The tilt of our earth
- Thread starter timojin
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exchemist
Valued Senior Member
Is the Earth heavier above the equator? Why yes. That is why it tilts, because it can't stay upright, due to the excess weight at the top.
The fact that the earth is tilted is most probably a result of when the solar system was born, and also probable early astronomical collisions with other bodies early in the solar systems history.
Worth noting also the near zero axial tilt of bodies like the Moon and Mercury, allows zones on those bodies around the polar regions that hardly ever get to see the Sun, and in any case would be only receiving the Sun's energy and light at near right angles: Which is why we probably have water ice in those regions on the Moon, and probably also Mercury:
Once knew a guy who said that "all rivers flow towards the equator... because water flows downhill."
I asked him about the Nile and showed him a map. It seemed to confuse him.
Janus58
Valued Senior Member
The tilt of the Earth's axis, or the obliquity, is simple the difference between the plane of the equator and the plane of the Earth's orbit around the Sun, or the ecliptic. As pointed out earlier, this came about due to the various trajectories of the bits and pieces that came together to form the Earth. It also was likely effected by the collision from which the Moon is believed to formed from.
The Earth's obliquity varies in value by a few degrees over time due to outside influences (For instance, perturbing effects caused by the other planets causes the orbital plane of the Earth's orbit to shift a bit over time)
Due the fact that the Earth is not a perfect sphere but rather a slightly oblate spheroid, both the Sun's and Moon's gravity pull on the equatorial bulge in attempt to align the Earth's rotation to them. This results in a precession of the tilt which causes the direction of the axial tilt to change over time in a cycle of ~25,000 years. This causes the equinoxes to shift slightly with regard to the Earth's orbit around the Sun. This precession of the equinoxes results in the Tropical year, which follows the seasons and upon which we base the calendar, to be slightly shorter than the time it takes for the Sun to make one full trip around the Sun.
The Earth's obliquity varies in value by a few degrees over time due to outside influences (For instance, perturbing effects caused by the other planets causes the orbital plane of the Earth's orbit to shift a bit over time)
Due the fact that the Earth is not a perfect sphere but rather a slightly oblate spheroid, both the Sun's and Moon's gravity pull on the equatorial bulge in attempt to align the Earth's rotation to them. This results in a precession of the tilt which causes the direction of the axial tilt to change over time in a cycle of ~25,000 years. This causes the equinoxes to shift slightly with regard to the Earth's orbit around the Sun. This precession of the equinoxes results in the Tropical year, which follows the seasons and upon which we base the calendar, to be slightly shorter than the time it takes for the Sun to make one full trip around the Sun.
DaveC426913
Valued Senior Member
Why would you speculate that the latter might follow from the former?
It's not like the plants are sitting on a cosmic table, with gravity pulling the Solar System from underneath!
Pardon what is meant latter and former in this case. This is not business is science it have to be more accurate
[QUOTE="Janus58, post: 3487852,
Due the fact that the Earth is not a perfect sphere but rather a slightly oblate spheroid, both the Sun's and Moon's gravity pull on the equatorial bulge in attempt to align the Earth's rotation to them. This results in a precession of the tilt which causes the direction of the axial tilt to change over time in a cycle of ~25,000 years. This causes the equinoxes to shift slightly with regard to the Earth's orbit around the Sun. This precession of the equinoxes results in the Tropical year, which follows the seasons and upon which we base the calendar, to be slightly shorter than the time it takes for the Sun to make one full trip around the Sun.[/QUOTE]
What is wrong in thinking when mass is larger on one hemisphere there should be an imbalance ,and the imbalance will produce a tilt ?
Due the fact that the Earth is not a perfect sphere but rather a slightly oblate spheroid, both the Sun's and Moon's gravity pull on the equatorial bulge in attempt to align the Earth's rotation to them. This results in a precession of the tilt which causes the direction of the axial tilt to change over time in a cycle of ~25,000 years. This causes the equinoxes to shift slightly with regard to the Earth's orbit around the Sun. This precession of the equinoxes results in the Tropical year, which follows the seasons and upon which we base the calendar, to be slightly shorter than the time it takes for the Sun to make one full trip around the Sun.[/QUOTE]
What is wrong in thinking when mass is larger on one hemisphere there should be an imbalance ,and the imbalance will produce a tilt ?
DaveC426913
Valued Senior Member
What would led to you speculate that the Earth's axis is tilted because its top is heavier?
To speculate such a thing would suggest that you somehow think the gravity in our solar system comes from below.
I find it very hard to believe someone could hold such a view.
Janus58
Valued Senior Member
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.
No body knows .
But it wouldn't surprise me that the tilt , is caused by volcantic and Earthquake activity .
The most earthquake activity is in the northern hemisphere as well as the most volcantic activity as well .
http://www.u-tokyo.ac.jp/en/whyutokyo/wj_001.html
Interesting
But it wouldn't surprise me that the tilt , is caused by volcantic and Earthquake activity .
The most earthquake activity is in the northern hemisphere as well as the most volcantic activity as well .
http://www.u-tokyo.ac.jp/en/whyutokyo/wj_001.html
Interesting
DaveC426913
Valued Senior Member
That would not cause a tilt, any more than activity in the Southern hemisphere would.
DaveC426913
Valued Senior Member
Paddoboy is correct. As far as we understand, Earth received a blow from a large body early in its life. The impactor imparted a portion of its momentum on Earth, and it was oblique.
There are theories about the detail of the event; what was left of the impactor may have disintegrated, it may have been sotly absorbed, or it may have continued on an altered trajectory. It may also have been the seed that created the Moon. There is some study that suggests Earth had an equatorial ring for a few hundred thousand years, which would have eventually come down as meteoroid rain.
There are theories about the detail of the event; what was left of the impactor may have disintegrated, it may have been sotly absorbed, or it may have continued on an altered trajectory. It may also have been the seed that created the Moon. There is some study that suggests Earth had an equatorial ring for a few hundred thousand years, which would have eventually come down as meteoroid rain.
DaveC426913
Valued Senior Member
The salient question is: why would it?
Yeah well I don't buy it .
For an object to hit the Earth would have done far more damage to the Earth .
It would have sent the Earth spining around on the axis , perpendicular to the contact of the object .
DaveC426913
Valued Senior Member
More damage than what?
It did.
If you set an object spinning, then give it a force in any oblique direction, the object will alter its axis of rotation and settle into a new axis that is a combination of its original rotation plus the additional force (for example: rotating at, say, 23.5 degrees from its former zero).
It's not like a spinning object just forgets its original spin when it get s a knock. That's a lot of angular motion, and it doesn't just go away.
But a collision , an actual phyical collision would do more , than a object that compressed the atmosphere of the Earth to tilt or push the Earth on an angle .
DaveC426913
Valued Senior Member
This collision was a planet-cracker. It deformed the Earth, sent a large fraction of the Earth's material into space, and turned the surface molten.
It goes without saying that it occurred before life gained a foothold. (Or certainly vapourized whatever might have been there.)
Like, this kind of thing:
It's called The Giant Impact Hypothesis.
"...an impact angle of about 45° and an initial impactor velocity below 4 km/s..."
"The Earth would have gained significant amounts of angular momentum and mass from such a collision. "
" Theia's iron core would have sunk into the young Earth's core, and most of Theia's mantle accreted onto the Earth's mantle. However, a significant portion of the mantle material from both Theia and the Earth would have been ejected into orbit around the Earth (if ejected with velocities between orbital velocity and escape velocity) or into individual orbits around the sun (if ejected at higher velocities). The material in orbits around the Earth quickly coalesced into the Moon (possibly within less than a month, but in no more than a century)"
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This collision was a planet-cracker. It deformed the Earth, sent a large fraction of the Earth's material into space, and turned the surface molten.
It goes without saying that it occurred before life gained a foothold. (Or certainly vapourized whatever might have been there.)
Like, this kind of thing:
It's called The Giant Impact Hypothesis.
"...an impact angle of about 45° and an initial impactor velocity below 4 km/s..."
"The Earth would have gained significant amounts of angular momentum and mass from such a collision. "
" Theia's iron core would have sunk into the young Earth's core, and most of Theia's mantle accreted onto the Earth's mantle. However, a significant portion of the mantle material from both Theia and the Earth would have been ejected into orbit around the Earth (if ejected with velocities between orbital velocity and escape velocity) or into individual orbits around the sun (if ejected at higher velocities). The material in orbits around the Earth quickly coalesced into the Moon (possibly within less than a month, but in no more than a century)"
Yes I'm familar with the theory .
Don't buy it .