<div class="text-justify">The Earth is round and rotating is an undeniable fact of science. However, there are only ignorant people who want to obscure this fact with questions that are actually easy to answer if we understand basic physics correctly.


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One of the most frequently asked questions relates to the Earth's rotational speed of about 1600 km / h. This speed is very large, double the speed of aircraft, tens of times the average speed of cars on the streets. If the earth rotates so "fast", then why do we not feel it? Let's peel it thoroughly.

With regard to speed, there is an angular velocity and there is a linear velocity (tangential velocity) on moving objects rotating.

If it says the earth is moving very fast. Which speed is used? If the angular velocity is used, the numbers are very small. The angular velocity is 360 degrees (or 2π radians) divided by the travel time of one rotation.

The Earth rotates on its axis, with a one-time rotation of about 24 hours (exactly 23 hours 56 minutes 4 seconds, but we round it up 24 hours). Thus, the angular velocity is 0.0042 degrees per second or 0.00175 radians per second. Very small, Have you ever seen or boarded a carousel? Suppose that once the rotation takes 10 seconds, the speed of the merry-goose angle will be worth 36 degrees per second or 8600 times faster than the rotational speed of the earth's rotation.

Thus, the angular velocity in the case of the Earth's rotation is approximately one per 8600 times the angular velocity of the merry-go-round. Very slow, is not it? Well, to imagine the speed of the corner of the earth, let's just say we take a carousel and once the round takes 24 hours. Of course, the merry-go-round is very slow, is not it? Maybe we will not feel at home.
Then what about the linear velocity? Is not it very fast? Okay, let's learn first why it can appear the speed figure of about 1600 km/hour as mentioned at the beginning of writing. Remember again the lesson at school, the linear velocity formula (v) is the angular velocity (ω) multiplied by the radius (r). The radius used here is not the radius of the earth, but the radius of the earth is multiplied by the cosine of the location latitude (Ө).

In other words, r is the distance between the points on the earth's surface and the straight line of the earth's diameter connecting the north and south poles. The average radius of the earth is 6371 km. We can write:

v = ω R earth cos Ө

From this formula, for the person living on the equator (Ө = 0), the linear velocity is:

v = 0,000073 radians / sec × 6371000 meters × cos (0)

= 465 meters per second = 1670 km / hour.

Well, we've got the numbers that were spelled out very quickly. Note, however, that the velocity of 1670 km / h is the tangential velocity of the point at the equator around the diameter of the earth connecting the north pole and the south pole.


If the point on the surface of the earth is getting closer to the poles (north or south), the tangential velocity will be smaller as the value of cos Ө. So, if it says the speed of the rotating earth always reaches 1600 or 1670 km / h, that is not true because that number only applies on the equator. Try my own companion friends, in latitude 60 degrees, the linear speed drops to 835 km/hour. Even right at the point of the north pole (latitude 90 degrees), the linear velocity is equal to zero because cos (90o) = 0.

The question arises again if the linear velocity varies and depends on the latitude, should the people at the equator feel the most of the earth's rotation than elsewhere because of its greatest speed, but why in all places is as alike as not feeling? We can answer this question with the analogy of riding a vehicle. We must have been driving at a speed of about 80 km/hr. Maybe some of us also had a plane with a speed of approximately 800 km/hour. Why is our car or plane are we comfortable? That's because we're moving with cars or planes!

When it was airborne, the speed of the aircraft was approximately 800 km / h. To what? That's the speed of the plane against the ground or the earth's surface. Because we are stationary on the plane, our velocity relative to the plane is zero, whereas our speed to Earth is actually 800 km / h. Why does our speed on the plane in the plane equal to zero? Obviously, because we are told quietly in the plane, do not even run around in the plane.

How to prove our speed to earth when ride a car or plane is big enough? We can take the example of the car so easy. Visually, of course, we know when we get in the car our speed to the ground is quite big when we see the house, the trees and so on that live on the ground. The house, the tree and so on will look away from us. Cars moving away from home (according to observers at home) were equivalent to moving houses away from cars (according to observers in cars).

Then, how does our body feel our considerable speed in the car? Well, this is actually a question whose consequences are very dangerous for our bodies.

In order for our bodies to feel our bodies move for a moment with a speed of 80 km / h, the car should be braked suddenly or experienced a collision. Shortly after the car stopped suddenly, our bodies will be thrown forward at a speed of 80 km/ hour. That is the importance of using seat belts.


Remember Newton's first legal consequence of the principle of inertia. An object will tend to maintain its previous state. We were in the car already moving forward towards the ground.

If the car is forced to stop, according to the principle of inertia, we will tend to keep moving forward so our bodies are thrown forward. So, whether it's a car speed of 80 km / h or a plane speed of 800 km / h against the ground, we both feel comfortable in the car or plane because we are in it.


Similarly, those on the surface of the earth. Both the equatorial tangential speed is 1670 km / h, which is 60 degrees latitude at 835 km / h, even at zero-speed poles, equally comfortable and "no sense" of rotation as both move alongside the earth's rotation.

Everything on the surface of the earth also rotates with the earth, even including air and atmosphere. Imagine if the everyday air does not go rotating with the earth, of course, the equator will feel the airspeed is 1670 km/ hour against us. Unbelievably chaotic!

Then, how our bodies at the equator feel the tangential speed of 1670 km /hour. By analogy like in the car crash above, As a result, all who are on the surface of the earth will feel the inertia so that a moment later everything immediately moves according to the speed of each rotation. 

The equatorial population will suddenly move thrown at a speed of 1670 km/ hour. The 60-degree latitude will move at 835 km / h. Surely this kind of event we do not want to happen now.


Why can we join the rotation of the earth together? This is because of the existence of gravity, something that some ignorant people reject (such as a flat earth tale creator) who lacks the understanding of physics.

The gravitational acceleration valued at about 9.8 m / s2 with the direction toward the center of the earth makes us "bound" on the earth's surface and participates in rotation with the Earth's rotation. In addition, in fact, due to the rotation of the earth, there are two additional types of acceleration called as centrifugal acceleration and Coriolis acceleration.

However, the magnitude of these two accelerations is much smaller than the acceleration of gravity so it can be ignored. We can only feel the effects of the two accelerations significantly if the speed of the rotational angle of the earth increases significantly.

##### Can be concluded
The velocity of the earth's rotation angle is very small, thousands of times smaller than the rotational angle of rotary speed.

The linear (tangential) velocity on the surface of the earth is large (and its value varies depending on its geographic latitude), but since we are rotating with the earth we do not feel the great linear velocity.


The reason why we on the surface of the earth join the Earth together is the earth's gravitational acceleration of about 9.8 m / s2 leading to the center of the earth round.

If the earth suddenly stops rotating, then a moment then man and all that is on the surface of the earth will feel the great linear velocity is due to the principle of inertia.

In addition to the points of this conclusion, we can also contemplate the consequences if the earth suddenly stops rotating or even changing the direction of rotation.

Perhaps, that is one possible occurrence of the great apocalypse on earth because all the existing universe systems are in disarray. Be thankful we are still given life on the earth's rotating and gravitational surface.</div>

#### Thank for taking the time to read my post

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