Is the Earth a "perpetual motion machine"?

In the history of mankind, a bold idea was born that it was possible to make a machine that, given an initial force, would keep moving and doing work without stopping.

Such an idea was born in India in the early thirteenth century. However, due to the limited level of science at that time, it remained only in the stage of fantasy. Although no one put it into practice, it did not prevent the idea from spreading quickly, and soon Europe also learned of the idea of perpetual motion and proposed a specific program.

Naturally, this solution soon failed in practice, but its once-and-for-all magic made people continue to conceive it, and Leonardo da Vinci in the Renaissance also made the so-called perpetual motion device. But when the theory became practice, he did not escape the fate of failure.

After that, experiments on perpetual motion continued until the middle and late eighteenth century, when the French Academy of Sciences announced that it would no longer accept designs related to perpetual motion, and the craze gradually returned to calm.

So, is it possible to realize perpetual motion in an ideal environment?

Leonardo da Vinci's manuscript

An Impossible Idea

It may sound cruel to say that a concept proposed hundreds of years ago, which has been studied by countless people, can only be answered in the negative, but the perpetual motion is indeed an impossible idea.

In today's words, perpetual motion is equivalent to a kind of white whoring. But in the law of conservation of energy, energy does not disappear or arise out of thin air, only transfer or transformation of form, and in the process, the total amount also remains the same.

The principle of perpetual motion is to use the initial force to do work without consuming energy, which is not valid. Thus, the first type of perpetual motion machine is far from being declared a failure.

However, people did not give up the exploration of the perpetual motion machine, for this reason, the second type of perpetual motion machine. At this time, people realized that energy could not come out of thin air, so they wanted to draw thermal energy from nature and even space so that it could become the source of driving the work of perpetual motion.

But this theory also soon failed, because the conversion process between mechanical energy and internal energy is directional. Therefore, in the nineteenth century, John Gamgee's second perpetual motion machine did not succeed. He wanted to let the heat energy provided by seawater vaporize liquid ammonia and then drive the machinery. However, when the liquid ammonia was vaporized, it did not return to the liquid state without other heat energy.

After the failure of both ideas, it was then stated that according to Newton's law, an object can use inertia to do uniform linear motion even without force, in which case this idea can certainly be accomplished in space. However, according to Newton's law of gravity, all objects in nature are attracted to each other, so after being influenced by it, objects will also stop one day.

Just when people were ready to accept the fact that there is no perpetual motion machine, some defiant people found that the earth has been rotating for billions of years, but it has not stopped. Does this not mean that the earth is a perpetual motion machine?

The Earth's rotation and its causes

Such an idea falls into another misunderstanding. First of all, 4.5 billion years is indeed a long time, but it does not mean that it is the end of time, which means that although the Earth is still rotating now, it will not necessarily rotate in the future.

Secondly, the Earth's rotation is indeed slowing down in terms of the length of time it has been spinning.

About 6.5 billion years ago, the cloud of hydrogen molecules in the universe collapsed thus forming the Sun. After that, the rest of it became the protoplanetary disk, which eventually formed the eight planets and other small bodies.

The gravitational force of the Sun forced the Earth to rotate around the Sun. Amid the rotation, the Earth creates a part that bulges outward, but this part is pulled back by the Sun's gravity. To keep itself in balance, the Earth then has to rotate itself.

This is only one of the reasons for the Earth's rotation, and another theory is that an asteroid's impact on the Earth gave the Earth a prime mover. Either way, there seems to be no way to conceal the fact that the Earth rotates endlessly.

So is the Earth a perpetual motion machine? The answer is no.

When the Moon was born four and a half billion years ago, the Earth was gradually subjected to tidal locking. That is, in space, since the mass of the Earth is the largest object in the region, other small objects are forced by its gravity to revolve around it. However, when the Moon orbits the Earth, its gravitational force acts on the Earth, causing tides to appear on the Earth, and the Earth's rotation axis to shift.

In such a case, the rotation speed of the Earth will gradually slow down and its angular momentum will become the angular momentum of the Moon's rotation.

Due to the long-term tidal locking, the Earth's rotation speed becomes slower and slower, and the Moon gradually moves away from the Earth at a rate of 38mm/year.

Scientists speculate that the Earth had about 400 days in a year during the Devonian period. However, with the passage of time and the decrease of the Earth's rotation speed, the Earth in 200 million years may have only 300 days a year, and the length of a day may reach 30 hours.

In that case, the speed of Earth's rotation is gradually decreasing when a tidal lock appears. But this is not its only factor.

In addition to the slowing down of the rotation speed, there are periodic changes in the Earth's rotation. For example, in the 1950s, it was found that the Earth's rotation was faster in the spring than in the fall, and the influence of this is the climate.

In addition, nowadays, with the gradual development of science and technology, human activities also have a great impact on the rotation speed of the Earth, especially the artificial Earth satellites launched by the force of the Earth's rotation. Their reaction to the Earth has also contributed to the further reduction of the Earth's rotation speed.

The Earth does not move endlessly at a uniform speed, so the idea that perpetual motion can appear in space eventually goes bankrupt.

Whether the initial force of the Earth is due to its rotation and the gravitational pull of the Sun or whether the asteroids give an initial velocity is not conclusive, but it is a fact that the speed of the Earth's rotation is decreasing, and it is an indisputable fact that it is not a "perpetual motion machine".