Name: 宇宙之旅--生命。命運還是機會？ (Cosmic Journeys - Life: Destiny or Chance?)
Uploaded: 2021-01-14T05:15:08.000Z
Duration: 25 min 16 s
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Long ago, giant exploding stars spread clouds of cosmic dust.

Some of the dust coalesced into our solar system.

Over time, on this planet, Nature put it to use in an increasingly complex experiment

We've been using components of the dust cloud - iron, aluminum, and silicon -

What we've learned has only deepened the mystery of our place in the universe.

Scientists and philosophers alike want to know: Is life a fluke,

Or is the universe somehow fine-tuned to allow life to arise, and flourish

We are living in an age of precision cosmology. With new generations of giant telescopes on

land, and specialized instruments in space,

astronomers are probing the forces that shaped  our universe.

They are documenting its behavior on the largest of scales

going back to the first micro-moments of its existence.

They are charting its evolution hundreds of billions of years into the future.

For all we have learned about the universe as a whole, profound questions remain:

what does it all add up to? How do you explain this rise of complex life, intelligent life?

Some scientists point to the finely tuned interactions of gravity, electromagnetism,

and the strong and weak nuclear forces within the atom.

If the strength of any these forces had varied only slightly, the universe might  after

have flown apart and dissipated moments it was born.

Or gravity might have reined it in, forming one giant black hole.

In either case, the universe would have no galaxies, stars, planets, or life.

Was the basic layout of physical laws a coincidence? Or was it somehow meant to be?

One answer, from what's often known as the Anthropic principle, holds that the universe

To some, this implies that the universe is imbued with purpose. We, who are able to observe

the universe and document its workings, are proof that this is so.

But that conclusion, which can't be falsified, is more of a religious or philosophical concept

Consider the broad arc of cosmic history. Trillions upon trillions of years from now,

all the stars in the universe will slowly burn out. Much of the matter we see in galaxies

will gradually drift in toward their centers and be swallowed by black holes.

All will go dark, eventually fading into the dark reaches of infinity.

Overall, the evolution of life, and intelligent life, is a minor event, probably confined

There's another way to ask the question. Are the processes that give rise to life central

In search of answers, we'll explore the origin of two of life's most important components:

Our story begins in the earliest moments of time, when the universe was awash

Gravity drew it into denser and denser regions, where the earliest stars were born.

Generation after generation of stars formed and died.

In the larger ones, fusion produced the elements carbon and oxygen.

They became, by mass, the third and fourth most abundant elements in the universe.

Heavier elements followed, including those created in the violent death of large stars.

This animation depicts a supernova spotted by Chinese astronomers in the year 1054 AD.

The star was utterly destroyed, except for a spinning ultra-dense core the size of a

city, a neutron star, and an expanding cloud of gas and dust.

Astronomers have been poring over the Crab nebula, still growing at a rate of a thousand

What they found is that the filaments of matter that roared out of the blast contain large

volumes of dust, an array of mostly carbon or silicate compounds that absorb visible

These solid particles are crucial for the formation of solar systems. Within the Crab

nebula, there is enough dust to make some 30 to 40,000 Earths.

Over time, and after countless stellar explosions, dust has collected in dense pockets throughout

But dust grains can be found throughout intergalactic space as well.

Some might have come from the earliest supernovas.

Since the 1960s, astronomers have been studying bright beacons of light that shine from the

A quasar's power source, they've found, is a black hole that has grown to millions, even

billions, of times the mass of our own sun.

The thinking is that magnetic fields leap off a disk of matter that's spiraling into

the black hole, drawn by its extreme gravity. These fields channel a portion of the inflowing

The  jet is part of a larger rush of matter away from the black hole.

You can see it in a large spiral galaxy called NGC 3783, 30 million light years from earth.

Astronomers used the Very Large Telescope array in Chile's Atacama Desert to peer into

the core of this galaxy to study the environment of a supermassive black hole.

From a disk of matter flowing into the black hole, intense radiation had created a dusty

wind that is moving up and away from the black hole.

The source of the dust is likely generations of giant stars that lived and died in the

Black hole winds are now thought to have had a major impact on the universe at large.

You can see it in a simulation of early cosmic evolution.

It starts 12 million years after time zero, and evolves within a volume 350 million light

Not everything is known, including the nature of a dominant substance known as dark matter.

Gravity draws matter into filaments, where it heats up, forming a vast luminous web.

In time, tens of thousands of galaxies take shape.

The action heats up where filaments meet.

Giant bubbles of hot gas form and expand outward, pushing well beyond the central galaxies.

This happens when galaxies merge, sending streams of matter into black holes that lie

in their centers. These monsters, in turn, blast inflowing matter out in jets and winds.

This seeds the wider universe with dust and gas.

In our galaxy, dust has collected in star-forming regions, like the Orion Nebula, 1500 light

At its heart is a star cluster called the Trapezium, a brilliant formation first discovered

by Galileo. It pumps out a wind of ultraviolet radiation that clears the surrounding region

In its midst, perhaps a thousand hot young stars are being born. Some are blasting out

jets of radiation that carve out ghostly red shapes in their surroundings.

Around young stars like these, enshrouded in dust, nature sets the stage for the alchemy