How heavy is earth ? How do you measure it ?

Question: How heavy is earth ? How do you measure it ?
- Keywords:
  earth,
  mass,
  size
Asked by to Kate, Juan, Rosie on 18 Mar 2014. This question was also asked by , jakemorrey, lewisandrews.
- Rosie Coates answered on 18 Mar 2014:
  
  It has been estimated that the earth weighs 6,000,000,000,000,000,000,000,000 kilograms…. Heavy! Obviously no one can weigh the earth- you would need a pretty big set of scales!!
  
  The weight, or mass, is estimated by using an equation that was solved by Isaac Newton: F = G(M1*M2/R2)
  
  It looks complicated doesn’t it?? Well, it basically means that two objects (M1 and M2) exert a gravitational force on each other, and if we find out the size of that force we can find the mass of one of the objects.
  
  If we imagine that M1 is the earth and M2 is a bowling ball that weighs 1kg we can find out how big of a gravitational force the earth is having on the bowling ball. If we drop the bowling ball to the ground and time how long it takes to get there we can get the acceleration of the ball and this is the F in the equation above.
  
  G is a constant, 6.67384. This means that it has the same value in every equation. G is also known as the universal gravitational constant or Newton’s constant.
  
  R is the distance between the centre of the bowling ball and the centre of the earth.
  
  If we put all of the numbers into the equation and rearrange it a bit we can find out M1, or the mass of the earth.

Question: How heavy is earth ? How do you measure it ?