Descending Moon

Is the moon moving away from the earth?

Yes, over time the moon is gradually moving away from the earth.

This is a result of Tidal forces. As the earth spins, the gravity of the moon pulls water, air and even land up towards it in a bulge called the 'tide.' On the oceans, this tide often rises several feet. But the spinning earth pulls the tide 'ahead' of the moon. So the tide is not truly directly under the moon, but just east of it. Then the increased gravity effect from the tide, racing ahead of the moon, gradually, and ever so imperceptibly pulls the moon forward in its own orbit even faster. The end result is a kind of tidal 'sling shot' effect that pulls the moon forward in its orbit, faster and faster over time, causing it to speed up. As it speeds up, it moves farther away from the earth. This is the mechanism that has caused the moon to 'recede' from the earth by many hundreds of thousands of kilometers, in the billions of years since it was formed, after the earth underwent a collision with another, Mars sized planet, in the early days of the solar system.

It is calculated that currently the orbit of the moon increases in diameter by about 3.8 cm (about 1 1/2 inches) every year, a surprisingly large amount, as a result of this tidal sling shot effect. Over millions and billions of years, this sling shot effect adds up. The moon is currently moving away from the earth approximately 3 to 4 times faster than is has through much of its history, because the spacing of the major oceans and continents allows for a larger tidal-gravity sling shot effect than in the past. But it will not continue this way indefinitely. As the continents continue to drift (thus affecting the tides) the rate that the moon recedes will also change.

Someday, if the earth itself stops spinning, or if it loses all of its air and water and no longer has any significant tides, then the tidal sling shot effect will stop, and the moon's orbit will gradually start to decay. So the day may come when the moon might come crashing down upon the earth, but that day would certainly be billions of years in the future. In fact, current calculations are that the moon would finally stop moving away from earth approximately 15 billion years from now, but the sun will likely develop into a red giant and incinerate both the earth and the moon before then, in only 6 or 7 billion more years...Read more

Earth Without a Moon

Tides will still exist from the sun. It is the moons gravitational pull acting on the water as the earth turns under the moon which causes the rise and fall of the sea level. That however might have a much more profound effect. Some biologists believe that the tides may have played a major role in the evolution. Tidal areas, with water gently flowing into and out of sand or clay or rocks may have been necessary for the emergence of the first life forms from nonliving matter. Or that same tidal action, creating an area which was always wet but not always covered with water, may have provided an important environmental stress which helped with the evolution of land plants and animals from sea plants and fish. Thus it is at least possible that, were there no moon, life never would have developed at all or that the evolutionary course of life would have been vastly different from what it was.

Life without a moon

Life With No MoonIt is also theorized by some that life itself would be virtually impossible without a moon, since the moon has a stabilizing effect on the orientation of earth's axis. Without the moon, the north-south axis would vary tremendously-- to the point where the poles would sometimes be in our orbital plane. These changes would mean that there would be no stable seasons, and it's questionable whether or not the planet would be able to sustain life.

I would like to point out that Venus has no moon, and no problem with axial instability. Venus is almost asVenus large as earth. Mars has two tiny moons, and again, no axial instability. It is likely that the lunar influence on life is miniscule. Life has indeed adapted to the presence of a moon and tides. But life would simply have taken a different course had there been no moon. The night sky would be as dark as any new moon night. Nocturnal birds and other animals would have more difficulty seeing by only starlight. I'm not certain, but I suspect owls hunt better in partial moonlight than they do during the new moon.

No tides, but that is nearly irrelevant in terms of lakes and streams. There would still be ocean waves, earthquake driven tsunami, and the like. The moon could drift away entirely and the earth would not miss it all that much. A century ago everyone knew the lunar phases, because they depended on them for light. Today, in the industrial world, few people have any idea how long the lunar month is, or when the next full moon will occur...Read more

Meteors

Meteorite impact

In the history of the Earth, it is widely accepted that several large meteorites have hit Earth. The Cretaceous-Tertiary asteroid, for example, is theorized to have caused the extinction of the dinosaurs. If such an object struck Earth it could have a serious impact on civilization. It's even possible that humanity would be completely destroyed: for this, the asteroid would need to be at least 1 km (0.6 miles) in diameter, but probably between 3 and 10 km (2 - 6 miles). Asteroids with a 1 km diameter impact the Earth every 0.5 million years[4] on average. Larger asteroids are less common. The last large (>10 km) impact happened 65 million years ago. So-called Near-Earth asteroids are regularly being observed.

Some scientists believe there are patterns in the number of meteorites hitting Earth. An interesting explanation of such a pattern is given by the hypothetical star Nemesis. This hypothesis states that a star named Nemesis regularly passes through a denser part of the Oort cloud, causing meteorite rains to collide onto Earth. However, the very existence of this pattern is not widely accepted, and the existence of the Nemesis star is highly contested.

A star passage that will cause an increase of meteorites is the arrival of a star called Gliese 710. This star is probably moving on a collision course with the Solar System and will likely be at a distance 1.1 light years from the Sun in 1.4 million years.

Watch "Meteors: Fire in the Sky" which airs on the History Channel and History International this month...

Elaborate computer graphics and visits to impact sites worldwide highlight this look at the extra-terrestrial visitors that have helped shape our planet. * Computer simulations reveal what impacts with earth could be like. * A fascinating look at the vagabonds that litter the solar system. * Hear from experts like David Levy and Carolyn Shoemaker, discoverers of a comet that collided with Jupiter....They cross the solar system and hold clues about our planet and universe. Can they destroy civilizations? Did they wipe out the dinosaurs? Have they brought life to our planet? And when will the next one hit?

Aided by elaborate animation and live-action footage, METEORS explores what likely happened 65-million years ago, when an object plowed into the Yucatan Peninsula. See how certain spectacular meteor falls advanced our understanding of what they are and the danger that they pose. Meet leading experts, astronomers and geologists like David Levy and Carolyn Shoemaker, co-discoverers of a comet that fell into Jupiter in 1994. And talk to NASA scientists possible ways to move Earth-threatening asteroids and comets out of our way. Because it isn't a question of if the next deadly impact will take place, but when.

Alien Invasion

Invasion from Aliens?

A number of other scenarios have been suggested. Massive objects, e.g., a star, large planet or black hole, could be catastrophic if a close encounter occurred in the solar system. Another threat might come from gamma ray bursts; some scientists believe this may have caused mass extinction 450 million years ago, but still others see extraterrestrial life as a possible threat to mankind; although alien life has never been found, scientists such as Carl Sagan have postulated that the existence of extraterrestrial life is very likely. In 1969, the "Extra-Terrestrial Exposure Law" was added to the Code of Federal Regulations (Title 14, Section 1211) in response to the possibility of biological contamination resulting from the US Apollo Space Program. It was removed in 1991 because scientists consider such a scenario technically possible, but unlikely.

The following episode of "Ancient Aliens" proposes that aliens have contacted man as recently as the 20th century, citing examples such as the Battle of Los Angeles and the Roswell UFO Incident. It also looks at the modern SETI project and speculates what would happen if aliens answered back what protocols exist to determine who would speak on behalf of mankind, and how we would communicate.