Why can Rupert's tears stop bullets?

Because Rupert's tears come from the internal unbalanced pressure: when the molten glass drops into ice water, the glass surface cools rapidly to form a shell, and the glass under the shell is still liquid.

When the glass in the core is also cooled, the condensation volume becomes smaller, and the liquid glass naturally pulls the solid shell to shrink, resulting in great compressive stress on the glass near the surface, and at the same time, the core position is pulled around and subjected to tensile stress.

When the outside is damaged, these residual stresses are released quickly, which makes the cracks spread all over the body and fragmented. According to the observation of high-speed photography technology, the propagation speed of cracks can reach1450m-1900m per second.

Extended data:

The history of Rupert's tears;

The earliest inventor of glass in the world was the ancient Egyptians. Glassware was excavated in ancient Egypt and Mesopotamia. After modern scientific and technological appraisal, these glasses have existed for more than 5000 years.

Then in Europe in 2000 BC, the Phoenicians accidentally ran aground while transporting natural soda at sea. When they were cooking on the beach, they found that these natural sodas reacted with quartz sand on the beach under the action of flame to form glass.

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