It turns out that in some places you will feel slightly heavier than others. A low spot can be seen just off the coast of India, while a relative high occurs in the South Pacific Ocean. The cause of these irregularities is unknown since present surface features do not appear dominant. NASA's GRACE twin satellites, launched in March 2002, are making detailed measurements of Earth's gravity field which will lead to discoveries about gravity and Earth's natural systems.  
2. Atmosphere 'escapes'
Due to thermal energy, some of the molecules at the outer edge of the Earth's atmosphere have their velocity increased to the point where they can escape from the planet's gravity. This results in a slow but steady leakage of the atmosphere into space. Because unfixed hydrogen has a low molecular weight, it can achieve escape velocity more readily and it leaks into outer space at a greater rate. For this reason, the Earth's current environment is oxidizing, rather than reducing, with consequences for the chemical nature of life which developed on the planet. The oxygen-rich atmosphere also preserves much of the surviving hydrogen by locking it up in water molecules.
3. The Earth is slowing down
As a result of variation in gravitational forces due to the moon, the sun and other planets in the solar system, displacements of matter in different in different parts of the planets and other excitation mechanisms, the rotational speed of the Earth about it's axis varies in time. Recently, days have been getting shorter by hundredths of a second, which implies that the angular velocity of the Earth has been increasing. The factors causing this increasing in the Earth's rotational velocity have not been determined. The rotation data shows oscillations over several different timescales. The one with the largest variation is seasonal: Earth slows down in January and February.   
4. Van Allen radiation belt
The Van Allen Radiation Belt is a torus of energetic charged particles (plasma) around Earth, held in place by Earth's magnetic field. Apollo astronauts who traveled to the moon spent very little time in the belts but probably have a slightly higher risk of cancer during their. NASA said that they deliberately timed Apollo launches, and used lunar transfer orbits that only skirted the edge of the belt over the equator to minimize the radiation. Besides, there have been nuclear tests in space that have caused artificial radiation belts. Starfish Prime, a high altitude nuclear test created an artificial radiation belt that damaged or destroyed as many as one third of the satellites in low earth orbit at the time.  
5. Moon is moving away from Earth
The reasons why have to do with tides and conservation of energy and angular momentum. Measurements have been collected now for over 25 years, and it is clear that the Moon's orbit is slowly growing larger and that the Moon is moving away from the Earth. The net result is that the Moon is receding from the Earth at about 4 centimeters a year. However, astronomers have predicted that when the Sun enters the red giant phase in around 5 billion years - during the red giant phase of the Sun - both Earth and Moon will be affected by the Sun's extended atmosphere and will aproach again. Then the Moon will swing ever closer to Earth until it reaches a point 11,470 miles (18,470 kilometers) above our planet, a point termed the Roche limit. The result: Moon will be torn to pieces and will be scattered to form a spectacular 23,000-mile-diameter (37,000-kilometer) Saturn-like ring of debris above Earth's equator.  
6. Moon has a tidal effect on the atmosphere
The Moon have a tidal effect on the atmosphere as well as the oceans. Theory predicts stronger lunar pressure oscillations in the tropics but their amplitude rarely exceeds 100 microbars or 0.01 percent of the average surface pressure. Detection of such a tiny signal masked by much larger pressure variations associated with weather phenomena required the development of special statistical techniques and the accumulation of a long series of regular observations. It is common for atmospheric waves to grow in amplitude with height as the air becomes thinner. The lunar tide, however, remains weak compared to the solar tide in the upper atmosphere.
7. The Chandler wobble
The Chandler wobble is a small variation in Earth's axis of rotation, discovered by American astronomer Seth Carlo Chandler in 1891. It amounts to 0.7 arcseconds over a period of 433 days. In other words, Earth's poles move in an irregular circle of 3 to 15 metres in diameter, in an oscillation. The cause is unknown. On 18 July 2000, the Jet Propulsion Laboratory announced that "the principal cause of the Chandler wobble is fluctuating pressure on the bottom of the ocean, caused by temperature and salinity changes and wind-driven changes in the circulation of the oceans. However, on janauary-february 2006 scientist noticed the Chandler wobble had stopped and there was a near six week period in which a significant pause occurred. This anomaly has been of great interest in gaining a better understanding, but it is not yet known if this has or will cause any catastrophic changes in the overall rotation axis of the planet. 
8. Earth electric charge
Since 1917 scientists have known that the earth's surface is charged with negative electricity, but no one knew for sure what keeps it charged. In areas of fair weather, an electric current flows between the earth and the air in a direction which would tend to dissipate the charge. It is not much of a current: only about 1,500 amperes, not much more for the entire earth than flows in a few power lines. But the electricity taken from the earth must be restored somehow or the earth's electric charge would soon drain away. An obvious guess is that thunderstorms somehow restore the lost charge, but no one had proved it. Three years ago the institution borrowed airplanes from the Air Force and began to measure electrical stirring in the still air above active thunderheads. Sure enough, the instruments showed a current moving in the opposite direction to the current in fair-weather areas. The scientists figured that all the thunderstorms going on at one time generate a net current of about 1,500 amperes, just enough to balance the drain and keep the earth's charge constant. 
9. Tons of interplanetary dust reaches Earth every year
According to space.com, about 30,000 tons of interplanetary dust reaches Earth's surface every year. Most asteroids roam around the Sun in a belt between Mars and Jupiter. The fragments of their collisions, and the dust, can be drawn toward the inner solar system and sometimes approach Earth. Dust and rocks moving fast in relation to Earth frequently slam into the atmosphere and burn up, generating shooting stars. Stuff moving more slowly relative to Earth can be captured by the planet's gravity and survive the plunge. 
10. Earth's magnetic poles change places
The poles on the Earth have changed places - many times! We can tell this has happened because the magnetic moment of the rocks that make up the ocean floor have an alternating direction. Which direction they exhibit depends on which way the poles were oriented when the rocks were being formed at the mid-ocean ridge. During a reversal, which can take thousands of years, the magnetic poles start to wander away from the region around the spin poles, and eventually end up switched around. Sometimes this wandering is slow and steady, and other times it occurs in several jumps.
See also: 101 Amazing Earth Facts
Wanna digg it?
29 junio 2007
1. Gravity is not the same over the surface of the Earth