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Thread: Speed of Dark ???

  1. #51
    Master OptiBoarder Darryl Meister's Avatar
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    I think that "ten dimension" stuff was a way for theoretical physicists to reconcile certain problems in the string theory. Probably all quantum mechanical voodoo. ;)

    Best regards,
    Darryl

  2. #52
    OptiWizard
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    WOW! you all must have way more spare time than me.:D

    A question I had is, Several have referred to the speed of Gravity but I thought gravity was an acceleration. i.e a force that would change the speed of an object (or light).

    Also, isn't the reason a black hole appears black is because the the light is traveling into it not toward our eyes, therefore if you were inside the black hole (theoritically, I know we would all be crushed by the gravity) wouldn't we see alot of light coming in?
    I guess like most things, it depends on your perspective.

    Clearly I am no astrophysicist but just some questions and thoughts I had while reading some of your great posts.

  3. #53
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    There is a book by the brilliant Stephen Hawking called "A Brief History of Time." I read it a few years ago, and understood the first 2 or 3 chapters. After that, he lost me and I gave up reading the rest. But it's about exactly what this thread is discussing. I highly recommend it for people who are really into this stuff.

  4. #54
    Master OptiBoarder Darryl Meister's Avatar
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    I thought gravity was an acceleration. i.e a force that would change the speed of an object (or light).
    This is getting into a lot of theoretical speculation. "Gravity" is a force, but how does the force interact with an object? When you have two large bodies, at some distance apart, interacting with each other through gravity, what is really being exchanged between them? Physicists speculate that invisible, massless paticles called gravitons are responsible for this force. Consequently, we are really asking how fast these gravitons travel.

    Also, isn't the reason a black hole appears black is because the the light is traveling into it not toward our eyes
    Objects are visible because they either emit light (a "primary source") or reflect light (a "secondary source"). The sun emits light, while the paint on your car reflects it.

    Here is my understanding... When a massive star burns out and collapses, it becomes much more compact and dense, creating a much stronger gravitational field near its surface. For a given body, a certain "escape speed" is required for an object to escape its gravitational force and leave. The escape speed for the Sun, for instance, is 620 km/s.

    Now, once a star collapses and becomes extremely dense, its gravitational field may require an escape speed greater than the speed of light (300,000 km/s). Hence, light can no longer "leave" the star, so to us it appears as though there is nothing there to emit or reflect light: a black hole.

    However, since the speed of light is constant, so gravity really can't "slow it down" (as it would for any other object trying to escape the star), we assume that the path of the light is actually bent by the gravity of the star, and that space-time becomes "curved." Or something like that. Keep in mind that most of this is theoretical and the existence of "black holes" is still unproven.

    There is a book by the brilliant Stephen Hawking called "A Brief History of Time."
    Definitely recommended.

    Best regards,
    Darryl

  5. #55
    Just An Optician jediron1's Avatar
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    Big Smile

    Darryl Meister said:
    I think that "ten dimension" stuff was a way for theoretical physicists to reconcile certain problems in the string theory. Probably all quantum mechanical voodoo.

    Darryl your right. Most physicists who are dealing with quantum
    physics contend there are 10 dimensions. Four are knowable and
    the others are in the string theory, where the deminsions come because they believe they are curled forming other deminsions.
    Granted these are all on a sub atomic level but they are still there.
    :bbg: :D

  6. #56
    Just An Optician jediron1's Avatar
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    Big Smile

    Darryl said:
    However, since the speed of light is constant, so gravity really can't "slow it down" (as it would for any other object trying to escape the star),

    I beg to differ with you. In recent articles from leading physicists
    around the world there are some who believe that the speed of
    light is not a constant but in the past eons may have been faster
    then it is now. From articles I have seen they believe the speed of light is actually slowing down, if you can call 186,000 miles per second slowing, but that is the lastest belief.
    :bbg: :D

  7. #57
    Master OptiBoarder sandeepgoodbole's Avatar
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    The Indian Philosophy

    Oh Lord !
    Tamaso ma Jyotir gamay

    Take me from the (Tamas) Darkness( of not known) to the
    (Jyoti) Light (of the Knowledge)

    Asato ma Sat gamay

    (Asat) Falsehood to the (Sat) Truth

    Mrutyorma Amrut gamay

    (Mrutyu= Death )Perishability to( Amrut) Eternity

    Gamay = Take me.

    Lack of Knowledge = Darkness
    Falls and Untrue /behavior = Darkness
    Death = Darkness

  8. #58
    Just An Optician jediron1's Avatar
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    Just to point up that physicists do believe that light may be slowing: By using the redshift/distance they are pretty sure that
    there are anomalies that show light could have been faster in the distance past and is now slowing down.

    Excepted:
    "Headlines in several newspapers around the world have publicized a paper in Nature by a team of scientists (including the famous physicist Paul Davies) who (according to these reports) claim that ‘light has been slowing down since the creation of the universe’ ".
    1.Davies, P.C.W., Davis, T.M. and Lineweaver, C.H., Black holes constrain varying constants, Nature 418(6898):602–603, 8 August 2002.

    "Evidence suggesting that the velocity of light, c, has been slowing down throughout history was first reported by Barry Setterfield and Trevor Norman for some years."

    As can be seen there are some scientists who believe that light
    is slowing down and on the flip side there are scientists who believe that it is not slowing down, so take your pick. If you want
    you can read through the astronomical data, but all the formulas
    on the redshift and distance equations can become tedicious.

    :bbg: :D

  9. #59
    Master OptiBoarder Darryl Meister's Avatar
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    I beg to differ with you. In recent articles from leading physicists around the world there are some who believe that the speed of light is not a constant but in the past eons may have been faster then it is now.
    This sounds more like conjecture in order to explain various observed phenomena, and not necessarily that these scientists have actually convinced themselves (or anyone else) that light has, indeed, been slowing down. Until it's something more than a loosely supported theory, is it really a far cry from certain scientists claiming that the world would end during that last planetary alignment because of gravity or other scientists claiming that they have actually transmitted a signal faster than the speed of light? ;)

    Also, even if light does slow down over the course of billions of years, did these scientists actually assert that gravity can slow it down? If not, the theory on black hole formation would remain largely unchanged, though the "escape speed" bit may change slightly over the course of billions of years. This assumption may also suggest that the speed of light will vary from star to star, depending upon its gravitational field, which a clever scientist might be able to prove or disprove with the right measurements.

    Best regards,
    Darryl

  10. #60
    Just An Optician jediron1's Avatar
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    Darryl I said nothing in my two previous post to or about black holes. I was just pointing out a fact that there are reputable scientists who disagree about the speed of light. Through there
    calculations in the redshift they believe they have found a very
    pronounced repositioning which can only be explained by that the
    speed of light has been slowing down. If you read the articles by
    Setterfield and Norman you would see there conclusions, the same conclusions that Davis and others have arrived at. Whether
    you believe it or not is just conjecture on your part. The findings they have are in black and white or should we say in the red-shift. As I said before just go through there calculations in the redshift and distance formulas and you can see where they are coming from.:bbg: :D

  11. #61
    Just An Optician jediron1's Avatar
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    Darryl said:
    This sounds more like conjecture in order to explain various observed phenomena, and not necessarily that these scientists have actually convinced themselves (or anyone else) that light has

    I beg to differ with you on your above point. These are not your run of the mill hamburg scientists. Paul davis is a world renowned
    physicist. Setterfield and Norman are just as renowned but not in
    the same category as Davis, but still highly regarded.:bbg: :D

  12. #62
    Master OptiBoarder Darryl Meister's Avatar
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    I beg to differ with you on your above point. These are not your run of the mill hamburg scientists. Paul davis is a world renowned physicist.
    Renowned or not, 1) It's still only theory, 2) They're certainly not infallible, and 3) It probably won't have any effect on the theory of black holes. ;)

    Best regards,
    Darryl

  13. #63
    Just An Optician jediron1's Avatar
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    Renowned or not, 1) It's still only theory, 2) They're certainly not infallible, and 3) It probably won't have any effect on the theory of black holes.

    Best regards,
    Darryl

    So I guess Einsteins theory E=mc2 is as you said "still only a theory" or the redshift "still only a theory" So the caveman who killed the bear to eat is only a theory because it can't be proved
    and it's "still only theory" they ate bear, because really they could have eaten berries. But that to could only be a theory!:hammer: :drop:

  14. #64
    Master OptiBoarder Darryl Meister's Avatar
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    So I guess Einsteins theory E=mc2 is as you said "still only a theory" or the redshift "still only a theory" So the caveman who killed the bear to eat is only a theory because it can't be proved and it's "still only theory" they ate bear, because really they could have eaten berries. But that to could only be a theory
    I consider your statement concerning the slowing of the speed of light a "theory," and really even calling it a theory in the scientific sense may be a bit of a stretch, depending upon what these scientists specifically concluded. But to answer your question, Yes, relativity is a theory as well, albeit a theory with a great deal of support and some experimental evidence to back it up.

    Maybe in fifty years, we'll refer to certain relationships in the theory of special relativity, like the energy-mass equivalence formula, as "laws." And it's important to remember that, in science, "theories" are subtly different from "unproven ideas." Any speculation, scientific or otherwise, that has yet to be proven is a theory in the general sense of the word.

    However, in physics, the term theory is often used to describe the proposed mechanism associated with a certain relationship. If the relationship, itself, has been verified and accepted, it is often referred to as a law. Newton's law of gravity describes a relationship between two bodies, while Einstein's theory of general relativity provides a possible explanation as to why this relationship exists.

    For that matter, even "proven" theories and laws, such as those proposed by Newton, are not necessarily immutable or beyond review, and may be refined as our understanding evolves. But, more to the point, for every theory or law you see in a physics textbook, there have probably been a dozen others that were eventually abandoned, even by scientists as "renowned" as Isaac Newton.

    In this case, you speak as though you believe that once a physicist submits a hypothesis to the scientific community, it is automatically accepted as the definitive explanation, and all other theories and opinions on the matter are immediately discarded. This is obviously not the case, no matter how renowned he/she is.

    Even at this moment, there are several theories about the formation and expansion of the universe; they can't all be right, though.

    Also, no one is questioning "redshifts," which are simply an example of the doppler effect applied to light.

    Best regards,
    Darryl

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