Search results

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    Netflix/Pandora and Neural Networks

    While Netflix almost certainly uses something a bit more complicated. Try: https://en.wikipedia.org/wiki/Collaborative_filtering
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    Are their super heavy/dense stable elements we haven't discovered?

    Technically speaking, a neutron star is one big atomic nucleus. But in that case it's gravity binding everything together instead of the strong force. Though nuclear physics isn't my area of expertise, finding stable nuclei in the very high nucleon numbers is kind of the holy grail in that...
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    Actual Gravity Tests

    I don't think measuring the freefall time is the best way to measure local gravity. Mostly due to DrPizza's objections, but this was figured out centuries ago. A much more precise and repeatable way of measuring gravity is to use a pendulum, again figured out centuries ago. Incidentally, since...
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    Effect of high intensity electric and magnetic fields on gravity

    That's the thing, gravity *is* curved spacetime, and an energy density curves spacetime. Therefore, energy density = curved spacetime = gravity. Next point, electromagnetic fields have an energy density associated with them, you just square the fields (E and B) with the appropriate constants...
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    Effect of high intensity electric and magnetic fields on gravity

    We don't really expect large electric fields to exist except perhaps locally since a charged body will quickly find it's opposite and neutralize. We do see some pretty big magnetic fields. Basically, the energy associated with either field goes into the stress-energy tensor from GR and does all...
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    Thermodynamics: Melting ice cream (cool wind vs still air)

    To really answer this, we would need to know what the temperature of the air was outside *and* the temperature in the trunk. Given that you said the car was outside for a long time in the cold, it's probably a safe assumption to say that the air temperature was the same outside as it was for...
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    Can the microwave affect the fridge?

    I think even in the worst case scenario with the magnetron sitting naked on the counter next to the fridge, you would have a tough time affecting anything in the fridge, including the electronics. I mean, a fridge is a pretty good faraday cage itself with it being encased in sheet metal and...
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    Geometric Time - another theory against the Big Bang

    Hubble's expanding universe *was* the main evidence for the Big Bang. Until the CMB and its associated power spectrum were discovered. Now that is our smoking gun for Big Bang plus standard inflation. This isn't to say that this is definitely correct, but it is certainly our leading theory by...
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    nuances in the imagery of Nolan's 'intestellar'

    First, though I am an astrophysicist, I don't profess to be an expert on GR, especially the Kerr metric. That said, as to the reason why the high gravitational force doesn't crush you, I think you are on the right track with your guess. As for his hand waving about the tidal forces, I...
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    What would happen if the Earth had a total blackout for a few days?

    Perhaps this might help: https://www.youtube.com/watch?v=qF3ejw7JJuc
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    If i am reading this correctly, it is about the Heisenberg uncertainty principle ?

    Thinking about the uncertainty principle like the Fourier Transform is no mere analogy either. The uncertainty principle is a direct result of position and momentum being Fourier Transform pairs within a factor of h (you can arrive there using Plancherel's theorem). I can't help but think...
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    This gravity simulation looks a lot like ...

    Neutron stars and black hole mergers are simulated quite often. The physics is very demanding as it requires solving some very tough GR and in the case of neutron stars, nuclear physics. In addition, accretion disks and magnetic fields tend to confuse a lot of things. That said, there are...
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    This gravity simulation looks a lot like ...

    I'm not entirely sure how to answer that. The virtual particles being created near the event horizon is effectively Hawking Radiation. As far as the compression and expansion of space due to a moving black hole...changes to the metric propagate at the speed of light and so all GR effects...
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    This gravity simulation looks a lot like ...

    I quickly perused the article, it looks like this is the distortion of starlight around a spinning black hole + accretion disk. The coordinates are strange and they didn't provide any caption or anything. It does appear that any similarities you are seeing between the dipole field of the...
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    This gravity simulation looks a lot like ...

    It's not entirely coincidence, GR and EM theory can be unified at a certain energy scale. You can even see the similarities in the simplified force equations (Newton vs Coulomb law): F_coulomb = k q1 q2 / r^2 F_gravity = -G m M / r^2 But there are some very important differences, the...
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    Help with vector math please?

    Simply put, \nabla is a vector which is in 3 dimensions (\partial_x, \partial_y, \partial_z). A is also a vector (assuming 3 dimensions) (A_x, A_y, A_z). \nabla(A) then is a 3x3 matrix from the multiplication. \nabla^2 should be read as \nabla \cdot \nabla, so this makes it a scalar...
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    How far away is it now?

    So, wikipedia naturally has a entry on variable speed of light: http://en.wikipedia.org/wiki/Variable_speed_of_light The last few sections are particularly relevant. The claim is that, changing a dimensionful constant like the speed of light doesn't do anything if the value of the fine...
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    How far away is it now?

    You are correct, somewhere between typing the distance the light traveled I missed the explanation of the Hubble expansion and proper distance calculation. I believe Carl Sagan was once an expert witness at a trial and was asked a similar question (how do we know the laws of physics apply...
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    How far away is it now?

    I suspect you may be under some misconceptions about distance and cosmology. 13.3 Billion Light Years away, means that it takes the light 13.3 billion years to get here and is roughly how far away it is *now*. When the light was emitted, the universe was much smaller and we (our galaxy...
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    Noise Cancelling an entire room

    Have you considered water cooling? That removes a lot of fan noise and means you can even relocate where the fans are to a certain extent (i.e. you could move them outside the room). And cuts off the component noise through the fan 'holes'. You would need to worry less about heat in the...
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    The Supernovae Postulate

    Well, the (roughly) spherical explosion of a supernova begs the question: What happens if you were to focus that energy? That is what we think causes long duration gamma ray bursts -- i.e. the most energetic things in the entire universe. Inserting my own scientific bias here, if you took a...
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    The Supernovae Postulate

    What is even crazier, is that of all the energy released in the supernova, less than 1% of it is in the form of photons. Or light. The rest, neutrinos. Expanding on this, during the collapse of the star, it is thought that the density is so high in the collapsing material that the neutrinos can...
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    the event horizon of a black hole should be colorful

    Basically, every object is supported against gravity by some pressure. This is called hydrostatic equilibrium. If you remove the pressure, a simple application of newton's laws will lead to this object collapsing. In ordinary everyday sized objects, electrostatic forces are enough to keep an...
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    the event horizon of a black hole should be colorful

    That is correct, Security Theatre. I didn't elaborate very much, but that is included in the outward pressure in the form of degenerate matter. For a white dwarf, that is electron degenerate matter. After the Chandrasekhar limit, neutron degeneracy and a speculative quark degeneracy after...
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    the event horizon of a black hole should be colorful

    As was mentioned before, Leonard Susskind has an excellent video series where he outlines his holographic principle as a way of avoiding nasty information theory issues with black holes. But first, Hawking radiation is actually pretty simple to understand in a basic, if somewhat flawed way. It...
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    Bit coin mining

    Ah, I see now. Bitcoin (and litecoin) can be mined on the CPU, however, they are pretty well useless. If you pay for your power you will *lose* money. The GPU is the only semi-profitable way, and only if you have a GPU that has a good hash/Watt ratio. As for running in VM's, not...
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    Bit coin mining

    The USB miners only use a little power and don't really use the CPU all that much. They should be fine in a virtual machine, a lot of people use a raspberry pi and a usb hub to run them. That said, I do not recommend them at all. The rate of return on them is terrible, even at 40$ or whatever...
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    the event horizon of a black hole should be colorful

    The flavour of the neutrino doesn't matter all that much, they are sort of different sides of the same particle. As to the whether they are dark matter or not: Whether they have mass is critical to if they could be dark matter (Dark matter is simply matter that we can not see, or it...
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    In a time far, far away...

    @sm625 -- This is true, however we have good constraints on Andromeda's proper motion: "Constraints on the Proper Motion of the Andromeda Galaxy Based on the Survival of Its Satellite M33" http://iopscience.iop.org/0004-637X/633/2/894
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    In a time far, far away...

    Let me attempt to parse this.... I think you mean, how do we know the Andromeda galaxy is headed our way and that we are going to collide. And, if we collide, what will happen? So, 1) We know quite a lot about Andromeda since it is nearby. Among the things we know, are its mass and velocity...
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    Universe expansion is accelerating ?

    There are many reasons why our accuracy will decrease as distance increases. Background and foreground objects "polluting" the spectra for one. I think the major cause is probably because you are taking a Fourier transform of whatever is in the "beam" of the telescope. For a resolved star...
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    the event horizon of a black hole should be colorful

    I think he means the last stable orbit of a black hole is one where your orbital velocity is the speed of light. Thus, there should be a "ring" of photons at this radius. They won't be separated by frequency though, only the speed matters and like you said, c. But, even if you expect some...
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    Universe expansion is accelerating ?

    Velocity Doppler shifts are relatively easy to measure. So we can get the radial velocity (the velocity along our line of sight). For nearby objects, our spectrometry is good enough to measure 1 m/s radial velocities. A characteristic profile for spectral lines can show rotation, one side...
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    I have a problem with the ONE or psst physicists, in here pls

    "In physics, a virtual particle is a transient fluctuation that exhibits many of the characteristics of an ordinary particle, but that exists for a limited time." -- wikipedia Where does that say "short amount of time"? Also, re-read the quote (again from wikipedia) that I posted earlier...
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    I have a problem with the ONE or psst physicists, in here pls

    Who said they only exist for a short time? Or that they "exist" at all?
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    Bit coin mining

    I calculate that at 0.10$/day using coinwarz. The pool is really up to you, there is a lot of confusing data out there, but really they all average to the same over long time periods. deepbit eligius mining.bitcoin.cz Those are pools that I've tried. Check out coinwarz and see my...
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    Bit coin mining

    Litecoin uses a different hashing algorithm that is memory intensive, and thus expensive to implement on an FPGA or ASIC. I use bfgminer/cgminer which can mine either SHA256 or scrypt, you just point it at a pool. The main problem I see with the ASIC is that it is really hard to actually...
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    Bit coin mining

    What's been alluded to already, is that SHA256 mining is not lucrative at all. Maybe with specialized hardware, like ASICs. But you probably won't pay those off before the difficulty rises really high. My advice is to mine Litecoin or something similar, GPU's are still king in this regime. My...
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    I have a problem with the ONE or psst physicists, in here pls

    The virtual particles are limited by the speed of light, just like real ones. Relativity and quantum mechanics are quite compatible (Dirac?), for a solution to the EM problem you need to use the retarded time. Maybe this quote from the wikipedia page on virtual particles will help. "The term...
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    What happens to light at the end of the universe?

    I suppose I probably could have been a bit more clear there. Let me try that sentence again: Space is expanding at a uniformly accelerated rate (in places where things aren't gravitationally bound, like our solar system or galaxy). The implications are that, relative to us, things move...
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