nik

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Posts posted by nik

  1. Posted

    (I absolutely cannot believe I'm about to say this.)

     

    Took my shirt off and flexed in the men's bathroom mirror.

     

     

     

     

     

    So who was in there with you nik???? :clap: :huh:

    Well.... see, that's the really bad part. I was in the middle of a nice ab shot.... and

    my boss walked in....

     

    Fortunately, he is a pretty understanding guy, and of the opinion that what one does in the bathroom mirror is one's own business, but had a good laugh about it. Talk about embarrassment!

  7. Posted

    Why magnetic north is not geographic north? More appropriately, why is goegraphic north not magnetic north. There's two simple answers, and I leave you with a question. The first answer is: It probably never was. When the Viking first started using lodestones to find their way in the fog, and rennaissance thinkers began to think about maps, there may have been some discrapancy in the determination of "north" based on astronomical observations, and the way

    the compass needle pointed.

    The second answer is that the geomagnetic north pole drifts. It moves measurably over the span of a year. Pretty cool, huh?

     

    Why does it drift?

  9. Posted

    I disagree, nik, I think it's immeasurable. That's just my opinion. :clap:

     

    The distance light travels in one year, yes, a Parsec is X 3 :huh:

    OH! THE UNIVERSE! I thought you were talking about a parsec being immeasurable. Well.... you might be right....

  10. Posted

    There are four differential equations developed about the turn of the 20th century to explain electromagnetic phenomena. They were named after C. Maxwell, though he wasn't the only one to bring the work to fruition. Many of these also are named for great scientists who made previously developed observations. I will explain these in words, since I don't have math fonts.

     

    Gauss's law: The "strength" of an electric field (penetrating a closed surface) is proportional to the charge contained within that surface.

     

    (Unnamed): There are no magnetic monopoles.

     

    Faraday's law: The induced electric field about a closed loop is proportional to the time rate of change in magnetic flux through that loop.

     

    Lenz's law, Magnetic analog to Faraday's law: The induced magntic field about a closed loop is proportional to the time rate of change of the electric flux through that loop and to the current through that loop.

     

    This is a general explanation for Maxwell's equations in space, but can take on additional terms for "sources" of magnetic and electric field. The last two can be used to derive the speed of light, which is an electromagnetic "disturbance."

  11. Posted

    Very close. The distance light travels in a year is a light year. Question: If light travels 2.99*10^8 m in one second, how far does it go in a year?

    A parsec is 3.26 light years. How do we get this?

    Parsec is a term invented by the astronomers. It's an abbreviation for "parallax

    of one second of arc" or something like that. We can measure distances by looking at

    an object when the earth is on one side of the sun, then when the earth is on the other, and then then see what the angle is between measurements. It turns out that an

    object one parsec away will result in a differenc in angle of one arcsecond, or

    1/60 or 1/60 or a degree.

     

    Try this: go to one side of your yard, face the street, and look at your mailbox. Note how you have to "angle" your head to see the mailbox (assuming your mailbox is on the street like mine). Walk to the other side of your yard, still facing the street, and look at your mailbox. You have to look at a different angle. That's how parsec works.

     

    Interesting Note: The known universe it about 20 billion light years in radius. Pretty big, huh?

     

    Make sense?

  13. Posted

    By the way, Jeanway, we're pretty sure that the speed of light is a great cosmic speed limit. Nothing moves faster.

    what do you think happens when a particle moving at, say, 80% (0.8c) the speed of light in air enters water, in which the speed of light is only 75% the speed of light in air

    (0.75c). Is the particle moving faster than the speed of light?

  14. Posted

    ANYONE CARE TO EXPLAIN?

    See the other thread on this topic. However:

     

    The speed of light can be determined from solving the Maxwell equations (in any medium). These equations result in a second order linear differential equation. The

    result of this equation in space is a sinusoidally varying waveform (in electric and magnetic fields). The "constant" of this equation is the product of the permeability and the dielectic constant of free space, which we call the speed of light. It's fascinating

    to think that we were able to determine the speed of light before we could measure it.

     

    Albert Einstein spent some time trying to find a way around Maxwell's equations for moving reference frames. His final conclusion was that these two constants mentioned above are constant in all reference frames, and thus the speed of light is constant in

    all reference frames. Pretty cool stuff.

     

    Some other fascinating results are solving Maxwells equations for various matterials:

    glass (not too hard), two different glass interfaces, metal, a plasma (why AM radio works well at night), and wave guides. We can get some neat results.

  15. Posted

    Consider this. Think of a boat in the middle of the water bobbing up and down slightly so that it produces ripples. You're standing on shore with a stopwatch and you

    measure the time between wavefronts as they hit the shore. Now imagine that the

    boat is moving toward you, (but still making ripples at the same rate, as far as the

    boat is concerned). Well, as it turns out, the ripples are closer together when they reach you. Now think of a third scenario. The boat is stationary, but you are moving

    towards the boat. You encounter the ripples sooner. In either of these cases, the

    wavefronts seem "compressed" or at a higher frequency/shorter wavelength.

    Moving objects relative to each other will emit "waves" at different wavelengths.

     

    Here's a good question:

    What will happen if the boat moves away from you? You from the boat? (I will not answer this.)

     

    This is called the Doppler effect, and it applies to nearly any moving object that emits waves of some sort - light, sound, wakes, etc.

     

    Now, talking about my job again. One of my projects involved superluminal jets from active galactic nuclei. That is, jets of hadronic matter that apparently were emitted very fast from the cores of quasars. How did we know they were moving fast? Well, the light from them was Doppler-shifted. In fact, we had to apply relativiistic corrections to these jets. It's amazing that the light emitted may have been visible light (or whatever) but was radio waves when it reached us, or X-rays.

     

    Another cool thing is that the universe is expanding. The farther out we look, the faster things are moving away. (Think about how this can be in a uniformly expanding universe. Or... think about how this can be in a uniformly rising loaf of raisin bread. They are analogous.) We can get a good estimate as to how far something is away by how much its light is Doppler shifted.

     

    Jeanway, I bet you can think of about dozen more questions about this.

     

    Other applications of the Doppler shift:

     

    A train coming and going.

     

    Police cars moving towards and away from you. This one is fascinating because a police siren is a superposition of at least two waves, and both are shifted.

  16. Posted

    Velocity of either depends on the medium. However, in air at sea level:

     

    Sound: 343 m/s

    Light: 2.99*10^8 m/s

     

    In water:

     

    Light: 2.25*10^8 m/s

     

    In NE-213 liquid scintillator (Xylene or tetrachloro-something or other):

    1.998*10^8 m/s

     

    A nice problem to do:

    Determine the speed of light in a tube of water moving at 0.5c relative to a stationary observer.

  17. Posted

    ...do you think a computer can learn, on it's own? I mean, uh, help me out here someone. Hmmm, perhaps I not saying this correctly.  By a sereis of random programs it may eventually do something, not bad , but unexpected? Cross-referencing and........Understand? :clap:

    By the way, this is an impressive use of intuition, Jeanway. This is sort of thinking has been known to spawn great ideas.

  23. Posted

    Right now, I'm thinking that I'm really speechless and flattered that anyone wants to know what I think. However, since you asked, here are some statements that have gone through my mind in the past 24 hours:

     

    "The relaxing aspect of the game lies in the fact that it's sequential."

     

    "My gosh! He's young!"

     

    "By what process were the molecules formed?"

     

    "Incredible that they all exhibit a 99.9% purity in chirality! How did that happen? The process reminds me of that which caused baryonic asymmetry in the universe. But what process?"

     

    "I really need to clean my office."

     

    "Indecision is a decision."

     

    and finally and most importantly:

     

    "It is a special type of mind that seeks to know the thoughts of others. A truly inquisitive and thoughtful mind. One that sees beyond oneself to the multitude of living universes inside the heads of others. Science at its purest."

     

    Who else has a thought?

     

    (I hope I haven't disappointed, Jeanway, but you really caught me off gaurd on this one! Good job!)

  24. Posted

    Here's an interesting notation. Let's assume that we want to use nuclear "bombs" to

    propel a small craft, say the size of the space shuttle (100 metric tonnes empty). Getting it to the 10% of the speed of light would require about 11000 Megatons of

    energy from the reaction. That assumes that ALL of the momentum goes to forward propulsion, which it probably would not (in fact, in the case of currently speculated

    Orion designs, I would expect no more than 70% efficiency, more like 50% or less).

    Currently, the planet earth has about 18000 Megatons of nuclear warhead capacity.