Everyone watching a science program on the rockets could hear "xx" rocket has reached the first cosmic speed... However, \"the speed of the universe\" exactly is what mean? It contains what content? Let's look at today.
The human space activities, and not blindly to escape from the earth. Especially the application of the spacecraft, the need to fly around the earth, which make the spacecraft as a circular motion. As is known to all, must always have a force on the spacecraft. Its size is equal to the speed of the spacecraft paths of square times its quality divided by the orbital radius, namely F = ^ 2 mv/r. here, just can make use of the earth's gravity. Because the gravity of the earth to objects, and objects curve centrifugal force in the opposite direction of the movement. Through calculation, on the ground, the object's velocity is 7.9 km/SEC, it produces centrifugal force (effect), equal to its gravity coincide with earth. This rate is called speed around.
Speed of the universe is the object from the earth, in the gravitational field of object motion, four more representative of the initial velocity. Spacecraft according to its mission of different, need to be one of the four speed of the universe.
7.9 km/SEC (satellite do approximate circular motion around the earth's maximum speed around)
Firing artillery rounds into the distance on the ground, projectile velocity, the higher the farther flight, when the shells at the speed of the "7.9 km/SEC, no longer fall back to the shell (regardless of the atmospheric effect) on the ground, and a circular flight around the earth, this is the first cosmic velocity.
The first cosmic speed is also near the ground satellite do "uniform circular motion around the earth must have the speed. But with the increase of the height, the gravity drop, speed required to orbit the earth was also lower, all of the spacecraft is flying high from the ground outside the atmosphere, so their speed is lower than the first cosmic velocity. At the same time is also called speed around the first cosmic velocity.
The first cosmic velocity calculation formula is:
V1 =) (gR) (m/s), including g = 9.8 (m/s ^ 2), R = 6.4 * 10 ^ 6 (m).
Need to emphasize that the first cosmic velocity has a dual meaning. When it is not only the launch of the spacecraft, the minimum velocity, is also a spacecraft orbiting the earth's largest speed round (circle).
11.2 km/SEC (fly away from the earth into orbit around the sun, the minimum speed)
When an object (craft) speed is 11.2 km/s, can cast off the yoke of the earth's gravity, fly away from the earth to orbit around the sun, no longer revolves around the earth. The minimum speed out of the earth's gravity is the second cosmic velocity. A variety of planetary probes starting speed is higher than the second cosmic velocity.
The second cosmic velocity V1 (V2) when the spacecraft over first cosmic velocity reaches a certain value, it will be out of the earth's gravitational field and become artificial planets around the sun, this rate is called the second cosmic velocity, also called escape velocity. The second cosmic velocity can be calculated according to the mechanics theory V2 = 11.2 km/SEC. Because the moon is not beyond the scope of the earth's gravity, so the lunar spacecraft fired from the ground, the initial speed of not less than 10.848 km/SEC.
Suppose in the earth will be a quality for m satellite launch into orbit around the sun need the minimum launch speed V;
The satellite motion around the sun can be considered to be not affected by gravity, infinite distance from the earth;
Think infinity is gravitational potential energy 0 potential surface, and the rate of fire is the minimum speed, the satellite just can reach infinity.
By the kinetic energy theorem
1/2 * mV ^ 2 - GMm/r = 0;
Solution to (2 gm/r) V =)
This value is the square root of 2 times the first cosmic velocity.
(also known as the escape velocity) : refers to the launch of the objects on the earth from the sun's gravity, the minimum velocity required to fly out of the solar system. Its size is 16.7 km/s.
Surrounding the speed and escape velocity can also be applied to other objects. Calculate the speed around Mars and escape velocity, for example, only need to put the formula of M, R, g, for Mars, radius, and the quality of the surface gravity acceleration.
The fourth cosmic velocity, refers to the launch of the objects on the earth get rid of the Milky Way's gravity, the minimum velocity required to fly out of the Milky Way, is about 110-120 - km/s, in most of the parts inside the Milky Way sailing speed you need. Such as make full use of the speed of the solar system around the galactic center, minimum sailing speed to 82 km/s. Because humans know little about the Milky Way, the number is need a long time to the public opinion formation. For the most part refers to the galactic place need to escape velocity. At present can not draw the fourth speed of the universe, the reason is for the quality of the galactic center and radius values.
Fifth cosmic velocity refers to the spacecraft is launched from earth, fly out of the cluster size of the minimum speed, due to this, the quality of the radius of the clusters of galaxies are not enough accurate data, so cannot know accurate data size. Now scientists estimate that this group of galaxies about 500-10 million light years away, as such, should need to fly at a speed of 1500-2250 km/S, but the speed to human's current level of scientific development, at least hundreds of years to achieve, so now is just a fantasy.
Cosmic velocity 6 refers to the spacecraft is launched from earth, fly out of the universe the size of the minimum speed is visible universe (accurately), but because of the visible universe specific radius, such as quality data is unknown, and it is well known that the universe is expanding, so the data should be uncertain, people also don't know whether the universe outside and bounded. So 6 is still a topic to be studied in the speed of the universe.
