BBC presenter Brian Cox’s gravity experiment a few days ago was spectacular.
Cox, a physicist and former musician, went to America, to NASA’s Space Power Facility (SPF), to observe the gravitational force applied when dropping a bowling ball, and a feather, from a height.
Near Cleveland, Ohio, NASA’s SPF is the world’s biggest vacuum chamber. It’s used to test spacecraft in the conditions of outer space, doing so by pumping out the 30 tonnes of air in the chamber, until there’s just two grammes left.
According to Galileo Galilei's discovery, in vacuum, if two objects were dropped from the same height, they would fall on the surface at exactly the same time. The theory states that the weight of the objects should not affect the experiment.
Before the vacuum took place, Cox released the bowling ball and feather from a significant height in the chamber, explaining how both objects, according to the laws of gravity, should drop at the same speed.
“Galileo’s experiment was simple: He took a heavy object and a light one and dropped them at the same time to see which fell fastest,” explains Cox as the objects are released.
What happened, rather more predictably, was the bowling ball travelling at a far higher velocity – the wind resistance on the feather was too great, slowing it down significantly.
The scientists at the SPA then spent three hours pumping the air out of the facility, setting up new conditions to test the drop in.
This time, both the feather and the bowling ball fell at the exact same rate, not a flicker in the feather, just straight down like a dart, hitting the ground at the same time – gravity at work in its purest sense.
But Cox then spoke of Albert Einstein’s “happiest thought”.
“The reason the bowling ball and the feather fall together is because they’re not falling. They’re standing still,” he says.
“There’s no force acting on them at all. He reasoned that, if you couldn’t see the background, there would be know way of knowing that the objects were accelerating to the earth. So he concluded… that they weren’t.”
Mind successfully blown.
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