How is it possible to explain that, aboard a space orbiter (the Earth), which travels at a mind-boggling speed of 108 thousand kilometers per hour around a star, we do not feel any type of movement, even with this vehicle rotating around the your own axis every 24 hours? After all, it’s like riding a Ferris wheel in a swivel chair!
The truth is, even if it was on a slow carousel, you would feel yourself being pulled slightly off. But standing on the surface of our much faster planet, why aren’t we holding on to some support bar to keep from falling? And, on a rocky world, why don’t we even feel the Earth’s rotation?
Although they seem puerile, these questions are difficult to answer, as they involve some complex concepts of physics, sensory perception and movement, as well as an understanding of what inertia and inertial reference are.
After all, why can’t we feel the Earth’s rotation?
In truth, There are two main reasons why we don’t feel the Earth’s rotation, and the first is that it is smooth. For astronomer and content strategist at Chile’s Vera C. Rubin Observatory, Stephanie Deppe, “if you are in a car and driving at a constant speed on the highway, if you close your eyes and tune out the road noise, you will feel stopped. ”.
However, the astronomer explains to Live Science, all it takes for the car to brake suddenly is for you to immediately know that it was moving. You just don’t have this perception because, when maintaining a constant speed, you felt completely immobile.
Professor of physics and optical sciences at the University of North Carolina at Charlotte, Greg Gbur, puts it another way: “We know that there is no absolute movement. The only thing that matters is relative movement.”, he told Live Science. And he recalled Galileo’s thought experiment, in which a person inside a ship in calm waters cannot discern whether the vessel is sailing or docked in port.
Gravity is the second reason we can’t feel the Earth’s rotation
The second The reason we don’t feel the Earth’s rotation is gravity. According to Deppe, “the force of gravity that holds us to the Earth is much, much, much stronger than the force that would make us fly out.” This feeling of being pulled out of a tagada disc (amusement park ride) or a car doing a “hobby horse” is called centripetal acceleration, says Gbur.
The force of gravity holds us to the Earth stronger than centrifugal acceleration.Source: Getty Images
This happens due to inertia, that is, “your body wants to continue in a straight line, but if you are in the car, the car is trying to pull you in a circle”, explains the physicist. This also happens in the Earth’s rotation, which creates a centrifugal force that appears to “pull” people away from the center of rotation. But the force that keeps everything stuck to the ground wins the fight.
In physical terms, explains Gbur, the acceleration due to gravity on the Earth’s surface is about 9.8 m/s2, but, due to the planet’s rotation at the equator, where objects move faster, there is a reduction in this acceleration, of about 0.03 m/s2. Although measurable, it is too small a loss in relation to the main gravitational force we feel, to be able to perceive it.
Is it possible to observe the Earth’s rotation?
Foucault’s pendulum was presented at the Paris World’s Fair in 1851. Source: Arnaud 25/Wikimedia Commons
If you can’t feel it, At least it is possible to observe the Earth’s rotation. And one of the easiest ways to do this is to observe the apparent motion of celestial bodies, explains NASA Goddard Space Flight Center project manager Stephen Merkowitz to Live Science.
“This movement is most noticeable when the body is close to the horizon, where you have parts of the Earth in view as a reference”, says the scientist. For example, when you see the sunset, which seems to sink into the horizon, is its location on Earth, which is gradually rotating away from our star.
But the definitive visual proof of the Earth’s rotation is the so-called Foucault pendulum, presented by the physicist of the same name at the Museum of Arts and Crafts in Paris in 1851, where it remains today.
Attached to the ceiling by a 67 meter long rigid wire, a 30 kg sphere releases fine sand, which drips during its movement. The sand marks do not overlap, marking the ground as proof of the Earth’s rotation.
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