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Welcome to the Bedtime Scientist.
Tonight we aren't crossing land.
We're going somewhere that even fewer human beings have reached than the moon.
We're heading far below the open ocean.
Before we go, take a deep breath in.
Let it out.
Close your eyes and imagine.
You're in the middle of the Pacific Ocean.
It's night above us.
A wide sky full of stars.
The water below is calm and dark, stretching in every direction.
Floating nearby is a deep ocean craft.
We climb in through the hatch.
Two cushioned chairs.
A curved viewing window.
Panels glow with muted green and amber light.
A low, steady hum. moves through the floor.
Above us, the hatch closes with a gentle dull tone.
And slowly, very slowly, we begin to go down.
At first, the water beyond the window glows deep blue.
Moonlight still reaching this upper layer.
Then color begins to leave.
Red is the first to go.
It vanishes within the top five meters, absorbed by the water almost immediately.
The way a thick wall absorbs sound.
Orange follows by about 25 meters.
Yellow by 50.
Green lingers the longest of the warm colors, fading out about 100 meters.
Below, that is the aphotic zone, the zone without light where the sun has never reached and never will.
Outside our craft, a creature drifts by.
It's long, nearly transparent, and from somewhere deep inside it, A soft blue light begins to pulse, slow and steady, like a heartbeat made of light.
This is bioluminescence.
It isn't electricity or fire.
It's a chemical reaction between two molecules called luciferin and luciferase.
When they meet in the presence of oxygen, they release energy not as heat, but as cold, quiet light.
This evolved independently in dozens of different lineages.
Fish, squid, jellyfish, worms... bacteria, each finding the same solution in the dark.
More than three-quarters of all deep ocean creatures carry some version of it.
The creature drifts past.
The blue pulses once more, then fades back to black.
Below us now, a faint pale plain comes into view, soft as anything you've ever touched.
This is a layer of sediment made entirely from the remains of tiny creatures that once lived near the bright surface far above us.
When their time ended, they began to fall.
Very slowly.
So slowly that a single grain can take six months to sink just four kilometers.
Imagine a single snowflake falling so gently, so slowly. that half a year passes before it lands.
That's how this floor was built, flake by flake, year by year, over millions of years.
Then the ground falls away.
It opens into something vast.
This is the mariana trench.
It formed when two great plates of earth's crust slowly met the pacific plate sliding beneath the mariana plate in a process called subduction, bending downward into the mantle, carving this deep canyon over 50 million years.
That's 50 million years of slow, patient movement, a few centimeters a year, age by age.
The trench curve 400 kilometers.
We guide the craft downward along its inner wall.
6,000 meters down, 9,000 meters.
The walls rise high on either side, far beyond the reach of our light.
Outside, The pressure is now approximately 1086 times what you feel at the surface, pressing in from every direction.
But the craft we're in is shaped as a sphere, so that force arrives evenly. and cancels itself out.
Nothing inside has to resist it.
We remain warm, still, at ease, and at last, the very bottom of the canyon comes into view.
We settle gently onto the deepest known point in the ocean, the Challenger, Deep 10935 meters below the waves.
If Mount Everest, which is 8849 meters tall, were placed here, its peak would still be more than two kilometers underwater.
Only a Fewer than have walked on the moon.
Beyond the window, something moves.
Small pale creatures drift and skitter across the sediment.
Amphipods.
A kind of crustacean, distantly related to the shrimp on your dinner plate but adapted to live here and nowhere else on Earth.
Scientists have found them carrying microplastics in their body, a reminder that even the deepest place on the planet is not entirely untouched by the world above.
Larger still, spread across the sediment like enormous snowflakes, are single-celled organisms that can grow to 20 centimeters across, making them the largest individual cells known to exist anywhere on Earth.
One cell, 20 centimeters wide. living in the dark at the bottom of the ocean.
The mud itself is alive with bacteria, drawing energy not from the sun there is no sun down here but from chemicals seeping up through the seafloor.
This process is called chemosynthesis.
Life running on a completely different engine than almost everything on the surface.
No sun is required.
No photosynthesis.
Just chemistry and pressure and time.
When scientists first discovered life around hydrothermal vents back in 1977, they found tube worms nearly two meters long, ghostly crabs, fields of mussels.
It genuinely changed what we understood life to be.
We had assumed sunlight was the foundation.
It isn't.
Life just needs energy, and the Earth provides it in more ways than one.
That discovery sent scientists looking outward.
Jupiter has a moon called Europa.
It's wrapped in a shell of ice.
But beneath that shell kept liquid by Jupiter's immense gravity, is a dark saltwater ocean estimated to be between 60 and 150 kilometers deep.
For comparison, the average depth of Earth's oceans? is just 3.7 kilometers.
Saturn's moon Enceladus, actively vents water vapor from cracks near its south pole, carrying with it organic molecules and heat from a liquid ocean hidden beneath its frozen surface.
Both of these worlds may have seafloors not unlike the one outside our window right now.
Dark and cold and pressurized.
And possibly home to things we've never imagined.
If life can hold on here, at the deepest part of our ocean, without a single photon of sunlight ever reaching it, then the universe begins to feel less empty.
Sit with that thought for a moment.
Nearly 11 kilometers of water above our head.
Ancient rock below single-celled organisms the size of coins, moving slowly through the oldest quiet on earth.
The motor of our craft deepens in tone and very gradually, very slowly, we lift from the canyon floor.
Dark surrounds us for a long time.
Then faintly, the black softens.
Blue returns.
The water warms layer by layer.
Green joins the blue.
Then, far above. the faint silver glow of moonlight on the surface.
At last our journey is done.
We rise into open air.
The hatch opens.
Night surrounds us.
The ocean rocks us gently beneath a sky full of stars.
Let your thoughts drift the way the ocean does, slow and soft, without effort.
And just before you drift off to dream about the quiet deep of the ocean, I want you to know something about you.
Your mind is a wonderful thing, so full of curiosity.
And I, like your mind, just the way it wonders.
I'll be back again soon to wonder more with you.
