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Posts posted by Sisyphus

  1. As I understand it, the speed of light can be infinitely approached but doing so requires enormous amounts of energy-input for relatively little speed-gains. So, to give a clear but surely inaccurate example, accelerating from 0.85C to 0.95C may require less energy than acceleration from 0.95C to 0.98C (apologies if this isn't accurate examples, but you get my point).


    Yes. So for example an object at 0.99C has about 40 times the kinetic energy as an object at 0.5C.


    So my question is when something is accelerating at relativistic speed with decreasing speed-gain, doesn't the energy still have to be conserved?




    So does that energy get released as the particle or object decelerates a relatively small amount from near-C speed?


    What energy? It takes the same amount of energy to "decelerate" something from 0.98C to 0.95C as it does to accelerate it from 0.95C to 0.98C. There is no extra.


    If so, is or could this be related to the changing energy-levels of electrons as they absorb and emit photons, since relatively large amounts of energy could be stored as relatively small increments of speed-change, which could be so small that they become quantized? I admit this is a grand conclusion to stretch from my initial question, and if necessary I am happy to repost in speculations - though I am still interested in the application of established knowledge to this question of energy-storage in relativistic speed-increases.


    I don't really know what this means, so I'll just say to keep in mind that kinetic energy is relative. The object might be going at 0.98C in our rest frame, but there is also a reference frame in which its velocity is zero. There is no event that can occur at 0.98C that wouldn't happen for an object at rest, because it is also at rest.

  2. Is there any logical relationship between a static magnetic field and one that occurs because an electrical field is moving?


    All magnetic fields are ones that occur because an electrical field is moving. If you're thinking of something like a bar magnet, then the motion is the spin of the electrons contained therein, all aligned in the same direction.

  3. It's not different from meters. In fact, that's the example I used. Graphs of y=2x, y=x^2, or y=x^37 are all showing a relationship between two variables, the horizontal and vertical dimensions. There's no reason they can't be in units of meters. "The vertical height is proportional to the 37th power of the horizontal distance." No 37-dimensional object need be involved.


    Now, if you were going to graph y=x+z, you would need three dimensions.

  4. Interesting comment.

    The curve is one dimensional.

    The graph is 2 dimensional.

    And if you put units on X (say meters), then Y are square meters: 2 dimensional. I guess the growing graph of increasing surfaces can be represented 3D (a pyramid).


    Oh, I'm sure it can be represented by objects of any number of dimensions, but the point is all you need is two. You also only need two to represent y=x^3, or y=x^1000, since they're all just representing the relationship between 2 variables. Acceleration is not adding a dimension, it is just a non-linear relationship between two dimensions.

  5. Take a cube, slide it, or rotate it, and you get the 4th dimension through motion.


    If you take the cube and let it fall down, you are in fact using twice the time dimension because a free falling body is accelerating (m/s^2). It could be considered as a 4 dimensional event taking place in time: in other words maybe a 5 dimensional event.


    No more than the curve graphed by y = x^2 is three dimensional. Which is to say, it isn't.

  6. To me, the one who keeps the rod in his hands knows better than the others.


    I don't know how to respond to that. It's not true. What difference does holding in the hand make?


    Or, ok, how about this. I'm holding two identical boxes in my hand, containing the same number of hydrogen atoms. However, the hydrogen atoms in box A are moving around faster than in box B. Box A will be heavier. Relativity, right in the palm of your hand!


    Does that mean that space contraction & time dilation do not actually happen?


    It actually exists. "Happen" implies that something is changing, so no. Though certainly you can have changes if you involve acceleration between frames, as with the twin paradox, etc.

  7. Woops, you are sliding from a subject to another. If we cannot even agree on what distance is, it is useless to jump into further considerations.


    Unfortunately it's difficult to consider one aspect without the other. Kinetic energy, like distance, time, and relativistic mass, depends on frame of reference. Relative to someone sitting inside it, the plane has no kinetic energy. Relative to the ground, it has a lot. Relative to Mars, it has a lot more than that.



    I don't expect you to argue that the small dots left & right are actually dancing like that just because an observer happened to travel accelerating rapidly?



    Of course nothing is changing. But no perspective is more real than another. That's the point.


    There is one reality, but one reference frame is only a slice of that reality. The image is cycling through a range of slices.

  8. I have read several times from other forum members that length contraction "actually happens".


    Yes, the object actually is 10cm in one frame and actually is 20cm in another.


    I agree that it is all a question of measurements. But usually when I say that someone comes and hit my fingers.


    Perhaps you're not clear or consistent about what "a question of measurements" is supposed to mean.


    Discussion was about space & time.

    You talk about mass.




    (emphasis mine)


    Are you talking about rest mass?


    Because IMHO rest mass corresponds exactly to the "answer is right in some absolute sense".


    I'm talking about relativistic mass.

  9. I agree with this description.

    This description corresponds to perspective, or optical deformation: the book intrisically does not change because someone somewhere is observing it. What is changing is the point of vue of the observer and his measurements of the phenomena "book".

    I suppose that some other people here will disagree, saying that following Relativity, the book "really" contracts.


    What happen with Relativity is that it is not an optical deformation (only), it is also a duration deformation, and a gravitational deformation. As a sum, it is a deformation of all measurements and as such, physicists may consider it is a physical deformation. But IMHO the book does not change and the rod does not contract.


    But no one is saying it is a physical deformation, just that no measurement is more "real" than the other, which is to say that they are both real. It is 20cm long, and it is 10cm long, and it does not change.


    That's not a contradiction.


    I think a good way to think of it is to keep in mind that objects simply do not have single, absolute properties like length, but rather length in a given reference frame. For some reason people find this a lot easier to grasp for some properties than others. What is your velocity? Not an answerable question unless you specify a reference frame. What is your length and mass? Also not answerable, for the same reason.


    I suppose it's just a matter of direct experience. People can handle measuring a car's speed relative to a road while knowing the road is on a spinning planet orbiting a star, or measuring walking speed inside an airplane they know is moving far faster than that with relative to the ground. But we have no direct experience with speeds and masses large enough for relativity to matter, and so "what is your mass relative to X" still sounds strange to most people, who insist that one answer is right in some absolute sense while others are just illusion.

  10. They do often use NaCl on the roads, so it will certainly work. The other salt they use is CaCl2, which works faster and at lower temperatures and is less environmentally damaging, but is also somewhat more expensive and can be slippery itself.


    I wouldn't use salt to melt a big pile of snow, though, just because you would need a lot. Better to shovel, then use salt, so the last bits melt and traction improves. There's a reason they plow the roads and then salt them.

  11. If you really want to read the research paper and actual lab experiments performed to qualify this simple explanation then ask the author:




    The author posted a comment on this topic and offered a simple explanation as to why it does reverse. The idea is easy to grasp, as opposes to no explanation of causation. If anyone can find a more precise explanation then offer one.


    Perhaps the irregular intervals of reversal are due to our position in space relative to other planets, galactic core, or the so called binary companion (second sun).


    That is not a research paper. And almost all of the basic facts are wrong. For example, we are nowhere near the galactic equator.

  12. The galaxy's mass is mostly in a fairly flat disk shape for the same reason the orbits of all the planets of the solar system are close to being in the same plane. It's a spinning, gravitationally bound cluster of matter, and that is the plane of its total angular momentum. The spiral arms are not fixed structures, but waves of high density, like traffic jams on a highway.

  13. Sisyphus: There is a group of scientific outsiders who claim that the 25-hour diurnal cycle experimentally revealed for humans in contrast to all other beings suggests that we really come from Mars, not the Earth, as other species do.


    So in other words, it is not even true, as I suspected. The 25 hour thing for humans was based on flawed and now discredited research, and humans are not at all unique in not keeping perfect 24 hour time themselves:



  14. Here is another factoid regarding this idea- The transit time from the north to the south pole, or the opposite, is slightly less than 42 minutes. Another question- In this transition, what is the region of maximum and minimum acceleration? SM


    Just like with a spring, there would be highest acceleration (but zero velocity) at either end, and it would be 9.8m/s^2. The lowest acceleration (but highest velocity) would be passing the center of mass, at which point the acceleration would be zero.

  15. I use Firefox too and like it, though the only others I have experience with are IE and Safari.


    So what add-ons do you other Firefox users have? I'm using:


    Adblock Plus: No ads!

    Download Statusbar: puts download manager on the status bar instead of a separate window

    Downloadhelper: download and/or convert embedded flash or videos

    NoScript: Blocks all javascript/java/flash until you give permission, allows whitelist and blacklist for familiar sites

    Screengrab: Button to save all or part of web page as an image

    Smoothwheel: Smooths out scrolling for ease of reading and allows customization

  16. Experiments with human subjects kept for extended periods of time at the bottom of a mineshaft with no natural light sources and no clocks, and thus no ability to receive cues from the environment as to what time it is, have shown that they all quickly adjust to a 25-hour wake-sleep cycle. This finding has been cited to explain why humans need alarm clocks to wake up at the same time every day, while other animals seem to maintain a 24-hour cycle naturally. So how can this latest discovery be reconciled with those previous results suggesting a natural 25-hour diurnal cycle for humans?


    It doesn't seem credible that humans would naturally have a 25 hour cycle while all other animals would naturally have a 24 hour cycle. Do other animals, when kept for extended periods of time at the bottom of mineshafts, maintain 24 hour cycles? How consistent is the 25 hour cycle for humans? Is it merely an average in a wide range?


    Do all other animals, in fact, keep rigid schedules by clock's time, or do they, for example, go by sunrise and sunset?


    Furthermore, just anecdotally, I get up at the same time every day, without an alarm clock. (I have one, but I haven't failed to wake up shortly before it goes off in probably years.)

  17. lemur, it seems like you are insisting on a "qualitative model" to be some robust analogy to a classical physics situation. Why?


    I'll tell you why not: because it doesn't work. It is impossible to model an atom with classical physics. That's why there is quantum physics.


    So what's the appeal of it? "To understand what it actually is," sure. But what does that mean? Would picturing it as little balls orbiting around a center make it more understood? No. It would just make it more familiar, which is not the same thing. And it would make it so you could have a mental image of it, which is not the same as understanding it, either.


    The fact is that quantum behavior, which is outside our ordinary experience, is what is real. And ordinary experience, with things like orbits and solid objects that have particular locations at all times, are the illusion. Or rather, they are emergent phenomena, but simply not how the world works on a fundamental level. Put together enough little wavicles, and you start to get something that looks like a coffee mug (for example). Just like if you put together enough ones and zeroes, you start to get something that looks like Firefox (for example). And what you're essentially saying is that for any of those ones or zeroes, there simply must be some way to model it as a web browser, or else we don't really understand what a one or a zero is.


    Does my tortured analogy make sense?

  18. So, one might reason that the light wave itself does not change. In the instant of time where the the space ship and the planet are the same distance from the galaxie, they both experience different results. Therefore: Distance or space is also irrelevant.


    Not exactly. The light wave itself is red in one frame of reference, and blue in the other. It is in fact a property of the light itself.


    Also, note that the distance is not the same in both reference frames. When the ship is next to the planet, observers on the planet and on the ship will disagree as to how far away the galaxy is. And they would both be correct.


    Therefore one might reason that:

    All three bodies must be experiencing seperate moments of present time, defined by the momentum of their own past, that is reflecting a future as color according to the distance direction to be achieved in the next instant of present time.

    In other words, the color of the light observed is a matter of the interactions of the seperate time dialation waves of the three seperate bodies involved.


    Or ?


    I don't understand any of the above. It seems like word salad.

  19. Total energy difference 5oCwater 1g minus 4oCwater 1g is 1cal from cal definition.


    Actually, no, it isn't. It is approximately 1 calorie. The energy needed to raise the temperature of water is not entirely constant.


    But, is statistical mechanical total energy difference 5oCwater 1g minus 4oCwater 1g is 4.184J?

    Work energy 4.184J ---------> 1cal yes

    Heat energy 1cal -------------> 4.184J ??


    Joules and calories are not measures of "work energy" and "heat energy." They are measures of energy. The same thing.

  20. My apologies for my poor choice of wording. I am enjoying all the responses, and am trying to respond to them all thoughtfully. Please clarify what you mean by "So expressing it like "A & B exchanging info at 1.7 c" could be interpreted as slightly misleading".


    It is misleading because nowhere is information traveling at greater than C, relative to any observer.


    It seems to me that the collision is an event that all parties can set their watches by


    Nevertheless, it is impossible to "set their watches" between reference frames, and have them agree on the time that other events occur.


    - I understand that EO's knowledge of the event will be delayed by the time it takes the light to reach him.


    That doesn't really matter. The lack of simultaneity is not the result of just travel time for the information. That can be compensated for.

  21. Back in my original post, one of the questions I posed was - would A & B somehow merrily continue to exist in their own spacetime continuum, or reference frame, even AFTER EO sees them collide? I was hoping for a simple "yes" or "no", not "it depends".


    If they collide in one reference frame, they will collide in all reference frames. It's the "at the same instant" that is the problem, because there is no such thing.

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