“Never look down to test the ground before taking your next step; only he who keeps his eye fixed on the far horizon will find the right road.” -Dag Hammarskjold
One of relativity’s oddest predictions is the existence of black holes, objects so dense and massive that nothing, not event light can escape from them. But that lack-of-escaping is limited to a certain volume of space: that within the black hole’s event horizon. Although black holes have been detected and identified, an event horizon has never yet been imaged. That, however, is likely about to change when the Event Horizon Telescope comes online.
The Atacama Large Millimeter submillimeter Array (ALMA) are some of the most powerful radio telescopes on Earth. They are only one small part of the array forming the Event Horizon Telescope. Image credit: ESO/C. Malin.
Given the general relativistic prediction of the size of the supermassive black hole at the center of our galaxy — 37 microarcseconds — and the resolution of the EHT that spans the diameter of Earth, its event horizon should be visible. Speculations about black holes date back to 1783, and just a few decades after the first black hole candidate was identified, ...