For anyone who’s ever played hide-and-seek, the rhythm of counting “One-one-thousand, Two-one-thousand, Three-one-thousand,” with eyes closed, is a familiar way to gauge a second. Over an average lifespan of 80 years, this adds up to over 2.5 billion seconds, with each flashing by in a blink. Normally, we think in terms of much longer periods—minutes, days, or years. However, for elite athletes, even fractions of a second can be the difference between an Olympic medal and nothing.

But what if we could examine events on an even shorter timescale? Imagine having a “temporal microscope” that could focus on time just as microscopes allow us to see the tiniest details of the physical world.

Enter the realm of attoseconds, where a select group of scientists, including Nobel laureates, are pushing the boundaries of how briefly we can observe molecular and atomic phenomena. This fast-paced scientific field utilizes advancements in laser technology to study events happening at the scale of quintillionths of a second.

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In the attosecond world, scientists observe the ultra-fast processes that are fundamental to physics and chemistry. This is where electrons and light interact in almost unimaginably brief moments, exchanging energy in ways that are crucial for everything from plant photosynthesis to the mechanisms of human vision, not to mention the vast chemical industry.

Using cutting-edge lasers and detectors, researchers like Stephen Leone from the University of California, Berkeley, explore these minute slices of time. Leone, who describes his career in attosecond chemistry in an autobiographical essay, highlights the ability to see the instantaneous actions of electrons which play a critical role in forming or breaking chemical bonds.

One attosecond is to a second what a second is to about 31.71 billion years—the age of the universe. In the time it takes for light to travel the length of one atom, an attosecond passes. This tiny unit of time is critical for understanding how atoms and their electrons behave, notes John Gillaspy from the National Institute of Standards and Technology.

The process starts with advanced femtosecond lasers which are then fine-tuned using a technique called high harmonic generation (HHG), a method so precise it garnered its inventors the 2023 Nobel Prize in Physics.

These high-tech tools allow for pump-probe studies where Leone and his team can observe how photons interact with electrons in various substances, capturing these interactions in real-time, which can provide a frame-by-frame view of molecular processes.

There are as many attoseconds in one second as there have been seconds ticking since the Big Bang.

Leone details the subtle shifts in energy states and behaviors he can now observe—insights that are transforming our understanding of how chemical reactions happen, and potentially leading to breakthroughs in fields like genetics and disease detection.

Inside these quiet, dimly lit labs, researchers work surrounded by intricate apparatus designed to manipulate and measure the smallest occurrences in time. These setups often include components that finely control the timing and path of laser pulses as they interact with samples.

“It’s essentially a highly sophisticated camera capturing the briefest events humans can produce,” says Daniel Keefer of the Max Planck Institute for Polymer Research, emphasizing the complexity and precision of these experiments.

“It’s all a very complicated camera to produce some of the shortest events in time that humans can produce.” —Daniel Keefer

Such detailed studies have helped unveil how crucial biomolecules like DNA and RNA manage to quickly rid themselves of harmful UV energy, protecting genetic integrity from potential damage caused by sunlight exposure.

Accelerating into the Fastest Lane

To create attosecond pulses, initial interactions involve an infrared laser agitating atoms, which then emit higher-frequency light waves, similar to acoustic overtones in music. These higher frequencies are key for probing deeper into the behavior of molecules and atoms.

As scientists dream of future technologies, like zeptosecond pulses, the potential applications become even more profound, says Gillaspy. Concentrating enough energy in these short bursts could, theoretically, allow scientists to manipulate the fundamental properties of the vacuum of space itself.

Meanwhile, Jun Ye of JILA is exploring how to use these principles to detect dark matter by measuring subtle energy shifts in atomic nuclei, potentially revealing interactions with this elusive substance.

The pursuit of these technologies not only advances our understanding of the universe but also opens up possibilities for new discoveries across physics and chemistry, driven by curiosity and the continuous push into these incredibly brief moments in time.

This article originally appeared in Knowable Magazine, an independent journalistic endeavor from Annual Reviews. Sign up for the newsletter.