[BLANK_AUDIO] Let's talk about conditions on the early Earth and the conditions in which life
emerged. But, before we do that, we first of all
need To understand how the earth formed in the
early solar system. The solar system formed like all star Systems in the universe, in a molecular
cloud. A molecular cloud is a region of the
universe where hydrogen, helium and some Other elements reach densities that are
high Enough for structure to begin to form. And for the clouds to begin to collapse
under their own weight. This is an example of one. NGC-281. It's a bustling region of star formation
about 10,000 light years away. As the clouds begin to collapse under
their own Gravitational influence, some of this
material forms a protostar, Which is a region of much higher density
at The center of a nebula swirling around
this star. Structures begin to form in these nebula.
For example, this is a bipolar outflow. And what's happening here is the material
is collapsing into the protostar. And the new solar winds being generated by
this early star Is pushing the material out and forming
these outflows around the nebula. So structure begins to form in the
molecular Cloud as well as the star at the center. The most crucial event In the formation of a star system in the
ignition of the Nuclear furnace inside the center of that
protostar in middle of the nebula. And this occurs by a process called
nuclear fusion. This is an example of a reaction of
nuclear fusion where Deuterium is fusing with tritium and
forming helium and also a neutron. And in that process, much energy is
released. The nuclear furnace is ignited, and The star produces light and energy. And it's this light and energy that will
be responsible for driving the rest
Of the processes that are occurring in
this nebula as planets begin to form. Beyond the star in the nebula, material
begins to coalesce and form planets. Beyond the line called ice line volatile
like water, hydrogen, Helium begin to coalesce and become giant
gas planets such As Jupiter, and Saturn in our own solar
system. In the inner regions of that nebular,
smaller pieces of rock begin to coalesce. These planetesimals come together and
eventually form Small rocky planets like Venus, Earth, and
Mars. So there's a very distinctive separation
in the Types of planets that can be formed in
nebulae. Now of course it's worth saying that
things are not quite this simple. Planets can also migrate. It's thought, for instance, that Uranus
and Neptune Have migrated in their past. And the solar system will also pick up Rocky debris in the outer regions of the
nebula. But in the inside of the solar system, in
the inner regions of That solar system, the terrestrial rocky
type planets will form like the Earth. And once Earth had formed, the stage was
then set For conditions to become better and more
appropriate for life. So, what have we learned in this very
brief summary? We've learned that Clouds of gas form that are relatively
dense compared to interstellar space. In these molecular clouds, these star
forming regions, the Gas collapses and leads to the formation
of a protostar. This is called the nebular hypothesis. Eventually, fusion is initiated in the
star, and It starts to give off heat and energy. During this process, material in the
nebula Also begins to collect and form planets. Giant gas planets far away from the star
and rocky Planets further in, as material coalesces
and gathers to form planets.
