The tilt of our earth

Janus58 said:
First, I'm going to assume that you are thinking along these lines: If the North hemisphere is heavier, then it would be attracted to the Sun more than the Southern hemisphere and that his imbalance of attraction would cause the Earth to tilt.
This fails for at least a couple of reasons.
Since the North hemisphere leans towards the Sun in Summer and away in Winter, the "imbalance" would work towards increasing the tilt in the summer and decreasing it in the Winter. Over the course of the year, the effects would average out and you would see no net change in the tilt. If the Earth wasn't tilted in the first place, this couldn't produce a net tilt. ( or at best would produce a situation where the North pole always tilted towards the Sun, which it does not presently do.)

Secondly, even with a more massive Northern hemisphere, there would be no tendency for it to want to tilt towards the Sun. The Earth is in orbit, which is a state of free fall. The Northern hemisphere would not want to fall towards the Sun more than the Southern hemisphere does for the same reason that if you drop a heavy object and light object together they don't fall at different speeds. There would be no net effect acting on the mass imbalance to induce a tilt.

If I have assumed wrong as to what you were thinking, then I, like DaveC426913, am at a loss to why you think such mass imbalance would cause a tilt. There is nothing about the laws governing rotating rotating bodies that says that this should be the case.
Click to expand...
 
Your and Daves explanation are good, but because there are some that there are some change in angle every 40000 years grant you small but there are , or some fluctuation in the Sahara desert must or can be a sign of change in the in the tilt.
 
timojin said:
Your and Daves explanation are good, but because there are some that there are some change in angle every 40000 years grant you small but there are , or some fluctuation in the Sahara desert must or can be a sign of change in the in the tilt.
Click to expand...

Change in angle every 40,000 yrs. ?

Interesting where did you get this info ?
 
Axial tilt, the second of the three Milankovitch Cycles, is the inclination of the Earth's axis in relation to its plane of orbit around the Sun. Oscillations in the degree of Earth's axial tilt occur on a periodicity of 41,000 years from 21.5 to 24.5 degrees.
 
sculptor said:
Axial tilt, the second of the three Milankovitch Cycles, is the inclination of the Earth's axis in relation to its plane of orbit around the Sun. Oscillations in the degree of Earth's axial tilt occur on a periodicity of 41,000 years from 21.5 to 24.5 degrees.
Click to expand...

But what is the essence of these , oscillations ?

Why do these oscillations occure in the first place ?
 
river said:
But what is the essence of these , oscillations ?

Why do these oscillations occure in the first place ?
Click to expand...
Because Earth is not a perfect sphere and the Sun and Moon act on it.

"The precession of the equinoxes is caused by the gravitational forces of the Sun and the Moon, and to a lesser extent other bodies, on the Earth. It was first explained by Sir Isaac Newton.[19]

Axial precession is similar to the precession of a spinning top. In both cases, the applied force is due to gravity. For a spinning top, this force tends to be almost parallel to the rotation axis. For the Earth, however, the applied forces of the Sun and the Moon are nearly perpendicular to the axis of rotation.

The Earth is not a perfect sphere but an oblate spheroid, with an equatorial diameter about 43 kilometers larger than its polar diameter. Because of the Earth's axial tilt, during most of the year the half of this bulge that is closest to the Sun is off-center, either to the north or to the south, and the far half is off-center on the opposite side. The gravitational pull on the closer half is stronger, since gravity decreases with distance, so this creates a small torque on the Earth as the Sun pulls harder on one side of the Earth than the other. The axis of this torque is roughly perpendicular to the axis of the Earth's rotation so the axis of rotation precesses. If the Earth were a perfect sphere, there would be no precession."

https://en.wikipedia.org/wiki/Axial_precession#Cause

Or don't you "buy that" either? :smile:
 
DaveC426913 said:
Because Earth is not a perfect sphere and the Sun and Moon act on it.

"The precession of the equinoxes is caused by the gravitational forces of the Sun and the Moon, and to a lesser extent other bodies, on the Earth. It was first explained by Sir Isaac Newton.[19]

Axial precession is similar to the precession of a spinning top. In both cases, the applied force is due to gravity. For a spinning top, this force tends to be almost parallel to the rotation axis. For the Earth, however, the applied forces of the Sun and the Moon are nearly perpendicular to the axis of rotation.

The Earth is not a perfect sphere but an oblate spheroid, with an equatorial diameter about 43 kilometers larger than its polar diameter. Because of the Earth's axial tilt, during most of the year the half of this bulge that is closest to the Sun is off-center, either to the north or to the south, and the far half is off-center on the opposite side. The gravitational pull on the closer half is stronger, since gravity decreases with distance, so this creates a small torque on the Earth as the Sun pulls harder on one side of the Earth than the other. The axis of this torque is roughly perpendicular to the axis of the Earth's rotation so the axis of rotation precesses. If the Earth were a perfect sphere, there would be no precession."

https://en.wikipedia.org/wiki/Axial_precession#Cause

Or don't you "buy that" either? :smile:
Click to expand...

But what you have discribed has not shown why the Earth tilts in the first place .
 
river said:
But what you have discribed has not shown why the Earth tilts in the first place .
Click to expand...
I did that in post 19. Remember?

270px-Artist%27s_concept_of_collision_at_HD_172555.jpg
 
river said:
In my post #30 you gave no evidence on why the Earths tilts in the first place .
Click to expand...
It was already answered in post 19.
Would you feel better if I reposted #19 in direct response to your post 30?

Q:You asked why the Earth tilted in the first place.
A: We have strong evidence that it was due to a giant impact very early in Earth's history.

Are you merely being argumentative?
 
DaveC426913 said:
It was already answered in post 19.
Would you feel better if I reposted #19 in direct response to your post 30?

Q:You asked why the Earth tilted in the first place.
A: We have strong evidence that it was due to a giant impact very early in Earth's history.

Are you merely being argumentative?
Click to expand...

No just trying to understand , without somebody trying to ram a said theory down my throat .
 
river said:
No just trying to understand , without somebody trying to ram a said theory down my throat .
Click to expand...
There is a fair amount of evidence of an early impact. The Moon itself is probably the largest exemplar.

But recall, it's more a hypothesis. There are competing hypotheses out there, but this one fits the data best.

"This sort of formation would explain why the moon is made up predominantly of lighter elements, making it less dense than Earth — the material that formed it came from the crust, while leaving the planet's rocky core untouched. As the material drew together around what was left of Theia's core, it would have centered near Earth's ecliptic plane, the path the sun travels through the sky, which is where the moon orbits today."
https://www.space.com/19275-moon-formation.html
 
DaveC426913 said:
There is a fair amount of evidence of an early impact. The Moon itself is probably the largest exemplar.

But recall, it's more a hypothesis. There are competing hypotheses out there, but this one fits the data best.

"This sort of formation would explain why the moon is made up predominantly of lighter elements, making it less dense than Earth — the material that formed it came from the crust, while leaving the planet's rocky core untouched. As the material drew together around what was left of Theia's core, it would have centered near Earth's ecliptic plane, the path the sun travels through the sky, which is where the moon orbits today."
https://www.space.com/19275-moon-formation.html
Click to expand...

Theia , hit Earth , dead on .
 
river said:
Theia , hit Earth , dead on .
Click to expand...
I am not sure why you say that.

From my post 19:

" Theia is thought to have struck the Earth at an oblique angle when the Earth was nearly fully formed. Computer simulations of this "late-impact" scenario suggest an impact angle of about 45° and an initial impactor velocity below 4 km/s."
 
You must log in or register to reply here.
Back
Top