Tag Archives: Einstein

What are the quanta in quantum gravity? A hundred years ago Einstein said “space”. So where are we now?

Quantum gravity is all the rage in physics these days. There are books about it but none say what quantum gravity is. And none report real progress. We should be upset about this. Really! Quantum gravity tries to reconcile our two immensely successful—but mutually inconsistent—theories about the world: quantum theory and relativity. A quantum theory […]

Until recently our cosmic neighborhood was growing faster than the speed of light. Now it’s run into a roadblock.

“From a physical point of view everything that is outside our neighborhood is pure extrapolation.” – Willem de Sitter (1932) Physics is coming up against two fundamental limits: It can never observe the biggest and the smallest things that it needs to study. Some seem satisfied this is the end of our search for ultimate […]

An amazing birthday present: a universe that allows time travel and helps us understand our existence

In 1949 Austrian-American logician Kurt Gödel gave a friend a strange birthday present: a rotating universe. Gödel is widely regarded as the world’s greatest logician. Albert Einstein, the greatest physicist, was his best friend. For years they walked home from the Princeton Institute for Advanced Study almost every day. The present—for Einstein’s 70th birthday—dealt with […]

What is Planck-scale physics and why does it matter?

The Planck-scale physics story begins long ago. In 1901 German physicist Max Planck publishes an explanation for strange properties of radiant heat. He says its energy is quantized. In other words, it radiates in distinct little bits. He sees this as a mathematical convenience and doesn’t really believe it. His math requires a constant he […]