00:00You, of course, know that the Earth is bathed in sunlight every day.
00:05Every day we flicker different light sources on and off, mechanically, without even thinking
00:10about it.
00:11But imagine that one day, you casually flicker the lights off, fall asleep, and wake up in
00:17a completely different era.
00:18Let's see how it happened, and what it has to do with light.
00:23Quantum physics is quite crazy.
00:26Quantum physics is like a movie projected from start to finish, while the quantum world
00:30is like having an ability to take the remote control and manipulate scenes you're watching.
00:36Fascinating and mysterious.
00:38Let's say you have a regular light switch that can be either on or off.
00:43That's like a regular bit in computers, which can be in one of two states, 0 or 1.
00:48But in quantum computers, there's a special kind of switch, a switch called a qubit.
00:53Unlike the regular bits, a qubit can exist in multiple states at the same time.
00:58It can be both 0, 1, and all things in between, like having lights on and off simultaneously.
01:05Yeah, our universe has some weird rules.
01:08This mysterious property, called superposition, allowed us to do something incredible recently
01:14to reverse time back.
01:16At least in a tiny experiment with quantum computers.
01:21It's the autumn of 2022.
01:24Two groups of scientists, one from Oxford and the other from Vienna, decided to conduct
01:28a weird experiment.
01:30They played around with a quantum computer to create a program that reverses time.
01:35They took a tiny electron and tried to make it go backward for a time for just a fraction
01:39of a second.
01:41It would be like breaking a billiard ball triangle where the balls go from order to
01:45chaos and then magically reverse.
01:48But don't get too excited about time travel yet.
01:52Unfortunately, we're not sure if it's possible to recreate it in real life.
01:56The scientists cracked some numbers and found out that if we observed 10 billion localized
02:01electrons every second for the entire age of the universe, we'd only see something
02:06like this happen once.
02:08And it would only take the electron back a tiny fraction of a second.
02:13So they didn't invent a time machine.
02:15They just managed to create this simulation in quantum computers.
02:19There's another catch too.
02:21The larger the simulation, the more complex and less accurate it becomes.
02:25In our experiment, we only used one qubit, and we managed to reverse time.
02:30In a 2-qubit setup, scientists could reverse time only in 85% of cases.
02:36And in a 3-qubit setup, it dropped to 50% with more errors.
02:40If we keep adding more qubits, we won't be able to pull this off at all.
02:44Plus, the success depends on the amount of information the system can store.
02:49For example, teleporting a person would be almost impossible because humans have so much
02:54information inside them.
02:56So unfortunately, no time machine so far.
03:00But there are some possible uses of this discovery.
03:03Reversing qubit states in a quantum computer can help correct errors during development.
03:08Sort of like a little Ctrl-Z in real life.
03:11So it was a tiny step to more exciting discoveries in the future.
03:15For example, recently they demonstrated another crazy little thing – send light itself back
03:21in time.
03:23Now light isn't mere luminary.
03:25It has superpowers that we can't even imagine.
03:28The ancient Greeks believed that our eyes emitted visionary beams.
03:32Sir Isaac Newton proved them wrong hundreds of years later when he conducted his experiments
03:37with prisms.
03:38The prism broke the pure white light into a beautiful palette.
03:42And that's how we found out that light actually consists of tons of different colors.
03:47Many years later, scientists learned even more that light is a wave.
03:51And even later, in the 20th century, we discovered the final paradox – that it's both a wave
03:56and a particle, a dual existence in one photon.
04:01And the more we learn about light, the more crazy things we find.
04:05In 2016, scientists managed to freeze the light in time.
04:10They put photons, the tiniest light particles, in ultra-cold atomic clouds.
04:15Then they managed to stop it, again, for just a moment.
04:19But the fact that it's even possible is already incredible.
04:23Then scientists got even bolder.
04:25They decided to try not only to freeze the light, but to move its direction in time.
04:30They took a special crystal and passed a photon through it, thus initiating the so-called
04:35quantum time reversal.
04:37As a result, the photon started moving into both the future and past at the same time.
04:43The science magic behind this involves two quantum principles – superposition and quantum
04:49symmetry.
04:50We already mentioned the first one – it allows tiny particles to exist in multiple
04:54states at once.
04:56Now the second principle says that even if you flip particles around like a mirror, they'll
05:00still follow the same laws.
05:03Combining this, scientists crafted a photon that defied the usual forward march of time.
05:09But again, it's nothing super fancy yet.
05:12This time flip only works for specific particles, not entire humans.
05:16And even if it did work for us, rewinding a person even for a second would take a super
05:21long time and a lot of energy.
05:25But the fact that we can change the light's speed and make it change directions is already
05:30amazing.
05:31And scientists already see some possible applications to this.
05:35For example, Harvard researchers suggest a cool way for spacecraft to zip through space
05:40at the speed of light – by hitching a ride on supernovas.
05:45Usually traveling to other stars takes an insane amount of energy, but these scientists
05:49have a wild idea.
05:50They think that spaceships could use natural events like hypervelocity stars and meteors
05:56zooming from supernovas to reach super-fast speeds.
05:59It's kind of similar to how sailing ships catch the wind.
06:04Advanced civilizations could use these energy bursts to speed up their spacecraft.
06:09Imagine a cool spacecraft with solar or magnetic sails harnessing the power of a supernova
06:14boom.
06:16These sails could use the pressure of the Sun's radiation to work, so that we wouldn't
06:20need any traditional engines or fuel.
06:23Plus these sails concepts are much lighter and cheaper to launch into space compared
06:27to regular spacecraft.
06:29The team is already working on a light sail, accelerated by lasers, to reach 20% the speed
06:35of light.
06:36It might not sound like a lot, but it's actually an insane speed.
06:40Their dream is to help humanity make a swift journey to Alpha Centauri in just two decades.
06:47Isn't it amazing how many things we can do with light, and not just in our imagination?
06:52Let's go to more practical achievements.
06:54Recently, a Canadian camouflage company called Hyperstealth Biotechnology Corporation has
07:00crafted an actual invisibility cloak.
07:04The wizardly cloak doesn't need any power source, is as thin as paper, and won't break
07:08the bank.
07:11Hyperstealth envisions a world where this material can cloak people, vehicles, ships,
07:15spacecraft, and even entire buildings.
07:18It's still in a prototype phase, but it already works pretty well.
07:23They name this incredible technology Quantum Stealth.
07:26It bends light in a way that can make objects disappear from sight.
07:30It can render objects nearly invisible, not only in the visible spectrum, but also in
07:35ultraviolet, infrared, shortwave infrared, and it even throws in thermal spectrum blocking
07:40for good measure.
07:42The technology works thanks to the lenticular lens, a corrugated sheet with outward curving
07:48lenses.
07:49When stacked in a specific way, these lenses refract light at various angles, creating
07:54spots that block light and conceal the object behind the material.
07:58Unfortunately, it doesn't give you a full invisibility effect.
08:03But maybe someday we'll achieve it, if we keep working on it.
08:07If you hide behind it, it will look like a little dirty or blurred glass, but you won't
08:11be visible.
08:12If you put this veil in front of your body, you'll look like a floating head.
08:18Scientific progress is in full swing.
08:20Maybe one day we'll be able to reverse time not only for little light particles, but for
08:25entire humans.
08:27Until then, let's enjoy our invisibility cloaks and stay curious!
08:31That's it for today, so hey, if you pacified your curiosity, then give the video a like
08:36and share it with your friends!
08:38Or if you want more, just click on these videos and stay on the Bright Side!
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