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A collection of questions/ideas

  1. Aug 25, 2004 #1
    I only have 6 physics hours under my belt and my math background is in boolean algebra, so please ignore this if you like to beat on the uneducated.

    1) Is there a singular dimension among the 7 folded dimensions that is different from all the others? or are all 7 the same? or perhaps do they all have different properties?

    2) Are there times in theoretical physics when it would be convenient to think of velocities as being probabilities, where a velocity is actually the probability that the particle will move one planck length in the next minimum unit of time (if you don't believe in quantum time, just ignore this). The speed of light would have a probability of 1 (which is aesthetically pleasing to me).

    3) Is the universe rotating? Can it be proved one way or the other?

    4) Dark matter doesn't interact with ordinary matter (or itself) except through gravity, so what happens when dark matter encounters a black hole? Also, will the distribution and motion of dark matter around a black hole be different from the distribution and motion of normal matter. Will that difference if any, affect the rate at which it flows into the black hole?

    5) I read somewhere that as you approach an event horizon, that space time rotates and time becomes spacelike and space becomes timelike. What is the nature of that rotation? Will an observer close to the event horizon now perceive movement towards the singularity as being movement forward in time (or perhaps backwards in time?)

    6) If to an outside observer, it takes an infinite amount of time for an object to reach the the event horizon, and to that same observer, the black hole will eventually evaporate in a finite amount of time, does this mean that the only way to reach the event horizon(from the outside observers point of view) is for the radius of the black hole to increase such that the event horizon passes over the object?

    7) Will astronomers and physicists of the future have a need for a "solar positioning system" similar to global positioning system (GPS).

    8) 3D television sets using many very dim narrow beamed lasers sent into an aerogel medium from many different angles, intersecting at single spot to make an active pixel. I'm thinking nano mirrors as a possible method making the lasers scan. Anybody feel like trying this?

    9) Please don't kill me. Has SETI tried looking near the galaxy's central black hole for signals from bug eyed aliens? Was just thinking that if I was a little green man, I would go to the most interesting spot that I could get to.

    10) I cant remember if you guys had decided if neutrino's had mass or not. If the question is still up in the air, are there an observations that could be made of the galactic black hole that would shed any light on the matter? If they do have mass, wont the GBH be acting as kind of a neutrino lens?

    11) Is there a relationship between the dark energy and the total entropy of the universe? Can the universe be said to have a surface? Does that surface have an area? If there was a law that said the area of the surface of the universe must be proportional to the entropy in the universe (both possibly infinite?) would that explain dark energy?

    12) Here is where I go totally off the wall. There are some theories that have proposed the creation of parallel unverses due to quantum fluctuations. It hurts my head to try to imagine a bifricating structure that would encompass something like that. A much simpler structure would be a collection of universe-instants, infinite in 3 spacial dimensions, but only a minimum time length in duration. The probability of any universe-instant coming into being would be determined by the probability of the existence of multiple precursor universe-instants and the probability of those UI's transitioning into the UI in question in the next instant of time (I use the terms transitioning, next, time, and "coming into being" very loosely). The probability of a generic sentient being finding himself in a particular UI would be proportional to the probability of that UI and number of sentient beings in that UI. Time would still exist, but our perception of past, present, and future would be illusions. UI's would would only be connected to each other by probabilities.

    13. Off the wall and down the street --- In the next hundred years we should have identified many distant worlds that will be well suited to human habitation. Suppose we find that the only way that we can populate these worlds is by growing human embryos and putting their safety and education into the hands of rudimentary AI's. How could we test the system?
  2. jcsd
  3. Aug 25, 2004 #2
    Mach's Principle says that rotation of the whole universe is meaningless. In this respect general relativity is non-Machian as it allows for rotation of the universe. A rotating solution was found by Godel, and it certainly differs from a non-rotating universe in that it allows closed timelike curves.

    Dark matter will fall into a black hole just as normal matter. Normal matter tends to reach a high temperature which acts against the inflow to some extent i.e infalling particles will scatter from other infalling particles. Dark matter is not affected by this (but we don't know how the dark matter particles interact with each other)

    Yes, the progress towards the singularity is timelike. That is why hitting the singularity is inevitable within a given proper time. The spherical coordinates stay the same, but I'm not really sure what happens to the other dimension.:confused:

    The standard view about this is that the evaporation of the black hole doesn't prevent things from falling in. I find these arguments unconvincing. Your idea of the black hole increasing in size to swallow an infalling object is one possibility which I've looked out for but I've never found it put forward in arguments for the standard view. You can read more of my views at
  4. Aug 25, 2004 #3
    Thank you VERY MUCH for your answers.

    With regard to your answer involving dark matter interacting / not interacting with itself - intuitively, based on dark matter's tendency to not spend a lot of time in small/shallow gravity wells, I would guess that either it does not interact with itself, OR if it does, then it doesn't lose/transfer much kinetic energy in the process. But like I say, thats a purely intuitive guess.

    Thanks again.
  5. Aug 25, 2004 #4


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    1)There are some models in which one or more of the extra dimensions is an extra time dimension, rather than another spacial one.

    5)More revealing to say that the observer at the EH will see all movement forward in time as movement toward the center. From the EH on inward, all timelines (all futures) progress toward the center.

    10) It's been supported to the point of near-certainty that neutrinos do have mass. But even if they didn't, the gravitation of a GBH (or any object with mass, for that matter) shouldstill have the same effect on them. One of the consequences of General Relativity is that an object does not necessarily require mass to be effected by gravity. If gravity is a curvature of spacetime, then anything that travells through spacetime will have its path altered by gravity, as viewed by a distant observer.
    Last edited: Aug 25, 2004
  6. Aug 25, 2004 #5

    Thanks for the answers :smile:
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