| | {{infobox |
| | | title = Zeptosecond |
| | | image = lhcb-rich-detector.jpg |
| | | caption = Instruments like LHCb chase physics at zeptosecond and zeptometre scales (CERN, CC BY-SA 3.0) |
| | | symbol = zs |
| | | length = 10⁻²¹ seconds — one sextillionth of a second |
| - | | smaller_than = A zeptosecond is to a second what a second is to ~31,700 trillion years |
| + | | smaller_than = A zeptosecond is to a second what a second is to ~31.7 trillion years |
| | | record = 247 zs — fastest process ever timed (Frankfurt, 2020) |
| | | named_after = SI prefix zepto- (10⁻²¹), adopted 1991 |
| | }} |
| | |
| | A **zeptosecond** (symbol **zs**) is one sextillionth of a second — 10⁻²¹ seconds, a one followed by twenty-one zeroes worth of time. It is the shortest unit of time that physicists have ever actually measured something in: in 2020, a team in Frankfurt timed a photon crossing a hydrogen molecule at **247 zeptoseconds**, setting the record for the fastest process ever observed. Below the zeptosecond lies only one shorter named SI interval — the **yoctosecond** (10⁻²⁴ s) — and beyond both, the Planck time (~5.4 × 10⁻⁴⁴ s), where physics itself may stop making sense.[[cite: Grundmann et al., *Science* 2020; SI Brochure, BIPM]] |
| | |
| | ## The ladder of small time |
| | |
| | Time gets small fast. Each named step is a thousand times shorter than the last: |
| | |
| | ```flow The small-time ladder — every rung 1000× shorter |
| | nanosecond 10⁻⁹ s — light travels ~30 cm (one foot) |
| | picosecond 10⁻¹² s — chemical bond vibrations |
| | femtosecond 10⁻¹⁵ s — fastest chemical reactions (Nobel 1999) |
| | attosecond 10⁻¹⁸ s — electron motion (Nobel 2023) |
| | zeptosecond 10⁻²¹ s — photon crossing a molecule; nuclear photons |
| | yoctosecond 10⁻²⁴ s — quark-gluon plasma flashes; hypothetical physics |
| | Planck time 10⁻⁴⁴ s — below this, "time" may not exist |
| | ``` |
| | |
| - | To feel the scale: a zeptosecond is to one second as one second is to about **31,700 trillion years** — roughly 2,300 times the current age of the universe. Light, the fastest thing there is, travels barely a third of a nanometre — about the width of a small virus — in one zeptosecond.[[cite: SI definitions; scale comparisons from attosecond-physics literature]] |
| + | To feel the scale: a zeptosecond is to one second as one second is to about **31.7 trillion years** — roughly 2,300 times the current age of the universe. Light, the fastest thing there is, travels barely a third of a nanometre — about the width of a small virus — in one zeptosecond.[[cite: SI definitions; scale comparisons from attosecond-physics literature]] |
| | |
| | ## How do you even time 247 zeptoseconds? |
| | |
| | No clock ticks that fast — the measurement is made with interference, not a stopwatch. In the 2020 experiment, Reinhard Dörner's group at Goethe University Frankfurt fired an X-ray photon at a hydrogen molecule and measured *which* of the two atoms the photon hit first by watching the interference pattern of the ejected electrons. The difference between the two arrival readings — how long the photon took to cross the molecule — came out to **247 zeptoseconds** on average. It remains the shortest time interval ever measured.[[cite: Grundmann, Senftleben et al., "Zeptosecond birth time delay in molecular photoionization," *Science* 370, 339 (2020)]] |
| | |
| | The technique descends from **attosecond science**, the field that won the 2023 Nobel Prize in Physics — Anne L'Huillier, Pierre Agostini and Ferenc Krausz showed how to generate and use light pulses lasting attoseconds (10⁻¹⁸ s) to photograph electrons in motion. Zeptosecond measurements push the same idea three orders of magnitude further.[[cite: Nobel Prize in Physics 2023 — attosecond pulses]] |
| | |
| | ## Where zeptoseconds live in nature |
| | |
| | * **Light crossing a small molecule** — ~100–500 zs |
| | * **Fluorescence of a photon inside a nucleus** — nuclear gamma emission times can reach the attosecond-to-zeptosecond range |
| | * **Quark-gluon plasma** — the "soup" of free quarks produced in heavy-ion collisions lives and dies on timescales of ~10⁻²³–10⁻²⁴ s — deep yoctosecond territory |
| - | * **The [[zeptoverse]]** — the newly opened realm of physics at 10⁻²¹ *metres*: a photon crosses a zeptometre in about three thousandths of a zeptosecond, and the rare decays that probe that realm unfold over femtosecond-to-picosecond beauty-particle lifetimes |
| + | * **The [[zeptoverse]]** — the newly opened realm of physics at 10⁻²¹ *metres*: a photon crosses a zeptometre in about three billionths of a zeptosecond, and the rare decays that probe that realm unfold over femtosecond-to-picosecond beauty-particle lifetimes |
| | |
| | ## Units smaller than this |
| | |
| | Only the **yoctosecond** (10⁻²⁴ s) is smaller among named SI units — invoked for the fleeting lifetime of quark-gluon plasma states. Below named units entirely sits the **Planck time**, ~5.4 × 10⁻⁴⁴ s — the time light takes to cross one Planck length — which many physicists suspect is not a small quantity so much as a boundary: the point where "before" and "after" may stop being meaningful concepts. Nothing shorter than a Planck time is measurable even in principle under current physics.[[cite: quark-gluon plasma literature; Planck units]] |
| | |
| | ## See also |
| | |
| | * [[zeptoverse]] — the realm at 10⁻²¹ metres |
| | * [[smallest things ever measured]] — the full gallery of tiny records |
| | * [[scientific notation]] |
| | * [[history of physics]] |
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| | ## References |
| | |
| | - Grundmann, Senftleben et al. — "Zeptosecond birth time delay in molecular photoionization," *Science* 370:339 (16 October 2020) |
| | - Nobel Prize in Physics 2023 — attosecond light pulses (L'Huillier, Agostini, Krausz) |
| | - BIPM — SI Brochure, decimal prefixes (zepto- and yocto- adopted 1991) |
| | - ALICE collaboration — quark-gluon plasma lifetime measurements, CERN |
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| | [[Category:Science]] |
| | [[Category:Physics]] |
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