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Speaker 1: What if I told you that time travelers aren't just characters,

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you know, stuck in sci fi movies or books. What

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if they're actually already among us right now. And I'm

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not talking about like Deloreans flashing through time or anything

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like that. No fancy gadgets.

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Speaker 2: Right, no flux capacitors needed, exactly.

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Speaker 1: We're talking raw, undeniable physics. So today we're taking a

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deep dive into whether time travel is actually real and.

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Speaker 2: The truth might be well a lot stranger than fiction.

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Speaker 1: Honestly, it sounds like it really redefines the whole idea,

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doesn't it. Yeah, So okay, let's impact this. What does

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it actually mean scientifically speaking to be a time traveler?

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Speaker 2: That's absolutely the place we need to start, because, you know,

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our gut feeling, our intuition about time, it's usually that

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time is this constant river flowing the same for everyone everywhere.

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Speaker 1: Yeah, like a big universal clock just taken away. Same

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for me, same for you, same for someone on marketing.

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Speaker 2: Exactly. We feel it's steady, but the science, the real

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world data, it tells it well different. Story time is

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much more fluid, maybe even personal. Yeah, So our mission

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today in this deep dive it isn't just to lay

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out the facts. It's really to try and shift your

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perspective a bit, to get you thinking differently about time itself,

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one of the most fundamental things in the universe. We'll

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look at things we can actually see happening, some really

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key experiments that frankly blew people's minds, and then we'll

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dip into the more theoretical side. The goal isn't just

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asking if time travel.

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Speaker 1: Is possible, but how it's already happening.

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Speaker 2: In a very real, measurable way. Yes, it's already part

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of how things work, whether we notice it day to

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day or not.

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Speaker 1: Okay, so when you say time travelers are among us,

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you're not hinting at like secret agents from the future.

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Speaker 2: Huh No, definitely not that. We're talking about real people,

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incredibly dedicated, smart people like Scott Kelly. You know, the

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American engineer retired astronauts.

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Speaker 1: Oh, yes, Scott Kelly did amazing work on the ISS.

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Speaker 2: Exactly, multiple missions commanded the International Space Station, just incredible stuff.

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But one mission in particular really brings this whole time

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travel thing into focus.

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Speaker 1: The year long one.

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Speaker 2: That's the one well three hundred and forty days technically,

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he was up there on the Iss, this giant lab

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orbiting Earth, doing all this genius level stuff, improving water recycling,

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testing how heat moves in microgravity, basically figuring out how

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humans can live further out in space.

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Speaker 1: Right, vital work for future exploration.

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Speaker 2: Absolutely vital. But while he was doing all that, something

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else was happening, something really counterintuitive. He was actually aging

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differently compared to us down here on Earth.

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Speaker 1: Eging differently, you mean slower or faster?

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Speaker 2: Slower, just a tiny bit slower, but measurably slower. And

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that's not just a quirky fact. It's a direct result

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of his journey through space time.

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Speaker 1: Wow. Okay, so how do we even know that? How

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can you measure such a tiny difference in aging? Ah?

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Speaker 2: Well, that's where it gets really neat. It comes down

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to comparison, and Scott Kelly has the perfect comparison, his

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identical twin brother, Mark Kelly, also an astronaut, also an astronaut. Yes, now,

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Mark was actually born six minutes before Scott, so technically

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Mark was the older twin by six minutes.

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Speaker 1: Okay, makes sense.

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Speaker 2: But then Scott does his three hundred and forty days

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stand up on the ISS when he comes back. Scientists

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did incredibly detailed comparisons biological markers, the telomeres in their DNA,

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and critically super precise time measurements, and guess what.

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Speaker 1: Mark was still older?

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Speaker 2: He was older, yes, but more older than before. Mark

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was now six minutes and five milliseconds older than Scott.

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Speaker 1: Five millisecond. That's that's incredibly small.

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Speaker 2: It is incredibly small to us, like the blink of

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an eye, but in physics, that five millisecond difference is huge.

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It's proof positive Scott aged just that little bit slower

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because he was orbiting Earth at incredible speed.

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Speaker 1: Speed is the key here.

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Speaker 2: Speed is absolutely key the ISS. It doesn't just float,

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it's zooms. We're talking seventeen thy five hundred miles per hour.

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It orbits the Earth roughly every ninety.

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Speaker 1: Minut that's blistering fast it is.

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Speaker 2: And the fundamental rule here, cornerstone of modern physics, is this.

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The faster you move through space, the slower you move

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through time relative to something moving.

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Speaker 1: Slower, so speed stretches out time.

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Speaker 2: It dilates. Time is the technical term. Time stretches out

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or slows down. For the faster object, the closer you

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get to the speed of light, the universe's ultimate speed limit.

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The more dramatic this effect becomes, you'd age much much

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slower compared to someone's stationary.

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Speaker 1: But did Scott Kelly feel time moving slower up there?

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Did things seem in slow motion?

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Speaker 2: No, not at all. And that's crucial. From Scott's perspective.

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Inside the iss, time felt completely normal. Seconds ticked by,

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just like they do for us. Clocks worked fine, He

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lived his day normally. The difference, the time dilation, it's

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only relative. It only shows up and you compare his

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clock or his biological age to a clock or a

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person back on Earth, like his twin brother Mark.

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Speaker 1: So it's a comparison effect.

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Speaker 2: Exactly, it's a compared effect. So pulling this all together,

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this isn't some SI plot device. It's real, it's measured.

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It happens. Every time an astronaut goes into orbit. They

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have effectively leaped forward in time, just by tiny fractions

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of a second relative to us.

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Speaker 1: Leaped forward.

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Speaker 2: And think about the implications for say, long term space travel.

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Imagine a crew going to another star system, maybe traveling

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for decades at very high speeds.

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Speaker 1: They'd come back and Earth would be centuries older.

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Speaker 2: Potentially yes, depending on the speed and duration. Imagine trying

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to reconnect with family or society. The data they collected

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might be ancient history by the time they returned. It

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really blurs the lines, doesn't it. Small time differences now

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could mean huge societal shifts down the line.

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Speaker 1: That's absolutely mind bending. So just to clarify for everyone listening,

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when we talk about real time travel here, we're not

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talking back to the future style jumps.

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Speaker 2: No instantaneous zapping through centuries.

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Speaker 1: Right, It's more like living in the future, but at

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a slightly different rate than someone else. Personal timestream is

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flowing a bit faster or slower than one second per

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second relative to another observer.

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Speaker 2: Precisely, it's about the rate of time passing being different,

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And like Scott Kelly shows us, it's measurable. It's happening now.

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Speaker 1: And you mentioned it affects technology too, like GPS.

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Speaker 2: Oh absolutely, GPS satellites are orbiting Earth very fast, and

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they're also further away from Earth's gravitational pull, which also

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affects time, something called gravitational time dilation, part of Einstein's

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general relativity.

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Speaker 1: So gravity affects time too, not just speed.

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Speaker 2: Yes, gravity also works. Spacetime clocks tick slightly faster further

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away from a massive object like Earth. Both speed and

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gravity effects have to be calculated for GPS to work.

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Without accounting for both special relativistic time dilation due to

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speed and general relativistic time dilation due to gravity, your

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GPS would become inaccurate incredibly quickly, like miles off within

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a single day.

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Speaker 1: So every time I use Google Maps and basically relying

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on the physics time travel.

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Speaker 2: In a very real sense, Yes, you're directly benefiting from

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our understanding that time is an absolute.

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Speaker 1: Okay, this is already stranger than I thought. So who

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figured all this out? How do we get from time

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is absolute? Too? Well?

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Speaker 2: This, well, that brings us to the giant himself, Albert Einstein.

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For centuries, the picture was dominated by Isaac Newton. Newton

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saw time as while absolute, universal, unchanging like that cosmic

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clock ticking the same everywhere.

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Speaker 1: Yeah, that feels intuitive. My Tuesday feels like your tuesday.

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Speaker 2: It does feel intuitive. It matches our daily experience perfectly,

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clock seems synchronized, days pass predictably. But then early twentieth

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century Einstein comes along and basically says, Hold on a second,

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it's it's not quite that simple. He dropped the bombshell.

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Time is relative.

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Speaker 1: Time is relative. We hear that phrase all the time,

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But what does it really mean, Because it seems to

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change everything.

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Speaker 2: It really does. What it means is that the amount

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of time that passes between two events isn't necessarily the

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same for everyone. It depends on how you're moving and

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where you are compared to someone else observing the same events.

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Speaker 1: So my five minutes might not be your five minutes.

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Speaker 2: Under the right circumstances. Yes, that was the core of

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his special theory of relativity. It starts with two postulates,

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two fundamental ideas. One, the laws of physics are the

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same for everyone who isn't accelerating.

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Speaker 1: Okay, that seems reasonable.

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Speaker 2: Two, the speed of light in a vacuum is constant.

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It's the same for all observers, no matter how fast

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they're moving. The second one, this is the one that

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has really weird consequences.

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Speaker 1: Constant speed of light. Ah, how does that lead to

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relative time?

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Speaker 2: Think about it. If the speed of light must be

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constant for everyone, but speed is just distance divided by time,

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then if observers moving differently relative to each other. Measure

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light traveling the same speed over different distances. Something has

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to give, and that something is time.

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Speaker 1: Ah, time itself has to change to keep the speed

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of light constant for everyone.

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Speaker 2: Exactly, time has to stretch or shrink depending on your motion.

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Let's use that analogy from the source material, the melting

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ice cream.

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Speaker 1: Okay, I'm going to park bench ice cream cone.

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Speaker 2: Right suns out, it's melting. Let's say for you sitting there,

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it takes exactly five minutes to melt completely. You time

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it on your watch.

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Speaker 1: Five minutes. Got it simple enough.

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Speaker 2: Now imagine your friend whizzes past in a super fast spaceship.

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Maybe it's say eighty percent the speed of light. They

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look out the window and watch your ice cream melt

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for them inside that speeding spaceship. That same event, the

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ice cream melting takes less time according to their watch.

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Maybe it only takes three minutes for them.

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Speaker 1: Wait, the same melting takes less time for them, how.

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Speaker 2: Because time itself is passing slower for them due to

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their high speed relative to you on the bench. Again,

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they wouldn't feel anything strange. Their thoughts, their heartbeat, their

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clock on the wall, all would seem normal to them.

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Speaker 1: But comparing their clock to my clock shows a difference.

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Speaker 2: Precisely. That difference is time dilation. Time literally moves slower

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for things moving faster relative to slower things. It's not perception,

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it's physics. It's the heart of special relativity.

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Speaker 1: Mind blown. Okay, so Einstein predicts this theoretically based on

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the constant speed of light.

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Speaker 2: That's a huge leap, a monumental leap. It completely re

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wrote our understanding of space and time, merging them into

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a single entity.

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Speaker 1: Space time with theories are one thing. You mentioned experiments earlier.

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How on earth did they prove something so bizarre back

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then before super precise space.

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Speaker 2: Measurements, right, Because these effects are usually tiny in everyday life.

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You need either incredible speeds or incredibly sensitive instruments. And

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that's where a really clever experiment from nineteen seventy one

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comes in.

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Speaker 1: Okay, what happened in seventy.

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Speaker 2: One two physicists Jesse fa Fayle and Richard Keating. They

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decided to test time dilation directly using atomic clocks.

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Speaker 1: Atomic clocks, those are the super accurate ones.

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Speaker 2: Right, insanely accurate. They measure time based on the resonance

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frequencies of atoms, usually caesium. We're talking accuracy down to

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nanoseconds billions of a seconds.

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Speaker 1: Okay, so what do they do with them?

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Speaker 2: It was elegantly simple, really. They took two of these

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clocks and put them on regular commercial airplanes. One flew

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eastward around the world. The other flew.

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Speaker 1: Westwards on passenger flights.

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Speaker 2: YEP, circumnavigating the globe. Meanwhile, a third identical atomic clock

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stayed put on the ground at the US Naval Observatory

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as the reference point.

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Speaker 1: Okay, so they flew clocks around the world and compared them.

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Why east and west? Does that matter?

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Speaker 2: It matters hugely. Think about the Earth's rotation. The Earth

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spins eastward. So the plane flying east was moving with

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the Earth's rotation, meaning its speed relative to the center

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of the Earth, or relative to a non rotating frame,

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was its own speed plus the Earth's rotational speed. It

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was moving.

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Speaker 1: Faster, okay, faster overall speed exactly.

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Speaker 2: The plane flying west was moving against the Earth's rotation,

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so its net speed relative to that same frame was

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its own speed minus the earth rotational speed. It was

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moving slower overall.

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Speaker 1: Clever, So you have one faster clock, one slower clock,

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and one stationary.

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Speaker 2: Clock, precisely, and after the trips they brought all three

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clocks back together and compared the times recorded it.

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Speaker 1: Did they see a difference? Please tell me they saw

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a difference.

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Speaker 2: They absolutely did, and it matched Einstein's predictions beautifully. The

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clock that flew eastward, the faster one, had lost time

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compared to the ground clock. It ran slightly slower, comer slower,

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about fifty nine nanoseconds slower.

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Speaker 1: Wow, okay, fifty nine billions of a second.

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Speaker 2: And the clock that flew westward, the slower one, relative

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to the non rotating frame, had gained time compared to

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the ground clock. It rans slightly faster.

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Speaker 1: Gain time how much?

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Speaker 2: About two hundred and seventy three nano seconds faster? Wait,

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let me double check that number from the source. Ah, yes,

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the source says two hundred and thirty seven nanoseconds. Game

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for the westward clock apologies, fifty nine lost eastbound, two

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hundred and thirty seven gained westbound.

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Speaker 1: Okay, fifty nine lost two hundred and thirty seven gained tiny,

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tiny amounts, but.

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Speaker 2: Consistent, consistent, and undeniable. These weren't errors. They were the

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direct measured proof of time dilation predicted by both special

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relativity due to speed and general relativity due to gravity.

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Altitude also played a small role, mostly speed in this case,

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but both effects were accounted for.

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Speaker 1: So have you and Keaty nailed it? They proved Einstein

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wright using airplanes and clocks.

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Speaker 2: They absolutely did. It was a landmark experiment, and it

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connects directly back to our astronauts. They're going way faster

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than those planes and for much longer.

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Speaker 1: So their time dilation is bigger than nanoseconds.

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Speaker 2: Bigger, yes, though still small in human terms. You mentioned

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Olig Kononenko earlier, the Russian cosmonaut who holds the record

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for cumulative time and space over eight hundred and seventy

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eight days by twenty twenty four. If you calculate his

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total time dilation from all that time orbiting at iss speeds,

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spending roughly one thousand days in space, means you'd effectively

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jump about point zero two seven seconds into the future

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relative to Earth.

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Speaker 1: Okay, point zero two seven seconds still not exactly whisking

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us off to next century, but it's real.

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Speaker 2: It's absolutely real, a measurable leap forward in time. Which

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inevitably brings us crashing back to the big question, the

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one everyone really wants to know about.

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Speaker 1: Can we go backwards? Can I go back and you

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know ace that test I failed in high school? Or

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invest in Applestock in nineteen eighty?

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Speaker 2: Ah, the dream going back to fixed mistakes, witness history,

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or maybe just relive the good old days. That's the

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holy grail of time travel, isn't it?

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Speaker 1: It really is. But based on your tone, I'm guessing

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the science is less optimistic.

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Speaker 2: That's putting it mildly. While forward time travel is proven,

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backward time travel is well, let's say, it's deep in

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the territory of theoretically maybe, but practically pretty.

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Speaker 1: Much impossible, pretty much impossible. Okay, why what are the roadblocks?

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Speaker 2: Well, the main theoretical doorway that physicists even consider for

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backward time travel involves something called a wormhole.

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Speaker 1: Wormholes like in the movies shortcuts through.

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Speaker 2: Space sort of. Yeah, The idea comes from general relativity.

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Imagine space time, this four dimensional fabric of the universe.

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Gravity bends it, right, like a heavy ball on a

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rubber sheet.

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Speaker 1: Okay, the trampoline analogy again.

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Speaker 2: Right, A wormhole would be like punching a hole through

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that sheet and connecting it to another point on the sheet,

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creating a tunnel, a shortcut. It could connect two distant

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places in space, or potentially two different points in time.

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Speaker 1: A tunnel connecting now to say yesterday.

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Speaker 2: Theoretically, yes, an Einstein rosenbridge, as they're sometimes called. You

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could potentially enter one end in the present and exit

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the other end in the past.

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Speaker 1: Okay, sounds promising. So where are the wormholes?

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Speaker 2: Ah? Well, first, we've never actually seen one. They're purely

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theoretical solutions to Einstein's equations. And second, even if they

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could form, there's a huge problem stability.

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Speaker 1: Stability.

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Speaker 2: Remember how gravity pulls things inward. It wants to crush things.

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A theoretical wormhole would be incredibly unstable the moment it formed.

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The intense gravity would try to collapse the tunnel instantly,

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sealing it shut before anything could get through.

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Speaker 1: So it slams closed before you can use it. Not

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very useful, not at all.

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Speaker 2: To keep it open. To make it traversible, you'd need

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something to prop the tunnel walls apart, pushing outwards against

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that crushing gravity.

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Speaker 1: Okay, what could possibly do that? Anti gravity?

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Speaker 2: You're actually remarkably close. The theoretical solution requires something called

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exotic matter, specifically matter with negative mass.

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Speaker 1: Negative mass. What on Earth is negative mass because that

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mean it weighs less than nothing.

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Speaker 2: It's weirder than that. It's hypothetical stuff that would have

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negative gravitational pull. Instead of pulling things together like normal mass,

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it would push them away. It would fall up in

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a gravitational fiell.

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Speaker 1: Okay, that's just bizarre.

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Speaker 2: It violates a lot of what we understand about energy

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and matter. But mathematically, if you had enough of this

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negative mass, you could theoretically use its repulsive anti gravity

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properties to line the inside of a wormhole.

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Speaker 1: Tunnel like structural supports.

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Speaker 2: Exactly like cosmic braces, holding the throat of the wormhole open,

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making it stable and traversible, potentially allowing passage to another

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time or place.

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Speaker 1: Okay, so the billion dollar question, have we ever found

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any negative mass?

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Speaker 2: Not a shred. It exists purely in the equations on paper.

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We have absolutely no experimental evidence that negative mass is

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real or even possible. To create it might require negative

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energy density, which is also highly problematic.

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Speaker 1: So wormholes need negative mass, but negative mass seems like

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pure fantasy.

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Speaker 2: Pretty much. It's a massive, maybe insurmountable roadblock without a

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way to stabilize them. Wormholes remain firmly in the realm

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of mathematical curiosities, not practical time machines. It's fascinating how

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the mass allows it, but reality seems to forbid it.

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Speaker 1: Okay, so building the time machine the wormhole is problem

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number one, and it's a huge one. But let's say,

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just for argument's sake, we somehow did it. We found

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negative mass, built our stable wormhole back to the past.

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Are we home free?

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Speaker 2: Not by a long shot. Even if you could travel back,

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you immediately run into another massive headache. Time paradoxes.

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Speaker 1: Ah, the paradoxes like if you change something small and

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accidentally erase yourself from.

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Speaker 2: Existence exactly those kinds of problems. They highlight a fundamental

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issue with causality. And there's a principle in physics that

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speaks to this, called the Novikov self consistency principle.

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Speaker 1: Self consistency meaning the universe tries to avoid contradicting itself.

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Speaker 2: That's the essence of it. The principle suggests that the

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universe inherently resists or maybe even forbids events that would

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create causal contradictions or inconsistencies. Basically, you can't create a

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situation where affect precedes cause in a paradoxical way.

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Speaker 1: So time travelers can't actually change the past in a

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way that creates a paradox.

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Speaker 2: According to this principle. No, the most famous example, the

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one everyone knows, is the grandfather paradox.

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Speaker 1: Right, go back in time stop your grandparents from meeting.

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Speaker 2: So your parents are never born, so you are never born. Right,

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So how did you go back in time in the

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first place to stop them?

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Speaker 1: Yeah, it makes my head hurt just thinking about. It's

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a total contradiction.

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Speaker 2: It's a complete logical impossibility. It breaks the chain of

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cause and effect, and the self consistency principle basically says Nope,

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can't have and the universe simply wouldn't allow that sequence

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of events.

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Speaker 1: So how would the universe stop you? Would the time

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machine break down? Would you slip on a banana peel

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at the crucial moment?

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Speaker 2: That's the million dollar question. The principle doesn't specify the mechanism,

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only the outcome. It suggests that somehow events would conspire

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to prevent the paradox. Your gun might jam, You might

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get delayed, your grandfather might have already met your grandmother

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earlier that day. Somehow history remains consistent, So no.

401
00:19:31,000 --> 00:19:35,319
Speaker 1: Free will to change the past. Essentially, your actions are constrained.

402
00:19:34,799 --> 00:19:38,039
Speaker 2: Within this framework. Yes, your ability to alter history in

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00:19:38,079 --> 00:19:41,960
paradoxical ways seems heavily restricted, if not impossible. There are

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other paradoxes too, like the bootstrap paradox.

405
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Speaker 1: Bootstrap, what's that?

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Speaker 2: Imagine you love Shakespeare? You travel back in time with

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a copy of Hamlet, meet Shakespeare and give it to him.

408
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He copies it out and claims it as his own.

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Centuries later, that play is preserved, and eventually a copy

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ends up in your hand, which you then take back

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to Shakespeare.

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Speaker 1: Wait, so who actually wrote Hamlet? In that scenario?

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Speaker 2: Exactly, the play exists, but it has no origin. It

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was just bootstrapped into existence by the time loop. It's

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information or an object without a creation point.

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Speaker 1: Okay, that's weird too. And you mentioned predestination right.

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Speaker 2: The predestination paradox is where your attempt to change the

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past actually becomes the cause of the event you were

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trying to prevent. You go back to stop a fire,

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but you accidentally knock over the lantern that starts it.

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Speaker 1: So you were destined to cause it all along. Wow,

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that really underminds free will.

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Speaker 2: It does. These paradoxes highlight the deep problems with tampering

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with causality. Now, some physicists propose ways around paradoxes, like

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the Many World's interpretation.

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Speaker 1: Many Worlds like parallel universes.

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Speaker 2: Exactly. The idea there is, if you go back and

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change something, you don't change your past. You just branch

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off into a new parallel timeline, whole new universe where

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things are different. Your original timeline remains until So you could.

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Speaker 1: Kill your grandfather in that timeline, but it wouldn't erase

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you from your original one.

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Speaker 2: According to Many Worlds, Yes, but that requires believing in

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an infinite number of parallel universes constantly splitting off, which

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is well, another huge theoretical leap with no direct evidence.

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Speaker 1: It seems like every solution just creates more questions. Is

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there any theoretical model for backward time travel that just

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avoids paradoxes altogether?

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Speaker 2: Well, there's one more really mind bending idea, one that

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suggests maybe the problem isn't paradoxes, but our very idea

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of time as a straight line.

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Speaker 1: Okay, what's the alternative.

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Speaker 2: What if time isn't a line but a loop, an

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endless loop with no starting.

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Speaker 1: Point, a loop like Groundhog Day sort.

446
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Speaker 2: Of, but woven into the fabric of space time itself.

447
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This is the realm of closed timelike curves or CTCs.

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Speaker 1: Closed timelike curves. Okay, what does that mean.

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Speaker 2: It means that the geometry of space time could theoretically

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allow for PABs worldlines that loop back on themselves. Your

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future could literally loop around and connect back to your past.

452
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Speaker 1: So the past and present are just blended together in

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one big loop.

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Speaker 2: In a sense, Yes, within a CTC, there's no changing

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things because everything that happens within the loop is already

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part of the loop structure. It's eternally consistent.

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Speaker 1: So if I were in a CTC, I couldn't change.

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Speaker 2: Anything according to the theory. No, Let's take your example

459
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from yesterday. You woke up, brush your teeth, worked eight whatever.

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If you could travel back to yesterday via a CTC,

461
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I'd just.

462
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Speaker 1: Do it all again exactly the same.

463
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Speaker 2: Way, exactly the same way, even if you consciously tried

464
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to do something different skip brushing your teeth, call and sick.

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The structure of the CTC would compel events to unfold

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precisely as they already did within the.

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Speaker 1: Loop, so my feeling of making choices would just be

468
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an illusion. The loop dictates everything.

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Speaker 2: That's the implication. In a CTC, You're not just moving

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along a path. You are the path, and so is

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every moment of reality within that loop. It has to

472
00:22:58,400 --> 00:23:02,000
be self consistent. Models like the godal universe or the

473
00:23:02,000 --> 00:23:06,279
theoretical Tippler cylinder explore these mathematical possibilities.

474
00:23:06,440 --> 00:23:09,880
Speaker 1: But are these CTCs actually possible or just maths?

475
00:23:10,559 --> 00:23:14,559
Speaker 2: Like wormholes? They require extreme conditions like an infinitely long,

476
00:23:14,839 --> 00:23:19,680
rapidly rotating massive cylinder, or specific cosmological models that seem

477
00:23:19,720 --> 00:23:23,759
physically impossible or don't match our observed universe. But the

478
00:23:23,839 --> 00:23:25,240
concept is intriguing.

479
00:23:25,440 --> 00:23:26,799
Speaker 1: Why what does it tell us?

480
00:23:26,960 --> 00:23:28,640
Speaker 2: It tells us that this might be the only way

481
00:23:28,680 --> 00:23:31,759
the universe could allow backward time travel without breaking causality.

482
00:23:32,200 --> 00:23:35,119
If time travel inherently forces you into a self consistent

483
00:23:35,160 --> 00:23:38,720
loop where paradoxes cannot form because everything is predetermined within

484
00:23:38,799 --> 00:23:40,680
that loop, then history is safe.

485
00:23:40,759 --> 00:23:43,359
Speaker 1: So even if we built a time machine, nature would

486
00:23:43,400 --> 00:23:46,480
find a way, maybe through CTCs or the self consistency

487
00:23:46,519 --> 00:23:48,559
principle to stop us from making a mess.

488
00:23:48,759 --> 00:23:52,079
Speaker 2: That seems to be the strong theoretical suggestion. The universe

489
00:23:52,079 --> 00:23:55,880
appears to have safeguards against paradox Whether it's the impossibility

490
00:23:55,880 --> 00:24:00,000
of building the machine, the Novakov principle preventing changes, or

491
00:24:00,119 --> 00:24:04,119
or the inherent determinism of a CTC, consistency seems to

492
00:24:04,160 --> 00:24:04,799
be paramount.

493
00:24:04,920 --> 00:24:08,799
Speaker 1: It's fascinating the universe protects itself, even if it means

494
00:24:08,799 --> 00:24:11,960
sacrificing our notion of absolute free will in the past.

495
00:24:12,240 --> 00:24:16,799
Speaker 2: It really highlights how intertwined time, causality, and the fundamental

496
00:24:16,880 --> 00:24:17,839
laws of physics are.

497
00:24:18,079 --> 00:24:21,519
Speaker 1: What an incredible journey today. Seriously, we've gone from astronauts

498
00:24:21,519 --> 00:24:23,440
aging fractions of a second slower.

499
00:24:23,240 --> 00:24:26,799
Speaker 2: Real proven science based on relativity confirmed.

500
00:24:26,319 --> 00:24:28,880
Speaker 1: By atomic clocks whizzing around the globe.

501
00:24:28,519 --> 00:24:31,559
Speaker 2: The hafelkeating experiment classic proof all the.

502
00:24:31,559 --> 00:24:35,599
Speaker 1: Way to the mind bending theoretical hurdles of going backward,

503
00:24:35,680 --> 00:24:38,319
needing impossible things like negative mass for.

504
00:24:38,279 --> 00:24:41,119
Speaker 2: Wormholes, theoretical hurdles that seem well.

505
00:24:40,920 --> 00:24:44,200
Speaker 1: Pretty darn high, and confronting the universe's apparent refusal to

506
00:24:44,200 --> 00:24:48,039
allow paradoxes, whether through self consistency, or these bizarre closed

507
00:24:48,039 --> 00:24:49,880
pime loops where history is immutable.

508
00:24:50,200 --> 00:24:53,000
Speaker 2: It really shows how the scientific reality of time is

509
00:24:53,039 --> 00:24:56,920
so much weirder and frankly more interesting than most fiction.

510
00:24:57,200 --> 00:25:01,079
Speaker 1: Absolutely, so we have the subtle proof even forward leaves

511
00:25:01,079 --> 00:25:05,799
happening now and the backward journey locked behind immense physical

512
00:25:05,799 --> 00:25:07,160
barriers in paradoxes.

513
00:25:07,240 --> 00:25:10,680
Speaker 2: That's a good summary. Forward travel is physics. Backward travel

514
00:25:10,880 --> 00:25:15,759
is mostly philosophy and extremely speculative physics at this point, So.

515
00:25:15,759 --> 00:25:17,640
Speaker 1: What does this all mean for you listening right now?

516
00:25:17,720 --> 00:25:18,640
What's the big takeaway?

517
00:25:18,960 --> 00:25:21,720
Speaker 2: I think the biggest takeaway is that our everyday perception

518
00:25:21,799 --> 00:25:25,319
of time, you know, that's steady TikTok. It's just our

519
00:25:25,400 --> 00:25:28,640
local view. It's not the whole picture. The universe operates

520
00:25:28,640 --> 00:25:33,039
on a grander, more flexible timescale, where time is relative, malleable,

521
00:25:33,119 --> 00:25:34,759
intertwined with space and gravity.

522
00:25:34,880 --> 00:25:37,480
Speaker 1: Our experience is just one slice of reality exactly.

523
00:25:37,519 --> 00:25:40,759
Speaker 2: And when you really internalize that that forward time travel

524
00:25:40,839 --> 00:25:44,079
is a certainty, even if small for now, and backward

525
00:25:44,079 --> 00:25:48,160
travel seems fundamentally constrained by causality, it does make you wonder,

526
00:25:48,200 --> 00:25:52,039
doesn't it wonder about what well it poses this profound question.

527
00:25:52,920 --> 00:25:56,400
If the universe works so hard to prevent paradoxes to

528
00:25:56,480 --> 00:25:59,920
keep the timeline consistent. Does that mean our timeline is,

529
00:26:00,519 --> 00:26:04,559
in some deep sense fixed? Is the future in some

530
00:26:04,680 --> 00:26:08,119
way already written or at least heavily constrained to ensure

531
00:26:08,160 --> 00:26:09,519
consistency with the past.

532
00:26:09,880 --> 00:26:12,799
Speaker 1: So the question of free will comes roaring back.

533
00:26:12,920 --> 00:26:16,440
Speaker 2: It absolutely does. If backward steps are forbidden or only

534
00:26:16,519 --> 00:26:19,960
possible in predetermined loops, does that limit our freedom? Moving

535
00:26:19,960 --> 00:26:23,039
forward to are we participants writing the story or are

536
00:26:23,079 --> 00:26:25,400
we actors reading lines in a script that ensures the

537
00:26:25,480 --> 00:26:26,799
universe remains logical.

538
00:26:27,000 --> 00:26:29,720
Speaker 1: That's a heavy thought to end on fixed timeline versus

539
00:26:29,720 --> 00:26:30,160
free will.

540
00:26:30,359 --> 00:26:33,480
Speaker 2: It's one of the deepest questions prompted by these explorations

541
00:26:33,480 --> 00:26:36,359
into the notture of time. There's no easy answer, but

542
00:26:36,440 --> 00:26:39,480
thinking about it really stretches your understanding of reality itself.

543
00:26:40,000 --> 00:26:42,680
It's why exploring these frontiers of physics is so vital.

544
00:26:42,720 --> 00:26:44,200
It pushes us to question.

545
00:26:43,960 --> 00:26:47,079
Speaker 1: Everything, keep asking questions, keep exploring. A perfect place to

546
00:26:47,160 --> 00:26:50,079
leave it. Thank you so much for this incredible deep dive.

547
00:26:50,000 --> 00:26:52,119
Speaker 2: My pleasure. It's always fascinating to talk about time