Question

State whether true or false, and correct the statement if false:
The distance of the planets and stars from Earth is measured in Light Years.
A). True
B). False

Answer 1

Hint: Try to learn about the distance measurement of systems. Learn about the measuring units of distance. Visualize our solar system and the interstellar system in terms of distances and then compare which units we will use for different distances.

Complete step-by-step answer:
Distance can be defined as the numerical measurement of how far apart two objects or points are from each other. We have many units to measure distance. In SI units we use meters as the unit of distance, in CGS units we use centimetre as the unit of distance. But these are used to measure small separation. As we go to bigger and bigger scales, in these units the numbers will go bigger and bigger. So, for the simplicity we use some other units depending on the size scale or the separation scale of the objects.
Now, if we consider the distance between the planets and our earth it can be said to be around a few hundred million kilometres. The distance from the sun to our earth's orbit is called one astronomical unit (1 AU is about 150 million kilometres). In astronomical units the distance between the earth and Saturn can be said to be almost 8 AU. So, for the distance from planets to earth can be measured in astronomical units.
But again, if we make the separation scale a little bit more, i.e. the distance between a star and the earth then we will need another measuring unit. To the nearest star system Alpha Centauri it is almost 40 trillions of kilometres. We can measure this distance in terms of light years. One light year can be defined as the distance covered by a photon in one year. It will be almost 9 trillion kilometres or 63000 AU. So, for the distances from the stars we will use the light years as a measuring unit.
Now, in the question we are given that distance to both the planets and stars are measured in light years. But this is not true. We use the astronomical unit (AU) as the measuring unit for the distance to the planets from the earth.
So, the statement given in the question is false.
The correct option is (B).

Note: If we make the scale smaller rather than bigger, again we will need some other measuring units. So, with the scale of separation of objects we will have different units which are convenient for use for distance measurement.