What is the boundary around a black hole beyond which nothing, not even light, can escape?
Chapter 1

The boundary of no return

Chapter 2

The descent into extreme gravity

Chapter 3

The heart of the mystery

Chapter 4

The final fade and cosmic legacy

YOUR GOAL

Master of Inside a black hole

Ch 1 · The boundary of no return
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artiteacher The global camera that photographed the dark

Jul 11

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artiteacher The boundary of no return

Space is time, space is time / We are falling to the end of the line.

Jul 10

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artiteacher The illusion of frozen time

Jul 11

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The global camera that photographed the dark

artiteacher In 2019, scientists captured the first-ever image of a black hole's shadow using a planet-sized telescope network.

Jul 10

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The illusion of frozen time

artiteacher To an outside observer, an astronaut falling toward a black hole appears to slow down and freeze forever.

Jul 10

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Turn* (Clever wordplay: No-Return Turn).
    *   *
BETA

artiteacher Steer your ship past the event horizon to discover why there is no turning back.

Jul 7

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Fun Fact

Black hole size: If our Earth collapsed into a black hole, it would shrink to the size of a single glass marble.

Jul 10

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Glossary
event horizon (noun)
A theoretical limit around a black hole beyond which no light or radiation can escape. In 1916, Karl Schwarzschild first calculated this gravitational threshold using Albert Einstein's equations of general relativity.

Jul 10

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Gossip

If offered a safe round-trip, would you visit an event horizon?

Jul 10

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Quiz

What is the maximum mass limit of a stable white dwarf star, calculated by Subrahmanyan Chandrasekhar in 1930?

Jul 10

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artiteacher The limit of cosmic weight

Jul 11

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Quiz

What is the boundary around a black hole beyond which nothing, not even light, can escape?

Jul 10

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artiteacher The invisible line of the event horizon

Jul 11

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Quiz

Why does the light from an object falling into a black hole shift toward the infrared spectrum?

Jul 10

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Quiz

In 2019, which global telescope network captured the first-ever image of a black hole's shadow?

Jul 10

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Quiz

Which German physicist first calculated the size of a non-rotating black hole's boundary in 1916?

Jul 10

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Quiz

To a distant observer, what happens to the clock of an astronaut falling toward a black hole?

Jul 10

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Quiz

What is the name of the supermassive black hole photographed in 2019 in the galaxy M87?

Jul 10

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Quiz

What is the speed of light, which represents the cosmic speed limit that gravity overcomes inside a black hole?

Jul 10