Please explain this...

Dear student,

The statement "Precise measurements of physical quantities are a need of science" is indeed true. Precise measurement of physical quantities such as length, time, mass, etc., is a basic requirement of development of astronomy, nuclear physics, medical sciences, crystallography, etc.
1.  In Space explorations, a very precise measurement of time in a microsecond range is needed. In determining the half-life of radioactive material, a very precise value of the mass of nuclear particles is required. Similarly, in Spectroscopy precise value of the length in Angstroms is required.
2.  In the measurement of astronomical distances such as the distance of the moon from the earth by laser beam, an accurate measurement of time is required.
A very small mistake in the measurement of that time can produce a large mistake in the accurate distance of the moon from the earth, which can be a cause of failure to reach the moon. This time is of the order of 10-9 sec.
3. In atomic or nuclear reactions, in nuclear weapons and in nuclear power plants, a precise measurement of mass and time is required which is of the order of10-30 kg and 10-9s. A small mistake can be a cause of an accident such as take place in Japan recently.
4. In medical sciences, a precise measurement of length is required to find location, size, and mass of tumors in the body. A small mistake in the measurement of its location, size, or mass can be a cause of damaging any body part in laser therapy.
5. Working with lasers we require length measurements to an angstrom unit (10−10m)or even a fraction of it. for estimating nuclear sizes we require a precision of 10−15m.


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