The distance from Earth to the sun — called an astronomical unit — is 92,, miles ,, kilometers , according to the International Astronomers Union.
That is the radius r. So in one year, Earth travels about million miles million km. So, Earth travels about 1. Related: How Fast does Light Travel? The sun has an orbit of its own in the Milky Way. The sun is about 25, light-years from the center of the galaxy, and the Milky Way is at least , light-years across. We are thought to be about halfway out from the center, according to Stanford University. Even at this rapid speed, the solar system would take about million years to travel all the way around the Milky Way.
The Milky Way, too, moves in space relative to other galaxies. In about 4 billion years, the Milky Way will collide with its nearest neighbor, the Andromeda Galaxy. The two are rushing toward each other at about 70 miles per second km per second. There is no chance that you'll be flung off to space right now, because the Earth's gravity is so strong compared to its spinning motion.
This latter motion is called centripetal acceleration. At its strongest point, which is at the equator, centripetal acceleration only counteracts Earth's gravity by about 0. In other words, you don't even notice it, although you will weigh slightly less at the equator than at the poles.
NASA says the probability for Earth stopping its spin is " practically zero " for the next few billion years. Theoretically, however, if the Earth did stop moving suddenly, there would be an awful effect. The atmosphere would still be moving at the original speed of the Earth's rotation. This means that everything would be swept off of land, including people, buildings and even trees, topsoil and rocks, NASA added.
What if the process was more gradual? This is the more likely scenario over billions of years, NASA said, because the sun and the moon are tugging on Earth's spin. That would give plenty of time for humans, animals and plants to get used to the change.
By the laws of physics, the slowest the Earth could slow its spin would be 1 rotation every days. That situation is called "sun synchronous" and would force one side of our planet to always face the sun, and the other side to permanently face away. By comparison: Earth's moon is already in an Earth-synchronous rotation where one side of the moon always faces us, and the other side opposite to us. But back to the no-spin scenario for a second: There would be some other weird effects if the Earth stopped spinning completely, NASA said.
For one, the magnetic field would presumably disappear because it is thought to be generated in part by a spin. We'd lose our colorful auroras, and the Van Allen radiation belts surrounding Earth would probably disappear, too. The amount of time it takes for the Earth to rotate once on its axis is known as a sidereal day — which is The amount of time it takes for the Sun to return to the same spot in the sky is called a solar day , which is 24 hours.
However, this varies through the year, and the accumulated effect produces seasonal deviations of up to 16 minutes from the average. At perihelion i. While its speed averages out to about At this rate, it takes the Sun the equivalent of 24 hours — i. Viewed from the vantage point above the north poles of both the Sun and Earth, Earth orbits in a counterclockwise direction about the Sun.
It is also for this reason that every four years, an extra day is required a February 29th during every Leap Year. In June and December, when the Sun is farthest from the celestial equator, a given shift along the ecliptic corresponds to a large shift at the equator.
So apparent solar days are shorter in March and September than in June or December. In northern temperate latitudes, the Sun rises north of true east during the summer solstice, and sets north of true west, reversing in the winter.
The Sun rises south of true east in the summer for the southern temperate zone, and sets south of true west.
This means that just by standing on the equator, a person would already be traveling at a speed in excess of the speed of sound in a circle. Not a major difference, but a difference nonetheless. Atomic clocks show that a modern day is longer by about 1. Before that, the Earth, the Sun and the rest of the Solar System were part of a giant molecular cloud of hydrogen, helium, and other heavier elements. As the cloud collapsed down, the momentum of all the particles set the cloud spinning. The current rotation period of the Earth is the result of this initial rotation and other factors, including tidal friction and the hypothetical impact of Theia — a collision with a Mars-sized object that is thought to have taken place approx.
This special shape of our planet means that points along the equator are actually further from the center of the Earth than at the poles. In ancient times, astronomers naturally believed that the Earth was a fixed body in the cosmos, and that the Sun, the Moon, the planets and stars all rotating around it.
As sea levels rise, this change in mass could result in Earth spinning faster and reducing the length of each day by 0.
Without a huge external force, this is impossible. Each side of the planet would get six months of continuous sunlight and six months of darkness. Without the centrifugal force of the spin, the oceans would gradually move towards the poles, creating a huge supercontinent across the equator.
In order for us to feel weightless, the centrifugal force would need to be ramped up. At the equator, Earth would need to spin at 28, kilometres per hour for us to be lifted off into space.
0コメント