Imagine like stepping into some futuristic machine, right?
You punch in a date.
Oh yeah.
And whoosh, you're just transported.
To another time.
Witnessing, I don't know, the pyramids being built maybe
or having tea with like a future version of yourself.
It's wild.
Time travel.
Yeah.
The stuff of dreams.
Oh sure.
Sci-fi movies.
Absolutely.
And maybe, just maybe.
Yeah.
Real science.
It's definitely one of those captivating ideas out there.
Right.
For sure.
You know, we haven't exactly cracked the code.
Yeah.
To building, you know, an actual working time machine.
Like.
A working time machine.
The idea itself, it's not totally crazy.
No, not at all.
It starts with Einstein, right?
His theories of relativity.
Those are like the rule book for how time works.
That's so cool.
Welcome to Cosmos in a Pond, our space and astronomy series.
Glad to be here.
Today, we're taking a deep dive into time travel.
Okay.
Is it pure fiction?
Yeah.
Or could physics actually allow this?
So, to really kind of wrap your head around time travel,
think of time like a river, right?
It's constantly flowing.
Yeah.
We experience it as this straight path.
Yeah.
But Einstein showed that it can be warped,
it can be stretched.
Oh wow.
Almost like, you know, a river bending around a mountain.
So instead of a rigid, like, clock.
Yeah.
Time is more like this flexible dynamic kind of thing.
Exactly.
Now, there are two basic types of time travel.
Forward and backward.
Traveling to the future,
that actually has some scientific backing.
Really?
Whereas going back in time, that's much more speculative.
Okay.
And honestly, just full of paradoxes.
Paradoxes, yeah.
Okay, so let's start with the future then.
Sure.
How can we possibly even travel, like, ahead in time?
So the key is this thing called time dilation.
Time dilation.
Yeah, which comes directly
from Einstein's special relativity.
Okay.
Imagine you have two identical clocks.
Okay.
One stays here on earth.
Okay.
The other one, we put it on a spaceship,
and this spaceship travels at an incredibly high speed,
close to the speed of light.
Okay, wow.
Now, when that spaceship gets back to earth,
Yeah.
the clock that was on the spaceship
is going to show less time has passed.
What?
Compared to the clock that stayed here.
So the clock on the spaceship
literally traveled into the future.
In a way, yes.
Wow.
The faster you move through space,
Yeah.
the slower time passes for you,
relative to someone standing still.
Okay.
It's like taking a shortcut through time.
That's wild.
Right.
But haven't we actually, like, seen this happen?
We have.
So astronauts on the International Space Station,
Right.
because they're orbiting earth at high speed.
Okay.
They actually age a tiny bit slower.
Really?
Than people on the ground.
Wow.
They're essentially time travelers,
but just on a teeny tiny scale.
So like, traveling to the future?
Yeah.
Even if it's just like a tiny bit,
it's actually possible.
It is, theoretically.
Wow.
But to really make these big jumps into the future,
we'd have to hit those speeds close to the speed of light.
Right.
Which is a whole other challenge.
It's a whole other thing, right.
Right.
Okay, that's forward time travel.
Yeah.
What about going back in time?
Yeah.
Is that even remotely possible?
That's where things get really tricky.
Okay.
Both scientifically and philosophically.
Okay.
Traveling to the past,
it's just riddled with paradoxes.
They really make your head spin.
Yeah.
Imagine going back in time.
Okay.
And you accidentally stop your parents from ever meeting.
Okay.
If they never met, you wouldn't exist.
Right.
So how could you have gone back in time in the first place?
That's like the classic grandfather paradox, right?
Right, the grandfather paradox.
It really makes your brain hurt a little bit.
It does, and there are other types of paradoxes too.
Oh, wow.
But even if we just put those aside for a moment,
the physics of backward time travel,
it's much more speculative.
Okay, so are there any actual scientific theories
about how backward time travel might work?
There are.
Okay.
But they all have major caveats.
One idea involves wormholes.
Wormholes?
These theoretical tunnels through space-time.
Okay.
That could connect distant points in the universe.
So like shortcuts through the fabric of reality.
Exactly.
Wow.
Now, if one end of a wormhole
were to experience really strong gravitational effects,
like near a black hole,
time would actually move slower at that end
compared to the other.
Really?
And that difference in the flow of time
that could, in theory,
allow travel between different points in time.
So you could potentially step into one end of a wormhole
and come out the other end
in a totally different time period.
That's the idea.
Wow.
But there's some big ifs involved.
For one, we're not even sure wormholes actually exist.
You're purely theoretical at this point.
And even if they do exist,
they're thought to be unbelievably unstable.
They would probably collapse
before you could even get close.
So it's not as simple as like
hopping into a cosmic subway.
Right.
And just like choosing your destination year.
Not quite.
There are other wild theories out there too,
like cosmic strings.
Cosmic strings?
Yeah, these super dense wrinkles
in the fabric of space-time.
Okay.
Left over from the Big Bang.
Oh, wow.
They could potentially create
what are called closed timelike curves.
Closed timelike curves?
Yeah, paths through space-time
that loop back on themselves,
allowing for backward time travel.
So like wrinkles in the universe
that act as time machines.
That's one way to put it.
Wow.
Very simplified.
But again, the existence of cosmic strings
is completely hypothetical.
Right.
And even if we found one
manipulating it to actually enable time travel,
that would be something else entirely.
Seems like every potential method, right?
For backward time travel
comes with a whole bunch of problems.
It does.
What about black holes?
Don't they have something to do with time?
They do, specifically rotating black holes.
Okay.
Known as Kerr black holes.
Kerr black holes.
So they spin so rapidly.
Yeah.
They could potentially create a time loop.
Okay.
Around their singularity.
Oh, wow.
In theory, if you entered this loop,
it might allow for backward time travel.
So you could like swirl around a black hole.
Yeah.
And end up back in the past.
Potentially.
Isn't that a bit risky?
Risky is an understatement.
Right.
The gravity near a black hole.
Yeah.
It would crush anything that got too close.
Okay.
And even if you survived.
Yeah.
There's no guarantee you could escape the loop
or even control where you ended up in the past.
That sounds less like time travel.
Right.
And more like a cosmic suicide mission.
Yeah, kinda.
Okay, are there any other theoretical methods
that are a little less extreme?
One more intriguing idea
is this thing called the Tipler cylinder.
Tipler cylinder.
So it's a hypothetical infinitely long.
Infinitely long.
Spinning cylinder.
Okay.
Made of incredibly dense matter.
Okay.
Now if you could build one of these.
Yeah.
And spin it fast enough.
Okay.
It would warp space time.
Right.
Enough to potentially create a pathway for time travel.
An infinitely long cylinder.
Yeah.
That sounds.
It's out there.
A bit ambitious.
Even for theoretical physics.
It really pushes the limits
of what we can even imagine.
Let alone build.
Right.
And that's actually a common thread
running through all these theoretical methods.
They need stuff we've never even seen.
Like exotic matter with negative energy.
Or technologies way beyond what we can do right now.
Right.
Like way beyond.
Yeah.
Yeah, we're talking about manipulating
the very fabric of space time.
Right.
A feat that would need just an unbelievable level
of understanding and control of the whole universe.
It does seem like the more we go into backward time travel,
the more questions we have.
Exactly.
And some of those questions go way beyond just physics.
Really?
Yeah, they go into the realm of philosophy.
Oh wow.
For example, the whole concept of time travel
makes us rethink the idea of causality.
Causality.
The notion that a cause always comes before an effect.
Okay, right.
So like the classic example.
Yeah.
A butterfly flaps its wings in Brazil.
Right.
And it can eventually cause like a hurricane in Florida.
Precisely.
You mean?
But if we could travel back in time,
wouldn't we be able to mess with that whole chain
of cause and effect.
Yeah.
And create all sorts of crazy consequences.
It's like time travel throws a wrench
into the very order of the universe.
In a way it does.
It challenges our whole understanding of how time flows
and how events actually happen.
Okay.
And that leads to another really interesting concept,
the arrow of time.
The arrow of time.
Why does time seem to only move in one direction?
Right, from past to future.
Exactly.
And this idea is really closely tied
to this concept of entropy.
Entropy.
Which basically says that disorder in the universe
always increases.
So like, you know, if you drop a glass
and it shatters into a million pieces,
it's not just gonna suddenly reassemble itself.
Exactly.
Entropy like keeps things moving in one direction.
Exactly.
But time travel, especially going back in time,
seems to go against this whole principle.
Right.
That it's just move around freely in time.
Yeah.
Wouldn't that like mess with the arrow of time
and create just absolute causal chaos?
And like time travel could just like unravel
the fabric of reality.
Yeah, and that's a concern.
Yeah.
Many physicists and philosophers have thought about.
Right.
But there are some theories that try to reconcile
time travel with this arrow of time.
Okay.
And one of the most fascinating ones.
Yeah.
Is this idea of the multiverse.
The multiverse.
So not just one universe.
Yeah.
But many.
Oh wow.
Yeah, some theories suggest that time travel
doesn't actually change the past in our own timeline.
Okay.
Instead, it makes a split.
Okay.
It creates this branching off point
where a new parallel universe is born.
Really?
With a different version of those events.
So instead of like rewriting our own history.
Yeah.
We'd be creating completely new universes.
With different timelines.
That's the idea.
It's like having infinite parallel worlds.
Wow.
And then having our own unique set of events happening.
Okay.
What we do in the past wouldn't erase our present.
Right.
But it would put us on a different path
in this massive multiverse.
It's a pretty mind boggling concept.
It is.
But it does seem to like address
some of those paradoxes we were talking about.
It does.
The multiverse theory gives us a possible solution
to the grandfather paradox.
Okay.
For instance, imagine you went back in time
and you changed events.
Yeah.
And it would be different to you existing.
Right.
Well, you wouldn't be erasing yourself
from that original timeline.
Right.
You'd just be moving to a different branch
of the multiverse where you still exist.
It's like having this cosmic safety net.
Right.
That makes sure that even the most crazy changes
to the past don't completely like destroy reality.
In a way, yeah.
The multiverse theory allows for more flexibility
when it comes to time travel.
Okay.
It suggests that the results of changing the past
might not be as bad as we think.
Okay.
It's a really awe-inspiring idea.
It is.
But it also shows us just how much we still don't know
about the universe and what time really is.
Right.
Yeah.
Absolutely.
Time travel really pushes us to the edge
of what we understand.
It does.
It makes us face the limits of like our current models.
Yeah.
And think about possibilities that just seem,
you know, completely fantastical.
Right.
So backward time travel.
Yeah.
It's still very much in the realm of speculation.
For sure.
It does make us ask these like really deep questions.
It does.
About reality, causality, and the limits of what we know.
Absolutely.
Speaking of understanding,
can we shift gears a little bit?
Sure.
Let's talk about like actual scientific research
that's being done in relation to time travel.
Okay.
We've talked about the theories,
but what about the evidence?
You mean there are scientists out there
actually studying time travel.
Yeah.
It's not just like theoretical physicists and sci-fi writers.
Right.
So we haven't built any working time machines,
but there are some real scientific observations
that support the idea that time is a lot more flexible
than we usually think.
Okay. I'm intrigued.
Give me some like concrete examples.
Okay. So remember time dilation.
Yeah. The slowing down of time
for things moving really fast.
Yeah. So that's not just a theory.
It's been proven many times using atomic clocks.
So scientists have actually measured
time dilation happening.
They have.
For example, they've flown atomic clocks
on airplanes and satellites.
Okay.
And they show a little difference in time.
Okay.
Compared to clocks that stayed on the ground.
Right.
The clocks that traveled at higher speeds
show that a tiny bit less time has passed.
Wow.
Exactly like Einstein's theories predicted.
So it's not just some hypothetical thing.
Yeah.
Time dilation is something we can measure.
That's incredible.
And these measurements just prove
that time isn't this fixed thing.
Right.
It's relative, it's affected by things like speed
and gravity.
That brings us back to Einstein
and his revolutionary theories.
Right.
Are there any other observations that support this idea
of time being malleable?
There are.
We've also observed what's called
gravitational time dilation.
Okay.
The slowing down of time in strong gravitational fields.
Right.
Like the ones you'd find around massive objects
such as black holes.
Wait, so time literally moves slower near a black hole?
That's right.
Wow.
Observations of stars orbiting close to black holes
have actually confirmed this.
Really?
The intense gravity warps space time so much.
Yeah.
That time itself slows down near it.
It's almost like black holes
are like these cosmic time machines.
Uh-huh.
Distorting time around them.
In a way, yes.
Wow.
These observations not only strengthen
our understanding of general relativity,
but also provide more evidence that gravity
can change the very nature of time.
It's like a glimpse into a world where time itself
bends to the will of these huge objects.
It is.
It's mind boggling.
It's mind boggling and as we keep exploring the cosmos,
studying black holes and these other crazy environments,
we're bound to find even more mind blowing stuff
about the nature of time.
It's amazing to think that we've gone
from these theoretical predictions.
Yeah.
To actually seeing this stuff happening in the universe.
It is.
It really shows the power of scientific exploration.
Yeah.
And how our understanding of the cosmos keeps growing.
Right.
But it's not just about observing from afar.
Right.
Scientists are doing some cutting edge experiments
here on Earth too.
Really?
Yeah, they're going into the quantum realm.
Oh.
To search for clues about time and causality.
Quantum experiments.
What do those have to do with time travel?
The quantum world is this strange
and counterintuitive place.
Okay.
Rules of classical physics don't really apply.
Right.
And within that world,
there might be these hidden pathways, these mechanisms
that could maybe let us manipulate time
in ways we can't even imagine yet.
So we're talking about using the weirdness
of quantum mechanics.
Yeah.
To unlock the secrets of time travel.
In a way, yes.
Researchers are looking into things
like quantum entanglement.
Quantum entanglement.
Where two particles are linked
in such a way that they share the same fate.
Okay.
Even when they're separated by huge distances.
It's like this spooky connection
that goes beyond space and time.
Exactly.
Wow.
And while entanglement itself
doesn't directly lead to time travel.
Right.
It does give us valuable insight.
Okay.
Into how interconnected the universe is.
Okay.
And the strange ways information can be sent.
Yeah.
Maybe even across time.
It's a reminder that the universe is full of mysteries
we haven't figured out yet.
It is.
And that the search for time travel could lead us
to discoveries.
Yeah.
That completely change how we understand reality.
It could.
Wow.
It's a journey worth taking.
Yeah.
Even if we don't know where it leads.
Right.
Speaking of journeys,
what about those massive experiments?
Yeah.
Like the Large Hadron Collider.
Right.
Does that play a role in understanding time travel?
It does.
The Large Hadron Collider, or LHC,
is the most powerful particle accelerator in the world.
Wow.
It smashes atoms together at crazy speeds.
Okay.
Recreating the conditions that existed
just fractions of a second after the Big Bang.
It's like looking back
to the very beginning of the universe.
It is.
Yeah.
And by studying the pieces from these collisions.
Yeah.
Scientists are learning so much
about the fundamental building blocks of matter.
Okay.
And the forces that control the universe.
Right.
This knowledge could help us figure out
how to manipulate space time itself.
So by pushing the limits of energy and matter.
Yeah.
These experiments could show us new particles
or things to shed light on.
Like the nature of space time.
Exactly.
Oh.
The LHC and other advanced research facilities
are tools for looking into the deepest mysteries
of the universe.
Trying to find answers to some of the most profound questions
about time, space, and our place in it all.
It's a truly awe-inspiring endeavor.
It is.
Filled by human curiosity and this desire to learn more.
Absolutely.
Okay.
So after all of this.
Yeah.
Where do we stand?
Right.
Is time travel actually possible?
Yeah.
Or is it just this really cool idea.
Right.
That's always gonna stay in science fiction.
Well, it kind of depends on what kind of time travel
we're talking about.
Okay.
When it comes to forward time travel.
Yeah, traveling to the future.
Yeah, I'd say it's a cautious yes.
A cautious yes.
We know time dilation is a real thing.
Right.
And so technically traveling to the future
is already happening in a way.
We talked about astronauts aging a little slower in space.
Right.
But to make those like really big jumps into the future.
Yeah.
Wouldn't we have to go to like almost as fast as light?
That's the thing.
Right.
Getting to those speeds would take technology
way beyond anything we have now.
We'd need completely new ways to like make energy
and move through space.
Yeah.
And there's serious protection
from all the crazy forces involved.
Right.
It's a huge challenge to say the least.
So while forward time travel might be based in physics.
Yeah.
It seems like those big jumps into the future.
They're still in the world of sci-fi.
For now at least, yeah.
Okay.
But the possibility is there.
Right.
Now backward time travel.
Yeah.
That's a whole other story.
Right, we've talked about all the paradoxes.
Yeah.
The lack of like any real evidence.
Right.
And just how mind blowing it all is,
is going back in time.
Yeah.
Even a little bit possible scientifically speaking.
It's highly speculative to be honest.
Okay.
The challenges are enormous.
Yeah.
Those paradoxes, they make you wonder
if backward time travel could ever make sense.
And then there's the energy problem.
Yeah.
To mess with space time that much.
Yeah.
You'd need a ridiculous amount of energy
like more than we can even imagine.
And we haven't even like talked about the actual problems
of building a time machine.
Right.
Assuming we even could.
Yeah, all those ideas we discussed,
wormholes, cosmic strings,
Tipler cylinders.
Right.
They all need things we've never actually seen.
Or technology that's way beyond what we can do.
Sounds like the idea of hopping in a time machine
and going back to the past.
Yeah.
Is probably gonna stay just that.
Right.
An idea.
It might, but even if building a time machine
turns out to be impossible.
Yeah.
Just thinking about these ideas is valuable.
Okay.
It makes us think hard about time, cause and effect.
Yeah.
And the limits of what we know.
Okay.
It pushes science forward
and makes us use our imaginations.
It reminds us that there's still a lot about the universe.
Oh yeah.
That we just don't understand.
For sure.
And that we're not done discovering things.
Absolutely.
Who knows, maybe someday some genius
will figure something out.
Yeah.
That changes everything.
Right.
Maybe there are these hidden laws of physics out there.
Yeah.
That could make time travel real.
It's both exciting and a little scary to think about.
It is.
But even if we never actually travel through time.
Yeah.
Just trying to understand it.
Has helped us learn more about the universe
and where we fit in.
It's a testament to human curiosity.
And our need to explore the unknown.
Definitely.
Well that brings us to the end.
Yeah.
Of our deep dive into time travel.
It has been a journey.
It's been a really wild ride
through physics, philosophy and imagination.
We've looked at the possibilities, the challenges
and what it would all mean if we could actually control time.
And while we still don't know
if we'll ever be able to time travel.
Right.
One thing's for sure.
What's that?
Exploring these ideas keeps inspiring us.
Yeah.
And making us wonder.
It does.
So as we wrap up.
Yeah.
We leave you with one last thought.
Okay.
If you could travel through time.
Yeah.
Where would you go?
Right.
And what would you do with that power?
That's a great question.
It makes us think about not just the science.
Yeah.
But also the ethics and what it all means.
Absolutely.
Until we figure all that out.
Right.
The answer is up to our imagination.
Yeah.
And maybe a little bit of cosmic wonder.
A little bit.
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Thanks for joining us on this amazing trip
through the mysteries of time and space.