attachments... please help me (in order to open it, save it to your desktop, and then press preview and scroll up or down to see the size)

It's far from widely known fact that before Einstein's theory, there was Heaviside's simpler approach to make gravitation Lorentz invariant - by using a second set of Maxwell's equations - with e.g. density of mass instead of density of charge http://en.wikipedia.org/wiki/Gravitomagnetism This much less philosophically controversial theory (matter is not prisoned in infinitely thin submanfold of something with which it doesn't interact ... not allowing for wormhole-like solutions...) agrees well with most of observations (?), even with Gravity Probe B. Some papers says that even in better way: http://www.mrelativity.net/Papers/14/tdm5.pdf There can be also foun…

Not sure if here or another board would be a better place for this topic but whatever. One popular argument against nuclear power is the possible risk of a nuclear meltdown makes it dangerous, no matter how less and less likely a nuclear accident gets as technology improves, because IF such an accident were to happen, the results would be disastrous. Well, IF such people supported fossil fuels, recent events show their point to be quite moot. But on other forums, I've found that those who actually address this tend NOT to be in favour of fossil fuels, but instead tend to be in favour of wind and/or solar power; which begs the question; how feasible are wind an…

Momentum is a vector quantity, in the same direction as speed, and velocity is the magnitude and direction of said speed, with mass being the scalar coefficient by which velocity is multiplied to yield momentum, right? So let's say we're taking the derivative of momentum with respect to time (seeing as how that's what net force actually is) and mass of a particular object is transferring elsewhere... if we're analyzing the momentum of the object in particular, and both mass and velocity are changing at the same time, would the rate of change in momentum be: (dp/dt) = (dm/dt)*(dv/dt) OR (dp/dt) = m*(dv/dt) + v*(dm/dt) OR would it be something else because o…

Ok, so the kinetic energy of an object is supposed to be proportional to the mass of the object, and to the square of the speed of the object, and speed is basically the magnitude of velocity, right? Also, velocity depends on the reference frame in which it is measured, so long as said reference frame is also of a constant velocity, right? So if we were considering a moving object from two reference frames, one that treats the object itself as a reference frame, and an external reference frame, from which the object was moving... would that imply different kinetic energies?

Today I noticed a "chained pen" (assuming that's what it called; though the "chain" was a series of metal beads connected by an apparently-metal string) with the pen and chain removed from its holder but still connected to each other. I then proceeded to pick it up and, while holding the pen, spin around the "chain" in a circular motion. (Sort of like a standing wave, except instead of up and down it goes around and around... heh, that rhymes.) I noticed that the faster I spun the "chain" the more of a "pull" it felt like there was on the pen... anyone here know what this is?

With the world cup stopping me from doing any real work I've taken it upon myself to create my Physicist football squad. It's been the best hour I've spent recently and I recommend it! Positions and places in the squad are not completely based on ability as a Physicist: Goal: Rutherford, Left Back: Archimedes, Right Back: Bohr, Centre Back: Einstein, Centre Back: Newton, Left Mid: Schroedinger, Right Mid: Faraday, Centre Mid: Galileo, Centre Mid: Maxwell, Striker: Heisenburg, Striker: Boltzmann. On the bench: Curie, Feynmann, Laplace, Dirac, Thompson, Kepler, Pauli. Thoughts? …

Treating air resistance as negligible for this case, suppose we have three objects thrown FROM one vertical position TO another vertical position; the initial and final vertical positions being the same for each object. They are thrown at the same speeds, but at different velocities; one is thrown at an upward angle, one is thrown at a downward angle, and one is thrown horizontally. Would they have the same speeds, or different speeds, upon hitting the ground?

I was recently thinking about centripetal acceleration (a=vv/r) and I have a few questions about it... 1. Since gravity's variation with depth has a corresponding air pressure variation with elevation, I was wondering if spinning an enclosed container (with air in it) around in a circle such that the same part of it was always facing the centre (ie. similar to how the same face of the moon is always pointed towards the Earth) then if the stronger forces towards the circle's centre (ie. where the radius is closer) would push air enough to the part of the container further from the centre to create a pressure gradient within the container, in addition to whatever pre…

If I had a combination of several AA and/or AAA batteries, and I had some sort of conductor (let's say a piece of aluminum foil) over all their positive terminals, and another conductor over all their negative terminals, then had some piece of wire go from one conductor, through a load, (like a voltmeter) to the other, would this function as batteries connected in series, or as batteries connected in parallel?

I can't describe in words, so here's a picture instead. What will happen if you put one end of a wormhole into the other end of the same wormhole?