How can there be no such thing as a perpetual motion machine?

I don't get your logic.  First you say it is "increasingly difficult", then you say it is "so damn easy"?  It has to do with the 2d and 3d Laws of Thermodynamics, which suggest that such a machine would have to reject heat at absolute zero, a temperature which can't be attained.

Because the idea of a perpetual motion machine is that it can somehow produce more energy than is put into it. This violates the First Law of Thermodynamics - Conservation of Energy. It states that energy cannot be created or destroyed, only transfered. Since it is not possible for any machine we have today to be 100% efficient, it would be impossible to have a perpetual motion machine (100+% efficiency).

Everything requires energy. As of right now, our science does not allow us to creat a machine that produces as much energy as it consumes due to friction for one.  Very low friction is possible but not zero. So any machine that we know how to build today has some friction that must be over come.  It takes energy to move an object.

Energy is not infinite.

In a perpetual motion machine, unless there is some divine intervention to make it so that there is zero friction of any kind, there will always be a point when there is not enough energy to complete it's movement.

Creating a perpetual motion machine is easy........ provided you have an infinite supply of energy, (which is obviously impossible......)

Thermodynamics says that (except on a subatomic scale,) no physical process can be 100% energy efficient.

That means that without an *external source of energy*, friction, and other internal processes will eventually bring the activity of any machine to a halt, no matter the circumstances. This would still be true, even if it were possible to completely eliminate friction, such as levitating a magnet over a superconductor in a vacuum.

In a more abstract sense, the second law of thermodynamics says that the amount of "entropy" in any self contained system can only *increase*, never decrease. Exactly what "entropy" is, is hard to define in in colloquial terms, but it can be variously described as "disorder", "chaos", or "homogeneousness." Thus, any "organized motion" within a machine, must eventually be all converted into "disorganized motion".........i.e. heat.

Why do you want one?  Aren't you happy with the etch-a-sketch we gave you at Christmas?

Besides, if you got it started, then you'd spend the rest of your life trying to figure out how to stop the damn thing...(!)