HOW TO MEASURE THE DISTANCE OF MOON WITH YOUR LITTLE FINGER?

In ancient times, how people measured size of earth, moon, distance of moon, distance of planets etc.? The stories sound like a detective story.

The man by name "Eratosthenes' measured the size of the earth 2200 years ago. He knew that the sun was straight overhead in the Egyptian city of syene at noon in the summer, but it was 7.2 degrees south of straight overhead in Alexandria, located 794 kilometers farther north at the same time. He therefore concluded that travelling 794 km corresponded to going 7.2 degrees out of the 360 degrees all around Earth's circumference. Hence the circumference must be 794 km/7.2 *360 degree = 39700.

It is remarkably close to the modern value of 40000 km.

Eclipses have inspired fear, awe, myths throughout the ages. When earth gets between the sun and the moon, it causes a lunar eclipse. Also, the shadow that earth casts on the moon has a curved edge. A man called Aristarchus saw the shadow and concluded that the moon is about 3.7 times smaller than the earth. Since he knew the size of earth, dividing it by 3.7, he got the size of moon. So, man finally measured the size of moon without going near it. A historical moment.

Please hold your hand up at arm's length and check which things around you can be blocked from view by your little finger, your little finger covers an angle of separation of about one degree.

If an objected is found at a distance of "115 times its size", a half-a-degree or half a little finger can cover it. Say, you are looking out your airplane window and can cover a 50-meter-wide swimming pool with half the little finger, you will know that your altitude is 115*50 m =6 km.

Aristarchus calculated the distance to the moon in the same way.

Distance between the Earth and Moon =115*moon's size =382680 km

This method is called parallax method.

The trio, Sun, Earth and Moon form a right-angled triangle at some point of time in a year. Hence trigonometry was used to calculate distance of sun. They got the distance.

The stories prove that even a blade of grass is a powerful tool for a smart man.

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