NBC news: Scientists have measured the shortest interval of time ever recorded, clocking how long it takes a particle of light to cross a single molecule of hydrogen.
 The ultra-quick journey took 247 zeptoseconds, according to a team of German researchers, with a zeptosecond representing a trillionth of a billionth of a second. This is equivalent to the number 1 written behind a decimal point and 20 zeroes.
 The findings are the culmination of global efforts to measure shorter and shorter time spans in physics, and they offer scientists a way to precisely measure atomic changes through what’s known as the photoelectric effect.
 Albert Einstein proposed a theory of the photoelectric effect in 1905, describing the phenomenon in which electrons can be ejected from atoms after they are hit by light. In 1999, an Egyptian chemist, Ahmed Zewail, used ultrashort laser pulses to observe how molecules change their shape. Zewail, who would go on to win a Nobel Prize for his research, measured these miniscule changes in femtoseconds; a femtosecond is one millionth of a billionth of a second. Now, scientists at Goethe University in Frankfurt, the Fritz Haber Institute of the Max Planck Society in Berlin and DESY, a particle accelerator in Hamburg, have measured an even shorter division of time. Their results were published Oct. 16 in the journal Science. The researchers fired X-rays from the PETRA III accelerator at a molecule of hydrogen.
, which is made up of two protons and two electrons. The scientists said they used a single particle of light, or one photon, to jostle the electrons free. They then used rapid bursts from a second near-infrared laser to detect the subsequent interactions.