Is it easier to break the discus record near the equator? It turns out that the Earth's gravity is playing tricks

In the men's discus event held at the 31st World University Summer Games, a Polish athlete won the gold medal with a throw of 63 meters, while Jamaican and Algerian athletes won the silver and bronze medals respectively.

This discus throw competition reminds me of a strange incident: a good thrower broke the 70-meter barrier in a men's discus throw competition in Guangzhou. Not long after, he was sent to participate in a sports meeting held in Harbin, Heilongjiang Province. In the competition, the good thrower tried his best but could not pass the 70-meter barrier. After returning to Guangzhou, his performance immediately returned to his previous level.

What is going on? It turns out that the Earth we live on is playing tricks. This is related to the change of the Earth's gravitational acceleration. The magnitude of gravitational acceleration varies with different locations on the Earth. In addition, the Earth we live on has a strange shape. It is not a perfect sphere, but an ellipsoid that is slightly flat at the poles and slightly bulging at the equator. Since the radius at the equator is longer, the acceleration of objects is small and the Earth's gravity becomes smaller; from the center of the Earth to the poles, the radius is relatively shorter, and the Earth's gravity is larger.

There is a formula in high school physics called G=mg. This formula refers to the weight of an object, G, which is equal to the mass of the object m multiplied by the gravitational acceleration of the object g. When the mass of an object is constant, the greater the gravitational acceleration of the object, the greater the gravity of the ground, and the greater the weight of the object. The gravitational acceleration changes from small to large from the equator to the poles. Guangzhou is close to the equator, the gravitational acceleration is small, and the earth's gravity is small. When the mass of the discus is constant, the weight of the Guangzhou discus appears light, and the throwing distance is farther; Harbin is close to the North Pole, the gravitational acceleration becomes larger, the earth's gravity is large, and the weight of the same discus becomes heavier. Therefore, even if this thrower uses all his strength, he can't exceed 70 meters.

Another time, someone loaded a batch of 5,000 tons of herrings onto a ship in the Netherlands, Europe, and sailed for half a month to an African city near the equator. When the ship docked and was weighed again, everyone was shocked to find that nearly 19 tons of herrings were missing. The herrings were clearly escorted all the way, so it was impossible to say that they were stolen. If there was any loss, it would not be that much. It turned out that this was also caused by the different magnitudes of the earth's gravity.

(The author is a director of the Hunan Science Writers Association)