Submitted by bringthelight2 t3_yi3t44 in explainlikeimfive
So on the first day of fall and spring, night and day are 12 hours each everywhere on earth.
But does the sun take the same path through the sky if the observer is on the North Pole vs the Equator?
Also, is there any day / location where the sun rises directly in the east, goes directly overhead, and then sets directly in the west?
It would seem that at the equator, on the equinox, the sun would indeed travel a line from due east to due west, directly overhead. Such a line would have no inclination and wouldn't be affected by Earth's tilt since the concepts of due east and due west are affected to the same degree.
I don't think that's quite right. The Earth is still tilted, just sideways with respect to the sun. So, for example, at the vernal equinox, the sun would just slightly to the north and set just slightly to the south
The sun will move in a line very close to a line from due east to due west, directly overhead. It is "close to" not "exactly in".
The problem is the equinox is a moment in time it is not a day. If you look at https://en.wikipedia.org/wiki/Equinox you can see the time was in March 20 15:33 UTC and on September 23 is was 01:04 UTC, those time are rounded to minutes. The day of the equinox is the day it occurs not that is during the whole day.
So it is only one moment in time the equator is in line with the ecliptic.
If we assume the rate of change of axial tilt is constant we can calculate the cage during the day, I believe this is an approximation because of the elliptic orbit of Earth but it is a good enough approximation for my point.
The change in a year is 4 x 23.4 degrees = 93.6 degrees. Per day it is 93.6/365 =0.27 degrees. So on the day of the equnox the sun is up close to 12 hours and the equator change relative to the ecliptic is 0.27/2 =0.135 degrees.
So during the time the sun is up on the day of the equinox, the equator will change its tilt relative to the ecliptic by around 0.14 degrees. So even if the sunrise is exactly due west it will set a small bit off due west. The difference can be even higher because for half of the equator it will be night when the equinox occurs so will be off it even before the day start or before depending on you relative direction, let's double the error and ger a max error of around 0.3 degrees
So if due east and due west mean within 0.3 degrees then the sunrise and sunset direction are correct. If it is 0 error then it is only one spot on earth it is true for sunset and one for sunrise, the spots when the events are on the moment of the equinox.
CJ says that at that exact moment, you can balance an egg on its end.
Ok so this means on the north pole the sun would appear to move “slower” as it would still take 12 hours to go from Southeast to Southwest, as opposed to the equator where it’s going from one far side to the other.
On the north pole, there is only south, the is no east-west or north. Talk instead of what latitude line the sun is over.
For any 12 hours period, the sun will move 180 degrees The angular speed of the sun is 15 degrees per hour regardless of where on earth you and what time of year. The sun's angular movement is a result of earth's rotation and it orbits around the sun, not the location on earth
Technically it changes a tiny amount because the time between two solar noons are 24 hours +-30s because the orbit is the ecliptic. The rate it move close to the horiont changes a bit to because of atmospheric refraction.
But the general idea of the angular speed of the sun in the sky is very close to 15 degrees per out is very close to correct for any location and day on earth, That is when the sun is in the sky.
At the equinox, the angle of the rising sun towards the north on the north pole will be accompanied by an angle of the setting sun to the south. This is also true if you are at the equator.
However, the sun will appear to be lower in the sky the closer you get to the poles. So you might say that the sun is moving slower, as its curve on the sky appears to be shorter.
In reality, your own rotation speed decreases when you get closer to the poles. If you are stationed 1 meter from the geographical north pole, then during the 12h equinox sun period, the earth rotation will have moved you approximately 3 (pi) meters. If you are stationed at the equator, the rotation will have moved you half of the earth's circumference, i.e. approximately 20,000,000 meters.
Not even remotely. The sun should follow an almost exactly the same path per latitude, but the path is different at every latitude. At the equator, the sun goes directly overhead on the equinox. The further from the equator you go, the lower the angle the sun rises from the horizon. The path is similar on the opposing latitude, but reversed from south and north horizons.
An interesting side point is that the tropic lines (tropic of Cancer and Tropic of Capricorn) are the lines where the sun goes directly overhead on the solstices. Outside of these lines, the sun never gets directly straight up. The opposite are the Arctic and Antarctic Circles. Those are the lines where the sun never sets around the summer solstice and never rises around the winter solstice. These lines of latitude move slightly every year to account for the irregular wobble of the earth and slight elliptical orbit.
[deleted]
_OBAFGKM_ t1_iuh3es9 wrote
> But does the sun take the same path through the sky if the observer is on the North Pole vs the Equator?
No: if you're on the equator the sun will be directly overhead, if you're at the north pole the sun will always be in the southern part of the sky.
> Also, is there any day / location where the sun rises directly in the east, goes directly overhead, and then sets directly in the west?
The closest you could get to this is being exactly on the equator during an equinox. It's still not perfect, the tilt of the earth makes what you're describing impossible, but it's pretty close.