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Solar time -

Throughout much of history, agriculture has been the primary concern for most of civilization. So it’s no wonder that the sun has been a huge factor in determining time, especially when measured across months and years.

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Sundials -

The sun has also been beneficial in allowing people to measure time in smaller increments. Sundials used to be a staple of most cultures, and while they have mostly gone out of use, they are still fashionably beautiful!

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Lunar time -

Civilizations have also relied on lunar cycles as a natural timekeeping reference. Many cultures designed their calendars based on these cycles.

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Water clocks -

Also known as clepsydras, water clocks date back to ancient civilizations and are based on the regulated flow of water from one container to another. The amount of water that flows through is used to measure time.

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Hourglasses -

Similar to the way that water clocks work, hourglasses use sand as a way of measuring time. Ancient civilizations used this technique as well. Indeed, the oldest known hourglass dates back to ancient Egypt around the 14th century BCE.

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Astrophysics -

Timekeeping in astrophysics is based on monumental scales. In fact, some astrophysicists work with time scales that span the entire history of the universe, such as the cosmic time since the Big Bang.

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Pulsars -

Pulsars are rapidly spinning neutron stars that emit precise radio pulses, which are also used by astronomers as cosmic timekeepers.

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Other phenomena -

Astronomical events such as supernovae and gamma-ray bursts can be analyzed by scientists to determine precise timing.

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Gravitational waves -

Detected by the Laser Interferometer Gravitational-Wave Observatory (LIGO) in the US, these ripples in spacetime provide a new tool for measuring cosmic events and understanding time.

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Particle physics -

Experiments at facilities like CERN, the European Organization for Nuclear Research, rely on precise time synchronization and particle accelerators, pictured here. These experiments help scientists understand the fundamental forces of physics.

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Atomic clocks -

These clocks are possibly one of the most accurate ways of measuring time. Atomic clocks use the vibrations of atoms to measure time, with incredible accuracy down to billionths of a second. In fact, these clocks use radiation to determine the accurate length of one second.

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Caesium standard -

The radioactive element known as caesium is used as a measurement for one second in atomic clocks. The atoms of this element consistently oscillate, and these vibrations are fundamental in timekeeping worldwide.

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Radioactive decay -

Other types of radioactive isotopes also serve as geological clocks, which allow researchers to radiocarbon date rocks and artifacts with remarkable precision.

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Deep Space Atomic Clock (DSAC) -

NASA's space-borne clock enables the space agency to navigate all their missions precisely without having to rely on any Earth-based systems.

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Optical clocks -

Using optical frequencies–which are basically the Earth’s electromagnetic field–these clocks promise even greater accuracy than atomic clocks, potentially redefining our standards of measuring time.

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Time dilation -

Einstein's theory of gravity predicts that gravity and speed greatly affect time. And so space exploration and the passage of time are influenced greatly by the velocity at which spacecraft travels.

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Chronometers -

These precision timepieces are used in navigation to measure longitude accurately by determining time differences between a specific location and a reference point, such as Greenwich Mean Time.

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Biological clocks -

These clocks can be found in all manner of organisms ranging from plants to animals. They regulate various physiological processes, such as sleep-wake cycles and seasonal behaviors, based on internal timing mechanisms.

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Leap seconds -

Leap seconds are occasionally added to Coordinated Universal Time (UTC), since the Earth doesn’t have a fixed rotation. Adding these seconds ensures that time on Earth correlates with astronomy.

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Network Time Protocol (NTP) -

NTP synchronizes computer clocks over the internet using algorithms, which is crucial for secure communications and transactions.

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Climate science - Accurate measurement of time helps scientists in understanding climate patterns, tracking changes, and predicting future trends.

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Geodesy -

In order to study Earth's shape and gravity field, scientists must rely on precise time measurements for GPS and satellite positioning systems.

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Different heights -

The laws of physics indicate that time is measured differently depending on how close you are to the Earth’s surface. Indeed, satellites need to measure time differently due to their high speeds and altitude.

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Telecommunications -

Communication networks around the globe rely on perfect synchronization in order to reliably and timeously transmit data across the continents.

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Aviation -

Commercial and military flights tend to have a habit of traveling across time zones, which can prove tricky if done improperly. Navigation systems depend on precise timekeeping for safe and efficient air travel.

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International Space Station -

Astronauts aboard the ISS utilize their own highly accurate clocks to synchronize activities and experiments in space.

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Time capsules -

Although these are not methods of exact timekeeping, buried time capsules function as a way to preserve a snapshot of culture and history for posterity.

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Quantum entanglement -

Scientists are trying to study particles at a quantum level as a way of measuring time, but this is still largely theoretical. They believe that the changes seen in ‘entangled’ particles can be measured to find an accurate passage of time.

Sources: (Encyclopedia of Time) (‘Of Clocks and Time’) (History of Astronomy: An Encyclopedia) (Engage Learning Magazine)

See also: What physics says about time travel

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