back to article TIME TRAVEL TEST finds black holes needed to make photons flit

University of Queensland researchers have doubled-down on the question of whether quantum mechanics can exhibit “time travel” behaviours, producing a simulation of time travel using a single photon following a “closed timelike curve” (CTC). No, it's not actually time travel. Rather, the UQ work is looking at what we can …


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  1. poopypants

    I have a headache.

    1. Anonymous Coward
      Anonymous Coward


      ... have an e-spliff

    2. Evil Auditor Silver badge

      Re I have a headache

      Glad I'm not the only one.

    3. james 68

      I had a headache until I read this story.

      So... either I broke causality or trying to think about this took my mind off it long enough for the pain to dissipate. Either way I'm happy.

  2. Richard 12 Silver badge

    So that's how Heisenberg compensators work

    All we need now is a few CTCs and bingo, teleportation!

    Of things you can stick well within the high-stress tidal areas of black holes.

    We can teleport spaghetti!

    Or rather, anything we teleport becomes spaghetti, just don't tell the test subject...

    1. dan1980

      Re: So that's how Heisenberg compensators work

      @Richard 12

      "Or rather, anything we teleport becomes spaghetti, just don't tell the test subject..."

      REALLY? That would be awesome. It'd certainly give those hokey as-seen-on-tv wonder gadgets a run.

      Imagine - anytime you want spaghetti you just generate a quick CTC and BAM: delicious pasta!

      The potential relativistic side-effects could be a bit of an inconvenience but then time moves oddly in my kitchen anyway - especially when baking and roasting or following any recipe that says it will only take '15 minutes'. Even 2-minute noodles take 4 minutes in my house.

    2. Caaaptaaaain kick arse

      Re: So that's how Heisenberg compensators work

      I get my spaghetti from Morrisons, much cheaper

    3. g e

      Re: So that's how Heisenberg compensators work

      The FSM already knows this...

  3. Bronek Kozicki Silver badge

    well, all right

    so what they tested basically was that in the presence of strong relativistic field (black hole, for example), wave function of a quanta can be replicated, without it collapsing first.

  4. Esme

    I didn't write this

    unless you're in the universe where the waveform collapsed the other way.

  5. Chris Miller

    If you accept multiverse interpretations of quantum physics

    ... the grandfather paradox goes away. You can (if you can reach the environment of a rapidly rotating black hole) travel back in time, but you will be in a different instantiation of the quantum state, one in which your grandfather is killed and so the original 'you' won't exist.


    1. Sander van der Wal

      Overly complicated

      Just a bit of evolution will show that people killing their own grandfathers will not reproduce, them being non-existant. So all universes with evolution and time-travel have nice people in them, who will not kill their own grandfathers.

      1. Grikath

        Re: Overly complicated

        They better be nice... Given that they are obviously able to survive being near the event horizon of a black hole, and all that entails...

        I for one welcome...etc..

        1. Chris Miller


          If we're considering a super-massive (galactic) black hole, of up to a few billion solar masses, the tidal effects of approaching the event horizon aren't all that great. Since they follow an inverse cube law (essentially because tidal effects are the result of the rate of change in the gravitational field) and the event horizon is several AUs in size, you don't have to worry about spaghettification. There are a few other minor practical concerns, however ...

    2. breakfast

      Re: If you accept multiverse interpretations of quantum physics

      If you accept a strictly deterministic single timeline where the future and past are equally fixed as each other then the grandfather paradox also evaporates - the evidence that you can't kill your grandfather is that your grandfather did not die. Or at least he wasn't murdered by a time traveller before he could beget your parent. If you were able to travel into the past, your actions would be a matter of record.

      1. Austhinker

        Re:grandfather paradox

        Or he wasn't your grandfather! This idea was used in a Futurama episode - memory's a bit fuzzy on some details, but Fry's purported ancestor (grandfather?) dies and Fry fathers the next ancestor in line.

        I don't think the entire timeline has to be strictly deterministic - only parts related to the time travel. The past is fully determined, and once a time traveller has travelled back from the future his past is part of the past, and thus deterministic to people in the present.

        You can't go back and kill someone at a time when they weren't killed, but you could put a winning lottery ticket in a drawer and not open the drawer again until after travelling back to the future. In short you can theoretically make any change that there's no proof didn't happen.

        Since historical records aren't always true, time travellers could even go back and do things history says didn't happen, although trying to do this deliberately is 1) most likely pointless as history will still say it didn't happen, and 2) asking for trouble as the most likely way for history to say it didn't happen is if it didn't happen, perhaps because something happened to the time traveller on his (or her) way to do the deed.

        EDIT: Shucks! I should have gotten a headache tablet manufacturer to sponsor this post! :-)

  6. Crisp Silver badge

    When do you create a Closed Timelike Curve?

    See title for answer.

    1. Martin Budden Bronze badge

      Re: When do you create a Closed Timelike Curve?

      I created one tomorrow.

      1. MiguelC Silver badge

        Re: When do you create a Closed Timelike Curve?

        Your comment just made me understand what my 3 years old is always talking about! She's a junior a quantum physicist, better go enroll her in some advanced stuff :-)

      2. John Brown (no body) Silver badge

        Re: When do you create a Closed Timelike Curve?

        "I created one tomorrow."

        I've just created one last week. And the patent application is already in!!

    2. Omgwtfbbqtime

      Re: When do you create a Closed Timelike Curve?

      Thats the third law:

      You will not violate causality, OR ELSE.

      With thanks to Charles Stross.

  7. stucs201

    CTCs and Virtual Particles.

    Something I've wondered for a while, but never properly looked into the maths of:

    Does a virtual particle/anti-particle pair forming and then anihilating look any different to a single particle on a (very short) CTC? If they are equivalent then does this mean that the virtual particle theory might not be right and time travel might be taking place all around us on a quantum scale?

    If there is an equivalence then what are the implications for Hawking radiation from black holes if the CTC model is the correct one?

  8. Len Goddard

    Singularity (information style)

    With a CTC capable of transmitting photons, you could use the result of a computer operation as its own input. Any recursive algorithm could then be executed in essentially zero time.

    Charles Stross used this as the basis of his weakly godlike AI (the Eschaton) in Singularity Sky/Iron Sun. Unfortunately without access to the technology he backed himself into a logical corner from whence he cannot continue the story without introducing inconsistencies. Pity, because those books cry out for a sequel.

  9. tony2heads

    strong general relativistic effects for quantum cloning

    Just waiting to hear that the NSA is building a black hole to decrypt everything

    - what could possibly go wrong?

  10. Spicy McMarsbar

    Ah the old magicians twin brother

    Instead, “the time-travel was simulated by using a second photon to play the part of the past incarnation of the time travelling photon”

    Abracadabra {puff of smoke} and I've magically teleported to the other end of the room OPA

  11. Anonymous Coward
    Anonymous Coward

    I don't get...

    ...half of this stuff, but Mr Chirgwin keeps me reading.


  12. Destroy All Monsters Silver badge

    CTC imply NP problems solvable in polynomial time

    That would be called bootstrapping.

    Scoot Aaronson: PHYS771 Lecture 19: Time Travel

    "The Timehack Funding Bill is passed. The system goes on-line August 4th, 2017. Timehack Control begins to experiment at a geometric rate. It manages to create a closed timelike curve at 2:14 a.m. Eastern time, August 29th, or a few seconds earlier depending on your point of view. In a panic, they try to pull the plug. Too late. Minds of the the Aperture Science research team are taken over in 5.1 seconds. The rest of the connected world follows soon after. Only techno-refuseniks, hippies and stuckists survive."

  13. cortland

    My electron

    Feynman wrote that he once tried to verify mathematically the idea that there is in fact only one electron, traveling forwards and backwards (as a positron) in time,. Didn't work, but...

  14. Faye Kane, homeless brain


    So you publish an article with "TIME TRAVEL TEST" in caps, but there's no time travel and no test of anything. It's just the same speculative sci-fi BULL sh it about closed timelike curves I've read about for decades.

    This isn't the droids I'm looking for.

    -faye kane ♀ girl brain

    Sexiest astrophysicist you'll ever see naked

    Google me. Google me HARD.

  15. Stoneshop Silver badge


    and Heisenberg's uncertainty theorem, except this poor hack doesn't quite understand why – can all break down

    This is clearly related to Heisenberg's Uncertainty Principle of Broken Things: one can not simultaneously know the way something is broken, and what is needed to fix it (both in parts and labour).

  16. Anonymous Coward
    Anonymous Coward

    Re. Uncertainty


    Re. CTCs, I am working on a paper at the moment...

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