From the Big Bang Onward
by Jeremy E., Creation vs. Evolution II Team Member
This is the scenario that scientists have proposed for the origin of the universe and the Earth: In the beginning of it all was a very small wad of pure energy, smaller than an atom. All of a sudden, it started expanding. A split second later, energy started condensing into matter. 100,000 years later, force carrier particles (like photons) and light atoms (hydrogen, helium) formed. A couple trillion years later, large clouds of gas (nebulas) are floating around.
Let's take a look at one of these nebulas. If it is between one tenth and ten solar masses, the energy released by its gravitational collapse will start a fusion reaction in its core, forming a star. In other words, it will ignite. It will "burn" hydrogen, converting it to helium. It will burn this helium when it runs out of hydrogen, and produce all the elements up to carbon. Thus we get the most important element for life on Earth.
On the other hand, if the cloud is from 10 to 30 solar masses, the resulting star will fuse all the way to iron, which will never produce energy from fusion no matter how big the star is. The core collapses less than a second later from its own gravity and the star ends in a supernova (a really big explosion). The supernova's intense heat produces elements all the way up to uranium. This provides metal for rocky planets like the Earth.
After a couple cycles of stars being formed and destroyed, there are enough heavy elements floating around the universe so that when stars form, planets do too. And around one star, nine planets formed, one of which would one day be suitable for life that would name it Earth.
Earth after formation was a huge spinning ball of molten lava pelted by meteorites. It was not a very hospitable place. It took around half a billion years before it had cooled enough for such interesting and useful things as an atmosphere and oceans to form. These things eventually led to life on Earth, or I wouldn't have written this.
Scientists have pieced this scenario together from the mathematics of physics and from observations using telescopes to look at other stars in the process of forming. There are two key evidences for the Big Bang: A "cosmic background" of microwave radiation at 3 degrees Kelvin and the fact that most of the observable universe is expanding.
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