-star heated up due to friction --> caused nuclear fusion, hydrogen atoms fused together to form helium and photons-

-matter began to form, creating space with great density as energy converted to matter.

-was observed in red shift of distant galaxies

-background radiation

-H, He abundance

Background Radiation --> the "original flash" of light, radiation persisting from the Big Bang once the Universe became transparent.

-It is so far red-shifted that we see it today as light in the radiowave (microwave) spectrum. It is the flash of the Big Bang!

-the free photons from the early glowing explosion are seen even today in the microwave background radiation.

-0.01 s after the Big Bang, the temperature was 100 billion degrees C. No atoms existed, only constituent pieces, electrons, positrons, neutrinos, photons. The density was 4 billion gm/cm3.

-1 second after, the volume of space was growing, rapidly decreasing the density of the Universe and letting it cool

-180 seconds after, protons and neutrons became stable forms of matter, providing H and He nuclei. The binding together of the Helium nucleus released energy, and is the process called fusion.

-From there on, expansion, cooling, aggregation into galaxies and stars (after a few billion years) took place

law: natural laws are invariant in space and  time

process: past results are outcomes of causes in operation today

rate: ordinary process working for a long time yields dramatic changes

conditions: no progress or direction in the system, equilibrium exists

Doctrine that changes in the Earth have often involved sudden events caused by physical forces operating in ways not routinely observed today.

-magma ocean

-earth was hotter by hundreds of degrees

-mantle convection more vigorous

-H20, c02 and other gases relased by intense volcanism up the atmosphere and hydrosphere

-granite rocks began to form continents

-big impactors replaced our entire atmosphere with rock vapor for a few centuries

Having segregated the iron into the core, the Earth was merrily on its way. Ahh, but wait. There were a few extra large planetismals out there still. One of these rare, large planetisimals about the size of Mars impacted the Earth. This sprayed much of the initial Earth's rocky mantle into space with a huge collision, converting the rocky material into liquid and even gas. While some material fell back to Earth and some escaped to space, a significant amount re-condensed and cooled, finally accreting to form the Moon.

What is the effect on evolution for suffering large impacts?

-Throughout this time there were continued large impacts that would burn off the atmosphere and oceans, disrupting any progress life was making.

-The primary layered structure of the Earth was established early on, during the core formation process, but the steady circulation of the rocky silicate mantle has resulted in melting of mantle rocks, from which the crust has been progressively extracted along with the bulk of the oceans and atmosphere.

-Each collision injects heat energy into the Earth, as the kinetic energy of the meteorite is converted to another form of energy: heat. Calculations of the amount of energy available from these impacts indicate that it is easily sufficient to melt the entire surface of the planet, and perhaps the whole interior. Thus, from 4.55-4.5 billion years ago the planet had a huge ocean of magma, or molten rock: a magma ocean.

Throughout this time there were continued large impacts that would burn off the atmosphere and oceans, disrupting any progress life was making. This is called Impact Frustration. The probability of impacts decreased with time as space cleared out in the inner solar system, and eventually the atmosphere and ocean built up to a degree that was never again obliterated by an impact.

1. Size: The Earth accreted enough mass to be the size that it is; not too profound of a point, seemingly, but in fact the mass of the Earth is important. For instance, the mass is sufficiently large to have enough gravity to retain large gaseous molecules, such as N, O, H2O, CO2, but to allow H and He to escape into space. In contrast, a massive planet such as Jupiter is burdened by huge amounts of H and He, held to the planet by its massive gravity.

2. Temperature: This is the 100 degree C range from boiling of water to freezing of water. The Earth conditions allow water in all three phases to exist on the planet (solid ice, liquid water, and gaseous steam). If the Earth were hotter all of the water would always be in vapor state in the atmosphere, whereas if it were colder it would all always be frozen in the ice caps.
3. Distance from the Sun: Earth is at a favorable distance from the Sun in that the amount of solar radiation which heats the atmosphere daily does not drive huge damaging storms continually. Also, the radiation received by the Earth is relatively mild, yet enough to provide good visible light and modest UV that produces mild rates of chromosomal mutation to facilitate evolution.