What is the reason why the motion of the Earth is slowing down each year?
- RaymondLv 75 months agoBest answer
Over hundreds of thousands of years, the Earth's rotation slows down by 1 second every 40,000 years, due to tidal friction (the oceanic bulge raised by the tides rubs against the bottom of shallow seas and coastal areas).
Over gazillion years, Earth's orbit moves away from the Sun by some fraction of an inch every million years, because the Sun turns mass into energy (e = m c^2); the Sun loses 4.5 million tonnes of mass every second (which, when compared to the Sun's total mass, is negligible).
On a year-to-year basis, the Earth's rotation may accelerate OR decelerate as earthquakes redistribute the mass around it rotation axis. For example, an earthquake that lifts an important section of a plate will slow down the rotation. However, one that lowers a hunk of mass will acceleration rotation.
Strong evaporation of the oceans, bringing rain to mountain tops, will slow down rotation. Heavy melting of mountain ice (allowing water to run down to oceans) will accelerate rotation.
Every year, Earth's mean distance from the Sun can change by as much as 500 km, due to the gravitational effect of other planets (mostly Jupiter and Saturn). This changes, ever so slightly, the real length of the sidereal year.
And so on...
- DixonLv 74 months ago
- Anonymous5 months ago
- 5 months ago
Gravity from the moon is stronger on the side of the earth facing the moon. This tends to pull ocean water away from the earth on the near side, and the earth away from the water on the far side. (Giving two high tides per day,) The rotation of the earth pulls the high tides out of alignment with the moon (in the direction of rotation). Since the pull of the moon's gravity is stronger on the near side high than on the far side high, the misalignment causes a retarding torque. The torque is transmitted from the water to the solid earth by friction. The sun also contributes, but its effect is much smaller.
The reaction force (gravity from the earth acting on the moon) has a small component in the direction of the moon's velocity. This causes the moon to gain angular momentum as it is being lost by the earth.
- What do you think of the answers? You can sign in to give your opinion on the answer.
- Jeffrey KLv 65 months ago
The rotation of earth is slowing due to tidal friction. The moon causes tides in the ocean. The friction of the water turns rotational energy into heat.
- Andrew SmithLv 75 months ago
Let us start with the moon. Its rotation has already slowed down to the point where one face of the moon is facing the earth permanently.
The tides on the moon have taken the energy of rotation and dissipated it. Angular momentum is conserved so the angular momentum of rotation has gone into the angular momentum of revolution around the earth.
The earth is spinning and energy is being given to the tides. So the rate of rotation of the earth is diminishing. It is losing rotational energy.
As angular momentum is conserved then this is transferred to the orbit of the moon. The orbit of the moon gets an hour later each day so it is orbiting in the SAME DIRECTION as the earth is rotating.
Hence as the earth slows down some of its rotation energy is given to the moon. It gains altitude and moves further from the earth. At this greater altitude its rate of revolution around the earth also slows.
Now we get to the sun. It also induces tides in the earth. This also reduces the rate of rotation of the earth.
What I don't know is the rate of revolution of the sun.
If it was spinning then the tides induced would alter the orbit of the earth around the sun.
I don't know the facts for this. However I have already stated what WOULD happen if the sun was spinning.
- poldi2Lv 75 months ago
If you are referring to its rotation, its due to friction of the tides on the shallow parts of the ocean.
- oubaasLv 75 months ago
friction : what else??
- MorningfoxLv 75 months ago
The Earth has many motions. Which one are you asking about?
If you mean the rotation of the Earth, it actually got FASTER in 2000, 2001, 2002, 2003, again in 2011, and 2015. It slows down in most years, about 60% of them, but not in every year. In about 40% of recent years, the rotation actually speeds up. We have good data since 1800.