How do we know that......?

Question

How do we know that one revolution around the sun has been accomplished in 365 days? thanks. anjum

Answer 1

If the Earth revolves around the Sun - and is not static in space - then it must be true that over the course of a year say, we observe differences - for example in:

i) the stars that appear at the same time in the night sky
ii) the altitude and azimuth (position with respect to the horizon's N, S points) of the Sun.

The first is easily verified, say over the course of obseving the night sky at the same time (say, 8 p.m. local time) each night. You will therefore see a procession of different stars, objects as time goes by.

This is the first indicator that Earth must be moving through space and not stationary.

A further observation to reinforce this is *revolution* and not merely linear displacement is obtained by repeating said observations *year after year* and making notes of the objects seen.

In the same 6-month period, therefore, you ought to see the same objects in the night sky at the same time.

This implies repetitive motion, and hence that the Earth is not merely linearly moving in space, but returning time and again to the same relative position in space (e.g. in it s orbit)

Second, the position, altitude of the Sun. If you do the same thing for the Sun, you will note its changing positions both in altitude - at specific calendar dates - and its rising (and setting) positions along the horizon.

Thus, it ought to be obvious - again, say over a 6-month period of observation - that these are changing.

Again, if you repeat them *year after year* you will see the exact same positions duplicated, suggesting that the Earth is returning to its same position in space relative to the Sun. (The seasons, of course, are also indicators of this)

Answer 2

By looking at the star just opposite to the sun, at night, one year apart. The star that would be in line with the Earth and the Sun, the one you would see right above you at midnight on the equator (which you can also see from point other than the equator, but the mental image is easier that way) changes from day to day. One year later, it is the same as one year before.

And in actual fact, it is not exactly 365 days either. The sidereal year is 365 days, 6 hours 9 minutes 9 seconds. And that does not match the leap year system either (tropical year 365 D, 5 h 48 m 45 s) because of the precession of the equinox.

But I am sure this answer is already more than what you asked.

Answer 3

Well, it's not exactly 365, it's 365 1/4 and change. The way we know, however, is easy to explain. We move around the sun against a background of stars. The sun is in a large galaxy, and the direction of various stars visible from our sky forms a sort of clock-face through which we move in the course of a year. This is called the Zodiac, and astrologers have been observing our movement through it for a very long time. Even before there were telescopes, back before light pollution was a problem, lots of people made a study of the positions of the stars in the night sky. And they return to the same configuration (that is, we return to our same position relative to them) once every 365.25 whatever days.

Answer 4

A very simple answer.
Gou outside and make a meridian line running north to south.
Log onto the GMT website to get the exact time of day.
When it is exactly midnight for you, identify a star that is presently transiting your meridian.
Do this every night until you see the exact same star transit again exactly at midnight. I think you'll find that in 365 days, you will see that same star very close to the meridian at midnight. The next year it will be farther away at midnight, and the third year will be even farther away at midnight, but on the forth year, you will find that particular star crossing your meridian exactly at midnight.

The reason the previous three years were off, was (as others have pointed out) a year is actually a little more than 365 days, and that little bit extra kept piling up for 4 years until in that last year a leap year day was added to correct the error.

Answer 5

By observing the location of the stars. As the earth revolves, the positions of the stars in the sky appear to change; after a year, the stars have returned to their original positions. Actually, a revolution takes 365.224 days, approximately. Read about calendars to find out the significance of the odd fraction.

Answer 6

The vernal equinox is the traditional marker point. This is the moment when the sun crosses the equator heading north. The time between vernal equinoxes is one year. Our calendar is based on the "mean tropical year", which takes the time it takes the Sun to return to a given point such as the vernal equinox, and averages it for all points. One mean tropical year is 365 days 5:48:45.

Answer 7

Actually 365 and 1/4 give or take a few minutes. You can check it by various means, such as where the sun rises or sets on the horizon, or by looking at our position relative to celestial objects such as galaxies, which to all intents and purposes are in a fixed position.

Answer 8

In the earlier times astromony was based on "The Celestial Sphere". By observing the varying positions (zenith)of the sun through various seasons it came back to relatively the same spot in the sky, this cycle was called a year.

Answer 9

by measuring the altitude of the sun

once its it is back in the same place and the changing (moving north or south) in the manner, its completed 1 revolution.

The tilt of the earth is constant one time the north is pointing to the sun, six months later (when the earth is on the other side of the sun) its the south.

Answer 10

you may study John 19:25 Now there stood with the help of the flow of Jesus his mom, and his mom's sister, Mary the spouse of Cleophas, and Mary Magdalene. 26 whilst Jesus hence observed his mom, and the disciple status with the help of, whom he enjoyed, he saith unto his mom, female, behold thy son! 27 Then saith he to the disciple, Behold thy mom! And from that hour that disciple took her unto his own residence. 32 Then got here the squaddies, and brake the legs of the 1st, and of the different which became crucified with him. 33 yet whilst they got here to Jesus, and observed that he became lifeless already, they brake not his legs: 34 yet between the squaddies with a spear pierced his area, and forthwith got here there out blood and water. 35 And he that observed it bare checklist, and his checklist is actual: and he knoweth that he saith actual, that ye might have faith. 36 for those products have been performed, that the scripture might desire to be fulfilled, A bone of him shall not be broken. 37 And returned yet another scripture saith, They shall look on him whom they pierced. 38 And after this Joseph of Arimathaea, being a disciple of Jesus, yet secretly for worry of the Jews, besought Pilate that he might eliminate the physique of Jesus: and Pilate gave him go away. He got here hence, and took the physique of Jesus. 39 And there got here additionally Nicodemus, which on the 1st got here to Jesus with the help of night, and extra a mixture of myrrh and aloes, approximately an hundred pound weight. 40 Then took they the physique of Jesus, and wound it in linen clothing with the spices, through fact the way of the Jews is to bury. 40-one Now interior the placement the place he became crucified there became a backyard; and interior the backyard a clean sepulchre, wherein became in no way guy yet laid. 40 two There laid they Jesus hence through Jews' coaching day; for the sepulchre became nigh to hand.