Your weight on a scale in the above experiment is a measure of the attraction of your mass and the mass of the Earth. ( Remember that mass is not weight. On the Moon, your mass would be the same, but your weight would be less, because the Moon, with less mass than the Earth, would attract you less. ) Being a physical object, the Earth occupies space and has mass. Mass is the amount of matter in an object. How do we know the Earth's mass? Mass ( the amount of matter in an object ) is also a "property of a body that is a measure of its inertia ( which ) causes it to have weight in a gravitational field." 8 Mass is a measure of inertia. Inertia is a property of matter by which a body resists change in its state of motion. Gravity is, therefore, indistinguishable from acceleration! 9 Due to this fact, the best way currently to measure the mass of the Earth is to time the orbital period of an artificial satellite. Kepler's third law says that the satellite's outward centrifugal force is balanced by the Earth's gravitational force. 11 The satellite Geosat has an orbital radius of 7168 km and takes 6037.55 seconds to orbit the Earth.
Using the orbits of the Lageos satellites, the best estimate for the mass as of the Earth of Dec 23, 2002 is: (5.972245 ± 0.000082) x 10^24 kg. 25 based on a new apparatus at the University of Washington that determined G = (6.674215 ± 0.000092) x 10^-11 m^3 /kg/s^2.
Put another way, the Earth has a mass of between 5,972,163,000,000,000,000,000,000 and 5,972,327,000,000,000,000,000,000 kilograms.
( One kilogram is about 2.2 pounds. )
According to the formula, then, the mass of the Earth times the gravitational constant G is 3.988708x10^14 m^3 s^2 10 We know the Earth's mass, but what about density? ( Is it more dense in the center, for example? ) The density of rock is roughly 3000 kg per cubic meter, but the average overall density of the Earth from mass measurements is 5520 kg per cubic meter. 10 ( This is also 5.52 g per cubic centimeter. ) Therefore, we can make a good guess that something inside the Earth is more dense than rock. This fits well with the accepted idea of a molten metal core. It does not fit the hollow earth idea.
The Earth's gravity constantly pulls in dust and meteorites that very slowly increase the mass of the Earth. The occasional asteroid or comet striking the Earth produces a somewhat larger mass increase. For very interesting evidence on just how much the Earth may have expanded over time, see this site.
Using satellites, (or pairs of satellites) scientists have mapped the Earth's gravity from space. The resulting lumpy gravity map is caused an uneven distribution of mass within the Earth. Watch the GRACE site for month to month gravity maps that will show Earth changes.
The Dyson sphere (or shell) was popularized in 1959 by the astronomer Freeman Dyson. The ideas is to build an artificial sphere the size of an planetary orbit around a star. In this way, you could harvest nearly all of the star's energy and you'd have a huge living space.
This idea is interesting because we can use formulas here for calculations that apply to the idea of the hollow Earth.
A Dyson sphere is an artificial shell built around a star. Is the Earth a small naturally occurring (?) Dyson sphere?
This article is still under development. If you have read this far, I hope you can understand how some people have come to this very strange belief, and why modern scientists such as seismologists, geologists and astrophysicists say that the Earth is not hollow. Feel free to send me ideas or thoughts: email@example.com
Have you ever wondered where you would emerge if you were to dig straight down through the Earth? Below is a map showing another view of the Underworld. For about 80% of the world's land (including the USA and Europe), you would end up in an ocean if you could pass straight through the Earth. There are, however, a hand full of cities (below) that are antipodal, that is, as far apart as possible on the globe.
These antipodal cities may also be the most expensive pairs of cities for air travel and telephone service for the reason that they are the most distant on the globe.
Svalbard, Norway McMurdo Sound, Antarctica La Coruna, Spain Christchurch, New Zealand Leon, Spain Wellington, New Zealand Seville, Spain Auckland, New Zealand Timbuktu, Mali Fiji Bermuda Perth, Australia Bogota, Colombia Jakarta, Indonesia Lima, Peru Bangkok, Thailand Asuncion, Paraguay Taipei, Taiwan Santiago, Chile Xian, China Buenos Aires, Argentina Shanghai, China Cordoba, Argentina Wuhan, China Bahia Blanca, Argentina Beijing, China
DIAMETER: The earth is 7920 miles in diameter. (That is, if you stuck a long straight stick through the center, the stick would be 7,920 miles long.) 7 As you can see from the figure for the earth's radius, different measurements can give or take 20 miles!
RADIUS: A modern estimate of the average radius (a line from the exact center to the surface) of the Earth is 6371 kilometers (km) or 3950.02 miles. For comparison, the driving distance from San Francisco CA to New York, NY is 2906.63 miles 12
VOLUME: A sphere with a diameter of 6371 km would have a volume of 1,080,000,000,000 cubic kilometers. Put another way, that's the volume of 3 trillion trillion 12 oz cans of beer. (3 with 24 zeros)12
MASS: The earth has a total mass of 5.97 trillion trillion kg.
DEEPEST CAVE: There may be a cave a mile deep, but none much deeper, as there is too much weight on top. nasa.gov
4. http://www.suite101.com/mylinks.cfm/BestWebSites (defunct)
45. As another example, in 1991, NEIC published 16,515 event locations based on 531,097 readings received in reports from 2,150 seismic stations. http://www.iris.iris.edu/HQ/Bluebook/chapter3.analogy.html
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