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Posts posted by J.C.MacSwell

  1. This seems like a good question' date=' and it deserves thought. I will think about it.


    However, if the universe has been here forever, then it has been passing through time forever. As it passes through time, it by necessity reaches points in time. [b']The fact that you and I are discussing this question is evidence that now is one of those points[/b].


    I am not sufficiently knowledgeable in the study of infinity to describe an answer to the question as you posed it. Perhaps someone else on the forum can lend a hand.


    This could be evidence of time with a starting point also.

  2. Very nice question. I think that this deserves some thought.


    Let me take an initial stab at a response:


    Even along a continuum that extends forever' date=' there are distinct points. Not all points on the continuum will be reached, or it would not be infinite. However, some of them must. We are now at some of those.[/quote']


    This is a good start, but if we now consider only the set from minus infinite up 'til now then the explanation (I think) breaks down. How did you ever get to the "last one" of that set?


    When Einstein was told by Hubble that the universe is expanding' date=' he introduced a cosmological constant into his equations for General Relativity. This term acts to counteract the gravitational pull of matter, and so it has been described as an anti-gravity effect.




    I think he introduced it earlier, then realized (or thought) he'd made a mistake after receiving Hubble's data.

  4. Please rephrase the question. I don't really understand what you are asking.


    If I asked you to pile an infinite amount of bricks prior to piling your favourite brick you named "now" how would you ever get to it, even given an infinite amount of time?

  5. Since you are asking me, then I will give you my answer. The answer is, as I have said, that there is no origination, as time is infinite in both directions.e.


    OK, so how could we possibly get to this point in time? I'm not saying I disagree, just curious as to how you view it.

  6. No. I am claiming that it is likely that space has a center, and that the center is at the site of the big bang, which will be the site of the big crunch.


    Well that would be right where I'm sitting then. It went for a drive this morning but now it's back. It's the only preferred reference point I'm aware of.

  7. OK. However, when I consider your example, I am free to recognize that what you call a 2d surface is actually a 3d surface, and therefore I may treat it as a 3d surface, such that I can find a center. In other words, I do not need to recognize, and I do not so recognize, your contention that this proves what you claim it proves.


    Are you claiming then, that space has a center, but not necessarily (personally I would suggest necessarily not) at any point in space?

  8. Self-referential statements... you have assumed his sentence referred to itself. Since he quoted me, I presumed he was referring to my sentence, which is my formulation of the basis of the logic I am using.


    In my twisted sort of way I was doing both. I was claiming it was false and providing evidence.

  9. Binary logic is a logic in which all operators are binary. That is' date=' the operators accept two arguments. And example is the "AND" operator. It takes two statements p,q to form the compound statement "p AND q". Compound statements in binary logic are truth-functional, which means that the truth value of the compound statement depends entirely on the truth values of the more fundamental statements (called "atoms" in some of the literature) and the meaning of the operator.


    It most certainly can not tell you whether the universe is deterministic, though.[/quote']


    Thanks Tom

  10. maybe we neither of us fully understand' date=' maybe we never will, maybe he is wrong, but let's think about what he says:


    he says that rotation is not relative to newton flat "absolute space"

    indeed absolute space does not exist it is one idealized case of the gravitational field which can occur only if there is no matter in the universe


    so the imagined rectilinear 3D or 4D graph paper of absolute space or spacetime simply is not real. (although all of newtons physics happens in it)


    [b']nor is rotation relative to the distant stars as Mach thought[/b]


    what rovelli says (and in this historical chapter he is summing up the lessons learned from Gen Rel which we have to take seriously because it has survived and indeed prevailed for the 90 years since 1915), what he says is the lesson of Gen Rel is that the rotation is

    "relative to a local dynamical entity, namely the gravitational field"

    this I think is very hard to understand. but as long as one is going to be puzzled one might as well be puzzled by the right thing




    What if you changed Mach's statement to "the distant stars in the distant past"?

  11. Is there any chance that the accelerating expansion of the universe is an illusion caused by relativistic redshift in stationary clouds of dust (see paper)?


    Such theories are unlikely because observations have almost firmly confirmed that the universe is accelerating based on CMB. The ΛCDM model is the best candidate.


    However cosmic inflation theory is still suspect. The graceful-exit problem is still not solved and again the only solution is string theory.


    String theory is the only one that explains what happened on the grassy knoll also. One particular solution (among many others) has Fidel passing Mother Teresa a loaded gun. :)

  12. It's the other way around. It's OK to violate conservation of energy, as long as you do it for a short enough time to keep from violating the HUP.


    I loaned Heisenburg $5 years ago and he still hasn't paid me back! :D


    You're right I got it backwords. I meant you could violate conservation of energy temporarily.

  13. I'm not sure what you're saying. In a rotating system there will be coriolis and/or centrifugal forces. If they vanish for a particular body under particular motion, then that body is in an inertial frame[/b'], e.g. someone running on a merry-go-round in the opposite direction but at the same speed.



    Yes, but it is also (like everything everywhere) in a (read infinitely many)rotating reference frame/s. We usually don't pick them for obvious reasons.


    Edit: in your example the body (runner) is in an inertial frame and at rest in that frame. So these pseudo forces/effects vanish. If we picked rotating reference frames as may sometimes be useful in engineering we may require pseudo force/effect "adjustments" to correctly use Newton's Laws.

  14. While reading this article on Foucalt pendulum I came across this:




    Is that a true statement' date=' that an inertial reference frame is one in which the coriolis and centrifugal forces vanish?


    I would like to discuss this at length.


    Thank you[/quote']


    What I don't see stated but I think is implied is that these "effects" vanish in an inertial frame for a body at rest. In a frame rotating wrt an inertial frame they would vanish for a body at a particular rotation. The math is greatly simplified by picking an inertial frame as a reference.

  15. What would happen if you were on a spaceship going .999999999[etc]c and you tried to move your hand foreward?


    To someone outside' date=' time would just slow down too much for my hand to reach c right?



    Is that what that equation accounts for?[/quote']


    If I (from my inertia frame) watch you do this my time does not slow down. Your time (from my perspective) would stay the same (almost, it would actually speed up as you lost momentum to your hand/arm), but your "hand's time" would slow down further. Only temporary (no pun intended) of course until your hand resumed the velocity of your body but from my perspective that could be a long time.

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