String theory, like most revolutions, had humble origins. It started all the way back in the 1960’s as an attempt to understand the workings of the strong nuclear force, which had only recently been discovered. Quantum field theory, which had been used successfully to explain electromagnetism and the weak nuclear force, wasn’t seeming to cut it, and so physicists were eager for something new.

Continue reading “How Supersymmetry Saved String Theory”## Holograms Might Save Physics

Even though the guts of General Relativity are obtusely mathematical, and for decades was relegated to math departments rather than proper physics, you get to experience the technological gift of relativity every time you navigate to your favorite restaurant. GPS, the global positioning system, consists of a network of orbiting satellites constantly beaming out precise timing data. Your phone compares those signals to figure out where you are on the Earth. But there is a difference in spacetime between the surface of the Earth and the orbit of the satellites. Without taking general relativity into account, your navigation would simply be incorrect, and you’d be late for dinner.

Continue reading “Holograms Might Save Physics”## Why the Universe Might be a Hologram

A quarter century ago, physicist Juan Maldacena proposed the AdS/CFT correspondence, an intriguing holographic connection between gravity in a three-dimensional universe and quantum physics on the universe’s two-dimensional boundary. This correspondence is at this stage, even a quarter century after Maldacena’s discovery, just a conjecture. A statement about the nature of the universe that *seems* to be true, but one that has not yet been proven to actually reflect the reality that we live in. And what’s more, it only has limited utility and application to the real universe.

## The Strangest Coincidence in Physics: The AdS/CFT Correspondence

Attempts to turn string theory into a workable theory of nature have led to the potential conclusion that our universe is a hologram: that what we perceive as three spatial dimensions is actually composed of only two. The greatest realization of this hologram-led program is a proposal that goes by the awkward and clunky name of the AdS/CFT correspondence, first proposed by string theorist Juan Maldacena in the late 1990’s.

Continue reading “The Strangest Coincidence in Physics: The AdS/CFT Correspondence”## Why String Theory Requires Extra Dimensions

String theory found its origins in an attempt to understand the nascent experiments revealing the strong nuclear force. Eventually another theory, one based on particles called quarks and force carriers called gluons, would supplant it, but in the deep mathematical bones of the young string theory physicists would find curious structures, half-glimpsed ghosts, that would point to something more. Something deeper.

Continue reading “Why String Theory Requires Extra Dimensions”## The Holographic Secret of Black Holes

As weird as it might sound, black holes appear to be holograms.

Continue reading “The Holographic Secret of Black Holes”## How Black Holes Consume Entropy

*Entropy* is one of those fearsomely deep concepts that form the core of entire fields of physics (in this case, thermodynamics) that is unfortunately so mathematical that it’s difficult to explain in plain language. But we will give it a try. Whenever I see the word entropy, I like to replace it with the phrase “counting the number of ways that I can rearrange a scenario while leaving it largely the same.” That’s a bit of a mouthful, I agree, and so *entropy* will have to do.

## The Origins of the Black Hole Information Paradox

While physics tells us that information can neither be created nor destroyed (if information could be created or destroyed, then the entire *raison d’etre *of physics, that is to predict future events or identify the causes of existing situations, would be impossible), it does not demand that the information be *accessible*. For decades physicists assumed that the information that fell into a black hole is still there, still existing, just locked away from view.

## The Maddening Simplicity of Black Holes

Black holes.

The name is said to come from the Black Hole of Calcutta, an infamous prison that you cannot escape from. It is a fitting name, for black holes are the ultimate cosmological prison.

Continue reading “The Maddening Simplicity of Black Holes”## Why Even Einstein Couldn’t Unite Physics

Near the end of his life Einstein worked tirelessly to find a way to unite electromagnetism with gravity. He could not, and never did, the notes scattered on his desk scrawled with fruitless probes and useless hypotheticals. Indeed, Einstein passed without even understanding *why* the two forces could not be united.