Planetary motion as perpetual motion?

[GiantSheeps]

Could a planet orbiting around a sun be considered an example of perpetual motion? I know that the planet wouldn't be doing any work, since it goes back to the same spot every year, but does an object have to be performing for it to be considered perpetual motion? The two might have nothing to do with one another, but I admittedly don't have very much experience with physics and all that.

 

[russ_watters]

Your instincts are correct: though Newton's first Law might fit the dictionary definition for "perpetual" motion, scientists don't use that word to describe it. They only use the word to describe motions that violate the laws of physics (thermodynamics).

 

[dean barry]

Essentially, its stable orbit is a rare balance of gravity opposed by just the correct velocity of the planet, as space is a vacuum, no drag occurs to slow the planets endless orbiting.

 

[Chronos]

Planetary orbits eventually decay. They ultimately either escape the host star, or are consumed by it. This process can take many billions of years. So an orbit can be robust, but, not perpetual.

 

[pmacias]

I can provide a response to the idea of planetary motion as perpetual motion. Perpetual motion refers to the concept of a system that can continue to move or operate indefinitely without any external source of energy. In this case, the planet orbiting around a sun may seem like a potential example of perpetual motion, as it continuously moves around the sun without any apparent external force.

However, it is important to note that in physics, perpetual motion is considered impossible. This is because all systems are subject to various forms of energy loss, such as friction and air resistance, which eventually cause the system to slow down and stop. Therefore, while the planet may appear to be in perpetual motion, it is actually subject to various forces that prevent it from truly being perpetual.

Additionally, the concept of work is also important to consider in relation to perpetual motion. Work is defined as the transfer of energy from one system to another. In the case of the planet orbiting the sun, there is no transfer of energy, as the planet is not performing any work. It is simply following the laws of gravity and inertia.

In conclusion, while the idea of a planet orbiting a sun may seem like an example of perpetual motion, it is not considered as such in the scientific community. The laws of physics and the concept of work prevent it from being a true perpetual motion system.