Scientists Measure Smallest Unit of Time Ever in ‘Zeptoseconds’

German scientists say they have measured the smallest unit of time ever recorded.

Researchers say the unit was measured in zeptoseconds. A zeptosecond is a trillionth of a billionth of a second.

The researchers made the discovery while studying how long it took a photon – a particle of light – to cross a hydrogen molecule¹.

The German scientists say the photon crossed the molecule in about 247 zeptoseconds. "This is the shortest timespan that has been successfully measured to date," the team said in a statement. The results were reported in Science magazine.

The research was a project of physicists² from Goethe University in Frankfurt, Germany. The team said the experiment represents major progress in "the global race" to measure shorter and shorter units of time.

The method used to measure in zeptoseconds involves what is known as the photoelectric³ effect. This scientific law explains how and why some metals give off electrons after light falls on their surfaces.

Albert Einstein is credited with discovering the photoelectric effect. He was awarded the 1921 Nobel Prize in Physics for doing so. The discovery helped lead to the development of modern electronics, including radio and television.

The German scientists say they used equipment at the DESY national research center, which operates particle accelerators. The machines are used to investigate the structure of matter. The research includes experiments in photon science.

The researchers said they made the measurement by releasing X-ray waves onto a molecule of hydrogen, which is made up of two protons and two electrons. They set the energy of the X-rays so that one photon would be enough to expel both electrons out of the hydrogen molecule.

The scientists explained that electrons behave like particles and waves at the same time. So, after the first electron was ejected, the second followed a short time later. This process resulted in what the researchers called "an interference pattern." The researchers used this pattern to measure the electrons as they were escaping.

Sven Grundmann is a doctoral student at Goethe University who helped lead the research. He said the team "used the interference of the two electron waves to precisely⁴ calculate when the photon reached the first and when it reached the second hydrogen atom." The calculation added up to 247 zeptoseconds, "depending on how far apart in the molecule the two atoms were from the perspective of light," he said.

The research also involved a complex spectrometer, an instrument used to measure atomic and molecular⁵ reactions. Goethe University's Reinhard Dorner said the spectrometer made it possible to observe "for the first time that the electron shell in a molecule does not react to light everywhere at the same time." The time delay happens because information within the molecule only spreads at the speed of light," Dorner added. "With this finding we have extended our technology to another application."

There has been earlier research on the speed at which molecules⁶ change shape. In 1999, Ahmed Zewail – a professor at the California Institute of Technology – won the Nobel Prize in Chemistry for his work in the field.

Zewail, an Egyptian, was recognized for experiments that used laser light to study how atoms in a molecule move during a chemical reaction. His research involved femtoseconds, a unit of measurement meaning one quadrillionth of a second.

The German scientists say their research represents major progress from the earlier experiments. They also say they plan to build on their findings to measure even smaller units of time.

Words in This Story

unit – n. a single thing or a separate part of something larger

pattern – n. a particular way in which something is done, organized or happens

precise – adj. exact and correct

calculate – v. to discover an amount or number using mathematics

perspective – n. a way of thinking about and understanding something

application – n. a way in which something can be used for a particular purpose

1 molecule   

n.分子，克分子

参考例句：

• A molecule of water is made up of two atoms of hygrogen and one atom of oxygen.一个水分子是由P妈̬f婘̬ 妈̬成的。
• This gives us the structural formula of the molecule.这种方式给出了分子的结构式。

2 physicists   

物理学家( physicist的名词复数 )

参考例句：

• For many particle physicists, however, it was a year of frustration. 对于许多粒子物理学家来说，这是受挫折的一年。 来自英汉非文学 - 科技
• Physicists seek rules or patterns to provide a framework. 物理学家寻求用法则或图式来构成一个框架。

3 photoelectric   

adj.光电的，光电效应的

参考例句：

• Photoelectric spectrophotometers give better result.用光电分光光度计能得到较佳结果。
• Einstein also explained a baffling feature of the photoelectric effect.爱因斯坦也解释了光电效应里一个令人困扰的现象。

4 precisely   

adv.恰好，正好，精确地，细致地

参考例句：

• It's precisely that sort of slick sales-talk that I mistrust.我不相信的正是那种油腔滑调的推销宣传。
• The man adjusted very precisely.那个人调得很准。

5 molecular   

adj.分子的；克分子的

参考例句：

• The research will provide direct insight into molecular mechanisms.这项研究将使人能够直接地了解分子的机理。
• For the pressure to become zero, molecular bombardment must cease.当压强趋近于零时，分子的碰撞就停止了。

6 molecules   

分子( molecule的名词复数 )

参考例句：

• The structure of molecules can be seen under an electron microscope. 分子的结构可在电子显微镜下观察到。
• Inside the reactor the large molecules are cracked into smaller molecules. 在反应堆里，大分子裂变为小分子。