Pound-Rebka experiment facts for kids

The Pound-Rebka experiment was a very important science test done in 1960 by two scientists, Robert Pound and Glen Rebka. This experiment helped prove a big idea from Albert Einstein about how gravity affects light. It showed that light can gain energy when it moves closer to a strong source of gravity, like the Earth.

What Was the Pound-Rebka Experiment?

The Pound-Rebka experiment was designed to check a prediction from Albert Einstein's general theory of relativity. This theory, which is about how gravity works, suggested that gravity doesn't just pull on things with weight. It also affects tiny particles of light, called photons.

Einstein's Idea About Gravity and Light

Einstein's theory predicted that if light travels towards a strong source of gravity, like a planet, it would gain energy. Think of it like a ball rolling downhill – it speeds up and gains energy. For light, gaining energy means its frequency changes. This change is called a blue shift, meaning the light's waves get shorter and closer together, shifting towards the blue end of the light spectrum.

How the Experiment Worked

To test this, Pound and Rebka set up their experiment in a tall tower at Harvard University's Jefferson laboratory. They sent gamma rays, which are a type of high-energy light, from the top of the tower down to the bottom. The tower was about 22.5 meters (73.8 feet) tall.

They used a special method called the Mössbauer effect to measure tiny changes in the light's frequency. This effect allowed them to detect if the light gained energy as it fell towards the Earth.

What Did They Find?

The results of the Pound-Rebka experiment showed that Einstein was right! As the light traveled down the tower towards the Earth's gravity, it did indeed gain energy. This caused a tiny but measurable blue shift in the light's frequency.

This experiment was a big deal because it was one of the first direct proofs of how gravity affects light, confirming a key part of Einstein's general theory of relativity. It helped scientists understand more about the universe and how gravity works on a very fundamental level.

Images for kids

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  Jefferson laboratory at Harvard University. The experiment occurred in the left "tower". The attic was later extended in 2004.

See also

In Spanish: Experimento de Pound y Rebka para niños