# Questions tagged [obliquity]

Questions about the angle between the rotational axis and the orbital axis of a celestial body. Obliquity is also known as axial tilt.

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### How to calculate the Sun's declination for a specific location based on the axial tilt of Earth throughout the year?

How to calculate the Sun's declination for a specific location (i.e. relative to a specific coordinate) based on the axial tilt of Earth throughout the year? Any algorithm for code available in this ...
154 views

### How to calculate the Earth's axial tilt (obliquity)

How can I calculate the Earth's axial tilt in degrees. I tried Skyfield, Poliastro and PyEphem. I know it's changing -0.47"/year, and it was ...
• 155
1 vote
72 views

### What is the difference between inclination and obliquity?

I'm trying to understand the differences between obliquity and inclination when it comes to a system of a planet orbiting a star. From what I understand, obliquity is the angle between the orbital ...
273 views

### Does the axial tilt of Mercury and Venus vary?

The axial tilt of Mars varies greatly over time, with a tilt varying between 15 and 25° over the last million years, and varying even more over the last 5 million years. The Earth's tilt on the other ...
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110 views

### Is there any thing special with an axial tilt of roughly 25°?

Half of the planets in the solar system have an axial tilt of $25.5\pm 3^\circ$: earth (23.5°), mars (25.3°), saturn (26.7°) and neptune (28.3°). If random collisions in the early solar system caused ...
• 16.7k
1 vote
206 views

### Why don't we see evidence of glaciation on Mars, similar to Earth's Ice Ages?

With all recent NASA activity surrounding Mars manned missions, it is surprising that given Mars orbital distance from Sun that there is not evidence of massive glaciation similar to Earth's Ice Ages. ...
1k views

### Effect of the obliquity of the ecliptic / tilt of the Earth on the equation of time

In attempting to answer the question “why aren’t changes in sunset and sunrise times symmetrical around the solstices ?” I’ve got stuck on being able to explain the effect of the obliquity of the ...
199 views

### What is the cause of the variation from high and low mean obliquity periods of Mars?

It is reasonably well known that Mars has a greater obliquity range than Earth, due to Mars lacking a stabilising influence of a large moon. However, the Martian obliquity seems to have gone through ...
301 views

### Is axial tilt direction correlated with semi-major axis direction?

Earth comes closest to the Sun every year around January 3. Winter solstice is at 21-22 December, merely some 12-13 days away. That means projection of Earth rotation axis onto the plane of its ...
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