# Seasons without axial tilt?

AThousandYoung
Posers and Puzzles 04 Mar '09 06:56
1. AThousandYoung
All My Soldiers...
04 Mar '09 06:56
Seasons are caused by the tilt of the Earth's axis of rotation. Now, imagine a planet which has an axis of rotation exactly perpendicular to the plane of it's orbit, yet still has seasons...how?

The planet's orbit is not circular. It's elliptical. Therefore the planet is sometimes closer to it's sun, and sometimes farther, and the distance is significant enough to change the average temperature.

As a result the equator experiences seasons, and there are two summers and two winters per revolution around the sun.

Assuming the planet is otherwise like Earth, and the sun is like our Sun...

Describe the ellipse necessary to create seasons comparable in average temperature to the ones we experience on Earth in the temperate zones.

ðŸ˜•
2. leisurelysloth
Man of Steel
04 Mar '09 08:16
Originally posted by AThousandYoung
The planet's orbit is not circular. It's elliptical. Therefore the planet is sometimes closer to it's sun, and sometimes farther, and the distance is significant enough to change the average temperature.

As a result the equator experiences seasons, and there are two summers and two winters per revolution around the sun.
Two summer and two winters per revolution? Why?
3. 04 Mar '09 08:35
Originally posted by leisurelysloth
Two summer and two winters per revolution? Why?
only explanation i can think of is the sun is smack dab in the middle of the two focii? and so at the edges of the minor axis of the ellipse earth is experiencing summer, and at the ends of the major axis earth experiences winter? but i don't know the physics behind why earth would be traveling around a relatively "central" point in an elliptical orbit... seems counter-intuitive to me.
4. 04 Mar '09 12:57
Originally posted by Aetherael
only explanation i can think of is the sun is smack dab in the middle of the two focii? and so at the edges of the minor axis of the ellipse earth is experiencing summer, and at the ends of the major axis earth experiences winter? but i don't know the physics behind why earth would be traveling around a relatively "central" point in an elliptical orbit... seems counter-intuitive to me.
The sun is always at one of the foci, isn't it?
5. 04 Mar '09 18:49
Originally posted by Schumi
The sun is always at one of the foci, isn't it?
that's the way it should work, but then annually there would be a summer a winter, and two similar seasons resembling fall and spring... but the OP said there were supposed to be two winters and two summers so i was trying to construct a way in which this was possible.
6. AThousandYoung
All My Soldiers...
04 Mar '09 20:00
Originally posted by Schumi
The sun is always at one of the foci, isn't it?
I got this from some other forum, and the same thing was pointed out. OK. Forget the two summers and winters then.
7. 22 Mar '09 02:46