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The density at the center is the same as in the PREM, but the surface density is chosen so that the mass of the sphere equals the mass of the real Earth. See also: Shell theorem An approximate value for gravity at a distance r from the center of the Earth can be obtained by assuming that the Earth's density is spherically symmetric.
For a metal, zinc has relatively low melting (419.5 °C) and boiling point (907 °C). [29] The melting point is the lowest of all the d-block metals aside from mercury and cadmium; for this reason among others, zinc, cadmium, and mercury are often not considered to be transition metals like the rest of the d-block metals. [29]
Pennsylvania population density map. As of the 2020 U.S. census, Pennsylvania had a population of 13,011,844, up from 12,702,379 in 2010. Pennsylvania is the fifth-most populated state in the U.S. after California, Texas, Florida, and New York. [94]
The use of housing unit density as an alternative minimum for inclusion: either 2,000 housing units or a population of 5,000 may qualify an area as an urban area. Previously, this minimum was 2,500 in population. The lowering of the allowable "jump distance" from 2.5 to 1.5 miles.
The specific weight, also known as the unit weight (symbol γ, the Greek letter gamma), is a volume-specific quantity defined as the weight W divided by the volume V of a material: = / Equivalently, it may also be formulated as the product of density, ρ, and gravity acceleration, g: = Its unit of measurement in the International System of Units (SI) is newton per cubic metre (N/m 3), with ...
The UN Population Division has calculated the future population of the world's countries, based on current demographic trends. The UN's 2024 report projects world population to be 8.1 billion in 2024, about 9.6 billion in 2050, and about 10.2 billion in 2100. The following table shows the largest 15 countries by population as of 2024, 2050 and ...
The Schiehallion experiment, proposed in 1772 and completed in 1776, was the first successful measurement of the mean density of the Earth, and thus indirectly of the gravitational constant. The result reported by Charles Hutton (1778) suggested a density of 4.5 g/cm 3 (4 + 1 / 2 times the density of water), about 20% below the modern ...
These figures should be compared with the temperature and density of Earth's atmosphere plotted at NRLMSISE-00, which shows the air density dropping from 1200 g/m 3 at sea level to 0.125 g/m 3 at 70 km, a factor of 9600, indicating an average scale height of 70 / ln(9600) = 7.64 km, consistent with the indicated average air temperature over ...