July 25th, 2012
The universe was created 13.73 billion years ago. At about 10-44 seconds after the big bang inflation kicked in and underwent a period of rapid inflation (expansion, this inflation force is thought to be dark energy depicted in Einstein’s lambda term (the cosmological constant) in the right hand side of his field equation describing the energy momentum of the universe.) The cosmological constant is a characteristic of the spacetime fabric of the universe related to its stretching energy (space energy density—commonly referred to as dark energy). The more the universe expands, the greater this stretching energy becomes. When the spacetime fabric stretches, the bodies of masses, such as galaxies, move farther apart by the stretching of space. The cosmological constant is in effect a pulling property that works against gravity. Since creation, the cosmological constant’s effect has been increasing.
Initial expectations were for the expansion to slow down and for the universe to collapse back in on itself. For instance, when a ball is tossed in the air its speed slows down and the ball falls to the ground. If the cosmological constant were applicable on the scale of tossing a ball in the air the ball would not slow down and return to the ground, it would actually increase in speed and move farther away from where it was tossed. This immediately leads to questions concerning the end of the universe. Either way, gravity contracts back in on itself or dark energy expands the universe to equilibrium (due to the cosmological constant’s effect), the universe is condemned to eventual futility. The advent of relativity theory and its application to cosmology altered the shape of the eschatological scenario on the basis of the second law of thermodynamics.
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July 12th, 2012
We know the universe began 13.7 billion years ago in an immensely hot dense state much smaller than a single atom. It began to expand about a million billion billion billion billionth of a second after the big bang. Gravity separated away from the other forces. The universe then underwent an exponential expansion called inflation. In about the first billionth of a second or so, the Higgs field kicked in, and the quarks, the gluons, the electrons that make us up got mass. The universe continued to expand and cool. After about a few minutes there was hydrogen and helium in the universe. That’s all. The universe was about 75% hydrogen, 25% helium. It still is today. It continued to expand about 300 million years. Then light was big enough to travel through the universe. It was big enough to be transparent to light, and that’s what we see in the cosmic microwave background. After about 400 million years, the first stars formed and that hydrogen, that helium, then began to cook into heavier elements… Stars were cooked up, exploded, and then re-collapsed into another generation of stars and planets. And on some of those planets in that first generation of stars could fuse with hydrogen to form water, liquid water on the surface… The laws of physics, the right laws of physics, they’re beautifully balanced. They couldn’t have been different. If the weak force were different then carbon and oxygen wouldn’t be stable in the hearts of stars and there would be none of that in the universe. And I think that’s a wonderful and significant story. (Brian Cox, TED2008, March 2008)
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June 8th, 2012
Reblogged from Philip Ball in Nature.
Black holes are staples of science fiction and many think astronomers have observed them indirectly. But according to a physicist at the Lawrence Livermore National Laboratory in California, these awesome breaches in space-time do not and indeed cannot exist.
Over the past few years, observations of the motions of galaxies have shown that some 70% the Universe seems to be composed of a strange ‘dark energy’ that is driving the Universe’s accelerating expansion.
George Chapline thinks that the collapse of the massive stars, which was long believed to generate black holes, actually leads to the formation of stars that contain dark energy. “It’s a near certainty that black holes don’t exist,” he claims.
Black holes are one of the most celebrated predictions of Einstein’s general theory of relativity, which explains gravity as the warping of space-time caused by massive objects. The theory suggests that a sufficiently massive star, when it dies, will collapse under its own gravity to a single point.
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