Why can three synchronously communicating planets cover the Earth?

In fact, geostationary satellites can only be above the equator, and can never cover the South and North Poles. ）

As the radius of the satellite increases, so does its observation range. When the central angle of the Earth's equatorial circle corresponding to the observed Earth range reaches 120°, then three satellites can cover the Earth. From the geometric relation, we can know the corresponding length relation r= 3r.

Let the orbit of the geostationary satellite r, the radius of the earth r.

The gravitational force of the satellite provides the centripetal force: gmm r = m(4 t )r to get r =

Earth's radius r=

r r 3, so only three are needed to cover the earth.

It is impossible for two to cover the whole world, this is easy to understand

Hope it helps you o ( o haha

Because there is no intersection between two parallel lines, it is not possible to cover the entire earth with two satellites, at least three, and the connecting lines form a triangle with an angle of 120 degrees.

Three communication satellites, each with a coverage of 120 degrees, can cover the whole world.

In the polar regions, the signal is still very weak, almost none. The real global communications project is multi-satellite, with equatorial satellites and polar orbits.

This is a simple trigonometric problem. Just do the math.

If the geosynchronous orbit communication satellite flies at an altitude of about 36,000 kilometers (the actual altitude is about 35,800 kilometers), the width angle of the satellite covering the earth (the angle between the satellite and the lines connecting the two ends of the earth) is.

Solving a triangle and using the formula of a circle to calculate it shows that the width angle covers the length of the Earth's arc is 12,756 kilometers, and the chord length is 18,100 kilometers.

The Earth's equatorial circumference is about 40,000 kilometers, and one satellite can cover 10,000 kilometers, so at least three satellites are needed to cover the entire Earth's surface.

There are two things to note. One is the use of three satellites, and there is some overlap in the area covered between the satellites. Second, even if three satellites are used to form a global satellite communication system, because the three satellites are all over the equator, the communication effect near the poles is actually very poor.

Because at both poles, all three satellites are near the horizon.

The geosynchronous satellite is located in the plane of the equator, directly above the equator, it is equal to the period of the earth's rotation and the central angle of the circle that it turns in the same time, its position relative to the earth's surface does not change, with the earth as a reference, the geosynchronous satellite is stationary; Geostationary satellites transmit information through electromagnetic waves

So the answer is: static; Electromagnetic waves

In fact, geostationary satellites can only be fixed above the equator, and can never cover the South Pole and the North Pole, and in any case the poles of the two poles should be blind spots, and the so-called coverage of the earth means to cover the area that can be covered.

Because the geostationary satellite is always above the equator at a certain altitude, a tangent line drawn from the location of the geostationary satellite to the earth's surface shows that the signal cannot be received in a small area around the polar regions.

1.The Earth's geostationary satellites are immobile relative to the Earth's surface, so the rotation period is the same as that of the Earth, i.e., t = 24 hours.

2.Let the height of the geostationary satellite be h, the mass of the earth be m, the mass of the satellite be m, and the distance from the satellite to the center of the earth be r, then Newton's second law can be known

gmm r 2 = m(2 t) 2r solves r so the height h=r - r ground 3Let the rate be v, then v=2 r t

1.Earthly.

Geostationary satellites. Relative to the surface of the earth is immobile, so and earthly.

Rotation period. is the same, i.e. t=24 hours of the world.

2.Let the height of the geostationary satellite be h, the mass of the earth is m, the mass of the satellite is m, and the distance from the satellite to the center of the earth is r, then there is.

Newton's second law.

It can be seen that gmm r 2=m(2 t).

2r solves r, so the height h=r-r, 3Let the rate be v, then v=2 r t

1.The Earth's standby synchronous satellite is immobile relative to the Earth's surface, so it has the same rotation period as the Earth, i.e., t=24 hours.

2.Let the height of the geostationary satellite be h, the mass of the earth is m, the mass of the satellite is m, and the distance from the satellite to the center of the earth is r, then Newton's second law can be known

gmm r 2 = m(2 t) 2r solves r so the height h=r - r ground 3Let the rate be v, then v=2 r t