a few weeks ago some very excitable science journalists were plastering the Internet with headlines like fifth fundamental force of nature discovered what was that all about is there really a new force can I finally get my x-wing out of that swamp let me make it sound a little less hyped there was something slightly weird about how a bunch of beryllium atoms were acting the told physicists that for a tiny fraction of a second an unknown particle may have existed hmm all right let me make it sound a little more hyped but also a lot more specific atomic nuclei have energy levels just like their electron shells do protons and neutrons can occupy excited states contain excess energy and when they settle down again they give off that energy as photons but also sometimes as a particle or a particle antiparticle pair one thing that comes out of a pile of beryllium eight atoms is a lot of electron positron pairs they can pop out at a lot of different energies researchers noticed a slight excess in their energies at 17 mega electron volts it's as though something with a mass energy equivalence of 17 MeV was decaying into those particles now this might sound a little bit familiar the same sort of excess in the photons emitted after proton collisions in the Large Hadron Collider led to the discovery of the Higgs boson just recently a new very slight excess of the LHC was originally thought to be a new particle but was discovered to have been a statistical fluke but this excess in the beryllium eight decay is not slight it's now a 6.8 Sigma X S which is statistic is for it being pretty done CERN that something weird is going on but why do they think that the mysterious 17 MeV particle is a new type of fundamental force well in short it's because the anomaly was observed for a very particular transition between the beryllium nuclear States that transition meant a difference in energy but also a difference in some other quantum stuff spin parity and isospin and the easiest way to explain this is if a spin one gauge boson was created such a particle would be a mild extension of the standard model not too crazy but certainly brand-new physics yes and new spin one gauge boson no seriously this is awesome if it's true see three of the four fundamental forces electromagnetism and the strong and weak nuclear forces are all communicated by these gauge boson things a new gauge boson means a new fundamental force why are we only spotting this thing now well the standard wisdom for finding new particles is to create higher and higher energies hence the Large Hadron Collider any particle capable of existing at lower energies should have been spotted but that's not true if the particle is a ninja by that I mean dr. electromagnetism and generally interacting with regular matter very little if that's the case it could be produced at much lower energies than the Giga electron volt energies produced in the LHC like the mega electron volt transitions of atomic nuclear energy levels if the decay product of such a transition is very weakly interacting these particles could be everywhere and we wouldn't know it like ninjas and like dark matter in fact this is a tantalizing possibility not that dark matter is ninjas although as a scientist I'd need to test that before I rolled it out no I mean that this new particle may have something to do with dark matter it's very weakly interacting but the researchers suggest it could mediate interactions between the so-called dark sector and the visible universe okay onto the solution to the quantum eraser challenge to summarize I asked you to tell me why it's impossible to send any real data back in time using the delayed choice quantum eraser experiment and so cheap on the lottery remember the landing location of each individual photon passing through to the interference screen of this experiment does seem to be influenced by a decision that is made regarding each of those photons entangled partners in the future that decision was whether we would know the path of the original photon thus eliminating an interference pattern or to erase our knowledge of that path which brings the interference pattern back that decision is made randomly by a beam splitter in the original experiment but it's conceivable that the experiment could be adjusted so that a person could make the decision so why can't I send winning lottery numbers back to myself the reason is that there's absolutely no way to tell if any given photon at the interference screen has a known path until you compare the results of the screen with the results at the detector in fact the distribution of photons at the screen always looks like a single blurred distribution there's no visible interference pattern at all it's only when you flag which photons have twins arriving at protectors a B C or D that you see patterns arise in fact even if you remove all of the a and B photons you still don't see an interference pattern until you distinguish C versus D and this is because those photons have interference bands that are exactly out of phase the peaks of C line up with the troughs of D and together they look like the same sort of blur you get if you combine a and B this is pretty insane the photon positions are decided and presumably those patterns are embedded in the distribution those embedded pens are set by the eventual destination of the entangled partners of those photons but the distribution may be in place long before those twins finish their journey yet we can't extract the patterns of the photons that landed at the screen until we get the information of which detectors they're entangled twins hid that information can't travel backwards in time or faster than light so unfortunately this means the information about the winning lottery numbers remain embedded in the pattern and lost to us until after the numbers of draw if your name appears below you've got this right and described your reason well you guys should email your names addresses us t-shirt sizes so small medium large etc to PBS space time at gmail.com also let us know which of these t-shirts you wants we'll send it right out to you for the rest of you you can still grab a space/time t-shirt of your very own via the link in the description okay that's the answer but there's still time for a mini rant about the role of consciousness in quantum mechanics the delayed choice in this experiment is whether or not to know the path of the original photon or whether to erase that knowledge but don't take this too literally we don't need to invoke conscious knowledge to explain the results if either detectors a or B are triggered then there's an asymmetry in the global wavefunction passing through one slit versus the other and this can lead to decoherence admittedly this decoherence appears to affect the wavefunction at times before the apparent cause of the decoherence but this doesn't end up violating causality and so it's way less out there than photon somehow knowing that in the future some conscious mind will know its path frankly it's all just so weird and amazing amazing enough without inventing mystical interpretations that somehow give us psychic wavefunction collapsing powers as much as we'd all like to believe we have them nonetheless there is a clue somewhere in all this weirdness to the fundamental workings of space-time [Music] you [Music]