Anonymous
Anonymous asked in Science & MathematicsAstronomy & Space · 9 years ago

# If Earth had a 0 degree tilt?

Would the earliest rise (and set) times of the Sun come closer to perihelion or aphelion?

Relevance
• DLM
Lv 7
9 years ago

Aphelion.

Let's think about why the solar mean day is about 4 minute longer than the sidereal day. The Earth is moving along in its orbit around the Sun as the day is going on. The Earth needs to rotate 4 extra minutes for the Sun to return to your meridian. A zero degree tilt eliminates seasonal rise and set time differences, so the only difference remaining now, is the varying speed of Earth's orbital velocity.

Since it travels faster at perihelion, it needs to rotate a little bit further than average for the sun to return to the same azimuth. This would be a later rise time than at aphelion, when the Earth has its slowest orbital velocity, and doesn't need to rotate as far for the Sun to return to its same azimuth.

• 9 years ago

Neither. If Earth had a 0 degree tilt, light and dark would be exactly the same length every single day. The difference in distance from the sun between aphelion and perihelion is so slight that it would not make any difference in the length of the daylight hours.

.

• Anonymous
9 years ago

This is a great question. Aphelion is the answer, because at aphelion the object is farther away. If it is closer it would have to rotate more to see the sun rise. The theoretical limit for aphelion is infinity and at that point you would have equal day and night. Closer objects (perihelion) have more night than day. Make sense?

• Anonymous
9 years ago

If there was no tilt then there would be no seasons and there would be 12 hours between sunrise and sunset and another 12 hours until the next sunrise all year long. Distance from the Sun doesn't have anything to do with sunrise and sunset time variation. The Sun is actually closest to the Sun around January 3 in the middle of northern hemisphere winter and at aphelion around July 4 when the northern hemisphere has the hottest weather.

http://curious.astro.cornell.edu/question.php?numb...

http://darkskydiary.wordpress.com/category/time-an...

The DATE that a particular location has approximately an equal amount of time between sunrise and sunset and the following sunrise is LATITUDE DEPENDENT BECAUSE OF THE TILT:

"...For observers within a couple of degrees of the equator, the period from sunrise to sunset is always several minutes longer than the night. At higher latitudes in the northern hemisphere, the date of equal day and night occurs before the March equinox. Daytime continues to be longer than nighttime until after the September equinox. In the southern hemisphere, the dates of equal day and night occur before the September equinox and after the March equinox. ..."

http://www.usno.navy.mil/USNO/astronomical-applica...

Stick some locations and dates around the equinoxes into these sites to see for yourself what I'm saying really is true:

http://www.usno.navy.mil/USNO/astronomical-applica...

http://www.usno.navy.mil/USNO/astronomical-applica...

The world site is somewhat of a hassle to use. It doesn't adjust for daylight saving time. The governments of other countries have similar almanac sites with interactive pages that are easier to use than U.S, Naval Observatory site is. I've been using this site for 16 years. They've updated the the U.S, web-page, but they haven't gotten around to updating the program for world page yet.

http://www.usno.navy.mil/USNO/astronomical-applica...

• Anonymous
9 years ago

the distance to the sun is so much that there wuld be no noticeable difference between times of sunriset aphlion or perihelion,

Throughout the year they would be the same at all latitudes

• 9 years ago

aphelion

• 9 years ago

No