## Planetary Motions:

Aryabhata was the first primary indian source to create a model of the planets. In this geometrical model he showed that planets moved in an epicycle. He showed calculations of how far each planet was from the sun. Though he was a tenth off for some of the distances, he was pretty accurate for the amount of technology he had at that time. Also, he did all the math by hand without calculators or the internet. He also calcuated the circumference of the earth in yorjans. One yorjan was 5 miles. He said that the earth is 4967 yorjans which equals to 24835 miles. The actual circumference of the eartch is 24902 miles which makes aryabhata off by 67 miles. This approximations was very accurate. He also mentions that the orbits of all the planets around the sun were not round but ellipses.

Aryabhata also finds out that the axis of the earth is tilted. He had a clear concept of relative motion but it was never used because no one believed it was true. This idea never spread until another astonomer, Coppernicus, brought it out in the 15th and 16th century. Since he knew that the earth was tilted, he calculated the time for one year. He got 365 days, 6 hours, 12 minutes and 30 seconds. He overestimated that just a little because the true time is just 365 days and 6 hours exact. Most of Aryabhata's calculations were perfect, and even if they were off, they were off by a very little amount.

Aryabhata also explained the concept of eclipses in his book Aryabhatia. He mentions that the lunar eclipse is caused when the moon comes in the shadow of the earth. He gives the calculations of the diameter of the earth and when the moon came in the earth's shadow to prove his theory. He gives accurate amount of durations of the solar and lunar eclipses to get rid of the belief that eclipses were caused by a demon.

Aryabhata also explained the concept of eclipses in his book Aryabhatia. He mentions that the lunar eclipse is caused when the moon comes in the shadow of the earth. He gives the calculations of the diameter of the earth and when the moon came in the earth's shadow to prove his theory. He gives accurate amount of durations of the solar and lunar eclipses to get rid of the belief that eclipses were caused by a demon.