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Thursday, June 25

Monday, June 22

  1. page General Relativity - Kevin Norris edited ... Kevin - Black holes don't have infinite mass. That would imply infinite energy, which is probl…
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    Kevin - Black holes don't have infinite mass. That would imply infinite energy, which is problematic under current assumptions. You can detect a black hole by gravitational lensing: the black hole acts as a lens for passing light, creating a double image.
    Douglas Chin - If one went back in time with a watch that was purposely set at the wrong time, would the watch fix itself?
    Kevin - I'm sorry, I don't understand the question. Are you traveling to the "wrong time?" Are you going by wormhole or some other means? If you travel by wormhole to the "wrong time," the watch should still be set to the "wrong" time and hence should be right. Otherwise you need to be more specific.
    Source: The information is based on Wikipedia's article on general relativity, but it is my own work and not cut-and-pasted
    The images were made in The GIMP by me
    (view changes)
    7:58 pm
  2. msg Danny Sheffield message posted Danny Sheffield What's interesting about general relativity is that it appears to be nonlocal -- that is, unlike th…
    Danny Sheffield
    What's interesting about general relativity is that it appears to be nonlocal -- that is, unlike the other three fundamental forces, it does not describe gravity as being mediated by a boson or other particle. Instead gravity is mediated by the curvature of space itself.
    7:54 pm
  3. msg A short query message posted A short query Well, there are two likely candidates: String theory and some sort of quantum gravity. String theo…
    A short query
    Well, there are two likely candidates: String theory and some sort of quantum gravity. String theory is very interesting, but until they're able to bring it down from about 300 separate theories to about five, it's untenable. Quantum gravity is incomplete. Newtonian gravity gives incorrect results.
    7:52 pm

Sunday, June 21

  1. msg A short query message posted A short query I'm sorry this is so late, but still . . . I understand the theory, but disagree with one tenet…
    A short query
    I'm sorry this is so late, but still . . .

    I understand the theory, but disagree with one tenet - that Einstein was right. Is there any other possible explanation for the phenomena he analysed? Why must light travel at constant speed through vacuum?
    9:05 pm
  2. page Supergravity - Philip Cohn-Cort edited ... >>On Earth, people shouldn't normally be affected greatly by supergravity - but the pros…
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    >>On Earth, people shouldn't normally be affected greatly by supergravity - but the prospect of gravity on a greater scale
    >>could have an effect on long-distance space travel.
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    radiation from
    > > > > > >
    something like
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    create its
    own
    own gravitational field,
    >>Indeed, as long as the radiation itself had mass. However, in the case of photons and other small particles, this is
    >>mainly relativistic mass, and thus subject to change as its speed changes due to the acceleration of gravity - in other
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    >>I refer you to Chan's answer. Consequences would be nearly undetectable outside the M-theory enthusiast groups.
    Douglas Chin - Do gravitons travel freely between interdimensional spaces then?
    >>Sorry to take so long - yes, gravitons travel through all dimensions. Mind you, modern physics assumes that just about
    >>any number of dimensions could exist, so 'interdimensional spaces' aren't very well defined.

    (view changes)
    8:56 pm
  3. msg Danny Sheffield message posted Danny Sheffield Meh, I wasn't really in the mood to create pictures - but I could give it a go if enough people ask…
    Danny Sheffield
    Meh, I wasn't really in the mood to create pictures - but I could give it a go if enough people ask.

    On other planets? Supergravity is found anywhere there is a great deal of mass, so I'd expect it to be much the same.
    8:46 pm

Wednesday, June 10

  1. page Magnetic levitation - Brandon Siegenfeld edited ... Answer- They are better for the environment because they are more efficient then regular train…
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    Answer- They are better for the environment because they are more efficient then regular trains. They also cut down on noise polution which makes it easier to place them in populated areas without disturbing the citizens in that area. Also Maglev Trains are a lot faster then normal trains which is a big benefit for commutors. And further research of maglev trains help open up new technological advances to science while also helping to improve current Maglev trains.
    Robert Lopez - How can the average person utilzie this in everyday life?
    Answer-No unless they ride on a maglev train or they use one of those levitating toy globes. No other current applications are out yet at least for the average person.
    James Song- What effects does the levitation have on the frog?
    Answer- Strong magnetic fields can cause non normal patterns of blood flow, perhaps from the iron content. It may also cause nerve excitablility. A freaked out frog. Other than that not too much.
    Kevin Norris - How do you correct for instabilities in EMS-based trains?
    Answer-There are sensors that will activate certain magnets if the train moves outside a certain distance of its track. This will help account for non normal circumstances like wind, rain, etc. that could throw the train off its track.
    Sam Edwards - How does the flux trapping effect work?
    Answer- This was an experiment that contradicted the meisner effect that included the trapping of permanent magnets by a superconductor.
    William Chan - What are the negative aspects of the Maglev Train?
    Answer-They as stated above are not really cost effective yet. They are expensive. And many of the forms of maglev are not fully perfected yet.
    Greg Sturm - Could a magnetic levitator be thrown off by external magnetic forces, such as the one from the Earth?
    Answer- The Earth's magnetic force is way to weak to throw off a maglev train, also any impact the field would have would be corrected for. However external magnetic forces would effect the train and that is the point of having the trains have sensors to activate certain magnets to keep the train on track.
    Ari Horowitz - How can super conductors be used for Maglev trains?
    Answer- Superconductors as shown in the video will actually mirror the poles of a magnet near by which creates a repulsive force, this is because the electrons more freely move throughout the conductor. This can be used to levitate the train, the other option would be for the superconductor to be used as wiring for the electromagnets and since superconductors have little resistance you could in theory increase efficiency. The problems come in when you have to figure out how to keep the conductors at cold temperatures.
    Douglas Chin - So is a railgun powered by magnetic levitation then?
    Answer-No that is based off the Lorenz force which causes the projectile to accelerate.
    (view changes)
    9:57 pm

Tuesday, June 9

  1. page Aerodynamics of Airplanes - Chan & Song edited ... http://quest.arc.nasa.gov/aero/planetary/atmospheric/aerodynamiclift.html Sonia Bansal - What…
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    http://quest.arc.nasa.gov/aero/planetary/atmospheric/aerodynamiclift.html
    Sonia Bansal - What exactly did the Wright Brothers do to create a plane that flew?
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    on a plane.plane and ran very very fast.
    Angad Sidhu - What are the physics behind the landing mechanisms?
    That is a whole new topic in itself, but generally the brakes on the landing gear and the flaps on the wings help the plane slow down.
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    The same principles apply such as pressure differences and such. But the force of lift is the dominating force so the helicopter must be directed to compensate for that
    Sohini Sheth- When you notice an airplane taking off or landing, there are flaps on the wings. What's the effect of either keeping the flat down or keeping it up during flight?
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    out for landing itlanding. It is used
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    down the planplane by creating more drag. OnDuring take off
    Greg Sturm - This doesn't have much to do with physics, but I found your history of flight interesting. I don't think China should get credit for simply dreaming about flying like a kite or a bird. I mean I could dream about teleporting across the world in a second but you can't attribute that to me if it is ever invented. And what exactly do you mean by "mimicking the way birds flew?" Just flapping their arms up and down?
    Yes eaxactlyexactly that, well
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    and such, thatbut also useused it during
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    warriors to itit, equiped with
    Douglas Chin - How is the Boeing X-48B blended wing prototype better than standard plane models used today?
    One way they are better is that this prototype is 30% more fuel efficient than an airplane of similar size that carries the same payload.
    (view changes)
    3:41 am

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