category: physics

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

Characterizing the 'arrow of time' in open quantum systems

Even in the strange world of open quantum systems, the arrow of time points steadily forward—most of the time. New experiments conducted at Washington University in St. Louis compare the forward and reverse trajectories of …

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 STRUCTURE OF SPACE ACCORDING TO THE GENERAL THEORY OF RELATIVITY

But it is conceivable that our universe differs only slightly from a Euclidean one, and this notion seems all the more probable, since calculations show that the metrics of surrounding space is influenced only to …

EUCLIDEAN AND NON-EUCLIDEAN CONTINUUM

It is a veritable wonder that we can carry our this business without getting into the greatest difficulties. We only need to think of the following. If at any moment three squares meet at a …

BEHAVIOR OF CLOCKS AND MEASURING RODS ON A ROTATING BODY OF REFERENCE

The observer performs experiments on his circular disc with clocks and measuring-rods. In doing so, it is his intention to arrive at exact definitions for the signification of time- and space-data with reference to the …

A FEW INFERENCES FROM THE GENERAL PRINCIPLE OF RELATIVITY

Should we be justified in saying that for this reason electrostatics is overthrown by the field-equations of Maxwell in electrodynamics? Not in the least. Electrostatics is contained in electrodynamics as a limiting case; the laws …

IN WHAT RESPECTS ARE THE FOUNDATIONS OF CLASSICAL MECHANICS AND OF THE SPECIAL THEORY OF RELATIVITY UNSATISFACTORY?

The objection is of importance more especially when the state of motion of the reference body is of such a nature that it does not require any external agency for its maintenance, e.g. in the …

THE EQUALITY OF INERTIAL AND GRAVITATIONAL MASS AS AN ARGUMENT FOR THE GENERAL POSTULATE OF RELATIVITY

Relying on his knowledge of the gravitational field (as it was discussed in the preceding section), the man in the chest will thus come to the conclusion that he and the chest are in a …