Hydrogen Levels in the Universe

Our Sun is significantly enriched, having formed when the Universe was more than 9 billion years old in the plane of a spiral galaxy, one of the most enriched places in the Universe. Yet, when our Sun formed, it was still made out of?—?by mass?—?71% hydrogen, 27% helium, and about 2% “other” stuff. If we convert that into “number of atoms” and treat the Sun as typical of the Universe, that means, over the first 9.3 billion years of the Universe, the fraction of hydrogen has gone down from 92%...

 The Strong Anthropic Principle

The weak anthropic principle is not very controversial. But there is a stronger form that we will argue for here, although it is regarded with disdain among some physicists. The strong anthropic principle suggests that the fact that we exist imposes constraints not just on our environment but on the possible form and content of the laws of nature themselves. The idea arose because it is not only the peculiar characteristics of our solar system that seem oddly conducive to the development of h...

 Origins of the Big Bang Theory and Evidence For It

That the universe is expanding was news to Einstein. But the possibility that the galaxies are moving away from each other had been proposed a few years before Hubble's papers on theoretical grounds arising from Einstein's own equations. In 1922, Russian physicist and mathematician Alexander Friedmann investigated what would happen in a model universe based upon two assumptions that greatly simplified the mathematics: that the universe looks identical in every direction, and that it looks tha...

 Everything Comes from Stars

What gravity is and why it is, no one knows. Albert Einstein spent most of his life trying to figure it out, but the secret eluded him. it is simply a fact that everything in the universe with mass pulls on everything else. If it weren't for the initial outward impetus of the Big Bang, gravity would have caused the entire universe to collapse into a heap. (Indeed, someday the cosmic collapse may happen, if and when the initial impetus is expended, although the best evidence suggests that the ...