Researchers have made a significant advance in atomic clocks by developing a laser to excite thorium-229 nuclei and connecting it to an optical clock.The world has evolved from calculating the position of the sun and moon to using atoms and their nuclei to tell time.
How Time Measuring Devices Evolved Throughout History
Historical Time Measuring Devices
- Sunclock: Ancient device that told time by casting a shadow of sunlight.
- Water clock: Time was measured by slowly filling a vessel with water.
- Hourglass: Sand was used instead of water to measure time.
The Evolution of Mechanical Clocks
- Early Mechanical Clock: Advanced water clocks included additional tanks, gears, and pulleys.
- Astrarium (medieval astronomical clock): A sophisticated device for tracking celestial movements.
- Pendulum Clock: Spring-driven clocks use coiled springs instead of weights.
Modern Clocks
- Electric Clock: These clocks, developed in the 19th century, use batteries or electric motors instead of springs or weights.
- Quartz Clock: These clocks use quartz crystals that oscillate when charged with electricity. These clocks are inexpensive and widely available, leading to the popularity of quartz clocks and wall clocks.
Atomic Clock
- Operation: Lasers and atoms of the same isotope are used to measure time. Time is determined by the frequency of radiation emitted by atoms during transitions between energy levels.
- As part of the One-Nation-One-Time project, India is installing atomic clocks across the country to ensure that the time on digital devices is in sync with Indian Standard Time.
- Caesium Atomic Clock: These use cesium-133 atoms and are highly accurate in maintaining IST.
- IST is a caesium atomic clock used at the National Physical Laboratory (NPL) New Delhi.
- Council of Scientific and Industrial Research-National Physical Laboratory (CSIR–NPL) maintains the IST.
- Next Generation Optical Clock: These use atoms such as strontium or ytterbium to achieve even greater accuracy of time.
Future Developments in Timekeeping
- Nuclear Clock: For even greater accuracy, the nuclei of atoms are used in making clocks. The emission frequency of these atomic clocks is around 2,020 terahertz which represents ultra-high accuracy.
How the History of Clocks Evolved in India
- The evolution of clocks in Indian history shows a rich mix of indigenous ingenuity and external influences.
- Various methods of timekeeping were used in ancient India, such as water clocks (known as Ghatika Yantra) and sun clocks used in temples and for daily activities.
- Ancient Indians used the positions of stars and planets (nakshatras) to accurately record important events to keep track of time.
- Time tables linked to planetary positions led to the development of astrology and the discovery of the influence of planets on human life.
- Despite the advanced system, daily timekeeping was often done in hours or pahars and simple clock towers were sufficient for general public use.
- With the advent of Islamic rulers, more advanced water clocks and astronomical instruments were developed, blending with local traditions.
- Mechanical clocks and pocket watches became popular during the colonial period.