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 […]

# Tag Archives: Einstein

# Albert Einstein showed that space has shape. Let’s take a look at this esoteric concept.

We now know that, far from being nothing, space is a something. Indeed space is a much more substantial something than the average density of all the matter that we see in the universe. We also know that space has shape as Albert Einstein showed. But what is the shape of space? How are we […]

# 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 […]

# Genius, Einstein and much ado about nothing: Let’s fix the fallacy of empty space

We think of space as empty. It’s not. Quite aside from stray hydrogen atoms and fleeting quantum particles in the vacuum, space is substantial. It has mass. Indeed Planck-satellite measurements now show space is three times denser than the average of the universe’s matter. Yet like the rest of us most physicists still treat space […]

# Understanding time travel . . . and travel time – Part II

Time is just a tale we tell ourselves to help us manage motion. Last week’s post rocketed you at near light speed to swiftly tour the center of our galaxy. The round trip took you about an hour. Arriving back you found the Earth was 50,000 years older. Time travel— predicted by Albert Einstein in […]

# Understanding time travel . . . and travel time

Albert Einstein predicted time travel in 1905. It was demonstrated in 1971 and many times since. The twin paradox provides a dramatic illustration of time travel: You travel to a distant star and return to find you are far into your twin’s future. No-one has done this; but it is a real effect. It has […]

# A new look at the tiny photon answers some vexing questions and offers a big opportunity.

Albert Einstein introduced the photon to the world more than 100 years ago. Though physicists doubted—even ridiculed—his idea for years, it set off a scientific revolution. The photon now underpins foundations of the world economy. Yet to this day it is a mystery. Even when we know a photon has gone from A to B […]