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00:00 Time travel has long captured the imagination of scientists and science fiction enthusiasts
00:05 alike.
00:06 The concept of travelling to the past, reliving historical moments, or correcting past mistakes
00:10 has been a recurring theme in literature and cinema.
00:13 But could it ever actually happen, or is it just a fantastic idea confined to the realms
00:17 of science fiction?
00:18 In this video, we'll delve into a fascinating world along the bleeding edge of theoretical
00:23 science, exploring how it might work, the potential applications, the paradoxes it presents,
00:29 and the technologies that would need to be developed for it to become a reality.
00:33 This is Unveiled, and today we're answering the extraordinary question; is backwards time
00:37 travel possible?
00:41 Do you need the big questions answered?
00:43 Are you constantly curious?
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00:50 To understand whether backwards time travel is possible, we first need to explore the
00:54 underlying principles and theories that might make it conceivable.
00:58 At present, the frameworks for time travel are mostly rooted in the realm of theoretical
01:02 physics and general relativity.
01:04 One of the most prominent theories involves the concept of wormholes - hypothetical cosmic
01:08 tunnels that connect any two points anywhere in space and time.
01:12 And while they're purely theoretical, the equations of general relativity do allow for
01:17 their existence.
01:18 If we could then manipulate a stable wormhole, it might serve as a bridge between different
01:22 points in time.
01:24 And then, travelling through that wormhole would enable us to access both the past and
01:28 the future.
01:29 Or that's the general theory, anyway.
01:31 All we need to do now is build or discover a wormhole to work with.
01:35 In the meantime, there are other potential methods that could also send us back to the
01:38 past.
01:39 Faster-than-light, or FTL, travel is another long-dreamed-for breakthrough that one day
01:44 could see us bending the temporal rules.
01:46 Of course, according to Albert Einstein's theory of relativity, nothing can move faster
01:50 than the speed of light in a vacuum.
01:52 However, and despite that, there are theoretical constructs, like tachyons - hypothetical faster-than-light
01:58 particles that could, in theory, allow for time travel.
02:01 Tachyons, if they do exist, are always travelling at FTL speeds, which means that they have
02:06 the potential to break fundamental causality in physics - meaning that the rules of cause
02:11 and effect no longer apply.
02:13 How exactly we'd use tachyons, if we could harness them, isn't entirely clear… but
02:18 some believe that they could pave the way towards jumping forwards, certainly, and backwards,
02:23 possibly, in time.
02:24 Importantly, and in general, the concept of FTL travel is highly speculative.
02:29 But it remains a topic of interest among physicists and would-be time travellers.
02:33 So, whether it's wormholes or FTL strategies, we do at least have some options to experiment
02:39 with.
02:40 And, indeed, there are studies ongoing in the here and now to turn time travel into
02:44 more than just a sci-fi storyline.
02:46 So, let's jump forward a little to imagine what would happen next if travelling back
02:50 in time was ever available.
02:52 Clearly, it would have a profound impact on various aspects of our lives and the world
02:57 at large, with intriguing applications across a range of fields.
03:01 Number one, historical research and education.
03:04 Imagine being able to witness historical events first-hand, rather than just reading about
03:08 them or watching a dramatised documentary.
03:11 If backwards time travel were here, then historians, researchers and, well, anybody would now have
03:16 been able to intimately observe all of the most significant moments that have ever happened,
03:21 gaining an unparalleled understanding of the past.
03:24 Then again, would all of those events happen in the same way, if time travel does ever
03:28 arrive?
03:29 It's a problem that we'll explore more in a moment.
03:32 Number two, catastrophe prevention.
03:34 Backwards time travel could potentially be used to stop or manage natural disasters or
03:39 other catastrophic events by altering key decisions and circumstances in the past.
03:44 For example, picture how an evacuation might be different if a hurricane or storm wasn't
03:49 only forecast to happen, but was literally foreknown.
03:52 There would still be a huge logistical challenge, but the entire thing would now be operating
03:57 on 100% certainties, without any unknowns.
04:01 Number three, the possibilities for temporal medicine.
04:04 Medical practitioners might use time travel to correct historical health issues or provide
04:09 treatments that were not available at the time, and in doing so could save countless
04:13 lives.
04:14 Backwards time travel would allow for today's medicines to be administered for sufferers
04:18 of yesterday's illnesses and plagues, as well as future medicines arriving to battle today's
04:24 conditions and problems.
04:25 Although, again, what might the repercussions be for such a dramatic alteration?
04:29 Finally, number four, personal time machines.
04:33 Individuals could use backwards time travel to revisit cherished memories, correct past
04:37 mistakes, or simply to relive moments of their lives.
04:41 Here, backwards travel amounts to the ultimate form of nostalgia and potentially of self-improvement.
04:47 There may even be some uses toward regaining memories to help with dementia, Alzheimer's
04:51 disease, or amnesia.
04:53 While the idea of backwards time travel is undoubtedly tantalising, however, it also
04:58 presents several paradoxes and challenges that need to be addressed.
05:02 The grandfather paradox is perhaps the most famous time travel conundrum.
05:06 It posits that if you were to travel back in time and prevent your own grandfather from
05:10 meeting your grandmother, then you would never be born.
05:13 This creates a paradox, because if you're never born, how can you travel back in time
05:17 to prevent your grandparents from meeting in the first place?
05:20 There's also the issue of causality loops - infinite, circular chains wherein events
05:25 in the past and future happen over and over again, because they rely on the existence
05:29 of time travel in the first place.
05:32 And again, quite famously, there's the butterfly effect, wherein small changes in the past
05:37 can have unpredictable, far-reaching and potentially major consequences in the future.
05:42 More broadly, even well-intentioned alterations, big or small, such as saving millions with
05:47 modern medicine, could lead to unintended and disastrous outcomes.
05:52 What's apparent is that this is not as simple as being a straight-up wonder technology.
05:56 There are various concerns at play.
05:59 Maybe it's a good thing, then, that we're not there yet.
06:01 And actually, not by quite a distance.
06:04 Yes, wormholes and FTL travel could make all of this possible… but how do we get there
06:09 to start?
06:10 If backwards time travel were to ever become a reality, it would necessitate the development
06:14 of advanced technologies and a profound understanding of the fabric of the universe.
06:19 First off, we'd probably need wormhole manipulation capabilities.
06:22 We'd need to know how to create stable and controllable wormholes as a cornerstone of
06:27 time travel technology.
06:28 We'd need to work out how to open, maintain and navigate through these cosmic tunnels.
06:33 Secondly, we'll need exotic matter.
06:35 It's thought that wormholes, if they are to exist, may require exotic matter with negative
06:41 energy density to keep them from instantly collapsing.
06:44 Developing and harnessing exotic matter, though, would be a monumental challenge… and it's
06:48 something that we haven't really even begun to do right now.
06:52 And thirdly, there's the challenge of energy.
06:55 First, how do we propel ourselves to a future time when all of this is even conceivable?
06:59 And then, how do we fuel all that we need once we get there?
07:02 For many, the key could lie in our gaining a deep understanding of quantum mechanics.
07:07 Only then, with quantum mastery, could we ever claim to wield enough energy potential.
07:12 In other words, time travel in real life could well demand that we somehow learn to control
07:16 and access every single particle of reality.
07:20 If you've got ideas on how we might do that, then let us know in the comments.
07:24 Or perhaps think about patenting it, because that is incalculably valuable knowledge.
07:29 For now, backwards time travel remains one of the most captivating and challenging concepts
07:34 in theoretical physics and science fiction.
07:37 But while the idea of revisiting the past is alluring, it's essential to recognise
07:41 the significant hurdles and paradoxes that must be overcome.
07:45 Do you think we'll ever get there?
07:47 Are wormholes enough to make it happen?
07:49 Could FTL travel allow us to not only move into the future, but also to anchor back to
07:54 history?
07:55 And what would you do if it were possible?
07:57 If you could choose one place or moment to travel back to, what would it be?
08:02 Some will choose the most massive and influential points in time.
08:05 Key dates in human history.
08:07 The arrival of the asteroid that killed the dinosaurs.
08:10 The emergence of life itself on Earth.
08:13 Others will opt for a more personal journey.
08:15 To more simply revisit events and people that they once knew.
08:19 Ultimately, the possibilities are endless.
08:23 What do you think?
08:24 Is there anything we missed?
08:25 Let us know in the comments, check out these other clips from Unveiled, and make sure you
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