question: How is the earths weight calculated?
comment: You can’t really tell the “weight” of the earth. Remember, weight is dependent on the gravity of the environment as well as it’s mass (weight=mass*acceleration of gravity, where the acceleration of gravity is different for each planet) so since the earth is sitting in space, it doesn’t technically weigh anything. You can calculate it’s mass though. Mass is like an intrinsic property, it’s the same in every environment. By the laws of gravity, Kepler’s laws mainly, we learned that gravity has a special relationship with mass. SO by looking and calculating the orbit of the Earth around the sun and with other planets we can “plug” that orbit in to an equation and derive the mass. I’m a PhD student in Astrophysics and I actually did an independent study last term in orbital mechanics. :)
passages: Section::::Mass.
  
  The force exerted by Earth's gravity can be used to calculate its mass. Astronomers can also calculate Earth's mass by observing the motion of orbiting satellites. Earth's average density can be determined through gravimetric experiments, which have historically involved pendulums.
  
  The mass of Earth is about .
  
  Section::::Structure.
   The mass of the Earth was first measured with any accuracy (within about 20% of the correct value) in the Schiehallion experiment in the 1770s, and within 1% of the modern value in the Cavendish experiment of 1798.
  
  Section::::Unit of mass in astronomy.
  
  The mass of Earth is estimated to be:
  
  which can be expressed in terms of solar mass as:
  
  The ratio of Earth mass to lunar mass has been measured to great accuracy. The current best estimate is:
  
  The "G" product for the Earth is called the geocentric gravitational constant and equals 
   The Earth mass excludes the mass of the Moon. The mass of the Moon is about 1.2% of that of the Earth, so that the mass of the Earth+Moon system is close to .
  
  Most of the mass is accounted for by iron and oxygen (c. 32% each), magnesium and silicon (c. 15% each), calcium, aluminium and nickel (c. 1.5% each).
  
  Precise measurement of the Earth mass is difficult, as it is equivalent to measuring the gravitational constant, which is the fundamental physical constant known with least accuracy, due to the relative weakness of the gravitational force.
   The main factor in mass gain is in-falling material, cosmic dust, meteors, etc. are the most significant contributors to Earth's increase in mass. The sum of material is estimated to be annually, although this can vary significantly; to take an extreme example, the Chicxulub impactor, with a midpoint mass estimate of , added 900 million times that annual dustfall amount to the Earth's mass in a single event.
   The mass of Earth is measured indirectly by determining other quantities such as Earth's density, gravity, or gravitational constant.
  
  The first measurement in the 1770s Schiehallion experiment resulted in a value about 20% too low.
  
  The Cavendish experiment of 1798 found the correct value within 1%.
  
  Uncertainty was reduced to about 0.2% by the 1890s, 
  
  to 0.1% by 1930.
  
  The figure of the Earth has been known to better than four significant digits since the 1960s (WGS66), so that since that time, the uncertainty of the Earth mass is determined essentially by the uncertainty in measuring the gravitational constant.
   If the actual force of gravity on the object is needed, this can be calculated by multiplying the mass measured by the balance by the acceleration due to gravity – either standard gravity (for everyday work) or the precise local gravity (for precision work). Tables of the gravitational acceleration at different locations can be found on the web.
   In modern notation, the mass of the Earth is derived from the gravitational constant and the mean Earth radius by
  
  Where "little g":
  
  Cavendish found a mean density of , about 1% below the modern value.
  
  Section::::History of measurement.:19th century.
  
  While the mass of the Earth is implied by stating the Earth's radius and density, it was not usual to state the absolute mass explicitly 
  
  prior to the introduction of scientific notation using powers of 10 in the later 19th century, 
   Before the direct measurement of the gravitational constant, estimates of the Earth mass were limited to estimating Earth's mean density from observation of the crust and estimates on Earth's volume. Estimates on the volume of the Earth in the 17th century were based on a circumference estimate of to the degree of latitude, corresponding to a radius of 5,500 km (86% of the Earth's actual radius of about 6,371 km), resulting in an estimated volume of about one third smaller than the correct value.
   Section::::History of measurement.:Modern value.
  
  The uncertainty in the modern value for the Earth's mass has been entirely due to the uncertainty in the gravitational constant "G" since at least the 1960s.
  
  "G" is notoriously difficult to measure, and some high-precision measurements during the 1980s to 2010s have yielded mutually exclusive results.
  
  Sagitov (1969) based on the measurement of "G" by Heyl and Chrzanowski (1942) cited a value of (relative uncertainty ).
   Said differently, a one-Megalithic-arcsecond-thick 'slice' of Earth (at the equator) weighs almost exactly , as though, according to the authors, the exact value of the pound had been adjusted so as to be a round subdivision of a one-arcsecond-thick slice of Earth in the Megalithic geometry.
  
  Section::::Critical reception.
  
  Publications in pseudoscientific metrology receive little, if any, attention from mainstream scholarship, by nature of being intended for the popular mass market.
  
  For French historian Lucien Febvre, Xavier Guichard's work was "time and effort lost based on wordplay."
   The Earth's gravitational field is not uniform but can vary by as much as 0.5% at different locations on Earth (see Earth's gravity). These variations alter the relationship between weight and mass, and must be taken into account in high precision weight measurements that are intended to indirectly measure mass. Spring scales, which measure local weight, must be calibrated at the location at which the objects will be used to show this standard weight, to be legal for commerce.
   There are significant uncertainties in the values of "r" and "m" as used in this calculation, and the value of "G" is also rather difficult to measure precisely.
  
  If "G", "g" and "r" are known then a reverse calculation will give an estimate of the mass of the Earth. This method was used by Henry Cavendish.
  
  Section::::See also.
  
  BULLET::::- Figure of Earth
  
  BULLET::::- Gravity (Gravitation)
  
  BULLET::::- Gravimetry
  
  BULLET::::- Geopotential
  
  BULLET::::- Gravity anomaly, Bouguer anomaly
  
  BULLET::::- Gravitation of the Moon
  
  BULLET::::- Gravitational acceleration
  
  BULLET::::- Gravity Field and Steady-State Ocean Circulation Explorer
  
  BULLET::::- Gravity Recovery and Climate Experiment
   About 90% of the mass of the Earth is composed of the iron–nickel alloy (95% iron) in the core (30%), and the silicon dioxides (c. 33%) and magnesium oxide (c. 27%) in the mantle and crust. 
  
  Minor contributions are from iron(II) oxide (5%), aluminium oxide (3%) and calcium oxide (2%), besides numerous trace elements (in elementary terms: iron and oxygen c. 32% each, magnesium and silicon c. 15% each, calcium, aluminium and nickel c. 1.5% each). 
  
  Carbon accounts for 0.03%, water for 0.02%, and the atmosphere for about one part per million.
  
  Section::::History of measurement.
   After a lengthy search over the summer of 1773, Mason reported that the best candidate was Schiehallion, a peak in the central Scottish Highlands. The mountain stood in isolation from any nearby hills, which would reduce their gravitational influence, and its symmetrical east–west ridge would simplify the calculations. Its steep northern and southern slopes would allow the experiment to be sited close to its centre of mass, maximising the deflection effect.
  
  Nevil Maskelyne, Charles Hutton and Reuben Burrow performed the experiment, completed by 1776.
  
  Hutton (1778) reported that the mean density of the Earth was estimated at 
   The combined effect is a net loss of material, estimated at per year. This amount is of the total earth mass. The annual net loss is essentially due to 100,000 tons lost due to atmospheric escape, and an average of 45,000 tons gained from in-falling dust and meteorites. This is well within the mass uncertainty of 0.01% (), so the estimated value of Earth's mass is unaffected by this factor.
  
  Mass loss is due to atmospheric escape of gases. About 95,000 tons of hydrogen per year () and 1,600 tons of helium per year are lost through atmospheric escape.
   (masses expressed in units of Earth mass or Solar mass) rather than mass in kilograms when referencing and comparing planetary objects.
  
  Section::::Composition.
  
  Earth's density varies considerably, between less than in the upper crust to as much as in the inner core.
  
  The Earth's core accounts for 15% of Earth's volume but more than 30% of the mass, the mantle for 84% of the volume and close to 70% of the mass, while the crust accounts for less than 1% of the mass.
   A "balance" on the other hand, compares the weight of an unknown object in one scale pan to the weight of standard masses in the other, using a lever mechanism – a lever-balance. The standard masses are often referred to, non-technically, as ""weights"". Since any variations in gravity will act equally on the unknown and the known weights, a lever-balance will indicate the same value at any location on Earth. Therefore, balance ""weights"" are usually calibrated and marked in mass units, so the lever-balance measures mass by comparing the Earth's attraction on the unknown object and standard masses in the scale pans. In the absence of a gravitational field, away from planetary bodies (e.g. space), a lever-balance would not work, but on the Moon, for example, it would give the same reading as on Earth. Some balances can be marked in weight units, but since the weights are calibrated at the factory for standard gravity, the balance will measure standard weight, i.e. what the object would weigh at standard gravity, not the actual local force of gravity on the object.
   because the absolute numbers would have been too awkward. Ritchie (1850) gives the mass of the Earth's atmosphere as "11,456,688,186,392,473,000 lbs." ( = , modern value is ) and states that "compared with the weight of the globe this mighty sum dwindles to insignificance".
  
  Absolute figures for the mass of the Earth are cited only beginning in the second half of the 19th century, mostly in popular rather than expert literature.
  
  An early such figure was given as "14 quadrillion pounds" ("14 Quadrillionen Pfund") [] in Masius (1859).
   The geocentric gravitational constant – the product of the mass of the Earth times the Newtonian gravitational constant – can be measured to high precision from the orbits of the Moon and of artificial satellites. The ratio of the two masses can be determined from the slight wobble in the Earth's orbit caused by the gravitational attraction of the Moon.
  
  Section::::More recent values.
   Section::::Accuracy of WIM and Quality of Data.
   Earth mass
  
  Earth mass (M or , where ⊕ is the standard astronomical symbol for planet Earth) is the unit of mass equal to that of Earth. 
  
  The current best estimate for Earth mass is , with a standard uncertainty of 
  
  It is equivalent to an average density of .
  
  The Earth mass is a standard unit of mass in astronomy that is used to indicate the masses of other planets, including rocky terrestrial planets and exoplanets. One Solar mass is close to 333,000 Earth masses.
   The track "Liberty Bell" was released as a single in Europe, as well as in Canada on a bonus CD distributed with issue 12 of the metal magazine "Brave Words & Bloody Knuckles".
   It is determined using laser ranging data from Earth-orbiting satellites, such as LAGEOS-1. The "G" product can also be calculated by observing the motion of the Moon or the period of a pendulum at various elevations. These methods are less precise than observations of artificial satellites.
  
  The relative uncertainty of the geocentric gravitational constant is just , i.e. times smaller than the relative uncertainty for itself. 
  
  For this reason and others, astronomers prefer to use the un-reduced "G" product, or mass ratios
   Relative uncertainty was cited at 0.06% in the 1970s, and at 0.01% (10) by the 2000s. 
  
  The current relative uncertainty of 10 amounts to in absolute terms, of the order of the mass of a minor planet (70% of the mass of Ceres).
  
  Section::::History of measurement.:Early estimates.
   With a value for the mean density of the Earth, Hutton was able to set some values to Jérôme Lalande's planetary tables, which had previously only been able to express the densities of the major Solar System objects in relative terms.
  
  Section::::History of measurement.:Cavendish experiment.
  
  The Henry Cavendish (1798) was the first to attempt to measure the gravitational attraction between two bodies directly in the laboratory.
  
  Earth's mass could be then found by combining two equations; Newton's second law, and Newton's law of universal gravitation.
  
presuppositions: The earth has a weight. The earth's weight can be calculated.
corrections: The earth does not have a weight, but a mass. The earth's weight cannot be calculated, but mass can be.
raw_presuppositions: The earth has a weight. The earth's weight can be calculated.
raw_corrections: The earth does not have a weight, but a mass. The earth's weight cannot be calculated, but mass can be.