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Shine light past a black hole: does it bend, or fall in for ever?
Black Holes lab · Last updated: 16 October 2026
You shine beams of light past a black hole and watch what happens: some bend and fly on, while others fall in for ever. Black holes are the most extreme objects in the universe, and seeing light itself captured helps you understand how powerful gravity can be.
What you'll discover
- Gravity bends the path of light, and near a black hole the bending is extreme.
- Light that passes far enough away curves round and escapes, while light that comes too close falls in.
- The event horizon is the point of no return: nothing that crosses it, not even light, can get back out.
The science in plain words
A black hole forms when a huge amount of mass is squeezed into a tiny space, for example when the core of a very massive star collapses at the end of its life. Its gravity is so strong that, close in, the speed needed to escape would be greater than the speed of light. Since nothing travels faster than light, nothing inside that boundary can escape. The boundary is called the event horizon.
Einstein's general theory of relativity says that mass curves space and time, and light follows those curves. Even our Sun bends starlight slightly, which astronomers first measured during a solar eclipse in 1919. Near a black hole the bending is enormous. A beam that passes well clear is deflected and travels on. One that passes closer can swing round the black hole before escaping. At about one and a half times the event horizon's radius, light can even circle it. Any beam aimed closer than that spirals in and is lost.
Black holes are not cosmic vacuum cleaners. Far away, their gravity is just like that of any object with the same mass. In 2019 the Event Horizon Telescope released the first image of a black hole's shadow, ringed by glowing gas, in the galaxy M87.
Where it fits
- India, NCERT: Goes beyond the NCERT syllabus for classes 6 to 10; it builds on Class 9 Gravitation.
- United States: Grades 6 to 12
Common questions
Why can light not escape a black hole?
Inside the event horizon, gravity is so strong that the speed needed to escape is greater than the speed of light. Nothing can travel faster than light, so light that crosses the horizon can never get back out. That is why black holes look black.
What happens if you fall into a black hole?
For a small black hole, the pull on your feet would be much stronger than on your head, stretching you out, which scientists call spaghettification. For a very large black hole you could cross the event horizon without feeling it, but you could never come back out.
Could a black hole swallow the Earth?
No black hole is anywhere near us. Far from a black hole, its gravity is the same as any object of the same mass. If the Sun were replaced by a black hole of equal mass, Earth would keep orbiting it, although it would become very cold and dark.
Related labs
- Orbital Mechanics: Newton's cannonball: how fast must you fire it sideways so it never lands?
- Star Life Cycle: Heavy stars have more fuel. So why do they die young?
- Bending Light: Shine a ray into a glass block. How much does it bend?
See all earth and space labs or every Taz science lab.
Try it yourself
The Black Holes lab is one of the interactive 3D science labs inside Taz. Change one thing, predict what will happen, then run it and watch. Labs open after you sign in.