Imagine a time of technological advancement far beyond anything we know today. You’re on board a spacecraft, traveling through space many thousands of lightyears from Earth. Eventually, you sense a faint rise in temperature. It doesn’t feel particularly remarkable – but it could be a sign that you’re approaching a black hole.
A black hole can be broadly characterized as specific spot in space defined by an extremely high level of density. Past a certain limit, nothing – not even light – is capable of ever breaking away from a black hole’s gravitational pull. This limit is what’s known as the event horizon.