Are We Getting Shorter as Earth's Rotation Slows Down?

The question of whether the slowing down of Earth's rotation and a supposed increase in gravity could affect human height is an intriguing one. Many have speculated that if Earth's rotation were to slow down, the centrifugal force that balances against gravity might change, leading to a decrease in human height. This article delves into the scientific explanation and dispels common misconceptions surrounding this phenomenon.

Centrifugal Force and Its Minimal Impact

Centrifugal force, which is a fictitious force often explained in rotating frames of reference, plays a minor role in counterbalancing the effects of gravity on a global scale. Scandinavians, for example, are on average taller than other Europeans, but this difference is more attributable to their diet and other environmental factors rather than centrifugal force. According to scientific studies, local gravity varies more due to surface rock composition, elevation, and other geomechanical factors than earth’s rotation.

Gravity and Earth's Mass

Gravity is not increasing. Instead, it is decreasing slightly due to the loss of Earth's mass. The amount of mass lost per year is approximately (10^{-17}) the mass of the Earth, making it negligible. The average radius of the Earth is also not changing, so the force of gravity remains consistent.

The Influence of Earth's Rotation

The rate of Earth's rotation is slowing down by about 17 billionths of a second per year, which may seem significant but is actually a change of about one part in 10^-11 over your lifetime. To put this into perspective, if you shower and postponed drying your hair for one minute each week, the extra downward force of the water on your hair would be much more considerable than the change in Earth's rotational forces.

Scientific Perspective

Most people understand the term "force" in a practical sense, such as the gravitational force. If Earth's rotation were to spin outrageously fast, humanity and the environment would be flung out into space. Conversely, if it slowed down enough to matter, it wouldn't significantly affect human height in our current lifespan. The rate of change in Earth's rotation is so slow that the impacts on gravity and human height are considered negligible.

Scientific Evidence

Earth's rotation is indeed slowing down by a few milliseconds over centuries, and gravity is increasing by a microscopic amount. The change in gravity over time is estimated to be on the order of a few thousand thousandths over centuries, making it difficult to measure with current technology. The impact on human height is infinitesimal.

Conclusion

The speculation that a slower rotation of Earth would lead to a decrease in human height is unfounded. The real factors influencing height, such as nutrition, genetics, and environment, far outweigh the hypothetical changes in Earth's rotation and gravity. As our scientific understanding continues to evolve, it is crucial to differentiate between real-world phenomena and misconceptions.