# Why is earth on an axial tilt of 23.4 degrees?

What were the influences for this to occur? Did some things play a bigger part that others?

An impact, possibly the same impact that caused material from earth to fly off to space and create the moon, tilted the earth to $23.5^o$

• Has this actually been proved or is it our best guess yet? Wondering if I should mark it as correct – Baconbeastnz Apr 1 '14 at 22:28
• I'm not 100% certain if its proven but to the best of my knowledge its our best educated guess. Its the dominant/currently accepted theory. – Constandinos Damalas Apr 1 '14 at 22:39

I thought the tilt was caused by the formation of the earth.

When the earth formed from the gas of the pre-solar system, the gasses rotated and created a disk with an axis of near 23 degrees. When the disk got dense enough, it condensed it to spheroid we know know and love, keeping its tilt from its gassy days.

Taking into consideration a collision that generated the moon, the collision could certainly have nudged the earth's tilt to the 23.5 degrees we know today.

• The moon was formed about 100,000 years after the earth formed. A computer simulation shows that a collision with an object about 1/3 the size (with the right conditions), would eject enough matter so the moon could form. This collision would have definitely changed the momentum of the earth, affecting the axis tilt and rotation. – LDC3 Mar 30 '14 at 22:31
• Oh, I see; but since the tilt of the earth is actually a mystery, my answer may still be correct, although augmented by the moon-generating collision. – user2738698 Mar 30 '14 at 22:38
• I would think that the most likely direction for the axis is normal to the elliptic plane. All the dust circling the start, joining together under gravitational pull, forming a sphere. Oh wait. There will be many, many, many collisions with various rocks which will affect the momentum of the earth. Although your idea has promise, I don't think you can say that the axis did not shift before the moon generating collision. – LDC3 Mar 30 '14 at 22:45
• That's what I'm saying, that I think the axis shifted to some degree before the moon generating collision, and then adjusted to the 23.5 degrees today after the collision. – user2738698 Mar 30 '14 at 23:12
• Oh, I thought you said "an axis of near 23 degrees". Anyway, here is the simulation video: youtube.com/watch?v=Fwl_JBQtH9o. Notice the violence of the collision. – LDC3 Mar 31 '14 at 0:45

It's not constant, so there is no magic about it. It varies within a range, reflecting stabilising interactions with the moon and the sun, and the equatorial bulge.

This would be better in astronomy since the earth collided with another planet size rock and the moon was the result. Since the center of the earth is fluid, the tilt of the axis would vary considerable, but the moon has a stabilizing effect.

## protected by Qmechanic♦Apr 25 '16 at 5:03

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