What is Tropic of Cancer and Tropic of Capricorn?

Few basic things to know before we understand the concept of Tropic of Capricorn and Tropic of cancer.

  1. Earth revolves and rotates around the sun and Sun rotates in its own place.
  2. Earth is not plane surface but it is tilted. The tilt is 23.5 degrees.
  3. Earth completes its one full revolution in period of 365 days which we celebrate as new year.
  4. In ancient days these 365 days were recorded as 360 degrees or and 12 zodiac signs. Each zodiac sign stays for 30 days or 30 degrees. Now we have those 12 zodiac signs as 12 months.
  5. Sun rotates every day and that’s how we enjoy day/night for equal time.

Now let’s get back to the topic. Ever wondered why Zodiac sign names are given to the geographical structure of the earth. Of all 12 why only Cancer and Capricorn? Let me tell you why is it so…

Firstly, I will give the details of each Zodiac sign and the dates of the signs

Sl. NO

Zodiac Sign

Telugu Names


Degree Wise

1 Aries Mesha March 21 – April 19 0-29
2 Taurus Vrishabha April 20 – May 20 30-59
3 Gemini Mithuna May 21 – June 20 60-89
4 Cancer Karkataka June 21 – July 22 90-119
5 Leo Simha July 23 – August 22 120-149
6 Virgo Kanya August 23 – September 22 150-179
7 Libra Tula September 23 – October 22 180-209
8 Scorpio Vrishchika October 23 – November 21 210-239
9 Sagittarius Danu November 22 – December 21 240-269
10 Capricorn Makara December 22 – January 19 270-299
11 Aquarius Kumbha January 20 – February 18 300-329
12 Pisces Meena February 19 – March 20 330-360


Why only Cancer and Capricorn?

The total number of latitudes that are present are 180. 90 on the Northern hemisphere and 90 on southern hemisphere. 90 on one side is called as cancer and another side of 90 is Capricorn. 90th latitude from equator to southern hemisphere is called as Capricorn and 90th latitude from equator to northern hemisphere is called as cancer.  They are located at 23.5 degree because earth is tilted 23.5 degrees.

We know that Earth revolves and it takes 365 days to revolve 360 degrees. So, on 1 day it approximately moves 1 degree. So that’s how it completes one degree each day to complete 360 degrees in a year. In the same time when earth is moving 1 degree per day it also tilts 1 degree in approximately 4 days and like that when it completes moving 90 degrees it tilts 23.5 degrees in the Northern Side. On 20th March Sun is at 0 degrees at Aries and it is also Equinox when it is at 0 degrees in tilt.

So, let’s say it’s zero degrees in revolution and zero degrees in tilt. So, for everyday sun revolves 1 degree and for every 4 days it tilts 1 degree. Then on 90th day Sun would be at 90 degrees in revolution and sun would be at 23.5 degrees in tilt. From the table 90 degrees marks the start of Cancer so 23.5 degrees north is called Tropic of Cancer. So, 90 days later on 21st June Sun will be at Tropic of Cancer and it is called as Summer Solstice or Summer in Northern hemisphere.

From 21st June for the next 90 days earth revolves from 90 degrees to 180 degrees and the tilt happens in reverse direction from 23.5 degrees north towards equator. That is on 22nd September 3 months from 21st June Sun will be again at the equator and the tilt is back to zero. From 22nd September for the next 90 days up to 21st December sun moves 90 degrees from 180 degrees to 270 degrees. The tilt also happens in the reverse direction towards South and on 21st December it would have tilted 23.5 degrees at the rate of 1 degree in approx 4 days.

From the table, you can see that 270 degrees corresponds to Capricorn in sun signs so 21st December is called Tropic of Capricorn or summer Solstice in southern Hemisphere. From then on for next 90 days the tilt happens in reverse direction from 23.5 degrees south to equator and sun revolves from 270 degrees to 360 degrees. Again, on 21st March sun is back to where it was and has revolved 360 degrees. The tilt is also completed and the tilt is at 0 degrees now. So, Sun at zero and tilt also at zero is the starting of Aries.

That is how 23.5-degree North is called Tropic of Cancer and 23.5-degree south is called as Tropic of Capricorn.