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The Dark Side of the Universe
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Back to the Big Bang

by Polly Hanson

June 22 , 2004 — When did the universe begin? When will it end? Take a look below at our basic timeline of the universe. Gain a little perspective on this expanse of time and space --the history of the cosmos.

  Follow this timeline throughout the history of space.

Big BangCooling OccuresFormation of HeliumOur universe begins expanding at an accelerated rateThe First Generation of StarsThe radiation EraThe stellar era endsSupernova 1987a explodesOur Solar system is formed

The Big Bang 13.7 billion years ago

The Big Bang -
At the moment of the Big Bang, the Universe was infinitely dense and unimaginably hot. In an instant an explosion occurred simultaneously everywhere, filling all space with energy. Unlike an explosion with a distinct center, the Big Bang stretched space between every object everywhere so that everything moved further away from everything else. Cosmologists believe that all forms of matter and energy, as well as space and time itself, were formed in this instant.

Cooling Occurs

One second after the big bang

Cooling Occurs -
As the universe cools after the big bang, the fundamental particles and energy which make up the cosmos such as quarks, electrons, photons and neutrinos smash themsleves together to form protons and neutrons.

The First Atom of Helium is Created 3 minutes after the big bang

The First Atom of Helium is Created- Approximately three minutes after the Big Bang, when the temperature fell to one billion degrees, protons and neutrons combined to form the nuclei of a few heavier elements, most notably helium. For a long time, temperatures remained too high for the formation of most other atoms we know of today.

The Radiation Era 10 thousand years after the big bang

The Radiation Era -
At high temperatures, pressures and densities it is more stable to produce energy than it is matter. In the early universe, basic matter was colliding with itself and being converted to energy faster than mass was being created. As a result, space was made up almost entirely of energy in the form of different wavelengths of light, X rays, radio waves and ultraviolet rays.

The First Generation of Stars 200 million years after the big bang

The First Generation of Stars-
Here we see the oldest light in the universe. As the universe cools --to 3000 degrees-- the atoms have neutralized and stabilized. It is at this time that we see the seeds that generated the cosmic structure we see today -- including stars

Our Universe started Expanding at an Accelerated Rate

Five billion years ago

Our Universe Started Expanding at an Accelerated Rate -
Scientists believe that approximately 5 billion years ago Dark Matter began losing its gravitational pull against Dark Energy's push outward.These Dark Energy forces pulling our universe apart have been observed as accelerating faster and faster over time.

Our Solar System Was Formed 4.5 billion years ago

Our Solar System Was Formed -
Scientists believe that the solar system was formed when a cloud of gas and dust in space was disturbed, maybe by the explosion of a nearby star. This explosion made waves in space which squeezed clouds of gas and dust. Under pressure the cloud starts to collapse. As gravity pulled the gas and dust together a solar nebula is formed.Under pressure and heat the gas and dust began to stick together and form clumps with some eventually forming planets or moons. Scientist are studying nebulae such as the Eagle Nebula to learn more about newly forming solar systems.

Supernova 1987A Explodes 170,000 years ago

Supernova 1987A Explodes -
Explosions of these massive stars distribute many common elements such as Oxygen, Carbon, Nitrogen, Calcium and Iron into interstellar space where they enrich clouds of Hydrogen and Helium that ultimately form new stars. They also create the heavier elements (such as gold, silver, lead, and uranium) and distribute these into the universe. Much of what is created in events such as these have allowed for the proliferation of life on our Earth.

The Stellar Era Will End 100 trillion years in the future

The Stellar Era Will End -
At the current rate of expansion -- and provided the universe does not collapse under the pull of it's own gravity -- astronomers project that the universe will gradually disappear. The forces of Dark Energy will expand forever, creating an increasingly cold and empty space. When the Stelliferous Era comes to a close, we will no longer see stars because the energy generated in the form of stars burning hydrogen will have dissipated from the expansion of the universe.


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