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Atomic Clocks – All Questions Answered

Atomic Clocks

To understand how atomic clocks work, it’s essential to first understand how a digital and pendulum clock (or grandfather clock) works.

Digital clocks count quartz crystal oscillations or power line oscillations to keep accurate time. However, US and European clocks count power oscillations differently, at 60 and 50 cycles per second.

A pendulum clock, as you might guess, has a pendulum or resonator and gears to help keep track of time. Essentially, it counts the pendulum swings, which resonate at the standard frequency of a swing per second.

How an Atomic Clock Works

Atomic clocks, meanwhile, rely on the resonance frequencies of atoms to act as the resonator. Thus, atom oscillations are similar to pendulum swings.

A more detailed explanation of how an atomic clock resonator works is that it’s regulated by the frequency of microwave electromagnetic radiation as it is emitted or absorbed by the energy change of atoms or molecules.

The basic working principle of an atomic clock is similar across all types of atomic clocks.

Initially, atoms get heated and bundled together into a beam. They are then separated into their only two possible energy states, or hyperfine levels – a ground state and an active state.

Atomic clocks use a magnetic field to remove atoms in one state entirely from the beam. Then, the remaining atoms undergo a microwave radiation treatment that causes some of them to change their state.

A second magnetic field removes the atoms that remained in their initial state and a detector counts the number of atoms that changed their state. A detector is then used to determine the number of atoms that changed their state in the process.

With cesium-133 atomic clocks, the goal is to achieve a correct frequency for the number of atom oscillations to find out when a second has passed.

Why Are Atomic Clocks So Accurate?

Monitoring the quantum transition or energy change in atoms or molecules gives atomic clocks unparalleled accuracy. For example, a caesium atom can resonate at the same high frequency as a different one. That means fewer external factors can influence how the atomic clock perceives time.

In contrast, a quartz clock has less accurate crystals because they are affected by temperature changes and various manufacturing tolerances.

What Is the Function of an Atomic Clock?

In essence, atomic clocks are designed to measure precisely how long an SI unit or atomic second takes to pass. Based on the cesium-133 atom used in atomic clocks, a second is as long as 9,192,631,770 radiation oscillations of a cesium-133 atom at rest or a temperature of 0 degrees Kelvin.

Atomic clocks help calculate the International Atomic Time that determines the Coordinated Universal Time (UTC) and other time zones. Such a clock can measure the base unit, or the atomic second, more precisely than any currently developed timekeeping device.

In addition, precise time management coming from the hundreds of atomic clocks in existence is vital. Global positioning system (GPS) satellites, Galileo, and GLONASS systems need excellent time management and time measurements to properly calculate global positions and display coordinates.

In other words, atomic clocks have multiple uses, from civilian to scientific to military applications.

How Many Types of Atomic Clocks Are There?

Although cesium atomic clocks are the most common, other clocks also use atoms to measure the precise length of a second, including:

  • Caesium clock
  • Hydrogen clock
  • Rubidium clock

Caesium clocks use cesium atom beams and separate cesium atoms of varying energy levels with a magnetic field. In terms of accuracy, cesium atomic clocks have an accuracy greater than one second per 100 million years. That’s due to their ability to oscillate or vibrate at exactly the same frequency, or inherent oscillation frequency.

Hydrogen atomic clocks work slightly differently. They preserve hydrogen atoms at specific energy levels in a specialized vacuum chamber to prevent higher energy states from deteriorating. Such precision makes hydrogen atom clocks up to 10 times more accurate regarding short-term time management and measuring.

Another type of atomic clock uses rubidium atoms. These clocks come with glass cells containing rubidium gas, which changes its light absorption properties based on the surrounding microwave frequency.

Is Atomic Time the Most Accurate?

Based on existing technology, atomic clocks and atomic time are the best ways to ensure precise time management. That’s mainly because most other methods of tracking time rely on periodic phenomena like the sun’s trajectory and speed relative to Earth.

However, many scientists agree that atomic vibrations produce much more stable periodic events that can be used for time management and observations.

Furthermore, research into entangled clocks and quantum entanglement determined that atom vibrations can provide much deeper insight into the passage of time than modern cesium clocks allow. For example, ytterbium atoms can oscillate at the same natural frequency as light in the visible spectrum.

That means they can vibrate 100,000 faster than cesium atoms in one second. This allows for the measurement of time with greater stability at a much higher frequency. Creating an entangled clock would enable much smaller interval breakdowns of the atomic second and a superior understanding of time.

How Many Atomic Clocks Are There?

Different locations around the world house about 400 atomic clocks, with all contributing to international time management to some degree.

Atomic clocks are found in universities, metrology institutes, observatories, military bases, physics laboratories, space agencies, and other facilities.

Can an Atomic Clock Be Wrong?

In theory, all atomic clocks are wrong, more or less. Each month, cesium atomic clocks lose their precision by a nanosecond or one billionth of a second.

However, that would still require 100 million years to pass for an atomic clock to be off by a full second. Hence, they are still the most accurate clocks for keeping time.

Depending on further research and development in the field of optical clocks, scientists will be able to tell how accurate or wrong atomic clocks really are. A working optical clock has the potential to drastically increase our understanding of a unit of time and redefine the international system for timekeeping.

Which Atomic Clock Is the Most Accurate?

The most precise clock in the world (not in development but in use) is the NIST-F1. This caesium fountain clock is at the National Institute of Standards and Technology in Boulder, Colorado. NIST developed it to replace the previously most accurate clock, the NIST-7, and improved timekeeping tenfold.

Purportedly, the clock won’t gain or lose a second in accuracy in 100 million years, should it endure for that long.

Indispensable to Measure Time But Not Irreplaceable

Although current atomic clocks are currently the most accurate devices for time tracking and management, there is a chance for the optical atomic clock to replace them in a couple of decades. At the moment, they’re instrumental in all applications involving timekeeping and global positioning.

But the gold standard for time measurement in the past almost 100 years may change. And it may happen within our lifetime.


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