Scientists: Time Travel Impossible

Discussion in 'Chit Chat' started by JamesL, Jul 26, 2011.

  1. JamesL


    Dashing the hopes of "Back to the Future" and "Bill and Ted" fans alike, a group of Hong Kong scientists claims that recent research proves that time travel is impossible.

    A team at the Hong Kong University of Science and Technology, led by Professor Shengwang Du, has concluded that single photons cannot travel faster than the speed of light in a vacuum. Unfortunately for time travel buffs, photons apparently obey the laws of physics, regardless of whether you have a magic phone booth or can get that DeLorean up to 88 miles per hour.

    "The results add to our understanding of how a single photon moves. They also confirm the upper bound on how fast information travels with light," Professor Du said in a statement. "By showing that single photons cannot travel faster than the speed of light, our results bring a closure to the debate on the true speed of information carried by a single photon. Our findings will also likely have potential applications by giving scientists a better picture on the transmission of quantum information."

    According to Du, the scientific community got all excited about time travel several years ago with the discovery of "superluminal propagation of optical pulses," which basically said that a group of optical pulses could move faster than the speed of the light. Du, however, said this was only a visual effect and could not actually be used to transmit real information. People then focused on a single photon moving faster than the speed of light, but "because of lack of experimental evidence of single photon velocity, this is also an open debate among physicists," Du said.

    As a result, Du's team measured the maximum speed of a single proton, which showed that it obeys the universe's speed limit and "confirms Einstein's causality; that is, an effect cannot occur before its cause," researchers said.

    In their tests, researchers managed to separate the optical precursor, a wave-like structure at the front of an optical pulse, from the rest of the photon wave packet. To accomplish this, Du's team created a pair of photons and passed one of them through a group of laser-cooled rubidium atoms, which allowed them to observe optical precursors for the first time.

    "The team found that, as the fastest part of a single photon, the precursor wave front always travels at the speed of light in vacuum," researchers said. "The main wave packet of the single photon travels no faster than the speed of light in vacuum in any dispersive medium, and can be delayed up to 500 nanoseconds in a slow light medium. Even in a superluminal medium where the group velocity (of an optical pulse peak) is faster than the speed of light in vacuum, the main part of the single photon has no possibility to travel faster than its precursor."

    So, until someone came come up with something that travels faster than the speed of light, it looks like time travel will be confined to movies and TV.,2817,2389132,00.asp
  2. I thought time travel has already been done???

    Avdeyev holds the current record for time dilation experienced by a human being.[1][2][3] In his 747 days aboard Mir, cumulative across three missions, he went approximately 27,360 km/h and thus aged roughly 0.02 seconds (20 milliseconds) less than an Earthbound person would have,[4] which is considerably more than any other human being. This is due to the special relativistic effect of time dilation and is not properly thought of as time travelling as described by mainstream culture. (screw mainstream culture :D) A common misconception is that the Apollo astronauts hold the record—they did go faster than Avdeyev, but they were only in space for a few days

    Time travel to the future in physics

    Twin paradox diagram
    There are various ways in which a person could "travel into the future" in a limited sense: the person could set things up so that in a small amount of his own subjective time, a large amount of subjective time has passed for other people on Earth. For example, an observer might take a trip away from the Earth and back at relativistic velocities, with the trip only lasting a few years according to the observer's own clocks, and return to find that thousands of years had passed on Earth. It should be noted, though, that according to relativity there is no objective answer to the question of how much time "really" passed during the trip; it would be equally valid to say that the trip had lasted only a few years or that the trip had lasted thousands of years, depending on your choice of reference frame.

    This form of "travel into the future" is theoretically allowed (and has been demonstrated at very small time scales) using the following methods:[22]
    Using velocity-based time dilation under the theory of special relativity, for instance: Traveling at almost the speed of light to a distant star, then slowing down, turning around, and traveling at almost the speed of light back to Earth[51] (see the Twin paradox)

    Using gravitational time dilation under the theory of general relativity, for instance: Residing inside of a hollow, high-mass object;
    Residing just outside of the event horizon of a black hole, or sufficiently near an object whose mass or density causes the gravitational time dilation near it to be larger than the time dilation factor on Earth.

    Additionally, it might be possible to see the distant future of the Earth using methods which do not involve relativity at all, although it is even more debatable whether these should be deemed a form of "time travel":
  3. Hong Kong scientists impossible
  4. Traveling back in time has already been done, by options holders.

    For you nitwits that think there is some way to go back and visit John Wilkes Booth at the playhouse, keep dreaming
  5. Lornz


    It's achievable to travel forward in time.
  6. sideway also pretty good:D
  7. I had a dream last night with Giorgio Armani.I tried on his new disigned jacket with a big hood, to left sleeve of wich a lite detachable bag was attached.Kind of a down-padded coat.Have you ever seen a jacket with a detachable bag to its sleeve?:D

    Lets see if i`m able to travel in time.:D
  8. In the famous words of Aleksey Vayner - impossible is nothing.
  9. rew


    Time travel is easy. It's fast forward and reverse that are difficult.
  10. Lucrum


    "Scientists: Time Travel Impossible"

    Bummer, I've always wanted to:

    * see a T-Rex...from a distance
    * Spend a week with a Neanderthal family
    * Hunt a wooly mammoth with a spear
    * participate in a Roman orgy
    * consume a few pints with some peasants of the dark ages
    * spend a few days in a castle as a knight in armor (with a Lady in waiting of course)
    * engage in a sword fight to the death
    * spend one day at Valley Forge 1777
    * fight in a major civil war battle (and survive)
    * participate in the Northfield, Minnesota shootout
    * fly WWI and WWII fighters in combat
    * do a tour in Vietnam
    * do drugs and be promiscuous at Woodstock
    #10     Jul 27, 2011