1.8. Birth of the Earth

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来自 University of Illinois at Urbana-Champaign 的课程

Emergence of Life

56 个评分

University of Illinois at Urbana-Champaign

Emergence of Life

56 个评分

How did life emerge on Earth? How have life and Earth co-evolved through geological time? Is life elsewhere in the universe? Take a look through the 4-billion-year history of life on Earth through the lens of the modern Tree of Life! This course will evaluate the entire history of life on Earth within the context of our cutting-edge understanding of the Tree of Life. This includes the pioneering work of Professor Carl Woese on the University of Illinois Urbana-Champaign campus which revolutionized our understanding with a new "Tree of Life." Other themes include: -Reconnaissance of ancient primordial life before the first cell evolved -The entire ~4-billion-year development of single- and multi-celled life through the lens of the Tree of Life -The influence of Earth system processes (meteor impacts, volcanoes, ice sheets) on shaping and structuring the Tree of Life This synthesis emphasizes the universality of the emergence of life as a prelude for the search for extraterrestrial life.

从本节课中

Week 1 - Geological Time and the Nature of Science

The week begins with a discussion of the historical and philosophical approaches that have been developed for the completion of scientific research, with the work of Professor Carl Woese evaluated as an example. The basic tools required for this type of scientific reasoning and the ability to overcome the challenging concepts of scale and complexity are then presented. Finally, we'll explore the dynamic formation of the Earth itself with respect to the environmental conditions present on the earliest and most ancient version of planet Earth.

1.1. Scientific World View8:03

1.2. Philosophical Benchmarks in Science10:21

1.3. Scientific Inquiry vs Scientific Method6:23

1.4. The Scale of Time and Space: Powers of Ten8:28

1.5. NASA’s Greeting Card to Aliens: The Golden Record11:38

1.6. Deep Geological Time4:40

1.7. The Structure of the Solar System7:57

1.8. Birth of the Earth7:35

1.9. The Perfect Storm: A Recipe for Life5:44

与讲师见面

Bruce W. Fouke, Ph.D.
Director of the Roy J. Carver Biotechnology Center
Department of Geology, Department of Microbiology, and Institute for Genomic Biology

[MUSIC]

So let's take a look quickly at the history of how our universe came to be as

a template for looking at evolutionary biology.

All matter in the universe was all compressed into one small point.

And that small point exploded with a force that we cannot imagine.

And that explosion we call the Big Bang.

Now it's possible that we had multiple Big Bangs, but

the most recent Big Bang that generated the universe that we're a part of started

at about 13.8 billion years ago.

So approximately 13.8 billion years is the jump start for

the modern day universe as we know it.

Now if that Big Bang theory is correct, and

it is being modified and thoroughly studied by many people right now.

So our hypothesis of how the Big Bang operates is constantly in flux.

But if that did take place,

then the universe consisted of a chaotic swirling cloud of hydrogen and helium.

These very essential elements that we call a nebula.

Then as the hydrogen and

helium nebula was spinning, it was full of a huge amount of heat.

It went through an ongoing process of rotation and heat loss.

And as it rotated, the rotating mass of gas and

essential elements were transformed into a spinning disk.

And in the middle of that spinning disk,

there was a center bulbous area that we call a Nebula.

And that bulbous Nebula continued to collapse inward on itself,

drawing in matter from the rest of this immense distribution of gas and elements.

Well in the middle of the Nebula, eventually there became a condensed,

very very tightly woven ball if you will of hydrogen atoms

that were colliding and fusing together to create more elements.

So we started off with just the basic element, hydrogen and then helium.

And then we moved to a condition where those elements were being compressed

on themselves and fusing.

And that nuclear fusion then, is what generated all of the rest of the elements

that we know of in our solar system.

So that initial nebula then, kept compressing and

generating through nuclear fusion all these elements, and then it formed a sun.

So this is the general concept of how then that sun is a body

of very condensed gasses and elements, and it radiates heat and light.

And then the solar system then forms around that,

as the sun nebulous center continues to evolve.

So, this is kind of the basic template, then to end up with a central star

that has a lot of elemental material that's spinning around it that can then

evolve to the next step of actually having a star with planets around it.

So one of the most famous and

important examples of this is what we call the Eagle Nebula.

And the Eagle Nebula was photographed by the Hubble telescope illustrating

the synthesis of stars through this nebulous spinning disc rotational process.

So, once we got a structure of a star going through nuclear fusion and

then having all this material swirling around it,

that material continued to cool and it also collided with each other.

And as you had very small elements start to fuse and come together.

Then they would stick together and form larger and larger masses of rock material.

So in this cooling, spinning process that's around the stars, then

that material would accrete together and merge to form what we call planetesimals.

Planetesimals are these proto, early types of coagulated groupings of

matter that are eventually then going to be turning into planets themselves.

Well, the planetesimals continue to collide.

They merge over and over again through this rotational process and

then we end up with a true planet.

Now the outer planets, in addition to having this kind of dense rocky

core that was from the secretion in the spinning around the star,

the outer planets also accumulated very huge amounts of gas.

So that's why we have this structure of the inner four planets are rocky,

the outer four planets are gaseous giants with a rocky core in them.

So in this process then,

then we finally establish a sun with a rotating series of planets around them.

And then we have a lot of material that has not been accreted together to

actually form a planetesimal or form a planet.

Then at that point, then the solar system and Earth itself began to take on

a structure that is not that dissimilar from what we see in the modern day.

So this model of a step wise progression from individual materials that

group together then to form larger materials called planets.

That puts into place then the idea of the structure of the inner and

the outer planets.

Now at that same time,

planet Earth itself was going through a very strong series of changes.

And when you first accrete together these individual fragments of ash and

dust and smaller particles that group and group together.

They begun to heat and they become compressed.

And when they do that, then that process drives what we call the differentiation or

the structural genesis of the Earth.

The modern day Earth has a solid and brittle crust that's on the outside.

Then, we have a very large component within the earth that's composed of

molten rock.

We call it the mantle.

And then within the core of the earth, we have a solid core and a liquid core.

So the Earth's structure of having a crust, a mantle, and

a core, that was all established in this early time period as well.

So, this idea of accreting smaller particles in the larger particles,

having those large particles form planets, and

then having that material become dense and hot.

When you get the large accretions of these into a planet sized object,

one of the results is that you have chemical transformations but

also physical transformations that make the center of the planet hot.

And then the heat is being dispersed outward from that.

Now one of the next questions is, well how do you make things round?

And the roundness of these acredite planetary bodies is caused by their

spinning rotations that go through the solar system.

So not only just the motion through the solar system, but

actually the spin of the planet itself.

And in the end, this makes a spherical body.

Now, the Earth is not perfectly spherical.

No planet is perfectly spherical, but for most practical purposes,

looking it as a sphere is a pretty useful model.

It's actually ellipsoidal in shape because of the stresses that

are put onto planet as it's rotating and spinning.

[MUSIC].

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