The Science of TIME TRAVEL to the PAST

this video is sponsored by one dream stay tuned to the end to find out more over 100 years ago in 1915 albert einstein changed the world forever with his theory of general relativity this new groundbreaking theory solved several mysteries including the procession of mercury but people probably could not have anticipated all the other things this theory would subsequently tell us some of the seemingly crazy predictions that have been confirmed by observation and that we've also talked about in prior videos are things like infinite mass density objects called black holes gravitational waves and light bending around massive objects in addition to these confirmed phenomena scientists have been able to find mathematically consistent if not creative solutions to einstein's field equations that can show for example how to build a space-time bubble or warp bubble that could theoretically travel faster than light now the question i want to ask is whether any solutions to these same equations of general relativity can show us a way to travel in time not forward in time because we've kind of figured that out but backward in time in a prior video i looked at how it could be done by traversing a time-like curve around a naked singularity which is an object arising from certain solutions to einstein's field equations it's like a black hole without an event horizon another solution to the same field equations predicts an einstein rosen bridge which is a type of wormhole this is a fascinating possibility because if wormholes are real they could also allow us to travel back in time how can we form wormholes and how would they allow us to travel backwards that's coming up right now wormholes have been a part of science fiction for a long time from star trek to interstellar now while some of these depictions take quite a bit of artistic license some are inspired by actual solutions to einstein's theory of general relativity einstein's field equations are nothing but a tool to understand how matter affects the curvature of space time and how the curvature of space-time affects matter so we can in principle imagine almost any creative space-time curvature that results in a wormhole and then by solving the field equations figure out how the matter in this space time must be configured to obtain that desired curvature so by using a specific configuration of matter and energy we can form a space-time curvature that is like a tunnel or shortcut between two points in space these different points can in principle be very far apart in space or they can also be far apart in time if you can travel between two distant points in space using such wormholes then you can effectively travel from one end of the wormhole point a to the other end point b faster than the speed of light the key is that the wormhole just gives you a much shorter path because it connects two distant points in space via curvature such that you don't need to physically travel within space faster than the speed of light keep in mind that these depictions are for visualization purposes only a three-dimensional wormhole would have entrances and exits that are three-dimensional spheres rather than two-dimensional rings like the mouths of a funnel as you see here it's usually shown this way so that we can visualize it by its 2d analog the actual higher dimensional wormhole is not possible to visualize so now the question is how would this allow you to go backward in time since you're just going from point a to point b very fast you might say i'm just traversing space not time caltech physicist kip thorne came up with a thought experiment to achieve this by the way kip thorne was also the technical consultant in the movie interstellar a good movie which i think got a lot of the science right because of him so here's what kip thorne thought of imagine sometime in the future let's say the year 2200 we create a stable and traversable wormhole and a lab on earth we then take one end of the wormhole and place it on a spaceship that can travel nearly at the speed of light let's say 99.5 the speed of light this is 200 years in the future after all the other end of the wormhole stays in the lab on earth so the spaceship leaves earth and travels 99.5 percent the speed of light a wormhole is such that the astronaut on the spaceship could in principle shake hands through the wormhole with the scientists in the lab regardless of how far apart the two ends of the wormhole are located now the spaceship travels at 99.5 percent the speed of light for a year according to special relativity the clock on the ship containing the astronaut and the wormhole will run slower compared to the clock on earth in fact about 10 times slower this is time dilation so by the time the astronaut returns to earth 10 years will have gone by for the scientists in the lab but only one year will have gone by for the astronaut and the wormhole on the ship so now the astronaut has traveled 10 years into the future the year is 22-10 but biologically he's only one year older now no wormhole is needed for traveling into the future just time dilation due to speed but because the wormhole in the lab 10 years earlier would have its clock synchronized with the wormhole on the spaceship even though the astronaut is physically in the year 2210 he could step into the wormhole on his ship and land in the lab in the year 2201 because only one year will have gone by for the two synchronized wormhole the astronaut would be able to travel back in time by the same token the scientists in the lab in 2201 would be able to step into her wormhole and land nine years into the future she would travel forward in time by the same token the scientists in the lab in the year 2210 would be able to step into the astronauts wormhole and travel back in time to 2201 as well now you might ask what about the wormhole in the lab in the year 2210 what would you see if you looked into that wormhole well presuming both the lab and the spaceship maintained their wormhole and kept it open the wormhole would take you nine years into the future to the year 2219 this would of course require both wormholes to be maintained open for the duration of this timeframe now if the spaceship could travel even faster then it could potentially end up hundreds of years or even thousands of years into the future allowing future humans to go back in time to the point where the wormholes were first created and for humans in the past to go to the future note that you would not be able to travel further back in time than the point when the wormhole was first created in other words the future humans could not travel further back than the year 2200 so this may answer the question if time travel is possible in the future why don't we see time travelers all over the place the answer could be that it's because a wormhole time machine hasn't been invented yet so now the question you might have is this looks great on paper what's the catch how realistic is this wormhole concept well no wormholes have been observed but it is possible that what we observe as black holes may actually be wormholes scientists are working out how they could tell the difference wormholes are a lot like black holes both objects are extremely dense with strong gravitational fields for their size the main difference is that no object can come back out after crossing the event horizon of a black hole not even light but things entering a wormhole could theoretically come right back out in a new paper published in the monthly notices of the royal society russian astronomers suggest that what we believe to be black holes at the centers of some bright galaxies may in fact be wormholes they propose that the way to tell the difference would be in the light signatures we would detect they reasoned that the matter entering one mouth of the wormhole could slam into the matter entering the other mouth of the wormhole at the same time a kind of event that would never happen with a black hole this would produce a spectacular display of gamma rays surrounding the object in a giant sphere whereas black hole gamma rays are ejected in the form of a jet if we don't ever observe any wormholes then wormholes may only exist if we artificially create them given unlimited technology and resources in the future could we do this one theoretical issue is that when you create a wormhole the high gravity near the center where the tunnel connects the two mouths causes it to collapse in on itself as soon as anything with mass or energy enters it this means that even a photon a particle of light could potentially collapse a wormhole in order to hold it open it requires exotic matter in other words matter with negative energy density or negative mass now what the heck is negative energy and negative mass negative mass is like negative one kilogram for example instead of positive one kilogram what does this even mean negative matter should not be confused with antimatter which is just like matter except with the opposite charge antimatter has positive mass and energy negative matter with curve space time in the opposite direction of regular matter two negative matter objects would repel each other instead of attract each other it's not known to exist but this doesn't mean that exotic matter isn't out there somewhere waiting to be discovered negative energy densities however have been shown to exist in the casimir effect where two smooth uncharged plates are attracted to each other due to a negative pressure differential created by virtual particles in the vacuum of space this however would be a very small amount of negative energy the amount needed to hold up a wormhole will be many magnitudes higher than this whether enough negative energy could be created for a wormhole is a question mark there are some proposals by scientists on how to create a wormhole for example in a 2020 paper by juan maldasena and alexi malenkin from princeton university they suggest wormholes could be made if they are charged yes black holes can have a charge but it's probably rare and if they can get a hold of something called dark sector which is a kind of exotic matter that has not been discovered yet so this could be a viable solution there are other scientists that have also proposed creating wormholes by connecting two oppositely charged black holes with cosmic strings to hold their mouths open cosmic strings are leftovers formed in the first fractions of a second after the big bang they're exotic objects no wider than a proton but one inch of their length would outweigh mount everest these have also not been confirmed to exist so we're not sure wormholes exist if we create one artificially we may not be able to produce enough exotic matter to hold it open but even if some future version of us could overcome all the technical barriers to create one we know that at least using the kipp thorne time traveling machine no one could travel further back in time than the moment when the wormhole was first formed if you think about it this makes our existence in the here and now so much more precious doesn't it because we will never be able to relive the moments we're living right now the beauty of earth the sky the moments with your friends and family will never be revisited by any future version of us the now is precious because it will be lost forever in the sands of time i'd like to give a big shout out to wondering today's sponsor i was inspired to make this video after watching a lecture series called how science shapes science fiction by professor charles adler of st mary's college it's a fascinating series looking at the science of popular movies like avatar the adventures and interstellar which i talked a bit about in this video professor adler also thought that movie got a lot of the science right although he didn't think the story was that good i thought the story was great it's a superb course that i highly recommend for movie and science buffs like me one vm is a bigger broader evolution of the great courses plus which you've heard me talk about for years they now have even more mind-expanding college-level in-depth educational courses you can not only enjoy these lectures by professor adler but also some of the best educators in the world will be hard-pressed to find a better online learning service than one dream i myself have been a member for a long time i can't recommend them enough you'll even see my testimonial on the bottom of one dream's homepage it's really easy to sign up right now because they're offering a free trial and you can cancel at any time so there's really nothing to lose if you want to support this channel and freely exceed the depth of your knowledge be sure to click the link in the description and if you have any questions or comments from me please leave them in the comments because i try to look at all of them i'll see you in the next video my friend [Music] you

Channel: Arvin Ash

Views: 114,927

Keywords: wormholes explained, wormhole time travel, time travel, can we travel back in time, wormholes, how wormholes work, how wormholes are created, is time travel possible, kip thorne time travel, kip thorne, the science of interstellar, time travellers, could we create wormholes, how to travel back in time, Einstein's predictions, time dilation explained, time dilation, special relativity, einstein rosen bridge, interstellar travel, time machine, wormholes time travel

Id: mZaG9YqzG6Y

Length: 13min 46sec (826 seconds)

Published: Fri Aug 13 2021