category: cosmology

There’s a glitch at the edge of the universe that could remake physics

RECIPE FOR A HOT UNIVERSE

Fortunately for the theoretical cosmologist, the same simple relation holds even when we take into account the fact that the radiation was not really expanding freely—rapid collisions of photons with the relatively small number of …

THE EXPANSION OF THE UNIVERSE 2

It was clear that these extended objects are not all the same. Some are obviously clusters of stars, like the Pleiades (M45). Others are irregular clouds of glowing gas, often colored, and often associated with …

THE EXPANSION OF THE UNIVERSE 1

Our knowledge of the expansion of the universe rests entirely on the fact that astronomers are able to measure the motion of a luminous body in a direction directly along the line of sight much …

THE ORIGIN OF THE UNIVERSE 1

I must not offend religious sensibilities, even Viking religious sensibilities, but I think it is fair to say that this is not a very satisfying picture of the origin of the universe.

THE FIRST ONE-HUNDREDTH SECOND BY STEVEN WEINBERG 3

So far our imagination carried us back to a temperature of 5,000 million million degrees, and we have had to deal with the strong, weak, and electromagnetic interactions. What about the one other grand class …

THE FIRST ONE-HUNDREDTH SECOND BY STEVEN WEINBERG 2

These rather intuitive ideas have recently been put on a much firmer mathematical foundation. In 1973 it was shown by three young theorists, Hugh David Politzer of Harvard and David Gross and Frank Wilczek of …

THE COSMIC MICROWAVE RADIATION BACKGROUND 2

The one piece of numerical data that was available to Penzias and Wilson was the intensity of the radio noise they had observed. In describing this intensity they used a language that is common among …

THE COSMIC MICROWAVE RADIATION BACKGROUND 1

Now we come to a different kind of astronomy, to a story that could not have been told a decade ago. We will be dealing not with observations of light emitted in the last few …

GALILEAN RELATIVITY 2

The principle of relativity was first enunciated by Galileo in 1632. Galileo's argument is clear and graphically put. Salviatus: Shut yourself up with some friend in the main cabin below decks on some large ship …

The Postulates of Relativity and Their Implications 3

The most profound conceptual implication of special relativity is the change it has brought about in our perception of the nature of time. Relativity requires us to reject the notion of absolute time, which was …

The Postulates of Relativity and Their Implications 2

Millikan's account paints a dramatic (and credible) picture. Yet in his own writings Einstein suggests that Michelson's experiment played at most a minor role in the genesis of special relativity.