Space oddity – first cover feature

My first cover feature article has now gone online on the New Scientist website. It’s about exploring how quantum behaviours – like entanglement of particles – might be affected by the space-warping effects of relativity. Writing it was really interesting, but quite tricky as the subject matter roved from the practicalities of quantum communication networks and designing satellites, to the abstractions of quantum field theory. I met lots of scientists, some already known to me and mostly over the phone, many of whom didn’t get a mention in the final edit unfortunately. So here are some names of those who spent time answering my many questions but aren’t included due to space restrictions: Lee Smolin, Matt Leifer, Sabine Hossenfelder, Dirk Englund, Brendon Higgins. Thanks so much for your help.

Advertisements

About sophiehebden

Science writer and editor, I mostly write about space and fundamental questions in physics.
This entry was posted in Science. Bookmark the permalink.

18 Responses to Space oddity – first cover feature

  1. piecubed says:

    Just read the feature, interesting stuff!

  2. Congratulations on the nice article :o)

  3. Roger Schafir (in London) says:

    Congratulations on your first cover article, and I thought it not at all a bad job. New Scientist articles on quantum mechanics don’t always show good grasp of the subject, and often seem to be the result of buttonholing by people with ideas of dubious validity, but yours was different.

    But can I comment on this matter of whether entanglement would be affected by relativity. The question of which direction the non-local inflence travels exists just as much in non-relativistic quantum mechanics, and I cannot see that it is affected by relativity. Given two observers (usually called Alice and Bob), all that every non-lcoality theorem ever derived says is that either Alice’s result would have been different if Bob had made a different choice of what to measure, or Bob’s would have been different if Alice had made a different choice of what to measure, or both, but there is no knowing which of these it is. There are reasons for thinking that this ambiguity is irremovable, i.e. it is not just that no one has succeded in finding a direction to the influence yet.

    You mention ideas by various people for testing whether relativity would put an end to an entangled state, but I am unclear which of several things these people have in mind. Are they suggesting that gravity would collapse the wave function (a speculation made by Penrose in the 1990s) or that the state would evolve (as opposed to collapse) into an unentangled state under the infuluece of gravity, or some other thing? That’s not clear, I think.

    • sophiehebden says:

      Hi Roger,
      In terms of what causes the wave function collapse in these different theories is different in each case – in the case of work by Ralph et al. they incorporated curved spacetime into QFT. I’m no expert on the maths but I think the photons, by going through curved space-time, get the phase shift that decorrelates the entanglement. You can read about the theory here: Quantum Connectivity of Space-Time and Gravitationally Induced De-correlation of Entanglement”, T.C.Ralph, G.J.Milburn and T.Downes, Phys.Rev.A. 79, 022121 (2009).

      The prediction of breakdown of entanglement by Fuentes et al. stems from their version of relativistic Quantum Field Theory. Entanglement breaks down in this scenario due to a dynamical cassimir effect, which creates particles and excitations in the quantum system, degrading the entanglement. Here’s a ref: D. E. Bruschi, I. Fuentes and J. Louko, Phys. Rev. D 85, 061701(R) (2012) and N. Friis, et al., Phys. Rev. Lett. 110, 113602 (2013).

      I would have loved to get Penrose’s thoughts on it, and after hounding him for several weeks, unsuccessfully, the deadline loomed and it was no longer possible to keep trying. Perhaps he hasn’t got anything to add on wavefunction collapse these days?

      Hope this helps,
      Sophie

      • Roger Schafir says:

        Many thanks for your reply and for the references. It sounds offhand as if both Ralph and Fuentes are believers in a decoherence explanation of wave collapse, much associated with the consistent-histories interpretation of quantum mechanics, though they are differing in their mechanism of how exactly this works. Bringing the Casimir effect into it sounds strange, but perhaps the idea is that it’s collision with virtual photons that decoheres a wave function.

        As far as your lack of answer from Penrose is concerned, of course he is now in his mid eighties, so is presumably winding down his degree of activity. When recently I met my old supervisor from my Ph.D. days at King’s College London, he, the same age as Penrose, told me that Penrose had told him that his last book, on entropy and the arrow of time, was likely to be his last effort.

        Anyway, thanks again, and I wish you success in your future career. Having got a cover article into a relatively mass circulation magazine, I would have thought there is every hope of going on to things like articles in the broadsheet newspapers, though I know that that one is a tough nut to crack.

        Regards,

        Roger.

      • Roger Schafir (in London) says:

        Many thanks for your reply and for the references. It sounds offhand as if both Ralph and Fuentes are believers in a decoherence explanation of wave collapse, much associated with the consistent-histories interpretation of quantum mechanics, though they are differing in their mechanism of how exactly this works. Bringing the Casimir effect into it sounds strange, but perhaps the idea is that it’s collision with virtual photons that decoheres a wave function.

        As far as your lack of answer from Penrose is concerned, of course he is now in his mid eighties, so is presumably winding down his degree of activity. When recently I met my old supervisor from my Ph.D. days at King’s College London, he, the same age as Penrose, told me that Penrose had told him that his last book, on entropy and the arrow of time, was likely to be his last effort.

        Anyway, thanks again, and I wish you success in your future career. Having got a cover article into a relatively mass circulation magazine, I would have thought there is every hope of going on to things like articles in the broadsheet newspapers, though I know that that one is a tough nut to crack.

        Regards,

        Roger.

  4. Dear Sophie,

    I deeply enjoyed your well written article and graphics in New Scientist April 20-26th 2013, regarding Quantum and Relative Physics. And I will review you other work at WordPress,as well. However my main point is to share with you my latest article that I posted today @ http://www.otterthink.wordpress.com Called “What causes Space to Curve Around Mass. (As if it actually did) I posted it largely on your behalf, as it relates much to “TIME” and the most fundamental of notions, we have [ I believe ] wrongly assumed. As I believe “TIME” does not change, it is sacrosanct. The only thing that changes is the mechanics of the clocks which are subject to gravities impacts on their mechanical workings. Hence Time Does Not and Cannot Change – Ever. Only the measuring devices change due to gravity. And measuring devices are not Time. Time stands alone as Space does, immutable and constant. If we took this fundamental nature of science and applied it to our views of “Time” slowing down or speeding up, we would unravel some additional truths…

    Great Success to you,
    Russ

  5. Dear Sophie,

    My first reply is awaiting “Moderation”? Did I suggest anything out of dis-respect or fully incorrect by your determination? I attempted to write my other blog at http://www.otterthink.wordpress.com based on your behalf, with great respect for your wonderful article. I love anything related to Quantum Physics, and yours was well laid out, in a manner that open’s minds…

    Cheers always, Russ

  6. Roger Schafir (in London) says:

    I assure Russ Otter that General Relativity does say that spacetime actually curves as a matter of physical fact. He may reject General Relativity, but it is a theory of gravity that has passed some very stringent tests.

    And in any case there is not the slightest doubt that Special Relativity is correct, and it does say that less time passes for some people than others. In particular you could go away in a fast spaceship and come back twenty years later according to yourself, and find a thousand years has passed on Earh. That is a physical fact.

    Russ Otter seems to be saying that it is not time which slows down but all the fundamental processes that take place in time. But I think most relativists would not accept that distinction.

    • Roger, I agree with your disposition, “that most relativists would not accept that distinction”. My question would be “Why?” as fundamentally, or physically it happens, which changes the scheme of our fundamental thinking.. My own observation of course, from a sense of logic that I find improbable to contest. But that is science and the beauty again of exploration…. Thank you for your thoughtful comments, Russ

      • Roger Schafir (in London) says:

        The reason they would not accept it is because there is no way even in principle of observing the allegedly two different entities. It is very much the outlook of modern physics to suppose that if something cannot be observed even in principle, that thing does not exist.

        But I will not take up more of your time in what could be interminable debate, so let’s leave it at that.

      • Roger, you are correct, once again, as this would be an interminable debate. But let me take one more liberty to suggest, that the Infinite and the Finite, are as different as an Elephant and a Stone. My point is that: when dealing with mathematics we are bound by the finite, as math breaks down at the Infinite. In other words: Variability rules the space and time we would discuss. Thermodynamics and Relativity are true in one place and time, but much different in another. Witness the Event Horizon and the strength of Gravity, vs. Gravity at a muon’s level. The 2 are the same, but the variability changes the rules of how gravity responds. Hence in a variable existence, things are not all they seem to the observer’s… Yet they are the same… Worth a Ponder or two. Thank you for your indulgence, as this article and subject matter is an inscrutably infinite road… And your scholarship and thoughts are much appreciated, equally as are Sophie’s for kicking it off! Russ

      • Roger Schafir (in London) says:

        Well just very briefly:

        (1) Sure the finite and the infinite are different, but mathematics is certainly not limited to considerations about finite sets. There is even a specific theory of infinite numbers, started by a mathematician called Cantor.

        (2) There has been a lot of work by astronomers and astropysicists trying to see if the laws of nature are different far away and at different times. So far the evidence is that they are the same everywhere and at all times.

        (3) Gravity is extremely weak between subatomic particles, but that doesn’t mean it’s inapplicable. There is no reason to doubt that electrons fall downwards in the earth’s gravity just like all other things do.

      • Roger… Well stated. Thanks, Russ

  7. sophiehebden says:

    The nature of time is an open topic of debate – there’s a vast array of different essays about it on the FQXi website here: http://www.fqxi.org/community/forum/category/10
    …worth dipping into when you have time (excuse the pun) although you can quickly get bogged down in detail in any one essay.

  8. I just read the article and found you here from that! Well written and highly informative. I just wanted to say well done and how useful it will be to me in my writings and with my Science students too. Best wishes 🙂

  9. Thanks for the article in NS. I had a wow moment when you wrote about the order in which quantum events happen when relativistic effects come into play.

    From what I understand, photons don’t experience time because they travel at the speed of light and have no mass, so spooky action at a distance is just two entangled photons behaving as if no time had passed. Only weird for us blobs of negative entropy stuck in a gravity well experiencing the Big Bang in ultra slow motion.

    • Roger Schafir (in London) says:

      But “spooky action at a distance”, i.e. non-locality due to entanglement, can also take place between particles going slower than light, such as electrons. So it can’t be explained as just the effect of zero time passing for photons.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s