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Posts posted by md65536

  1. I heard a story on coast to Coast about a guy who was driving a car down the road and someone pulled out in front of him. he was doing 90 and had no way of swerving to avoid the other car. the next thing he knew he was on the other side of the car. He looked in his rear view mirror and the guy in the other car was still sitting there looking in the direction in which the first guy came. I know that it is possible for a large macroscopic object to tunnel through a barrier but you would have to wait longer than the lifetime of the universe for such a tunneling to occur.

    If there was no chance of it happening then it didn't happen. The chance of something like a grain of sand "tunneling" through a piece of paper is a macroscopic event that is unlikely to occur in the lifetime of the universe (just a guess; can anyone confirm?). A car passing through another would be ridiculously less possible.


    A more probable situation is something like this: There was a way of swerving to avoid the car. Possibly the subconscious mind was able to react, and through a combination of quick reaction and luck, the driver was able to squeeze by. Meanwhile his conscious mind may have been in shock or otherwise unable to register or recall what happened in that short amount of time. So it only seemed that it happened too quick to be possible, according to the conscious mind.


    The story relies on human perception. It is astronomically more probable that that wasn't so accurate, than it is for a car to tunnel through another. It would also be more probable for the driver's brain to instantly completely spontaneously combust, than for a car to tunnel through another. It would also be less improbable for the driver's memories to be instantly randomly replaced by false memories of an entire alternate life, and to wonder why he'd suddenly teleported into a moving car.



    Is it possible that this occurred somehow. Other callers also called in and related stories of driving through other cars in an accident and appearing on the other side. Is anything like this possible or were they all lying? The only way I can see it happening is if the car tunneled or If what I suspect is right and we are in a simulation, they or something simply rewrote physics for that specific event. Also i was registered here and then i was not registered? did they do something to the accounts. because I posted this before and they moved it to pseudo. but then my account got deleted and I don't know what happened.

    It sounds like it was a glitch in the matrix.

  2. Yes, the speed of light is constant.


    A wormhole doesn't change the speed of light, but changes the distance between 2 points, providing a shortcut.

    It's kind of a cheat. If you measure the distance between the two points with ordinary space, but allow light to travel between the two along a different distance, then light can travel at c but for a much shorter distance. To calculate a faster than light speed, you'd use the longer distance, which is a cheat because light didn't actually travel that path.




    Personally I doubt that's possible. Defining distance with "ordinary space" seems to be consistent. Any cheats and corresponding violation of causality would probably involve inconsistencies, and the universe appears to be consistent as a rule.

  3. Your definition is good. Time as a length can be described as the length of an interval between two time frames in the same location. An extended definition might be:


    Time is a relative measurement of an interval of change that has occurred between two time frames, as calculated, or compared with the changes that have occurred within an elapsed-time measurement device and standard (such as a second, day, year, etc.).



    An oscillation is cyclic, which means that it will return to the same state again. The timing of one cycle of a clock is well-defined but doesn't require a net change. I suppose time can't be defined without some "difference" between two points in time (whether it involves a continuous change or whether it involves a static measure such as the spatial difference between 2 points). Since the difference between two reference points in time can result in no change, I don't think that "change" is quite the essence of time, at least not on a small scale...




    But then again, since an oscillation repeats, you'd need to distinguish between similar phases, such as by counting the cycles. On a larger scale or with more complexity, time may be a measurement involving change... though "entropy" seems a more appropriate word.


    The important thing I think is that it's not a measure of the amount of change itself, but rather a measure based on the regularity with which a reference (a clock or a timing process) oscillates.



  4. So perhaps the first hundred thousand years were not wasted sitting on our fat asses watching cave tv, but instead involved developing the prerequisite knowledge for graduating from "hunter gatherer". Developing language or communication skills, ability to use tools, building an understanding of plants, etc.

    Actually I must retract this proposition. I don't think that the development of knowledge could be passed down for say 5000 generations, and grow in a steady, stable way. It must have developed in a sort of punctuated equilibrium, with a lot of dead ends and lost knowledge. I still don't think there needs to be some effect that prevented the development of some specific technology in a timely way (for example, is there some force holding us back from developing the things that we've never imagined yet? Will future generations wonder why we didn't just do it?). But climate change definitely sounds like it would have a disruptive effect on development and hold back agriculture.

  5. Time is the phase of an oscillation. That's more of a functional definition; if you want to discuss the "essence" of time, that's metaphysics.

    Time exists like heat exists, being an emergent property of motion. It's a cumulative measure of motion used in the relative measure of motion compared to the motion of light, and the only motion is through space. So time has no length, time doesn't flow, and we don't travel through it.

    An oscillation is a "regular fluctuation".

    There is an inherent metric relating the different phases, or relating repetitions of the same phase (because of the regularity).

    So time definitively has a length.


    The phase of an oscillation is not absolutely meaningful; it only has meaning relative to other phases in the oscillation (otherwise it'd be just a state, not really a phase?).

    So I'd say that time's length essentially defines time. Time is a measure of length between events -- but since I don't know how to separate the spatial aspects of length from the temporal ones, I couldn't give a proper definition.


    But anyway, I think we could give several definitions of time that could be equivalent. Some of them conceptually simpler than others. Time defined as a length would require some oscillation to define the metric (such as light waves or caesium quantum transitions), so I guess it would not be functionally simpler.



    Edit: Upon further thought: Perhaps "time is the length between events occurring at the same spatial location". Remote events can be described in terms of information being received from that event, and the reception of that information can be considered a separate event. I defer to the experts however.



    "This result has let me to doubt how fundamental the four-dimensional requirement in physics is". In other words Dirac was doubting that most wonderful creation of twentieth-century physics: the fusion of space and time into space-time."(6)

    I disagree with the quoted interpretation of the quoted quote. Assuming that Dirac means that space and time are not intertwingled means that Sorli is assuming that 3 spatial dimensions are a requirement in physics. Another interpretation is that neither time nor distance are fundamental (they could both be emergent, as some conjecture), however they are still pretty mixed up together as relativity has proven.

  6. There is something about human societal development that I've always wondered about. H Sapiens evolved some 120,000 years ago (give or take). They are us, same brains, same intellect.


    So how come they sat on their fat, hairy arses for 114,000 years before developing societies above "Hunter gatherer"? Why was all the development in the last 6,000 years?

    Perhaps knowledge is the key factor?

    If you were raised by wolves and had no contact with humans, do you think you'd be planting and harvesting crops due to some instinctual knowledge? I don't.


    Another aspect is our accelerated rate of development. As we develop we get better at figuring things out and at passing on knowledge of what we've figured out.


    So perhaps the first hundred thousand years were not wasted sitting on our fat asses watching cave tv, but instead involved developing the prerequisite knowledge for graduating from "hunter gatherer". Developing language or communication skills, ability to use tools, building an understanding of plants, etc.


    Certainly climate has an impact on development. As we've developed, we've also gotten better* at reducing the disruptive effects of climate (through the use of fire, shelter, etc) on our ability to survive and develop further.



    * That is, until the modern era, I suppose...




    Anyway, I think your hypothesis sounds reasonable and intriguing. However I don't agree that a relatively short period of relatively rapid development implies that similar development "should" happen in another period requiring only similar environmental conditions.

  7. How can be time defined in the simplest way? According to my theory, time can be defined as 'change' in any form, any place in the universe. Any type of change in the real universe is called time. It can be changing of state, shape, size, color, temperature, force applied or the place etc.


    So we can say that if there no change in the universe, there is no time in the universe. Because time is the 4th dimension, so if time is not there, the whole universe becomes 3 dimensional. Then the universe will stay like a paused video if there is no time. Can you prove it is not?

    Any transfer of information across distance requires time (with a lower limited determined by c).

    The acceptance or use of any received information could probably be described by definition as a "change". For example, without time, light cannot propagate... nothing in the universe can be observed or interacted with.


    "What is the existence of something besides whatever information can be received from it (ie. what effect it has on others)?" is a question I don't think I could answer, which for me means that I wouldn't know what a "paused video game" universe would be (if anything at all!). Also, the lack of a tenable concept of a "universal instant" further complicates the idea of a universal paused state. What observer's instant would it be that everything is paused in? Would the state necessarily be different for different observer locations? This is not classical physics however.



    I think if you remove "change", a lot of other things become undefined. Also, I think it's possible to remove time without removing "change" simply by allowing causal relations without distance (like if you removed time and distance at the same time).


    I don't think my answer can be considered "accepted science", sorry.

  8. the same numbers that we measure time with. this being seid one second has been an infinite amount of time.

    However, information has a speed limit: c, which couples time and distance. If you want to have an arbitrarily long causally related sequence of events occur in an arbitrarily short period of time, it will have to occur in a correspondingly small enough space. There's only "an infinite amount of time" (or more precisely "an infinite rate of events" -- the reciprocal of time) in an infinitesimal space. c makes a rate of time finite for any non-zero distance.

  9. Mathematics alone, and math was my major in college, gives you little or no insight into what is happening. What would be the logical basis for SR, GR, or QM if there was an aether made up of dark matter, for instance.

    I believe that the ultimate understanding of something in physics comes from an understanding of the math.



    For example, you might say "The power density of a sound wave decreases as it expands" and that might give you a grade-school understanding of it, with very limited usefulness.


    Or you could say "The power density of a sound wave is proportional to 1/r^2" and that gives you a precise and useful mathematical understanding of it, but you might not know why it is so.


    Or you could say "The power of a sound wave propagating as a spherical shell remains the same as the sphere expands, and is spread evenly across the surface area of the sphere," but you might not know that surface area is proportional to r^2.


    The last two statements say the same thing, and they are both mathematical (area is a geometrical concept which is mathematical).

    Using just numbers and equations might work well but leave you unenlightened; using just words may give you knowledge without being able to apply it. Having the math and understanding why it works is in my opinion the essence of true understanding.



    That said, it must be noted that physics can progress just fine without knowing why the equations correspond to reality. Observations still give you useful data, and those data can be used to evaluate the equations and suggest new ones. I do believe that knowing "why" (and having logical explanations to go along with the math) does provide extra insights that suggest new ideas which lead to new experiments, observations, and theories. Logical explanations are a bonus; the math is required.

  10. Again what one model might perceive as evidence in favor of the model, another's interpretation and argument might be that the same observation provides evidence against the model.//

    Either the observation fits the model or it doesn't.

    I thought different interpretations of the same thing share the same predicted observations. Where the observations differ, the models differ (not just the interpretations).

    Can you give an example of what you mean?





  11. Straw man.

    It was parody, not a logical argument. If my post is treated seriously, the implication that my argument is equivalent to owl's is certainly a straw man. To brush it off as just a straw man is a good way to avoid thinking critically about one's own arguments.


    Perhaps it could be considered an extreme example of similar reasoning that owl is using, but that in itself does not prove that owl's flawed reasoning is flawed. It adds no weight to the argument but provides an opportunity for thinking about it in a different way.



  12. My understanding is that the equivalence principle strongly suggests that we live on a Lorentzian manifold.


    Section 4 of Carroll's Lecture Notes on General Relativity (arXiv:gr-qc/9712019v1) gives arguments as to why the equivalence principle implies curvature.



    That looks like an excellent resource, thanks.

    After a quick glance at the section it looks like his explanation works with simpler requirements (his works with slow-moving objects but mine requires high-speed oscillation of all masses).

    I'll have to spend some time trying to figure out the lecture notes.

  13. In various topics on this forum, I get the idea that it is still a mystery how or "why" spacetime curvature causes gravitational acceleration.

    Am I mistaken? Did Einstein and others who understand GR also understand that gravity immediately follows from spacetime curvature?

    It seems intuitive to me that it does (thus "why"), however the details are not at all intuitive, and I wouldn't even begin to know where to begin with the math.


    My basic "understanding" of how spatial curvature causes gravitation is as follows:

    1. Movement through curved space means that the distances between remote points changes as you move through space. I think this is because distances in curved space are defined in terms of local flat spatial curvature. For example, if you go to google maps, you get a flat representation of the curved Earth; if you scroll the page north or south, the map scale ruler will change in size, meaning that the relationship between pixels and meters changes. In real life, the scale ruler would stay the same size while the "map" (ie. your measurements of the universe) changed and scaled or warped.

    2. Uniform oscillatory motion of particles in a curved mapping of the curvature of space will tend to be non-uniform in a flatter mapping of the same space.

    3. Repeatedly moving according to one mapping of spatial curvature (eg flat), and then changing the mapping to fit the different curvature of the new location in curved space, will tend to accelerate you towards greater spatial curvature or whatever.



    As an analogy of this, consider a typical world map (Mercator projection). Uniform distances on these maps do not map to uniform distances on the Earth. A very small area around the poles is expanded to take up the entire width of the map.


    Imagine someone doing a random walk on the flat map, and then following that path on a globe. They could do this by picking a random direction to move, and moving by a fixed (or random) distance on the map. Clearly they would tend toward the poles more than toward any other specific point on the globe, because the poles take up so much more room on the map.


    An observer on the globe who is unaware of the map but saw the walker tending towards a pole might think that some force is drawing them there, but there is no force... just a uniform movement in one mapping that corresponds to non-uniform movement in another.


    Obviously this isn't exactly how gravity works because it's still a random walk, and the person will still wander away from the pole, and gravity is not evidently random. This map example ignores point 3, which would involve something like the walker creating a new and different map at each step, or perhaps changing step size with each step; so acceleration isn't demonstrated. The details of what such new maps (or step size) would look like is a complication that eludes me. They would certainly not be Mercator projections.




    Does this make sense?

    Is this a good analogy for how gravity works? Are there already similar analogies (and better)?

  14. How about the one in which earth is severely oblate? Or are you in the reality where it is nearly spherical. You still can't have it both ways if there is "one reality" and earth does not morph with each different frame of reference.

    I'm in the reality where North America is up, and Australia is down. I've heard there's another reality where Australia is "up" to some people in the southern hemisphere. If that were so, then North America would have to be down, to them. Since my "up" can't be "up" and "down" at the same time, and I haven't seen any evidence of up and down morphing (for example, if I woke up to find I'd magically floated to the ceiling during the night), this is obviously false. You can't have it both ways. Up is either up or down, not both. Some observer being somewhere else doesn't change which direction I fall.


    So I must conclude that Australia doesn't exist. I think this is compatible with your baseless objections to the modern concept of time. As long as we're rolling back science a few hundred years, why can't we roll back maps of the Earth too?

  15. Well no one seems to want to answer but I'm interested in whether my reasoning is right, so...



    In this example, the nebula would have greater pull.


    The area that an object with a given length and width takes up in the sky is proportional to r^2.

    Gravity is proportional to 1/r^2.

    This means that 2 objects of identical depth and density that look the same size from Earth, will have the same gravitational pull on us.


    This example nebula is on the order of lightyears in depth, while the moon is a fraction of a lightsecond in depth. The example nebula would have some millions or trillions of times the gravitational attraction as the moon, even though it is so much further away. Its mass is proportional to the cube of its dimensions, so it would have astronomically more mass.



    In reality however the moon has much stronger pull, because a nebula is so much less dense. While the nebula has millions or trillions of times the depth, it is so astronomically less dense that its density plays a much more important role than its size, and it would have probably negligible gravitational pull on us. While nebulae may be on the order of light years in diameter, they only have a mass of perhaps a few solar masses. A nebula formed from a supernova would have about as much pull on us as the star that it formed from.



  16. So in other words, you wouldn't measure anything greater than C because physics teach you an equation that considers that the speed of light is the limit and that's the only equation you use for velocity? I'm not saying objects actually "are" moving past the speed of light, I'm saying "appear" to be, and in that, I don't see why I need to imagine an observer in the middle when I can just observe the object moving away from me.

    No, the equations are based on mathematical and logical consequences of observations of the speed of light. Physicists determine the equations based on what is observed, not the other way around.


    Nothing will ever appear to be moving at greater than c, relative to any observer. If you can imagine objects moving relative to you at near c, then you'll also have to imagine length contraction and time dilation. If you do this (guided by the equations to figure out precisely what will happen), you'll see that time will dilate and space will contract and make it impossible for anything to actually move or appear to move faster than c relative to you.


    If you follow derivations of the Lorentz transformations you'll probably come to understand why--or at least that--this must be so.



  17. From an inertial frame you cannot measure anything to be travelling at greater than c, or two things separating faster than 2c.

    Out of curiosity, is it possible to define some type of abstract curved space where two things can separate faster than 2c?

    It would require that while each thing travels away from you at < c, the distance between the 2 increases at a greater rate than the sum of the change in distance relative to you.

    If possible, would it require that the 2 things are not traveling on the same geodesic which intersects you?


    Or would it simply require inhomogeneous spacetime curvature?


    OR is it true that the distance between any 2 points A and C is <= the distance from A to B + distance from B to C, for all possible points B? Is this true for any metric space? Or for any conceivable spacetime curvature?




    What's the thing I'm talking about called on that website?

    Probably "separation velocity" but after a quick glance at the website I didn't see anything specific. I think you may be giving a specific example of a situation that is handled by more general SR math that can be used to figure out that example as well as many more examples.


    To see what I mean, try flipping the problem over, and instead of imagining an inertial observer in between 2 relatively separating objects, imagine it instead from the perspective of one of the separating objects. For example, if one object C is moving away from another A at 0.9 c, and then you imagine a third object B in the middle that's moving away at half the speed -- from A's perspective nothing is moving relative to anything else at > c -- and then calculate the velocities relative to the middle object B you should find that A and C are each moving away from each other with a separation velocity greater than c...



  18. SR is GR in flat Minkowski spacetime. There, coordinate time and proper time are the same thing. This is because the spacetime manifold and its tangent space at any point are isometric.

    I don't think we're talking about the same thing here. Coordinate time and proper time of events are the same thing in SR only according to clocks that are at the same location of the events (or relatively at rest and synchronized to the observer's clocks) [second paragraph of http://en.wikipedia....Coordinate_time].


    When we speak of time dilation, we're speaking of one clock ticking at a different rate relative to another clock.


    The former refers to coordinate time (is this incorrect?), the latter to proper time.



    If I'm using the term coordinate time incorrectly, then what term should be used instead to describe the time according to a remote moving clock that ticks slower relative to "wristwatch time"?





    Edit: I think I see my mistake...s...

    - Coordinate time and proper time don't inherently refer to different clocks. In SR, the coordinate time and proper time of a given clock and observer are the same.

    - Each clock will have its own proper time.

    - The time of a remote moving clock is just the "time of that clock according to the observer"... it doesn't have a special name.

  19. Clocks measure the proper time of their world line. That is all that any clock measures.


    Coordinate time is a fiction. It is time as modeled in some choice of a coordinate patch, and would correspond to the time registered by a real clock only in the case of flat spacetime. It is an approximation that is reasonably accurate in approximately flat circumstances; i.e. away from large gravitational fields over moderate distances. Only coordinate time makes sense as a comparison of separated clocks. Special relativity, being a theory that excludes gravity, deals with a situation in which coordinate time and proper time coincide, but in the real world the time of special relativity is coordinate time -- SR is the local approximation to GR.

    Isn't the proper time of one observer a coordinate time of another observer?


    I don't understand how curved spacetime prohibits correspondence to a real clock.

    Any observations of a distant clock (or signals from one) would arrive via a geodesic, which would define a distance to the clock, and thus a specific time delay of the observation, regardless of curvature. So it seems that the observer could calculate the time registered by the real clock -- and wouldn't this correspond to the coordinate time?


    EXCEPT... the time delay would be measured in proper time. With SR you could just divide by gamma to find the delay in terms of coordinate time? Is there no similar thing in GR?



  20. Co-ordinate time is what someone who stays on Earth would measure for the time interval between your leaving Earth (event 1) and arriving on Mars (event 2). This observer is not present at both events (only at event 1). Co-ordinate time is not absolute. It is affected by relative uniform motion.

    The observer on Earth would use my clock (which travels to Mars) to measure coordinate time, correct?


    If they use their own clock, is that wristwatch time? It couldn't count as proper time. Or would it be coordinate time also? I was calling this "local time" but that seems a misleading phrase for measuring the time of remote events (using a local wristwatch).


    We could say that to an Earthbound observer, the time between my leaving and the observation on Earth of my arrival on Mars, can be measured in proper time.




  21. Is proper time equivalent to "local time in the frame of reference of an observer, for events that happen at the location of the observer"?


    And local time (is there a better term?) is a bit more general, because it can also be used to describe the timing of remote events?


    And is coordinate time then basically time according to any clock that is remote from the observer?



    Is it correct to use these phrases when speaking of relativistic scenarios? Eg. a traveling observer's ideal clock measures proper time and always ticks at a constant rate. For other observers the same clock measures coordinate time, which ticks at a variable rate in general.


    Are there other related or better terms for describing time according to various observers and clocks?

  22. Ok, cool your jets here... logic always yields to evidence, and assimilates it. Once a premise is shown to be false in a valid argument requiring that premise, logic removes that argument's soundness (its power of truth). I believe your assertion may be better served by the term 'intuition'... I understand you're using a connotative meaning of the word logic, but the nature of the concept begs to be used solely in a denotative fashion. I'd restate that as, "If the evidence contradicts an argument, a new argument must be formed."

    True, I was sloppy with semantics.

    To be precise I should have said that logical validity doesn't imply logical soundness.

    If correct evidence contradicts a logically valid argument, the premises are incorrect. The logic is still valid but it's useless. The examples in this thread suggest building logical arguments out of flimsy premises, as if the logic will solidify them. (Or more likely, the examples in this thread are also confusing 'logical' with 'intuitive'.)



    It is not just "formal verbal logic" or "common logic" that is important to science, but logical soundness, as you've pointed out. I don't know of any examples in science of where logical soundness is shunned, so I must disagree with the OP.

  23. Words words words hitting the same stone again: IMHO the Speed Of Light is constant, not absolute, if anyone here understands the difference. Showing maybe the importance of putting the right words after a commonly accepted mathematical concept.

    Can you explain which meaning of 'absolute' you're using, and if that doesn't make it obvious, describe how SoL is not absolute?




    So, even in the case of the sum of energy of the universe being zero, why do we have to suppose that in distant past the Universe was in a zero state?

    We don't have to suppose it, but we did.

    It's not about what we want to believe but what the evidence suggests.

    So far the evidence doesn't contradict it; it is within the range of what is possible.

    It's still an open question so of course the evidence isn't conclusive, however the evidence does rule out some other possible early universe scenarios that many people might find much more logical (young earth hypothesis, for an extreme example). If the evidence contradicts the logical, the logical is incorrect.




  24. there was alge placed in a lake at 12am the alge doubles every second the lake was full at 12:00pm. when was the lake half full?

    If it doubled for 12*3600 seconds there would be 2^43200 algae, which is quite a bit more than the number of atoms in the universe.

    I'd say that though the lake was full at 12pm, it was probably also full a lot earlier than that.

    I'd say it was half full within the first minute (~10^18 "alge").



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