گردآب و باتری

بررسی

Claim: If you put the battery in pure water, nothing will happen to the water, but if you do the same for a glass of water in which a good amount of salt (composed of sodium and chlorine) is dissolved, the positive ions (sodium) and negative ions (chlorine) will be affected by the positive and negative ends of the battery and the liquid starts moving. If this movement takes place near the edge, it will cause the liquid to rotate.

Well, I guess there is no need to overdo it. No matter how in length the claim may be written, and how eagerly it may try to fool us by a whole lot of positive and negative ion jargon attempting to justify what is shown in the film, it cannot hide at least two certain points:

1)Entropy decreases, in the video

2)Conservation of angular momentum is violated

In general, if you want to see if a video is playing in reverse, a good approach might be to look for things that, in a sense, become more orderly. Now, in this film, the main subject is automatically gaining in order. After the battery comes out, the slightly spinning water molecules, decide to gradually give more order to their collective rotation and the overall rotation increases. At first it was impossible to draw some work out of the water, but now it is enough to simply put a small watermill inside the glass and get some work done by it.

Entropy of a non-isolated system can decrease as long as the total entropy (including the system and other things around) increases. However, here the entropy of the system in question decreases and there is nothing else that its entropy increase can compensate for this particular entropy decrease. Imagine a glass falls to the ground and breaks. Naturally, glass hits the floor, and the strike propagates in the form of waves inside and on the surface of the ground. What you do not expect is that after a while the waves will return exactly in the same manner and in perfect harmony to strike back at the scattered pieces of the broken glass, and suddenly those pieces will start to shake in their places and then get closer and then weld to each other. Then a larger wave comes only to kick the glass high in the air and returns it to its original height. A strange picture as it is, the sequence described does not contradict the fundamental laws of physics, it is sufficient to reverse the velocity of all particles, atoms and molecules, at the same time and let the system evolve! However, these initial conditions are very incredibly rare, which greatly reduces the probability of their natural occurrence. The set of initial conditions that cause the glass to weld back and return to its original height is much smaller than the set of initial conditions that cause the glass to fall and break.

The second point concerns angular momentum. After the battery is removed, the amount with which the water is rotating increases with no external help. Due to Newton’s second law of motion, in order to move something, you will need to exert a force; similarly, a torque is needed if you want to bring something into rotational motion. The latter proposition is derived by the former. For example, opening a regular door, or you might say, rotating it around its hinge, we need a hand to force it to rotate, or in other words, to exert torque on it. Well, we need to ask, what provides this torque for the water after the battery is removed? Can you find anything? If we play the film correctly, we see what happens actually is that water is rotating at first and then the friction of the wall of the glass exerts an opposing torque on water and slows it down to eventually bringing it to a stop. But as it is played right now, i.e. reversely, there is nothing to help increasing the motion of the water; walls can only exert a frictional force which is opposing not supporting.

Therefore, this claim is clearly refuted.

We often come across claims that are similar to the one above, lengthy and trying very hard to justify a wrong statement. They even utilize emotions such as fear and hatred to get their own way. But it so happens that sometimes there are established facts that the claim, no matter how lengthy, cannot hide. I think the least we can do is not to turn a blind eye to some of those facts when we see them, so that hopefully we become less likely to deceive.