Welcome back to Cosmos in a Pod, Space, and Astronomy series.
Episode five.
Today.
Episode five.
We're diving into one of the biggest mysteries
in the universe.
Oh, yeah.
Dark energy.
It's a big one.
Yeah, it's a concept that really shakes up
our understanding of the cosmos.
It really does.
For a long time, we assumed the expansion of the universe,
first observed by Edwin Hubble, would gradually slow down.
You'd think so, right?
Because of gravity's pull.
Yeah, you would think.
But then something unexpected happened.
Something that turned the field of cosmology on its head?
Exactly.
In 1998.
Oh, wow.
Two independent teams of astronomers
were studying distant supernovae.
OK.
These exploding stars act like cosmic mile markers,
allowing us to measure distances across the universe.
I see.
What they found shocked the scientific community.
What was it?
The expansion of the universe wasn't slowing down at all.
Really?
It was speeding up.
So instead of the universe's expansion
slowing down like a ball rolling uphill,
it's actually accelerating like it's being pushed.
Like it's being pushed.
That's the puzzle.
Wow.
And the force behind this acceleration
is what we call dark energy.
So dark energy is like this invisible force
pushing everything apart.
That's the leading theory.
It's almost like an anti-gravity force,
counteracting the pull of gravity,
causing the universe to expand at an ever-increasing rate.
But if it's invisible, how do we even know it's there?
Yeah, that's the thing.
How did those astronomers make that connection?
Well, we see its effects.
Oh.
It's like trying to understand the wind.
You can't see the wind itself.
Right.
But you can see how it moves, leaves flags, and even
shapes the landscape.
OK.
Similarly, we can't see dark energy directly.
Right.
But we see its influence on the largest scales of the universe.
I see.
The way galaxies are moving away from each other
at an accelerating rate is our clue.
So it's like a cosmic ghost shaping the universe
from behind the scenes.
Kind of, yeah.
But what do we actually know about this mysterious force?
Well, we know surprisingly little about its true nature.
OK.
What we do know is that it makes up
a huge portion of the universe.
Like how much?
Roughly 68% of its total energy density.
Wow.
Imagine the vast majority of what makes up reality
is something we can't even detect.
OK, that's mind-blowing.
Yeah, it's a bit of a head-scratcher.
So we've got this invisible force
making up most of the universe and pushing everything apart.
That's the picture we're working with.
It feels like we're missing a big piece of the puzzle.
Definitely.
What are the main ideas out there
trying to explain what dark energy could be?
Well, there are two main contenders.
First up, we have Einstein's cosmological constant.
Einstein's cosmological constant.
Yeah.
Now, this might sound familiar because it's actually
an idea Einstein himself proposed way back in 1917.
Wow, way back then.
At the time, he thought the universe
was static, neither expanding nor contracting.
To make his equations work with a static universe,
he introduced the cosmological constant
as a kind of anti-gravity force that balanced out
the pool of gravity.
Wait, so he invented dark energy before we even
knew the universe was expanding?
He introduced the concept.
Wow.
Though he didn't call it dark energy back then.
Oh, yeah.
When Hubble discovered the universe was expanding,
Einstein abandoned the cosmological constant.
He did.
Famously calling it his biggest blunder.
Oh, wow.
The irony is the discovery of dark energy.
Yeah.
The cosmological constant is back on the table.
So maybe Einstein was onto something after all.
It's possible.
In this context, the cosmological constant
represents the energy inherent in the fabric of space itself.
It's a wild idea.
What is it?
Empty space actually has energy.
And as the universe expands, more space
is created, leading to more of this energy.
This, in turn, drives further expansion.
So it's like a self-perpetuating cycle.
Exactly, a kind of runaway train.
So option one is a constant energy built into space itself,
driving this relentless expansion.
What's the other big idea on the table?
The other contender is called quintessence.
Quintessence, OK.
Unlike the cosmological constant, which is unchanging,
quintessence suggests a dynamic energy field
that can vary in strength and distribution
across space and time.
Picture it like an energy fluid that's constantly in motion,
ebbing and flowing throughout the universe.
So instead of a constant push, we're
talking about a force that could be changing, maybe even getting
stronger or weaker over time.
Exactly.
And this variability could have dramatic consequences
for the ultimate fate of the universe.
You're telling me, if this force is constantly in flux,
it's almost impossible to predict
what will happen next, right?
It makes the future of the cosmos
a bit of a cosmic mystery.
Yeah, a bit of a mystery.
Which makes you wonder, how do we even study something
we can't see or touch?
Right.
It's like trying to solve a puzzle with missing pieces.
That's the challenge with dark energy.
But scientists are incredibly clever
when it comes to understanding the universe.
OK.
We've developed some ingenious methods
to study dark energy's effects, even
if we can't directly observe the force itself.
So what are some of the tricks of the trade
when it comes to unraveling this cosmic mystery?
One of the most powerful tools we have
is studying those distant supernovae we talked about
earlier.
Oh, right, those cosmic mile markers.
Exactly.
Remember, these exploding stars act as standard candles,
meaning we know their intrinsic brightness
by observing how bright they appear to us here on Earth.
Yeah.
We can calculate their distance.
And since light takes time to travel,
the farther away a supernova is, the further back in time
we're looking, right?
That's right.
It's like a window into the universe's past.
Precisely by observing supernovae
at different distances, I can track
how the expansion road of the universe
has changed over billions of years.
Wow.
And it's this historical record that
revealed the accelerating expansion.
And pointed us toward the existence of dark energy.
It's amazing how these ancient explosions happening
billions of years ago.
I know.
It's pretty incredible.
Can give us clues about the fundamental nature
of the universe.
The universe holds so many secrets.
Yeah, it really does.
We also study something called the cosmic microwave background
radiation.
Cosmic microwave background radiation.
Which is often referred to as the afterglow of the Big Bang.
OK, the afterglow of the Big Bang.
Imagine the universe just a few hundred thousand years
after the Big Bang.
OK.
It was incredibly hot and dense, filled
with a sea of particles and radiation.
Wow.
As the universe expanded and cooled,
this radiation stretched and cooled too.
So this cosmic microwave background
is like a snapshot of the early universe.
Yeah.
A relic from its infancy.
Exactly.
And this snapshot contains a wealth of information.
By analyzing the subtle patterns and variations
in this radiation, we can learn about the universe's
composition.
I see.
How much dark energy was present even back then.
And how it has influenced the universe's evolution over time.
It makes you realize how interconnected everything is.
It really does.
From the earliest moments of the universe to the present day.
It's all connected.
But these methods you've described
sound like they rely on observing incredibly faint
signals from billions of light years away.
Yeah, they are pretty faint.
How do scientists even do that?
It requires incredibly sophisticated instruments
and telescopes.
Some of the most advanced technology humans
have ever built.
OK, so like what?
Take the dark energy survey, for example.
The dark energy survey.
OK.
It uses a powerful telescope and camera
to map the distribution of galaxies
across vast stretches of the universe.
So it's not just looking at individual objects.
Right.
It's mapping the large scale structure of the universe.
Exactly.
To see how dark energy has influenced its evolution.
That's the idea.
And there are even more ambitious projects in the works.
Oh, yeah.
Like the Euclid Space Telescope and the Vera Rubin Observatory.
Those are going to be game changers.
Yeah.
Allowing us to study dark energy with even greater precision.
It's like we're constantly pushing the boundaries
of what's possible.
We are.
Building bigger and better telescopes
to peer deeper and deeper into the universe.
And every new observation, every new measurement
helps us refine our understanding
of this mysterious force that shapes our cosmic destiny.
But even with all these incredible tools,
there's still so much we don't know.
So much we don't know.
At the end of the day, we're left with the big question,
what's the fate of the universe given this mysterious force
driving its expansion?
Right.
Is it going to keep expanding forever?
It's the big question, isn't it?
Yeah.
Will it eventually collapse?
Yeah.
What are the options on the table?
Well, depending on what dark energy turns out to be,
the universe has a few possible endings.
OK, like what?
One scenario is called the big freeze.
The big freeze.
If dark energy continues to dominate and accelerate
the universe's expansion, indefinitely,
galaxies will continue to drift farther and farther apart.
So instead of being clustered together,
galaxies would become like isolated islands
in an ever-expanding sea of space.
Exactly.
Eventually, these galaxies would become so far apart
that they would effectively be invisible to each other.
Stars would burn out, and the universe
would become a vast, cold, and dark expanse.
OK.
That's somewhat bleak picture, I'll admit.
It's a little unsettling to imagine everything drifting
apart into this cosmic void.
Yeah, it's not the most cheerful thought.
There's another possibility, perhaps even more dramatic,
called the big rip.
The big rip.
Oh, yeah.
If dark energy becomes even stronger over time,
the expansion wouldn't just separate galaxies.
It would start to tear apart everything in its path.
That's the idea.
So not just galaxies drifting apart,
but everything being ripped to shreds.
In this scenario, galaxy stars, planets, even atoms themselves,
would eventually be torn apart by the overwhelming force
of dark energy.
So the universe would just disintegrate.
It would be the ultimate cosmic unraveling.
Yikes.
That sounds intense.
Just a pretty extreme scenario.
So those are the options if dark energy continues
to accelerate the expansion.
And usually those are the two main ones
for an ever-expanding universe.
But what if the quintessence theory suggests it's not
constant?
What if dark energy weakens over time?
Now you're thinking like a cosmologist.
So what happens then?
If dark energy weakens, gravity might regain control.
And instead of endless expansion,
we might see the universe begin to contract.
So instead of a big freeze or a big rip,
we could see a big crunch.
Precisely in this scenario, the universe
would eventually collapse back in on itself,
ending in a fiery singularity.
A reverse big bang, if you will.
It's pretty wild to think that the fate of the entire universe
could hinge on the behavior of this mysterious force.
It is, isn't it?
It highlights just how profound dark energy is.
But its impact goes far beyond cosmology.
Really?
It's forcing us to rethink our most fundamental understanding
of physics.
OK, I'm all ears.
How is dark energy shaking up the foundations of physics?
One of the biggest challenges is trying
to reconcile Einstein's theory of general relativity, which
explains gravity with the principles of quantum
mechanics, which governs the realm of the very small,
these two pillars of modern physics.
General relativity and quantum mechanics.
Which have been incredibly successful in explaining
so much about the universe.
Yeah, they have.
Seem to clash when it comes to explaining dark energy.
So dark energy is highlighting a potential conflict
between our two best theories of the universe.
It's forcing us to confront the possibility
that our current understanding might be incomplete.
I see.
Perhaps there's a deeper theory, a more fundamental framework,
that can unify general relativity and quantum
mechanics and provide a more complete explanation
for dark energy.
So instead of seeing it as a problem,
maybe dark energy is an opportunity
to revolutionize our understanding
of the universe.
Exactly.
It's a chance to push the boundaries of human knowledge
and potentially unlock entirely new physics.
That's exciting.
It is.
Who knows?
Maybe understanding dark energy will
lead to new technologies, new sources of energy,
or even new ways to travel through the universe.
It's almost like dark energy is a key
that could unlock a whole new level of understanding
about the cosmos.
And that's what makes this field so exciting.
It really is fascinating.
We're at the forefront of a scientific revolution,
trying to solve one of the biggest
mysteries in the universe.
It's a humbling thought realizing
how much we still don't know.
It is.
But also inspiring to know that there's
so much left to discover.
It really does make you realize there's so
much more to learn out there.
Yeah.
And for our listeners who share that curiosity
and want to explore this topic further,
we'll have links and resources in the show notes.
Oh, that's a good idea.
You can find more information about the latest research,
upcoming missions like the Euclid Telescope
and the Vera Rubin Observatory, and even
some interactive tools to help visualize
these complex concepts.
That's a great idea.
It's a great way to continue your own deep dive
into the mysteries of dark energy.
I like it, your own deep dive.
And speaking of deep dives.
Yeah.
I have to ask.
Go ahead.
What's one thing about dark energy
that really sticks with you?
Mm.
That's a good question.
What continues to fascinate you about this mystery?
For me, it's the realization that the majority
of the universe is made up of something we don't understand.
Wow.
It's a reminder of how much we still have to learn,
how much is still out there waiting to be discovered.
It's both humbling and incredibly exciting.
I totally agree.
Right.
It's like this cosmic puzzle.
Yeah.
And we're just starting to piece together the edges.
The edges, yeah.
And who knows what incredible discoveries await us
as we delve deeper into this mystery.
It's so exciting to think about.
It really is.
Maybe we'll find that dark energy is even stranger
and more wonderful than we can currently imagine.
Or maybe it will lead us to a completely new understanding
of the universe.
Yeah.
One that rewrites the textbooks.
Exactly.
And opens up possibilities we haven't even considered.
It's a journey full of unknowns.
Yeah.
That's what makes it so compelling.
Yeah, full of them.
It's a testament to the enduring power
of scientific inquiry.
Well said.
And for all our listeners out there,
whether you're seasoned space enthusiasts
or just starting your cosmic journey.
Yes.
Remember that the universe is full of wonder and mysteries
waiting to be explored.
Absolutely.
So keep asking questions.
Keep seeking answers.
Keep learning.
And never stop looking up at the stars.
I didn't agree more.
And on that note, we'd like to thank you
for joining us on this deep dive into the enigmatic world
of dark energy.
Yes.
Thank you for listening.
We hope you've enjoyed the journey.
I hope so too.
Don't forget to follow and subscribe to Cosmos in a Pod
for more explorations of the universe and its many mysteries.
And until next time, keep exploring the cosmos.