What is the boundary around a black hole beyond which nothing, not even light, can escape?
Event horizon
The answer was Event horizon. Here's the why, the decoys, and the source trail.
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The event horizon is the point of no return around a black hole. Once anything crosses it, the escape velocity exceeds the speed of light, so light and matter cannot get back out.
A good trivia question makes the wrong answers feel close. Here is the clean read on the set.
- Event horizon - correct answer.
- Accretion disk - a decoy; it may live near the same topic, but it does not answer this exact clue.
- Singularity - a decoy; it may live near the same topic, but it does not answer this exact clue.
- Photon sphere - a decoy; it may live near the same topic, but it does not answer this exact clue.
Event horizon is the one to remember. The event horizon is the point of no return around a black hole. NASA describes the event horizon as a black hole's surface-like boundary, even though it is not a solid surface like Earth or the Sun.
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Sources: NASA