- 7 weeks ago
- #brightside
- #brightsideglobal
In this video, we will explore the concept and the paradoxes of time travel, and whether it is theoretically and practically feasible. We will also learn about the scientific and philosophical arguments for and against the possibility of traveling to the past or the future. #brightside #brightsideglobal TIMESTAMPS: 0:01 Faster-than-light effect 08:07 Time travelers exist 17:25 5 Ways to time travel This video is made for entertainment purposes. We do not make any warranties about the completeness, safety and reliability. Any action you take upon the information in this video is strictly at your own risk, and we will not be liable for any damages or losses. It is the viewer's responsibility to use judgement, care and precaution if you plan to replicate.
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00:00As you may know, light is the fastest thing in the universe – 186,000 miles per second.
00:06A flight on an ordinary plane around the Earth would take about 50 hours,
00:10while a flight around the Earth at the speed of light would only take 0.134 seconds.
00:15But is it possible to travel even faster than that?
00:19Well, we can certainly try.
00:21This is an idea called faster-than-light travel, or FTL for short.
00:25This is what powers the coolest space stories, like Star Wars, where ships like the Millennium Falcon defy the rules
00:32of nature with their hyperdrive engines.
00:34Or think of Star Trek with its USS Enterprise and its warp drive.
00:39FTL would allow us to explore all the uncharted galaxies, maybe even meet some extraterrestrial life.
00:45In 1905, Albert Einstein introduced his theory of special relativity.
00:51This theory revealed some very important ideas.
00:53We learned that FTL travel could lead to some weird consequences.
00:58Let's imagine that you're in a starship, and someone is standing still and watching you from the outside.
01:04You try to go faster than the speed of light.
01:07To the observer, it seems like something really weird is happening to your spaceship.
01:11As you go faster, they see it like a sausage, squishing and getting shorter and shorter in the direction you're
01:17moving.
01:18This squishing effect is what scientists call length contraction.
01:22This isn't the only weird effect.
01:23Relativity also tells us that time starts acting really weird when you go that fast.
01:29As you speed up, time slows down for you, compared to someone watching from afar.
01:35So, the faster you go, the slower time feels for you.
01:39For you, it feels like just a few minutes have passed.
01:42But back on Earth, years have flown by.
01:45And if you have a family member patiently waiting for your return, that person ages a lot more than you
01:51do.
01:51So, when you finally come back to Earth, you might see that they became very old while you haven't aged
01:58at all.
02:04So, the faster you go, the more time dilation grows.
02:25Which means, when you go FTL, time might decide to go backwards.
02:30This happens because the math says you end up with a weird minus 2 result.
02:35In other words, going faster than light can actually lead to an accidental time machine.
02:40This opens a room for different problems and paradoxes.
02:44For example, let's say you showed up in the past and see yourself.
02:49Your own past self looking back at you.
02:52So, if you high-five them, who started the high-five idea in the first place?
02:56There's also a famous grandfather paradox.
02:59For example, if you go back in time and accidentally stop your grandparents from meeting,
03:04this means your parents are never born, so you shouldn't exist either.
03:08Sort of like the movie Back to the Future.
03:10But if you don't exist, how could you have gone back in time to stop your grandparents' meeting?
03:16Or the bootstrap puzzle.
03:18Imagine you travel back in time and give Beethoven his own music before he even writes it.
03:24He becomes famous for that music, but where did it really come from?
03:28Did you make it, or did Beethoven give it to you?
03:32All these crazy questions make us rethink how time works.
03:36However, these aren't the only things the theory of relativity teaches us.
03:40It also says that real life isn't sci-fi movies.
03:43And the way we understand how the universe works makes it pretty tough to do the FTL stuff.
03:49There are several reasons for that.
03:51First, when you travel so fast, you really bend the fabric of space-time.
03:57So let's imagine space-time as a big, flat piece of fabric.
04:01Objects with mass, like planets and stars, create dents or depressions in this fabric due to their gravity.
04:07In the normal way of traveling through space, you move along the fabric,
04:12following its curves and dips at a speed that's limited by the speed of light.
04:16But if you want to exceed it, you essentially need to find a way to cheat the rules of the
04:21game.
04:22You'd be like a magician who can warp or bend the fabric itself to create shortcuts.
04:28Basically, you fold the fabric in such a way that two distant points on the sheet come close together.
04:34This creates something called wormholes.
04:37Think of them as secret shortcuts that could connect different parts of space.
04:41If we could figure out how to use these wormholes, we could shortcut from one point of the universe to
04:46another.
04:47However, we haven't found any in space yet, and we have no idea if they can even exist at all.
04:55Another trick is that if you start going faster and faster, your spaceship gets heavier.
05:01It's like trying to sprint with a backpack filled with rocks.
05:04The more you try to run, the more tired you get, the heavier the backpack feels,
05:09making it harder and harder to pick up speed.
05:11No matter how much you push, you can never quite reach the speed of light
05:15because your spaceship's mass, its weight, keeps increasing into pretty much infinity.
05:21And finally, there's the photon paradox.
05:25Photons are tiny particles of light.
05:27The reason we see things is because photons reach our eyes.
05:31But when you decide to go FTL, these little particles quit their jobs.
05:36What happens next is a big mystery.
05:39Maybe your spaceship and everything inside falls apart into dust.
05:43Everything inside your ship probably goes haywire and causes pure chaos.
05:49All these things show that no matter how hard you try, you can never outrun the speed of light.
05:56Which is why most scientists think going faster than light is probably impossible,
06:01as well as time travel and all that good stuff.
06:04But there are still those who dream about it.
06:06For example, in the 1990s, Sergei Krasnikov had come up with the Krasnikov tube,
06:13pictured as a kind of super-fast subway for space travelers,
06:17where you can hop in and zip to your destination in a flash.
06:21But as you can see, we haven't built it yet.
06:24The problem is we need something called negative energy.
06:27Negative energy is a strange kind of fuel that only exists in math problems, not in real life.
06:33So, until we figure out how to make this make-believe fuel,
06:37these amazing spaceship ideas are still just dreams.
06:41And to build something like wormholes, we would need a negative mass.
06:45This is exactly what it sounds like.
06:47An object that not only doesn't weigh anything, it has a negative weight.
06:52What in the world does that mean?
06:54We have no idea.
06:55The main thesis is that if you pushed an object with negative mass away from you,
07:00it would accelerate towards you instead.
07:02And we really need that to teleport from one point of the universe to another.
07:07So, until we create this super-weird thing, we won't be able to do that.
07:12Another scientist named Eric Lentz also made something like a warp bubble.
07:16But it would take an incredibly huge amount of energy, like eating hundreds of Jupiters.
07:21However, NASA is still really interested in his idea,
07:25and they're hoping to solve the energy challenge with new discoveries.
07:28Meanwhile, a group of researchers from the University of Adelaide
07:32has been working on finding a way to bypass Einstein's equations.
07:36They want to remove the light speed limit entirely.
07:40And their early results show promise.
07:42Well, let's see if they figure it out eventually.
07:45In any case, traveling faster than light is still a wild dream and a big mystery.
07:50For now, we have no idea how to do that without breaking the laws of physics.
07:55But that doesn't stop us.
07:57We'll see what scientists come up with in the future.
07:59Until then, please have patience waiting in line at the airport for your flight.
08:10You know how Stephen Hawking said,
08:12The best evidence we have that time travel is not possible and never will be
08:17is that we have not been invaded by hordes of tourists from the future.
08:22But what if these tourists come to our time, but they do it secretly?
08:27You may even have met one of them.
08:30Let's see the most famous time travelers.
08:35Meet Orin.
08:37He's a cyborg who came to us from the year 2050 to stop the coming end of the world.
08:42In 2020, he appeared on a TV show where he said the whole world was inside the Matrix.
08:49Then he hit the headlines and gave an interview to a popular YouTube channel.
08:54As proof that he's a cyborg, he demonstrated his robotic voice,
08:58which can be made in a simple computer program.
09:02He also called himself We because he declared himself a collective consciousness
09:08that had come to save humanity.
09:12Orin became famous for his predictions about the near future,
09:16but it turned out that many experts had already announced these forecasts earlier.
09:20He also said that a huge corporation was suppressing humanity and we were inside a complex computer simulation.
09:28If we don't improve or care for each other and nature, the end will begin in 2050.
09:34Orin no longer appears on major shows,
09:36but he has a small fan base of people who love all sorts of fantastic theories.
09:45Another time traveler is Adam Archen, who came to us from 2045.
09:50There was an interview with him on YouTube where he shared some details about the future of the US,
09:56after which the video went viral and hit the lines in many newspapers.
10:02Archen reported that the last official president of the country would be the daughter of Martin Luther King III,
10:10and she would become the greatest US president in history.
10:15Another exciting event that Archen announced is supposed to happen in 2028.
10:20He said that people would learn about the existence of extraterrestrial civilizations.
10:25He added that these creatures wouldn't come from outer space.
10:29The traveler also noted that the world would switch to a single digital currency,
10:34and all cash would disappear.
10:37Of course, no one believed him, so the experts conducted a lie detector test.
10:42And Adam Archen successfully passed it.
10:45He said that he had a chip in his hand to facilitate time travel.
10:49An extraterrestrial civilization would arrive on Earth in 2028,
10:54and in 2045, people would be closer to robots.
10:59The lie detector didn't state that Archen was lying,
11:02but this doesn't mean he told the truth,
11:04since the device can be deceived with the help of special training.
11:08In any case, in 2028, we will find out whether Archen was right or not.
11:16All these time travelers arrive in the past and, for some reason, don't use knowledge from the future.
11:22What would you do if you could go back 50 years?
11:26Perhaps you would invest money in shares of some young company that will become a big, expensive corporation.
11:32In that case, everyone would believe that you really came from the past.
11:37And by the way, one guy did it.
11:39He invested $800 in the stock exchange and made $350 million out of it.
11:46This guy's name was Andrew Carlson, and he hit a big jackpot in 2003.
11:53However, he didn't manage to enjoy a rich life because the FBI came for him.
11:59Andrew sold some stocks and bought others and did this very successfully.
12:02Thus, in a few months, he became a millionaire.
12:07The Securities Commission couldn't believe in such coincidences, so it called the FBI.
12:14During the interrogation, everyone was sure Andrew would begin to justify himself and say he was lucky.
12:21But instead, he calmly replied that he came from the year 2256 with the help of a time machine.
12:29Of course, no one took it seriously.
12:32But when the FBI started looking for information about this man, they found nothing.
12:38Andrew Carlson had no documents.
12:40He was not in any database.
12:43He just appeared out of nowhere and started making a lot of money.
12:47He was interrogated for about four hours, and he behaved pretty calmly.
12:52It seemed as if he was telling the truth.
12:54However, he didn't tell them the time machine's location.
12:59When the press found out about this man, he immediately became a celebrity.
13:04Well-known news sites began to write about Andrew Carlson.
13:08Articles have appeared in Japan, Australia, Germany, the UK, and other countries.
13:13And of course, journalists started calling the FBI to find out more details about this guy.
13:19And the FBI told them that the whole story was fiction and that there was no Andrew Carlson.
13:25Information about him appeared on an internet resource known for its fake news.
13:31At some point, the article about the time traveler somehow got into Yahoo, where it went viral.
13:37So, as we see, all statements about time travelers are either fiction or a lie.
13:44Conversations about such travels appeared thanks to fantastic films and books.
13:49Pop culture has greatly influenced this fantastic concept and created several theories claiming that time travel is real.
13:58And some people believe that, especially those who are far from science.
14:03But what do real scientists think about this?
14:05Are such trips really possible?
14:07Let's try to find out.
14:11Scientists say, yes, time travel is real, because we're now traveling in time.
14:16Time is moving forward, and we're moving with it.
14:19We call it a journey.
14:21But if we need to get into the future or go back to the past, everything is much more complicated
14:27here.
14:28Remember Einstein's little theory of relativity?
14:31It says that time moves relative to the observer and has no constant value.
14:36To understand better, here's a simple example.
14:40Ten hairs on your head.
14:42Is it a lot or a little?
14:44Ten hairs in a bowl of soup.
14:46Is that a lot or a little?
14:48Everything is relative and depends on the conditions.
14:52The same thing happens with time and space.
14:55If we move at a tremendous speed, close to the speed of light, then time slows down for us.
15:02The perception of time becomes different for a person who's running and for one who's standing still.
15:08If we're near some heavy object, let's say a thousand times heavier than the sun,
15:13then the time next to this object also slows down, thanks to its strong gravity.
15:20In this sense, time travel is possible.
15:23If you're an old person and meet your friend as young as he was 50 years ago.
15:28Why are you so young?
15:30Oh, I've been flying in space at a tremendous speed all this time, that's all.
15:35But this doesn't mean that this friend just sat on the ship for 50 years and didn't age.
15:41No, time was different for him.
15:43Ten years for you on Earth is a long period of time.
15:46But for him, these ten years passed like half an hour.
15:51Gravity and speed bend time.
15:54For this reason, astronaut Scott Kelly, who spent a year and a half in orbit,
15:58became five milliseconds younger than his twin brother after coming to Earth.
16:05All this time Scott spent inside the ship flying in orbit at high speed,
16:09and he was also further away from the gravitational center of the planet.
16:14So, time was slower for him by five milliseconds than for his brother.
16:19Objectively, time always runs at the same speed.
16:22But its speed changes inside the perceptions of different observers under different conditions.
16:27That's what the theory of relativity is about.
16:31But what about jumping into the future or the past, like in movies?
16:36Wormholes will help you with this.
16:37This is something like tunnels that pass through space and time
16:41and can connect different time segments in different places in the universe.
16:46They are like cheat codes that can break the laws of the universe.
16:50Wormholes are elusive, have different sizes, are unpredictable, appear in space, and vanish.
16:56But their main problem is that wormholes only exist in theory and sci-fi
17:01and have never been noticed in our universe by scientists.
17:06Okay, so you've seen the movies and read the books on time travel.
17:10Most of them tell stories about entering some futuristic boxes.
17:13And in the blink of an eye, you're in some different epic.
17:18For now, this is just sci-fi.
17:20But there are ways to make time travel possible, at least theoretically.
17:25We just don't have the technology figured out yet.
17:28For starters, time travel to the future could be achieved by traveling at high speeds.
17:33But not just getting a ticket on the superhighway kind of speed.
17:37This is based on Einstein's theory of special relativity.
17:41It explains that time slows down for objects that move at really high speeds.
17:46And the good news is scientists have already tested this theory, and it looks promising.
17:51They did it with the help of two identical clocks.
17:54One was placed on a jet, and one stayed on the ground.
17:57They found that the clock on the jet ticked slower than the one on the ground
18:01because of how fast the jet was moving.
18:03The faster an object is moving, the more time will slow down for it.
18:08Currently, the fastest speeds achieved by human technology
18:11are seen in a special type of particles called neutrinos.
18:15Some of these can move at almost the speed of light.
18:18At these speeds, one second for the protons is equal to 11 months for us.
18:23Now, we might be able to time travel to the future with the use of gravity, too.
18:28This idea is based on Einstein's findings,
18:31namely his theory of general relativity.
18:34This theory explains that the stronger gravity is, the more slowly time moves.
18:39This means that as you get closer to the center of the Earth,
18:42the strength of gravity increases.
18:44And if you think about it like that,
18:46time actually passes more slowly for your feet than for your head.
18:50Now, is that why I'm always late for stuff?
18:52Hmm, good excuse.
18:54This effect has been measured, too,
18:56with the help of the same strategy with two identical clocks.
18:59Scientists placed them on shelves at different heights
19:02and measured the rate of ticking.
19:04The clock on the lower shelf ticked more slowly
19:07because it experienced a slightly stronger gravity.
19:10But this option comes with a catch.
19:12To be able to travel to the far future,
19:15you'll need to find a place with extremely strong gravity,
19:18like a black hole.
19:20That's a point in space where the gravity has so much force
19:22that even light cannot escape it.
19:24There, gravity becomes so intense that matter gets squeezed into a tiny space.
19:30The closer you get to the black hole, the more slowly time moves.
19:33However, traveling via a black hole is very dangerous.
19:37Mostly because it's a one-way ticket.
19:40Once you cross its edges, there's no coming back.
19:43Now, here's a fun fact.
19:44The GPS systems we use on our phones and in our cars
19:47already have to account for time dilation effects in order to work properly.
19:52That's because of the speed of the satellites they use
19:55and the gravity they feel here on Earth.
19:58Without these corrections,
19:59your phone's GPS wouldn't be able to pinpoint your location on Earth very precisely.
20:04Meanwhile, the third option has less to do with the universe's unknown forces
20:09and more to do with our own bodies.
20:12Scientists are trying to find ways to time travel to the future
20:15by slowing down the body's own processes.
20:18It's not time travel, per se.
20:20You wouldn't technically be going anywhere.
20:22But if your body stays put for a long period of time,
20:26you could eventually wake up in the future.
20:29Some animals, like bears and squirrels,
20:31can slow down their metabolism during hibernation,
20:34which means they don't need as much food and oxygen to survive.
20:38Specialists are trying to figure out if humans can do the same thing.
20:42They're working on ways to make people go into a short-term hibernation
20:46for a few hours to begin with.
20:48This could be helpful for medical emergencies, too,
20:51in order to help a person before they can safely get to the hospital.
20:55In 2005, scientists were able to slow down the metabolism of mice
21:00by exposing them to a small amount of special gas.
21:04However, when they tried to do the same thing with larger animals,
21:07it did not work as effectively.
21:09Our fourth option of traveling through time is really unique.
21:13It involves a special type of shortcuts that may exist in our universe called wormholes.
21:19Now, before we move on, let's try to understand what they are.
21:23You'll need to picture two balls and a trampoline.
21:26If there's no pressure applied on the trampoline, it stays flat.
21:30Now imagine the two balls placed on the trampoline symmetrically.
21:34If you look at them from this perspective,
21:36there's no possibility of them ever touching.
21:38But if you put enough pressure on the trampoline between the two balls,
21:43this flexible fabric can stretch so much that the two objects might potentially touch each other.
21:48The same thing happens with stars in different star systems.
21:51They're big enough to curve space around them.
21:54That's why most planets tend to orbit around a star.
21:57The tunnel between those two points would be a wormhole.
22:01These wormholes could be used to travel long distances,
22:04like a billion light years, or even visit different times.
22:07Now, many scientists, like Stephen Hawking,
22:10think that wormholes might appear and disappear but be very small, smaller than atoms.
22:16The problem is that we don't know how to catch one and make it bigger so that people can use
22:21it.
22:21This would take a lot of energy, and we don't know if it's even possible.
22:25Some astronomers say that even if we could find a wormhole and enter it,
22:30it would rapidly collapse on itself.
22:32Even the tiniest bit of extra mass, like that of our bodies, for example,
22:37can result in the wormhole slamming shut, like a rubber band that's been stretched too much.
22:43Now, the fifth solution for time traveling was proposed by an American physicist named Ron Mallet.
22:49It involves one resource that we know for sure is abundant in the universe – light.
22:54The scientist proposed a theory about time travel that would use a rotating cylinder of light.
23:00He believes that if something was dropped inside this swirling cylinder,
23:04it could be moved in both space and time,
23:07similar to how a bubble moves when you swirl it with a spoon in your coffee.
23:11According to Mallet, the right shape of the cylinder could allow for traveling to both the past and the future.
23:17The physicist has been trying to raise money for an experiment to test his theory.
23:22This experiment involves dropping tiny particles, called neutrons,
23:26through a circular arrangement of spinning lasers.
23:29However, other scientists say Mallet's theory is impossible,
23:32and there's no need to test it further.
23:35Well, even if we eventually figured out a way to travel back in the past or to the future,
23:40would it be safe?
23:42Scientists have been talking about a problem called the paradox of time travel for a long time.
23:47The main question is what would happen if you went back in time and did something that changed the future.
23:53However, a new study from researchers from the University of Queensland
23:57says that this problem might not be real after all.
24:01The scientists have done some calculations and found out that even if you had changed something in the past,
24:07the timeline would still end up the same way.
24:09Another variation of this problem is called the grandfather paradox.
24:13Imagine going back in time and preventing your own grandfather from having offspring.
24:19Come to think of it, it automatically means you shouldn't exist in the first place.
24:24If your grandparents didn't have your parents, how can you exist at all?
24:28Well, these days scientists are certain that even if you did experience something like that,
24:33you'd still exist in the present.
24:34That's because the timeline that already exists has a way of adjusting itself,
24:40regardless of where people are in time and what they do.
24:44Or somehow get 1.21 gigawatts in a DeLorean and make like Marty McFly.
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