Practical units used for measuring time

Table of Contents

Practical units used for measuring time:

(i) Solar day:

It is the time taken by the earth to complete one rotation about its own axis w.r.t. the sun.

(ii) Sedrial day:

It is the time taken by the earth to complete one rotation about its own axis w.r.t. a distant star.

(iii) Solar year:

It is the time taken by the earth to complete one revolution around the sun in its orbit.

1 solar year = 365.25 average solar days = 366.25 sedrial days

(iv) Tropical year:

The year in which there is total solar eclipse is called tropical year.

(v) Leap year:

The year which is divisible by 4 and in which the month of February has 29 days is called a leap year.

(vi) Lunar month:

It is the time taken by the moon to complete one revolution around the earth in its orbit.

1 lunar month = 27.3 days

(vii) Shake:

It is the smallest practical unit of time.

1 shake = 10-8 s

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