if the earth spin on it's axes, ( w/ 23degrees tilt) then why isn't the ecliptic on the same line as equator?

Question

please also explain why is it that people locate at any point on the same latitude on earth will see the same constellation but not their longitude? thanks

Answer 1

The earth's tilt is defined as the tilt of the equator with respect to the ecliptic. So if the earth's tilt were zero, the equator and ecliptic would be the same plane. Because the earth's tilt is 23.5 degrees, the equator and ecliptic cannot coincide.

For your second question, imagine two people on the same latitude but 15 degrees apart in longitude. Person A, to the east, sees certain constellations above his horizon at midnight. One hour later, the earth has spun 15 degrees, which puts person B, to the west, exactly where person A was (in space) at midnight. So they will see exactly the same constellations. Person B's local time is now midnight, while for person A it's 1 AM (because they are in different time zones).

Answer 2

The ecliptic isn't the same line as the equator BECAUSE it is tilted 23 1/2 degrees. Most globes are mounted in a way so that when set on a table, they are tilted at 23 1/2 degrees. The table represents the ecliptic. The ecliptic is the giant imaginary flat surface on which the Earths orbit could be drawn. It is the plane of the Earth's orbit. The Earth's rotational axis is tilted 23 1/2 degrees to that plane.

People can't see constellations from the wrong latitude because the Earth's rotation is constantly carrying you eastward, not southward. You will eventually rotate around to see any constellation that is over the eastern horizon, but never one over the southern horizon (assuming you live north of the equator, it would be the northern constellations you could not see from a place south of the equator).

This will be easier to visualize if you use a globe.

Answer 3

The answer to your first question is within the question itself. The reason the ecliptic is not on the same line as the equator is because of that 23 degree tilt. If the earth's axis was not tilted by 23 degrees, then the ecliptic would be on the same line as the equator.
The people on the same line of latitude see the same constellations each day, just not always at the same moment because the time is different in each time zone. The reason that they all see the same constellations is because the earth rotates from west to east. If the earth rotated from north to south or south to north, then they would not all see the same constellations.
The people at the same longitude do not see the same constellations each day because the earth rotates west to east. If the earth rotated north to south or south to north, the the people on the same longitude would see the same constellations each day as would also the people of the opposite longitude. (lon+180 or lon-180).

Answer 4

the earths axis is believed to have changed when a planetary body hit the earth, and created the moon. both objects have disproportionate mass now. that's why the moon always faces the earth, and the earth wobbles on its axis.