GK: Understanding Coriolis Force (GEOGRAPHY)

IMPORTANT: SPEED OF ROTATION AT DIFFERENT LATITUDES:

Earth's spin is constant, but the speed depends on what latitude you are located at. Here's an example. The circumference (distance around the largest part of the Earth) is roughly 24,898 miles (40,070 kilometers), according to NASA. (This area is also called the equator.) If you estimate that a day is 24 hours long, you divide the circumference by the length of the day. This produces a speed at the equator of about 1,037 mph (1,670 km/h).

IMPORTANT: SPEED OF ROTATION AT DIFFERENT LATITUDES:

That speed decreases more as you go farther north or south. By the time you get to the North or South Poles, your spin is very slow indeed — it takes an entire day to spin in place.

WHY SATELLITES ARE LAUNCHED FROM NEAR THE EQUATOR?

Space agencies love to take advantage of Earth's spin. If they're sending humans to the International Space Station, for example, the preferred location to do so is close to the equator. That's why space shuttle missions used to launch from Florida. By doing so and launching in the same direction as Earth's spin, rockets get a speed boost to help them fly into space.

UNDERSTANDING CORIOLIS FORCE:

The Earth rotates to the east at an effectively constant angular velocity, but different latitudes have different linear speeds. A point at the equator has to go farther in a day than a point in Ohio, so it must go faster.

However, when an object starts to move north or south and is not firmly connected to the ground (air, artillery fire, etc) then it maintains its initial eastward speed as it moves. An object leaving the equator will retain the eastward speed of other objects at the equator, but if it travels far enough it will no longer be going east at the same speed the ground beneath it is.

The result is that an object travelling away from the equator will be heading east faster than the ground and will seem to be forced east by some mysterious force. Objects travelling towards the equator will be going more slowly than the ground beneath them and will seem to be forced west. In reality there is no actual force involved, the ground is simply moving at a different speed than the object is "used to".

Consider the diagram to the right. The orange arrow represents some object sent north from the equator. By the time it reaches the labeled northern latitude, it's gone farther east than a point on the ground would have, since it kept its eastward speed from where it started. Similarly, the yellow arrow started away from the equator at a slower eastward speed, and doesn't go as far east as the ground at the equator...seeming to deflect west from the point of view of the ground.