Today, things are getting shorter. Scientists just measured the shortest unit of time ever recorded. It is a zeptosecond. This is tiny - a trillionth of a billionth of a second. It is a decimal point followed by 20 zeros and then a 1. The scientists study atomic physics. They used special tools to measure how long it takes a photon to cross a hydrogen molecule. The scientists said it took 247 zeptoseconds for this to happen. This is too fast for humans to see.
In 1999, a scientist measured the speed at which molecules change their shape. He found this was one femtosecond, which is a millionth of a billionth of one second. One millisecond is a thousandth of one second. This is the time it takes a neuron in our brain to fire. One nanosecond is one billionth of one second. The shortest unit of time it may be possible to measure is one Planck. This is a decimal point followed by 44 zeros and a 1.