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  1. 30 Dec '14 16:11 / 2 edits
    http://phys.org/news/2014-12-alternative-explanation-dark-energy.html

    So perhaps dark energy doesn't exist?
    If no dark energy exists, what are the implications of that for the chances of dark matter existing? I do not pretend to understand the theoretical relationship between the two.
  2. Standard member Soothfast
    0,1,1,2,3,5,8,13,21,
    30 Dec '14 22:45
    Originally posted by humy
    http://phys.org/news/2014-12-alternative-explanation-dark-energy.html

    So perhaps dark energy doesn't exist?
    If no dark energy exists, what are the implications of that for the chances of dark matter existing? I do not pretend to understand the theoretical relationship between the two.
    I'm skeptical of dark energy and dark matter. On the other hand I'm skeptical of a molecular biologist implying there's something wrong with the theory of special relativity. At least, the following quote seems to imply it:
    Special relativity is supposed to be reciprocal, where both parties will experience the same time dilation, but all the examples that we have right now can be interpreted as directional time dilation. If you look at the GPS satellites, the satellite time is slowing down, but according to the GPS satellites, our time is not slowing down—which would occur if it were reciprocal. Instead, our time is going faster relative to the satellites, and we know that because of constant communication with the satellites.
    What's Kipreos saying here? That physicists are oblivious to something obviously wrong with special relativity that only he can see? I don't get it.
  3. Standard member adam warlock
    Baby Gauss
    31 Dec '14 10:14 / 3 edits
    Originally posted by Soothfast
    I'm skeptical of dark energy and dark matter. On the other hand I'm skeptical of a molecular biologist implying there's something wrong with the theory of special relativity. At least, the following quote seems to imply it:
    [quote]Special relativity is supposed to be reciprocal, where both parties will experience the same time dilation, but all the exam ...[text shortened]... ious to something obviously wrong with special relativity that only he can see? I don't get it.
    GPS functions due to general relativity not due to special relativity. Since one of the frames isn't an inertial one (actually both of them aren't), we can't say that the observers on the sattelite are equivalent to the observers on Earth and that's why his argument (I'm using this word very charitably here) is unsound.

    Also this silly objection is a text book exercise to text an undergrad's understanding of GR. This biologist just got himself an F.

    Originally posted by humy
    So perhaps dark energy doesn't exist?
    If no dark energy exists, what are the implications of that for the chances of dark matter existing?

    Dark matter and dark energy are two concepts that are totally unrelated in most theoretical constructions that I know of, hence dark matter doesn't have to cease to exist just because dark energy ceases to exist.
    Remember that dark energy is a way to "explain" why the universe expansion is accelerating and that dark matter is a way to "explain" supposedly missing mass.

    Maybe this directional time dilation also explains the apparent gap of mass...

    Anyhoo I'll try to get a hold of this Absolute Lorentz Transformation theory besides judging it too harshly (which I'm already doing).

    Last edit: Here is the full article for who wants to read it: http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0115550

    Abstract

    An alternate Lorentz transformation, Absolute Lorentz Transformation (ALT), has similar kinematics to special relativity yet maintains absolute simultaneity in the context of a preferred reference frame. In this study, it is shown that ALT is compatible with current experiments to test Lorentz invariance only if the proposed preferred reference frame is locally equivalent to the Earth-centered non-rotating inertial reference frame, with the inference that in an ALT framework, preferred reference frames are associated with centers of gravitational mass. Applying this theoretical framework to cosmological data produces a scenario of universal time contraction in the past. In this scenario, past time contraction would be associated with increased levels of blueshifted light emissions from cosmological objects when viewed from our current perspective. The observation that distant Type Ia supernovae are dimmer than predicted by linear Hubble expansion currently provides the most direct evidence for an accelerating universe. Adjusting for the effects of time contraction on a redshift–distance modulus diagram produces a linear distribution of supernovae over the full redshift spectrum that is consistent with a non-accelerating universe.
  4. Subscriber joe shmo
    Strange Egg
    31 Dec '14 14:50
    Can someone explain my error in thinking here?

    If we have two identical grandfather type clocks (clock 1 & clock 2) that are idealistic ( in the classical physics sense with the frame of reference being approximately non inertial) on the surface of the earth. We get the clocks synchronized at a fixed unit of time ( identical pendulum amplitude) clock 1 stay at the surface, while clock 2 is move radially outward into toward space. If conservation of energy holds, as we approach space and "g" decreases the amplitude "h" of the pendulum increases, while the velocity at ( the zero potential energy datum fixed to clock 2 ) remains constant. Which means that clock 2's time would be slowed down relative to the clock that remained at the surface of the earth. Hense, time dilation resolved by classical mechanics?
  5. Standard member DeepThought
    Losing the Thread
    31 Dec '14 16:17
    Originally posted by joe shmo
    Can someone explain my error in thinking here?

    If we have two identical grandfather type clocks (clock 1 & clock 2) that are idealistic ( in the classical physics sense with the frame of reference being approximately non inertial) on the surface of the earth. We get the clocks synchronized at a fixed unit of time ( identical pendulum amplitude) clock 1 ...[text shortened]... that remained at the surface of the earth. Hense, time dilation resolved by classical mechanics?
    One problem with your argument is that it would not apply to an atomic clock where the force of gravity is too weak to affect the operation of the clock. In the case of a gravity driven clock the slowing down of the clock is explainable in terms of the strength of the gravitational field and would be perceptible to co-moving observers - which it shouldn't be for time dilation. The real killer is that the direction of the effect is wrong. The Scwartzschild metric is:
    dT² = A(r) dt² - B(r) dr² - r²dΩ²
    where dΩ² is the usual metric on a 2-sphere. dT is the change in proper time, in other words the duration of a small time interval as experienced by a stationary observer at r. dt is the corresponding elapsed time as experienced by an asymptotic observer (one an infinite distance away from r = 0). A(r) = 1 - s/r where s is the Schwartzschild radius. A(r) < 1 and is a monotonically increasing function of r, so for a given dt (1 second say) the clock advances more with height which means it's running faster and not slower.
  6. 31 Dec '14 16:54
    Originally posted by joe shmo
    Can someone explain my error in thinking here?

    If we have two identical grandfather type clocks (clock 1 & clock 2) that are idealistic ( in the classical physics sense with the frame of reference being approximately non inertial) on the surface of the earth. We get the clocks synchronized at a fixed unit of time ( identical pendulum amplitude) clock 1 ...[text shortened]... that remained at the surface of the earth. Hense, time dilation resolved by classical mechanics?
    A pendulum clock is not a good measure of time if gravity varies. You don't stop time by taking a sledgehammer and mashing a pendulum clock to bits.
  7. Standard member sonhouse
    Fast and Curious
    31 Dec '14 17:51
    Originally posted by joe shmo
    Can someone explain my error in thinking here?

    If we have two identical grandfather type clocks (clock 1 & clock 2) that are idealistic ( in the classical physics sense with the frame of reference being approximately non inertial) on the surface of the earth. We get the clocks synchronized at a fixed unit of time ( identical pendulum amplitude) clock 1 ...[text shortened]... that remained at the surface of the earth. Hense, time dilation resolved by classical mechanics?
    That is just proving classical physics not time dilation. If we just put one of those clocks on Jupiter (if we could) it would be in a 2X gravity field and would swing faster but that is not due to time dilation, just ordinary physics.

    Time dilation from atomic clocks on Earth and one on Jupiter WOULD show dilation.
  8. Standard member DeepThought
    Losing the Thread
    31 Dec '14 18:32
    Originally posted by adam warlock
    GPS functions due to general relativity not due to special relativity. Since one of the frames isn't an inertial one (actually both of them aren't), we can't say that the observers on the sattelite are equivalent to the observers on Earth and that's why his argument (I'm using this word very charitably here) is unsound.

    Also this silly objection is a ...[text shortened]... vae over the full redshift spectrum that is consistent with a non-accelerating universe.[/quote]
    Yes, but most of the effect is due to the relative motion of the satellite and not due to gravitational time dilation - whose effect in any case is in the opposite direction (see previous post).

    I don't think he's managed to justify ALT (Absolute Lorentz Transform). He starts the article by claiming that there is a PRF (preferred frame of reference) which his cosmological argument depends on. But later states that our speed relative to the CMB (cosmic microwave background) is too big for the CMB to provide a PRF and that local masses provide local PRF's. So he switches to having the largest nearby mass determine a locally preferred frame of reference, which is something the physics community has accepted since Schwartzschild wrote down his metric. The experimental evidence he cites is relevant to that rather than to a universally preferred frame.

    The interesting bit is his argument about time dilation and the type Ia supernova data as I don't think that his result depends on ALT particularly. His claim is that there is an additional time dilation effect. That would mean that cosmological time is different from the time coordinate that appears in the FLRW metric, which has time passing at the same rate in different cosmological eras. Working out which observer a given set of coordinates is physically relevant to isn't trivial in general relativity so I don't see any immediate objection to that claim.
  9. Standard member adam warlock
    Baby Gauss
    31 Dec '14 19:13
    Originally posted by DeepThought
    Yes, but most of the effect is due to the relative motion of the satellite and not due to gravitational time dilation - whose effect in any case is in the opposite direction (see previous post).

    I don't think he's managed to justify ALT (Absolute Lorentz Transform). He starts the article by claiming that there is a PRF (preferred frame of reference) ...[text shortened]... ant to isn't trivial in general relativity so I don't see any immediate objection to that claim.
    Yes, but most of the effect is due to the relative motion of the satellite and not due to gravitational time dilation - whose effect in any case is in the opposite direction (see previous post).

    I know that but my point is that saying that both clocks are equivalent while talking about GPS is wrong because GPS takes into account GR and with that being said one can never be surprised if one clocks shows time dilation while the other doesn't.

    I intend to go through his during the weekend (I just like to live dangerously like that!) and after that I'll get back to this.
  10. 01 Jan '15 08:43
    I have always doubted the dark energy as it is proposed. I don't believe in the repellant force that will accelerate Universe. I think it is just misinterpretations of the observations. Why don't people listen at me? Oh, I see, I don't have any PhD...

    Dark matter, on the other hand, has some validity.
  11. 01 Jan '15 16:39
    Originally posted by humy
    http://phys.org/news/2014-12-alternative-explanation-dark-energy.html

    So perhaps dark energy doesn't exist?
    Physsog, as you've shown time and time again, is a very dubious source on scientific "breakthroughs".

    In this case, the idea that dark energy is in fact the same thing as Einstein's "greatest error", the cosmic constant, is older than RHP itself - and frankly, is a matter of semantics alone, not of fundamental physical theory.
  12. 19 Jan '15 23:20
    Maybe the Big Bang's inflationary stage never ended...it also is the cause for gravitational waves..which haven't been yet confirmed.
  13. Standard member DeepThought
    Losing the Thread
    20 Jan '15 10:58
    Originally posted by woadman
    Maybe the Big Bang's inflationary stage never ended...it also is the cause for gravitational waves..which haven't been yet confirmed.
    If the inflationary era hadn't ended then we would not exist. No structure would be possible.
  14. Standard member sonhouse
    Fast and Curious
    20 Jan '15 19:01
    Originally posted by woadman
    Maybe the Big Bang's inflationary stage never ended...it also is the cause for gravitational waves..which haven't been yet confirmed.
    There are many things that can give gravitational radiation, like co-orbiting neutron stars or co-orbiting black holes. I think it is only a matter of time before the instruments get sensitive enough to directly detect such radiation.
  15. 21 Jan '15 03:36
    Originally posted by DeepThought
    If the inflationary era hadn't ended then we would not exist. No structure would be possible.
    The inflationary period has not ended....it has dissipated to almost zero....but not completely ...