Even as late as the America Revolution in the late 1700's, the idea of meteors was not widely accepted. Thomas Jefferson wrote that he would rather believe that a Yankee scientist would lie, than that rocks could fall from the heavens.
But over the past 200 years, we have come to accept the idea that rocks DO fall from the skies, and we all know that falling rocks HURT. So perhaps, if a falling rock was big enough, it might cause a lot of damage?
As late as the 1970s, scientists did not believe that meteoric impacts could pose an existential threat to humanity; that is, could threaten the very EXISTENCE of the human race. But Luis Alvarez hypothesized that a massive enough body, impacting the Earth at orbital velocities, could radically re-shape the Earth. And then he discovered sufficient evidence that 65 million years ago, such an event HAS HAPPENED. And now most people believe that the dinosaurs went extinct because an asteroid about 6 miles in diameter impacted what is now the Gulf of Mexico just off the Yucatan Peninsula.
And if it could happen once, it could happen AGAIN. In 4 billion years, it WILL happen again.
And if if..... WHEN it does, life on Earth will die. Unless we can prevent it.
So scientists over the past 15 years or so have started watching for large objects that might have a potential to someday collide with the Earth. We haven't found one yet - but we've found several that have come fairly close. In early October, 2009, an asteroid a half-mile long passed closer to the Earth than the orbit of the Moon, and in 2029 the asteroid Apophis will come closer to the Earth than a communications satellite.
There are some other dismal thoughts floating around. Many great scientists have wondered, "Where are the other intelligent races in the universe?" and "What if all the other intelligent races in the universe were destroyed!?!?" and "Are we NEXT!?!?" What if the average intelligent race in the universe is destroyed by a cosmic impact?
And so scientists have started watching the skies for objects that might pose a hazard. The odds of such an impact are very low - but the potential damage of such an impact are terribly high. So we are right to start preparing.
The impact of the Comet Shoemaker-Levy 9 into Jupiter in 1994 sparked increased interest in searching for Near Earth Objects (NEOs) due to the potential threat of an asteroid or comet colliding with Earth. This event highlighted the importance of monitoring and tracking objects in close proximity to our planet to assess potential impact risks.
It is the average distance between the centres of the two objects.
The system of latitude/longitude is an imaginary matrix that's pinned to the Earth's surface, and was created in order to describe locations on the Earth's surface. The system used to describe the locations of astronomical objects in the sky is similar but separate, and is pinned to the imaginary dome of the sky. You may have noticed that the position of astronomical objects over the Earth's surface is constantly changing ... it only takes a few minutes to notice the change ... and that the positions of the planets change even among the rest of the astronomical objects.
The so-called "astronomical unit" is often used for this. One AU (astronomical unit) is the average distance from Sun to Earth; it is about 150 million kilometers.
Earth is the planet that has 1 astronomical unit (AU) from the sun.
For astronomical objects, it is more appropriate to talk about the mass of an object, not about its weight. The Moon has a mass of 7.35 x 1022 kilogram, that is about 1.2% of Earth's mass.
An astronomical unit is the average distance that separates two bodies in space. The two objects linked to an astronomical unit is the sun and the earth.
An Astronomical Unit is the distance between Earth and the Sun and is used as a measurement unit for measuring the distances of other objects from Earth.
Astronomical Unit- The distance between objects in the solar system!
It is the average distance between the centres of the two objects.
The system of latitude/longitude is an imaginary matrix that's pinned to the Earth's surface, and was created in order to describe locations on the Earth's surface. The system used to describe the locations of astronomical objects in the sky is similar but separate, and is pinned to the imaginary dome of the sky. You may have noticed that the position of astronomical objects over the Earth's surface is constantly changing ... it only takes a few minutes to notice the change ... and that the positions of the planets change even among the rest of the astronomical objects.
Satellite objects are set at speed and distance that its' orbit around earth equal earth rotation. It's centripetal acceleration must be just balance with gravity of the earth or v2/r=GM/r2.
1 astronomical unit (earth - sun distance) = 1.5 * 1011 metresand 1 metre = 39.37 inchesso, (1.5 * 1011) * 39.37 = 5.9055 * 1012 inches
The so-called "astronomical unit" is often used for this. One AU (astronomical unit) is the average distance from Sun to Earth; it is about 150 million kilometers.
Earth is one astronomical unit away from the sun.
Earth is one astronomical unit (AU) away from the sun. An astronomical unit is the average distance between the Earth and the Sun.
Oh yes, all planets, and all stars, and all other astronomical objects have gravity, and indeed, all mass has gravity, although small objects have very little.
Earth is the planet that is one astronomical unit (AU) from the Sun, which is the average distance between the Earth and the Sun.