A City Map Where the Streets Stay the Same but the Distances Change
Imagine a city drawn on a sheet of paper. The streets are the same, the intersections are in place, but the distances between blocks have suddenly changed.
Quantum Geometry Imprints in the Black Hole Shadow
The shadow of a black hole is not just a dark silhouette. It is an imprint of the entire spacetime geometry, including the subtlest quantum effects.
A Black Hole in a Cloud of Dark Matter
A black hole is not just a void but a massive object that warps the space around it. If it finds itself in a cloud of invisible dark matter, matter that emits no light but makes itself known through gravity, its behavior changes.
A Vortex's Silent Patch Reveals Its Speed
In a water vortex swirling toward the drain, the flow speed near the center can exceed the speed of sound. Sound gets trapped: waves cannot escape back, forming a silent region — a sound shadow. Half a century ago, William Unruh realized that this is an exact copy of a black hole, but for sound instead of light.
Time Can Still Be Tricked
Some solutions to Einstein's equations allow closed timelike curves — loops that let you travel to the past. Two well-known designs, the Ori geometry and the Ahmed geometry, do without exotic matter, catching physicists' eyes.