Unclassified materials: who rolls steel balls in our houses at night

Anyone who has ever lived in an apartment building has probably encountered this mysterious phenomenon. Late at night, strange sounds are heard from above – as if someone is rolling large metal balls across the floor. This noise is especially frightening if you live on the top floor or know for sure that the apartment above you is empty. At such moments, thoughts about mysticism and the otherworldly become much more convincing than any rational explanation.

But is there a scientific basis for this phenomenon, or is it worth seriously considering the existence of brownies?

Most often, mysterious night rumblings are heard by residents of multi-story buildings built during the Soviet era. Interestingly, this sound occurs only at night, and its volume can vary from barely audible to frighteningly clear.

If you have already begun to suspect supernatural forces, we hasten to reassure you - scientists and engineers have found a logical explanation for this phenomenon. And not just one, but two at once.

One of the most common theories explains the noise by physical processes occurring in the reinforced concrete slabs of the floors. Inside these slabs are metal reinforcement rods. Following the laws of physics, the reinforcement expands when heated, during the day, and contracts at night, when the temperature drops by several degrees.

During the day, when the temperature is higher, the reinforcement expands slightly, and at night, when it cools down, it contracts. This slight displacement causes the metal to rub against the concrete, which is what produces the mysterious sounds.

Why do we hear them from above? The fact is that the floor in apartments is usually better soundproofed - it is covered with parquet, linoleum, carpet or even rugs. But the ceiling does not have such layers, so the noise coming from the floor slabs is more clearly heard from below.

However, not all experts agree with the first hypothesis. They claim that daily temperature fluctuations (10-12 degrees on average) cannot cause a noticeable change in the linear dimensions of the reinforcement. Skeptics believe that a difference of several tens of degrees is needed for a noticeable movement of the reinforcement.

An alternative explanation links the noise to the natural shrinkage of the building. Over time, the building gradually sinks under its own weight. This process occurs unevenly, which leads to microscopic displacements of the reinforcement inside the slabs. The voids in the floor slabs act as resonators, amplifying the creaking and friction of the metal. As a result, residents hear the very sound that is so reminiscent of rolling balls.

Naturally, paranormal enthusiasts have their own explanations. Some are sure that the noise is created by entities from the "subtle world" - spirits or brownies. Moreover, a simple trick can supposedly help: if you leave sweets in secluded places, the brownie will behave more quietly.

Skeptics are sure that if sounds prevent you from sleeping, it is better to soundproof the ceiling than to treat unknown night guests with candy.

What do you think causes this mysterious noise – physics or something otherworldly? Share your stories in the comments!