We all know about the law of universal gravitation: any objects and things are pulled down by the force of the Earth! Why don’t flies fall from the ceiling? Why don’t these insects succumb to a whole physical law by cunningly rubbing their paws? Let’s figure it out together!
A long time ago, when science was not yet so developed, people believed that flies could stay on the surface of the ceiling or walls due to the structure of their wings.
The fly has two pairs of wings. Some are for flight. They are large and quite powerful, as they occupy almost the entire space of her body. The second wings are called halteres. They are very small and are designed to keep the fly balanced during the flight. Previously, it was assumed that it was the presence of halteres that allowed insects to sit on walls and ceilings. Scientists thought that while the fly was «resting», the halteres were working.
But then it turned out that this is not so. And to verify this personally, you can conduct an experiment even at home. For example, put a fly in a transparent glass and watch it. You can see that the insect will still hold on to the edges of a transparent glass or jar and not fall, even when all pairs of its wings are in a non-working, motionless state.
It turns out that the fly violates all the laws of physics not at all because of the structure of its wings!
A little later, the researchers had another theory why the fly does not fall from the ceiling.
It was assumed that the fly does not fall due to the unique structure of its legs. They have many, many small claws in the form of hooks. They are almost imperceptible, if you do not look closely with the help of magnifying devices such as a microscope. It is thanks to the many such hair-hooks that the fly was believed to be held on rough surfaces. For example, on shrubs, leaves, tree bark, concrete walls or wallpaper, if they are rough.
Then it is logical to assume that the fly should immediately fall from glossy and smooth surfaces. After all, there is absolutely nothing to cling to! But this, nevertheless, does not happen. A fly can hang and rub the paws ruefully even on the smoothest ceiling, where there is not a single notch!
In the era when this hypothesis arose, magnifying glasses and the first microscopes were just beginning to appear. Therefore, it is not surprising that this hypothesis turned out to be erroneous.
The real reason
The real reason for the ability of the fly was discovered even later, when powerful microscopes were finally invented. Entomologists have finally been able to determine why gravity does not act on the fly.
It turns out that it really is in her paws. But not in the villi-hooks, but in a special sticky substance that they secrete!
Right on the fly’s paws are small pads. They cannot be seen without a microscope with a thousandfold magnification. As soon as the fly plans to land on a wall or ceiling, the pads begin to produce a sticky substance that looks like chewing gum. It is with his help that the fly does this trick.
The most interesting thing is that the sticky substance is released exactly as much as needed — not a drop more and not a drop less! It is for this reason that a fly does not permanently stick to the ceiling or that it falls off if the «gum» is not enough. She always calmly sticks to the surface and can also tear her paw off without the slightest difficulty.
If you observe this process under a microscope, you will notice that the same hooks help to tear off the foot from the ceiling or the wall of the fly.
This theory can even be tested! To do this, you can use special substances that dissolve fat. Why exactly them? Because gooey fly stuff is made up of carbohydrates and fats! If you let the fly “walk” on paper soaked in such an anti-grease solution and release it, you can see how the insect flies, but cannot cling to the ceiling.
By the way, in fact, the fly rubs its paws not because it has conceived something insidious against the laws of physics, but because in this way it cleans the dirt from its paws. Because the less dust particles on them, the better the grip of the «gum» with the surface.