Question

How far away from the earth is Halley's comet?

Answer 1

Hint: Halley’s comet revolves in a period of 75-76 years. It appears in the sky every 75 years when it passes close to the earth.
AU is the unit of measurement of distance. The distance between the object in outer space is so large that the conventional systems of distance measurement become inconvenient so, the scientists formulated AU as astronomical units for distance calculation in space to reduce the complexity of calculations

Complete step by step answer:
As Halley's comet is continuously moving it is impossible to predict the exact distance between the earth and the comet, however, we can give the distance for a particular time.
Astronomical Unit: For general reference, we can say that one astronomical unit (AU) represents the mean distance between the Earth and our Sun. An AU is approximately 93 million miles (150 million km). It’s approximately the distance covered by light in 8 minutes or we can that it is approximately equal to 8 light-minutes.
So, we can say that the distance of the sun from the earth is not constant; it varies with time, so take the average distance between the sun and earth as 1 AU.
Mathematically: 1 AU$ = 1.496 \times {10^8}$km
The current distance of Halley's comet from the earth is 5,101,059,701 kilometres
Or we can say that Halley's comet is 34.098478 AU from earth

Hence, The distance between Halley's comet and earth is 34.098478 AU which is equal to 5,101,059,701 km approx.

Note:
The comet is continuously moving in a period of 75 years so the value of the distance is always changing. AU is the biggest unit for distance measurement being 1AU=150 million kilometers. Light takes 4 hours, 43 minutes, and 35.3036 seconds to travel from Comet Halley and come to earth