.1. The Origin of Life
Life began so long ago that a lot of people believe it impossible to recreate the conditions which enabled life, the first cell. Such skepticism is understandable with the fact we don't have fossils from that period to study and our knowledge on prebiotic Earth is still rudimentary.
.1.1. The Big Bang
Everything in the universe was a soupy concoction of plasma compressed into an area smaller than a pinhead. There was no matter as we can find on the periodic table. Just some subatomic particles (BTW electrons, neutrons and protons are subatomic) brought together by the force of gravity. No one knows for how long the universe stayed in that state or even if time existed. We do know that it was extremely hot with temperatures exceeding 10 billon °C (50 billion °F), 1,000 times hotter than the Sun's core.
Eventually something happened (no one knows what), and that pinhead suddenly exploded 13.7gyr ago(we have an explanation on why the explosion happened here!). Within seconds, the temperature dropped enough for atomic nuclei (x neutrons & x protons) to form: after millions of years when the temperatures were low enough for the firsts elements to form. More on the Big Bang here!
The Sun's heat and luminosity are generated by nuclear fusion reactions (nuclear reactions, involve nuclei, while chemical reactions involve electrons). While 98% of the solar mass is hydrogen (H) and helium (He), 2% consists of heavier elements like nitrogen (N), oxygen (O), carbon (C) and traces of iron (Fe) and other metals.
Throughout the universe, young stars such as our Sun fuse hydrogen to form helium. As stars age, they use up all the hydrogen. without it, the star contracts and it's temperatures rise, making helium nuclei fusion possible, forming carbon (fig. 1). Carbon drives a cyclic nuclear reaction, the CNO cycle, forming isotopes[the number of nucleons (protons and neutrons) in the nucleus is the atom's mass number, and each isotope of a given element has a different mass number] of nitrogen, oxygen. Following nuclear reactions generate heavier elements through iron (Fe). Thus, most of the elements of biomolecules were formed in stars before our solar system was born.
The later reactions of aging stars generate elements up to iron (Fe). The star expands to form a red giant, supergiant,also called supergiant. When the sufficient mass expands, it explodes as a supernova. The energy released by the supernova creates in a brief time all the elements up to plutonium (Pu), number 94, and ejects them all at near light speed into interspace. Billions of years before our solar system was born, thousands of stars were created and died spreading all the elements of the periodic table through out our part of the multiverse.
fig. 1 Life Cycle of a Star and stellar origin of atomic nuclei.
In young stars, hydrogen nuclei fuse to form helium. In older stars helium nuclei fuse to form nitrogen, oxygen, carbon and all heavy elements up to iron. Supergiants explode as supernovas, spreading all elements across space. These elements form new stars. more on stars here!
As new stars form, and while those stars fuse new atoms, the existing atoms orbit around the them and they to create new clouds with a gravitational pulse, and with motion, they turn into spheres.
Now, there are two basic types of planets: rocky planets and gas or ice giant planets.
Rocky planets are planets primarily composed of silicate rocks or metals. In our solar system, they are located the closest to the sun, i.e. Mercury, Venus, Earth and Mars. They have a solid planetary surface, making them different from the giant planets, composed of H, He and H2O present in various states more on rocky planets here.
Gas giants are giant planets mainly composed of H and He, the other elements make up between 3 and 13 % of the mass. Saturn & Jupiter are the Solar System's gas giants. They are believed to have an outer layer of molecular hydrogen, in gaz form, surrounding a layer of liquid metallic hydrogen, a phase when it behave as an electrical conductor, with a molten rocky core.
The outermost portion of their hydrogen atmosphere is characterized by many layers of visible clouds that are mostly composed of water and ammonia. The gas giants cores are thought to consist of heavier elements at such high high temperatures (20,000 K) and pressures that their properties or poorly understood.
Ice giants are giant planet composed mainly of elements heavier than hydrogen and helium, such as oxygen, carbon, nitrogen, and sulfur. There are two known ice giants in the Solar System, Uranus and Neptune. Since 2014, there has been evidence of the existence of a third ice giant, which, if found, would be the solar system's ninth planet.
Ice giants consist of only about 20% hydrogen and helium in mass, as opposed to the Solar System's gas giants (Jupiter and Saturn), which are both more than 90% hydrogen and helium in mass. In the 1990s, it was realized that Uranus and Neptune are a distinct class of giant planet, separate from the other giant planets. They have become known as ice giants because their constituent compounds were ices when they were primarily incorporated into the planets during their formation, either directly in the form of ices or trapped in water ice. The amount of solid volatiles within the ice giants today is, however, very small.
.1.2. The Conditions For Life
Before the first cells could evolve, several basic conditions were needed, including:
- Essentials elements: all life is composed of molecules, so life needed the fundamental components required to create organic molecules.
- Continual source of energy: the generation of life needs a continual input of energy, ultimately dissipated as heat. The main source of energy for life is nuclear fusion reactions within the Sun.
- Temperature range permitting liquid water:Above 150°C, life's macromolecules fall apart;and below 0° metabolic reactions (all chemical reactions that happen in living organisms) cease. Maintaining the narrow temperature range conducive to life depends on the nature of our Sun, our planet's distance from the Sun and our atmosphere's heat trapping capacity.
.1.2.1. Elements of Life
The planet Earth combined elements together during the formation of the solar system 4.5 Gigayears ago (Gyr, Gigayear, in geological description, a billion years). The Sun, center to our solar system, is a "yellow" star of medium size and surface temperature (5,770 K, about 5,496.85°C, 9926.33°F). The Sun's surface temperature generates electromagnetic radiation across the spectrum, peaking in range of visible light. As we will see further on, the photon energies of visible light are sufficient to drive photosynthesis but not so energetic to destroy biomolecules. Thus, the stellar class of our Sun makes organic life possible.The Sun's heat and luminosity are generated by nuclear fusion reactions (nuclear reactions, involve nuclei, while chemical reactions involve electrons). While 98% of the solar mass is hydrogen (H) and helium (He), 2% consists of heavier elements like nitrogen (N), oxygen (O), carbon (C) and traces of iron (Fe) and other metals.
.1.2.2. Heavier elements, where do they come from?
Throughout the universe, young stars such as our Sun fuse hydrogen to form helium. As stars age, they use up all the hydrogen. without it, the star contracts and it's temperatures rise, making helium nuclei fusion possible, forming carbon (fig. 1). Carbon drives a cyclic nuclear reaction, the CNO cycle, forming isotopes[the number of nucleons (protons and neutrons) in the nucleus is the atom's mass number, and each isotope of a given element has a different mass number] of nitrogen, oxygen. Following nuclear reactions generate heavier elements through iron (Fe). Thus, most of the elements of biomolecules were formed in stars before our solar system was born.
The later reactions of aging stars generate elements up to iron (Fe). The star expands to form a red giant, supergiant,also called supergiant. When the sufficient mass expands, it explodes as a supernova. The energy released by the supernova creates in a brief time all the elements up to plutonium (Pu), number 94, and ejects them all at near light speed into interspace. Billions of years before our solar system was born, thousands of stars were created and died spreading all the elements of the periodic table through out our part of the multiverse.
In young stars, hydrogen nuclei fuse to form helium. In older stars helium nuclei fuse to form nitrogen, oxygen, carbon and all heavy elements up to iron. Supergiants explode as supernovas, spreading all elements across space. These elements form new stars. more on stars here!
As new stars form, and while those stars fuse new atoms, the existing atoms orbit around the them and they to create new clouds with a gravitational pulse, and with motion, they turn into spheres.
Now, there are two basic types of planets: rocky planets and gas or ice giant planets.
Rocky planets are planets primarily composed of silicate rocks or metals. In our solar system, they are located the closest to the sun, i.e. Mercury, Venus, Earth and Mars. They have a solid planetary surface, making them different from the giant planets, composed of H, He and H2O present in various states more on rocky planets here.
The outermost portion of their hydrogen atmosphere is characterized by many layers of visible clouds that are mostly composed of water and ammonia. The gas giants cores are thought to consist of heavier elements at such high high temperatures (20,000 K) and pressures that their properties or poorly understood.
Ice giants are giant planet composed mainly of elements heavier than hydrogen and helium, such as oxygen, carbon, nitrogen, and sulfur. There are two known ice giants in the Solar System, Uranus and Neptune. Since 2014, there has been evidence of the existence of a third ice giant, which, if found, would be the solar system's ninth planet.
Ice giants consist of only about 20% hydrogen and helium in mass, as opposed to the Solar System's gas giants (Jupiter and Saturn), which are both more than 90% hydrogen and helium in mass. In the 1990s, it was realized that Uranus and Neptune are a distinct class of giant planet, separate from the other giant planets. They have become known as ice giants because their constituent compounds were ices when they were primarily incorporated into the planets during their formation, either directly in the form of ices or trapped in water ice. The amount of solid volatiles within the ice giants today is, however, very small.
.1.2.3. Elemental composition of Earth
Our planet is, as I am sure you have
guessed, a rocky planet. When our planet was formed, because of Earth’s small
size, most of the hydrogen gas escaped from its gravitational pull very early. Much
of the iron sank to form the core. The iron core is surrounded by a core of iron
combined with less dense crystalline minerals such as silicates of iron and
magnesium, (Fe,Mg)2SiO4. The mantle is coated by The thin
crust. The mantle is covered by the thin crust composed primarily of SiO2,
also known as quartz or chert.
fig. 1.2 Life Cycle of a Star and
stellar origin of atomic nuclei.
The Inner Core
is about 1250 km thick and
is the second smallest layer of the Earth. Although it is one of the smallest,
the Inner Core is also the hottest layer. The Inner Core is a solid ball composed
of an element named NiFe. (Ni) Nickel. The Inner Core is about 5000-6000
degrees Celsius. It melts all metal ores in the Outer Core causing it to turn
into liquid magma. The Outer Core is about 4000-5000 degrees Celsius. The Inner
Core is so hot it causes all the metal in the Outer Core to melt into liquid
magma. The Outer Core is composed of iron and some nickel. There is very few rocks and iron and nickel ore left in the
Outer Core because of the Inner Core melting all the metal into liquid magma. The
Outer Core is about 2200 km thick. It is the second largest layer and made
entirely out of liquid magma. Because the outer core moves around the inner
core, Earth's magnetism is created. The mantle is divided into two
sections. The Asthenosphere, the bottom layer of the mantle made of plastic
like fluid and The Lithosphere the top part of the mantle made of a cold
dense rock. The average temperature of the mantle is 3000° Celsius. The
temperature of the mantle will become much hotter as you get closer to the Inner
Core The mantle is composed of silicates of
iron and magnesium, sulfides and oxides of silicon and magnesium. The mantle is
about 2900 km thick. It is the largest layer of the Earth, taking up 84%
of the Earth. Convection currents happen
inside the mantle and are caused by the continuous circular motion of rocks in
the lithosphere being pushed down by hot molasses liquid from the asthenosphere.
The rocks then melt and float up as molasses liquid because it is less dense
and the rocks float down because it is denser. The Lithosphere is the top half of the
mantle. It is a cold dense rock. This rock will be forced into the liquid in
the asthenosphere causing it to melt and be pushed back up again causing
the melted rock to cool off and return to normal rock. This is called Convection Currents. The Asthenosphere is the bottom half of the
mantle. It is a hot plastic liquid that is a liquid molasses like substance. This
hot molasses substance will be forced into the lithosphere causing the
liquid to cool off into rock, only to be forced back into the asthenosphere
causing the rock to melt. This is called Convection Currents. The Crust
is composed of mainly granite, basalt, and diorite rocks The Crust's
thickness can vary from wherever you are. From a continent to the edge of
the crust is about 60 km. From the bottom of the ocean to the edge of the
crust is about 10 km. The Crust's temperature
is different throughout the entire crust. The temperatures start at about
200°C and can rise up to 400°C.
In the Mantle there are Convection Currents which will be defined
more in the mantle section. These huge currents are causing the crust to
constantly move. These movements will cause earthquakes and volcanoes to erupt.
The moving of the crust is also known as The Theory Of Plates Tectonics.
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