What if you make a faster-than-light phone call?

oh hello i'm award-winning science educator in walmart jason mamoa kyle hill you know it's not easy keeping a world-class artificial intelligence like arya here up and running especially when you're banned from most of the world's universities for unspecified reasons that's why thankfully today's episode is brought to you by skillshare skillshare is an online learning community centered around thousands of classes and courses that inspire creativity and creation i just finished demystifying artificial intelligence understanding machine learning by christian hellman senior developer at microsoft and it gave me the fundamental knowledge to ensure that arya will be super computing and q bitten for years to come if you want to try skillshare like i did the first thousand of you nerds to go into the description below get to try skillshare premium for free on me and after that it's just about 10 bucks a month you're welcome now on to today's episode don't ask about the university thing episode time one day in 1907 albert einstein had an interesting thought as he often did if we could send messages fast as the light then theoretically we could telegram the past he thought but how would something like this be possible could we ever create an anti-telephone [Music] oh yeah no they're called minkowski diagrams yeah no problem bye that guy sounded a lot like me now entering the facility one of the most beautiful things about math and science as a whole to me is their ability to take something as infinitely complicated as the universe and simplify it down so that even a hairless ape on a galactic backwater can somewhat understand it one of the most powerful examples of this simplification is the diagra wait what are those called yeah hey what are those diagrams called again right thanks one of the most powerful examples of this simplification process is the so-called minkowski diagram this is a space-time diagram that looks very simple but if you put yourself at the origin of a graph make the x-axis space the y-axis time and give everything a speed limit according to the speed of light and these few lines describe everywhere you could possibly go in this universe past present and future pretty powerful right well it was these diagrams that einstein was thinking about when he was theorizing messaging the past but to see where einstein really got this idea in full we should delve a little bit more into our diagrams oh all right just let that go to voicemail it's probably some weirdo in pants that aren't as casual i like comfort like we said a so-called minkowski diagram can very simply show all of space and time it's in three dimensions and not four because one spatial dimension is suppressed to include time and i can't even show you what something in four dimensions looks like but you can imagine how you can go forward and back up and down left and right in space while time moves forward or up in this diagram the speed of light is usually put on these diagrams at a 45 degree angle for simplicity's sake and it represents distances that are untraversable in a certain amount of time rotate this boundary in three dimensions and you get what physicists call a light cone the region of space-time that contains everything that could be causally connected for an observer because information is also bound by the speed of light because the speed of light is the fastest anything travels everything every event occurrence or phenomenon outside of your light cone is impossibly inaccessible to you even if you really really wanted to go to glee max's party tomorrow night orbiting the fifth planet elf centauri sorry buddy you're not going it's elsewhere i'll tell them that you wanted to go though and that you were bringing spinach dip which they love out there still with me cool attendance is mandatory now imagine what it would look like in a diagram like this for me to make a phone call say i want to call one of my kevins who is some distance away from me in space and time i make the phone call and some finite it they're not picking up i hope they don't think i'm some kind of weirdo anyway i make the call theoretically in some finite amount of time later they pick up the phone or not in space-time speak we would say that me calling kevin causes kevin to pick up the phone or not the two events are causally linked in this way and this makes some intuitive sense to us things start to get weird though when events aren't so causally linked you better call me back too as we're going through this you can't just millennial ghost me i saw the red text receipt you're not fooling anyone the core insight of einstein's theories of special and general relativity was that no matter the observer no matter how they're moving if they are moving with a constant velocity accelerating or standing still the speed of light must be measured as equal for all of them in all possible reference frames arya you can remove the mustache now i like your funny words mustache man to accommodate what would become this fact einstein theorized that if you move at or near the speed of light space-time the fabric of space and time must warp itself around you if it didn't different observers moving differently would start disagreeing about how fast light traveled and therefore about causality itself this space-time warping embedded in our diagrams we've been going through is the direct cause of some weird physics-y results that you may be already familiar with from time dilation to me when i'm getting out of a pool and it's these effects and this space time that einstein was thinking about when he imagined an anti-telephone oh all right tell him i'm not here tell him i'm i'm busy dressing up as a giant vampire woman he'll have to believe that why wouldn't he many things stand out about einstein and his intellect of course but one of the most amazing things about him to me was his almost uncanny ability to use simple thought experiments to come up with some of the most revolutionary ideas ever case in point in 1907 the same year he was thinking about anti-telephones he was sitting at his desk in the patent office and he had reportedly the happiest thought in his life that happy thought was a dude like me across the street falling to his death from the roof who had made that thought so happy however was that einstein realized with no other reference points the falling man in free fall wouldn't be able to tell if he was under a gravitational force or not whether he was accelerating or not and because of this reference frame difference einstein started thinking of gravity not as a force itself but as a curvature to space-time a dimensional fabric and indeed this is how we understand the universe and gravity today all of this from a thought experiment over a hundred years ago from some dude with an awesome mustache at his desk thinking about a guy like me falling to his death that's incredible oh i should oh i should tell kyle if he oh does he know that story he better not be ducking my calls who doesn't have their voicemail set up in 2021 what year is this oh it's 2020. now that we know some of the fundamentals here we can get into how an anti-telephone is supposed to work and it's going to involve drawing our simple minkowski diagrams again but remember this time that space-time warps to accommodate the immutable speed of light so again i'm going to draw our simple diagram starting with both space and time for me and kevin here's our space and time i'm going to draw the speed of light boundary here in yellow and here's what we're going to do differently this time instead of sending a communication some information a phone call to kevin some vast distance away slower than the speed of light what are we using qriket wireless i don't know why i'm taking shots we're gonna send that signal faster than the speed of light and look how it crosses the light speed boundary and goes into elsewhere so sometime later in my future i send this red signal to kevin faster than the speed of light now on the face of it this looks all hunky-dory do people still say that i'm sending a signal just happens to be going faster than the speed of light kevin still receives it some finite amount of time later that's cool right wrong we're not considering like einstein foot the relativity of the situation now suppose that one of the many enemies i've made here with my work at the facility is trying to snoop on my communications to kevin they get in a spaceship with the hope of intercepting my signal to them so again the important thing to realize here is that when they get in the spaceship and start traveling quickly space time is going to warp for them so now i'm going to draw this spaceship's time and space as it changes here is where the anti-telephone weirdness comes in i'm now going to draw planes of simultaneity in this warp space-time and superimpose it on my call to kevin okay now do you see the issue in this warp space-time from this perspective of my enemy in this ship they actually encounter the signal in their space-time before it was sent in mine to them they encountered this message before it was sent so if something which we call an anti-telephone could send messages faster than the speed of light then from a certain point of view those messages could arrive before anyone sent them it's like messaging the past literally you could call yourself in the past and tell yourself to buy all that dogecoin or you could tell yourself in the past to stop talking about dogecoin before your marriage imploded that'd be nice but how theoretical is a anti-telephone-like device like this i mean could we actually build something like this oh yeah no hey i can talk no they don't look like that close though oh man oh i should call einstein on this thing a lot of our favorite science fiction depends on the existence of faster than light communication for example it would be downright impossible for a efficient galactic federation to exist when ships are half a galaxy apart without ftl comms science fiction and science fact alike has tried to get around this problem by stipulating the existence of faster-than-like particles like tachyons that could therefore transmit information at this faster than light velocity but while tachyonic anti-telephone is one of the coolest things that you could possibly say there has never been any evidence for anything like tachyons and their existence is wholly theoretical so we can't really make an anti-telephone today even if we could the problem is still that they would violate causality itself and the universe doesn't seem to like that kind of thing like you being able to phone yourself in the past to tell yourself in the future not to call yourself in the past but then how you in the future would call you see it's an issue at least with everything that we've learned today you can see why ftl communication is such a big obstacle for science fiction to get around and how all of this started with a simple thought experiment over a hundred years ago einstein was a pretty smart dude until next time very funny aria you think i want to talk i guess all the time it's not even fun to do i'm not even sure what accent this is anymore now exiting the facility thank you so much to the vera nerdy staff at the facility for their direct and substantial support in the creation of this here video today especially i want to recognize research assistant rodney and visiting scholar sean files duggan if you want to join the facility if you want to drape on a silky white lab coat if you want to get episodes early behind the scenes photos you want to talk to me every day in discord you want private members only live streams with yours truly not like that you can go to patreon.com kyle hilly and join the facility today and hey if you support the facility just enough get your name on alright here each and every week and as you can see there's literally hundreds and hundreds of you so i have no idea just a second i'm gonna make a phone call real quick hey can you talk yeah i bet you're but you're talking to some real dweebazoid looking nerdos huh okay love you bye oh this is an anti-telephone i know what i said but if you go back in the episode and you the order is it's always the future calling the pet i got it right go ahead check thanks for watching yeah no i'm still here yeah that was pretty sick

Channel: Kyle Hill

Views: 280,018

Keywords: because science, engineering, kyle hill, learning, math, physics, science, stem, the facility, einstein, relativity, antitelephone, minkowski diagram, light cone, tachyons, because science lightsaber, because science chernobyl

Id: wOvc5JdE-Gk

Length: 13min 46sec (826 seconds)

Published: Fri May 14 2021

Reddit Comments

[u/LateStageBureaucracy]

No matter how hard i try, I cannot wrap my mind around how FTL is time travel. My best guess is that it seems like an illusion from an outside viewer's perspective.

I still think FTL is impossible for a different reason. The technical, and energy requirements are so insanely gigantic that no civilization in the Universe's existence has either reached that level, or just doesn't bother with it as it's impractical compared to STL.

[u/MiamisLastCapitalist]

I've struggled to understand why any FTL drive would be considered a time machine, but I think Kyle is illustrating why at almost exactly 10:00.

IF SO my follow-up question is... Why is this useful or impactful? Because time and space are relative, and the events over there aren't effecting me over here (yet?). They are still separate frames of reference, right?

[u/McNastte]

I didn't watch video but a way I have been thinking about ftl as time travel is by considering relativity and the constant movement of all things and if you could move faster than light you would be getting to a place before the universe gets there