# The mass of the Earth

Tags:
1. Nov 1, 2017

### VASUbhagwat

Mass of the Earth is 5.9 x 10^24 kg . How long has it been at this value and why does it not change even when the population of the word has gone up by many folds , there have been new flora and fauna . when was this last measurement taken?

2. Nov 1, 2017

### DoItForYourself

Hi,

I have heard that the mass of earth is increased a bit because of the debris coming from space (do not know exactly the extent of the increase).

The increase of population does not change the mass of the earth/biosphere, because the matter of a person is not generated during birth.

3. Nov 1, 2017

### PeroK

Even if 7 billion aliens each with 100kg mass arrived from outer space, it wouldn't change the mass of the Earth to any significant degree.

4. Nov 1, 2017

### Staff: Mentor

Where does the matter making up living organism come from?

Source: https://www.nasa.gov/mission_pages/asteroids/overview/fastfacts.html

5. Nov 1, 2017

### Gigaz

Actually the Earth looses more mass than it gains because a bit of Atmosphere is blown away by the solar wind.

Anyways, the mass of the Earth is determined in a funny way. What you actually need to know is the constant of Gravitation G. It must be determined with test masses in a laboratory and it is only known to about four significant digits. The first one who did it was Henry Cavendish in 1798. The radius of the Earth was already known in ancient times. Once you have done all that, the gravitational acceleration on the ground g is given by g=G/r² m_E, which gives you the mass of the Earth.

6. Nov 1, 2017

### VASUbhagwat

yes g=GM/(r^2), does give the relation to determine the mass of the earth. But why does not the value of G change with times with so much of activities happening in the universe?? and when cavendish determined the value of G( i thought he was the one who determined the mass of the earth, stay my ignorance) in 1798...the entire population of the earth was surely much less than what it is now.....so does it lead us to a new determination of the value of G ???

7. Nov 1, 2017

### Gigaz

As other people already pointed out, there is generally a conservation of mass and the change of the Earth's mass over time is tiny compared to the total mass. And because G is not very well known you would have to crash a very large asteroid into Earth to make a change which is actually measurable as a change in Earths total mass.

8. Nov 1, 2017

### Staff: Mentor

http://geodesy.curtin.edu.au/research/resolution/
Edit: change G to g - thanks phyzguy
Check out the image on the first page. A really cool map of very local g values (short scale gravity field), demonstrating that g is not a constant value over Earth's surface. For example, it varies by latitude. The changes are small, BTW.

The first image shows the effect of mountain ranges in Asia, another image further down shows Ayers Rock.

Last edited: Nov 1, 2017
9. Nov 1, 2017

### phyzguy

G, the universal constant of gravitation, does not change. It is the acceleration of gravity g = GM/r^2 that is changing locally.

10. Nov 1, 2017

### Staff: Mentor

You are correct. Thanks.

11. Nov 1, 2017

### rootone

The new flora and fauna are not additional mass.
They are just new arrangements of existing atoms, most of which are in organic molecules.
Those molecules are there as byproducts of previous flora and fauna which died.
No new atoms are being created, matter is being recycled

12. Nov 3, 2017

### Staff: Mentor

You are what you eat!

13. Nov 7, 2017

### Ernest S Walton

Well I suppose everything is a rearrangement of existing atoms, and the mass of the Universe now is the same as at the moment of the Big Bang. [Sorry for being difficult].

14. Nov 7, 2017

### r8chard

We are all a portion of the Earth's total mass. Every person, every lifeform. Every breath we take, every drop of water. Just moving this planet's material about, from this continent to that one. Will have no measurable effect. You take four quarters from your pocket and move it to another pocket. You still have one dollar.

Even the space station. in such a close, protective orbit around the Earth, still contributes it's mass to the grand total of planetary mass.

It would take a stellar level cataclysmic effort to reduce the total mass of the Earth in any measurably substantial way.

15. Nov 7, 2017

### rootone

Sure, conservation of mass=energy is generally considered to be true.
No new stuff appears from nowhere, and nothing mysteriously disappears.

16. Nov 7, 2017

### phinds

Actually energy is NOT conserved on cosmological scales and it does in fact disappear as EM waves lose energy due to the expansion of the universe.

17. Nov 7, 2017

### rootone

Well granted, but apart from that, what has the universe ever done for us?

18. Nov 7, 2017

### phinds

In the grand scheme of things ... well ... chocolate.

19. Nov 8, 2017

### StandardsGuy

Never trust atoms. They make up everything.

20. Nov 8, 2017

### Staff: Mentor

we are now in the Comedy Show. While the jokes are fun and probably deserved, this thread longs for an ending. So here it is: locked.