# How can the Earth gain or lose weight? **URL:** \ **Category:** Factual Questions\ **Created:** [May 10, 2003, 1:57am UTC](https://boards.straightdope.com/t/how-can-the-earth-gain-or-lose-weight/174249 "2003-05-10T01:57:21Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Marine\_One](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/marine_one/32/3461_2.png) [@Marine\_One](https://boards.straightdope.com/u/Marine_One)\ **Post date:** [May 10, 2003, 1:57am UTC](https://boards.straightdope.com/t/how-can-the-earth-gain-or-lose-weight/174249/1 "2003-05-10T01:57:21Z")
The Earth weighs about 5.9 sextillion metric tons. To me, there should only be 2 ways the Earth can gain or lose weight: Gain: Meteors Lose: Space craft launched that never return to Earth. So the Earth has never been on a weight loss program until the first rocket/satellite that was launched stayed in space? Just wondering… ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [May 10, 2003, 2:02am UTC](https://boards.straightdope.com/t/how-can-the-earth-gain-or-lose-weight/174249/2 "2003-05-10T02:02:40Z")
Well, it lost an awful lot of weight very early in it’s history when a mars-sized planet smacked into it, ripping out a big chunk that became the Moon. This is called a _crash diet_. ---
**Author:** ![BuckleberryFerry](https://avatars.discourse-cdn.com/v4/letter/b/5f9b8f/32.png) [@BuckleberryFerry](https://boards.straightdope.com/u/BuckleberryFerry)\ **Post date:** [May 10, 2003, 2:05am UTC](https://boards.straightdope.com/t/how-can-the-earth-gain-or-lose-weight/174249/3 "2003-05-10T02:05:25Z")
:rimshot: ---
**Author:** ![Payton\_s\_Servant](https://avatars.discourse-cdn.com/v4/letter/p/3da27b/32.png) [@Payton\_s\_Servant](https://boards.straightdope.com/u/Payton_s_Servant)\ **Post date:** [May 10, 2003, 2:12am UTC](https://boards.straightdope.com/t/how-can-the-earth-gain-or-lose-weight/174249/4 "2003-05-10T02:12:33Z")
> [@](#): > > \*Originally posted by Q.E.D. \* > **Well, it lost an awful lot of weight very early in it’s history when a mars-sized planet smacked into it, ripping out a big chunk that became the Moon.** Is this true? I’ve heard it mentioned as **one** of the theories of how the Moon was formed but has it been settled upon as the one? And I would think that a Mars-sized object smashing into the Earth would have caused both the Earth and the alien object to shatter into billions of pieces. ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [May 10, 2003, 2:16am UTC](https://boards.straightdope.com/t/how-can-the-earth-gain-or-lose-weight/174249/5 "2003-05-10T02:16:29Z")
It’s the leading theory anyway. AFAIK, it’s the one most astronomers currently favor. And you have to remember that when this happened, the Earth was still almost entirely molten, with the consistency of hot lava. The Earth didn’t shatter any more than whipped cream can. ---
**Author:** ![MonkeyMensch](https://avatars.discourse-cdn.com/v4/letter/m/82dd89/32.png) [@MonkeyMensch](https://boards.straightdope.com/u/MonkeyMensch)\ **Post date:** [May 10, 2003, 2:32am UTC](https://boards.straightdope.com/t/how-can-the-earth-gain-or-lose-weight/174249/6 "2003-05-10T02:32:39Z")
And there is some loss from the atmoshpere. A tiny portion of the highest reaches are swept away by the solar wind. ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [May 10, 2003, 2:38am UTC](https://boards.straightdope.com/t/how-can-the-earth-gain-or-lose-weight/174249/7 "2003-05-10T02:38:46Z")
And occassionally, very large meteroid impacts can eject material out of orbit. Rocks from Mars have been found here on Earth, and there’s no reason to think that there might not be Earth rocks on Mars someplace, perhaps as a result of the KT asteroid impact at Chixulub. ---
**Author:** ![bugg](https://avatars.discourse-cdn.com/v4/letter/b/ecae2f/32.png) [@bugg](https://boards.straightdope.com/u/bugg)\ **Post date:** [May 10, 2003, 3:08am UTC](https://boards.straightdope.com/t/how-can-the-earth-gain-or-lose-weight/174249/8 "2003-05-10T03:08:06Z")
The earth, by our definitions, has undefined (or zero) weight. Weight on this planet is defined as the force between a body and the center of the earth. Treating the earth like a point particle (which is safe for obvious reasons in this example), the force between the earth and the earth is asking what the gravitational attraction is between two points with zero distance between them; any mathematician would look at the gravitational equation and tell you that’s undefined, any physicst would probably tell you it’s zero. If you’re asking about the mass of the earth, that’s a different question. ---
**Author:** ![Ale](https://avatars.discourse-cdn.com/v4/letter/a/f19dbf/32.png) [@Ale](https://boards.straightdope.com/u/Ale)\ **Post date:** [May 10, 2003, 3:43am UTC](https://boards.straightdope.com/t/how-can-the-earth-gain-or-lose-weight/174249/9 "2003-05-10T03:43:15Z")
Add to the diet the decay of radioactive elements… OK, not much for sure, but it has to account for something. 😛 ---
**Author:** ![Bob55](https://avatars.discourse-cdn.com/v4/letter/b/e9c0ed/32.png) [@Bob55](https://boards.straightdope.com/u/Bob55)\ **Post date:** [May 10, 2003, 4:26am UTC](https://boards.straightdope.com/t/how-can-the-earth-gain-or-lose-weight/174249/10 "2003-05-10T04:26:44Z")
I once took an astronomy class and read that something like 6 house-sized objects crash into the earth daily (mostly water?). I’ve also heard that if you multiply this out over the millinea this could account for all the water on earth. ---
**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\ **Post date:** [May 10, 2003, 5:27am UTC](https://boards.straightdope.com/t/how-can-the-earth-gain-or-lose-weight/174249/11 "2003-05-10T05:27:11Z")
> [@](#): > > \*Originally posted by bugg \* > \*\*The earth, by our definitions, has undefined (or zero) weight. > > If you’re asking about the mass of the earth, that’s a different question. \*\* Nah…the OP has it correct. 5.9 sextillion metric tons is based upon the kilogram. A kilogram is a measure of mass. Turns out that one kilogram of mass on the suface of the earth (or 1g of acceleration) also weighs one kilogram. Pounds are only a measure of weight be we’re ok using kilograms here. ---
**Author:** ![matt](https://avatars.discourse-cdn.com/v4/letter/m/a6a055/32.png) [@matt](https://boards.straightdope.com/u/matt)\ **Post date:** [May 10, 2003, 8:02am UTC](https://boards.straightdope.com/t/how-can-the-earth-gain-or-lose-weight/174249/12 "2003-05-10T08:02:37Z")
Yes, but he said the Earth _weighs_ about 5.9 sextillion metric tons. If you love to nit-pick, he should have said it _masses_. I remember some essay by Isaac Asimov that stated that the Earth loses hydrogen and helium continuously from the atmosphere. A significant fraction of the molecules of those gases exceed escape velocity at ambient temperatures. **Bob55** I would guess he was talking about cometary fragments, which are mostly ice of various sorts. No idea if it’s true. I could well believe the mass equivalent of five or six house-sized objects hit the Earth every day, but I’m not sure if they are literally that size. One for The Bad Astronomer, if he’s still posting! Remember the meteorite from Mars that may or may not display evidence of microscopic life? The theory is that the meteorite was lofted from Mars by a meteorite impact. That could possibly happen on Earth as well, so the Earth could lose material that way. Of course, it would get a net mass gain from the meteorite itself… ---
**Author:** ![shijinn](https://avatars.discourse-cdn.com/v4/letter/s/cc9497/32.png) [@shijinn](https://boards.straightdope.com/u/shijinn)\ **Post date:** [May 10, 2003, 9:28am UTC](https://boards.straightdope.com/t/how-can-the-earth-gain-or-lose-weight/174249/13 "2003-05-10T09:28:58Z")
lol **Q.E.D.** crash diet… 🙂 ---
**Author:** ![Skip](https://avatars.discourse-cdn.com/v4/letter/s/ebca7d/32.png) [@Skip](https://boards.straightdope.com/u/Skip)\ **Post date:** [May 10, 2003, 10:34am UTC](https://boards.straightdope.com/t/how-can-the-earth-gain-or-lose-weight/174249/14 "2003-05-10T10:34:15Z")
I think I read somewhere that somewhere between 2-6 tons of space dust alone are deposited on the Earth every hour. I might have the numbers wrong but it was definitely more than a town. ---
**Author:** ![Skip](https://avatars.discourse-cdn.com/v4/letter/s/ebca7d/32.png) [@Skip](https://boards.straightdope.com/u/Skip)\ **Post date:** [May 10, 2003, 10:41am UTC](https://boards.straightdope.com/t/how-can-the-earth-gain-or-lose-weight/174249/15 "2003-05-10T10:41:40Z")
uhhh… a ton, not a town. ---
**Author:** ![RM\_Mentock](https://avatars.discourse-cdn.com/v4/letter/r/e274bd/32.png) [@RM\_Mentock](https://boards.straightdope.com/u/RM_Mentock)\ **Post date:** [May 10, 2003, 11:27am UTC](https://boards.straightdope.com/t/how-can-the-earth-gain-or-lose-weight/174249/16 "2003-05-10T11:27:41Z")
> [@](#): > > \*Originally posted by Bob55 \* > \*\*I once took an astronomy class and read that something like 6 house-sized objects crash into the earth daily (mostly water?). I’ve also heard that if you multiply this out over the millinea this could account for all the water on earth. \*\* That’s Frank’s theory, it’s been criticized a lot [http://smallcomets.physics.uiowa.edu/bios.html](http://smallcomets.physics.uiowa.edu/bios.html) Some of his data seems to have been shown to be processing artifact, and the issue of how such impacts could have remained undetected by lunar seismometers is open. ---
**Author:** ![Achernar](https://avatars.discourse-cdn.com/v4/letter/a/e274bd/32.png) [@Achernar](https://boards.straightdope.com/u/Achernar)\ **Post date:** [May 10, 2003, 1:13pm UTC](https://boards.straightdope.com/t/how-can-the-earth-gain-or-lose-weight/174249/17 "2003-05-10T13:13:19Z")
Solar radiation hitting the Earth has a mass of about 167 tons per day. Of course, the Earth radiates about this much away itself. But in theory, there are other ways than the ones listed in the OP for the Earth to gain or lose mass. ---
**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\ **Post date:** [May 10, 2003, 3:29pm UTC](https://boards.straightdope.com/t/how-can-the-earth-gain-or-lose-weight/174249/18 "2003-05-10T15:29:29Z")
> [@](#): > > \*Originally posted by matt \* > Yes, but he said the Earth _weighs_ about 5.9 sextillion metric tons. If you love to nit-pick, he should have said it _masses_. Well…weight is dependant upon gravity (or acceleration which is indistinguishable from gravity) but if we put the earth on a scale with 1g of acceleration affecting then it _weighs_ 5.9 sextillion metric tons. I think it is ok to say that is what earth weighs since we generally assume 1g when weighing anything here on earth. I’m not the one nitpicking here as I think the sense of the OP comes across just fine whether saying mass or weight. YMMV ---
**Author:** ![LordVor](https://avatars.discourse-cdn.com/v4/letter/l/90ced4/32.png) [@LordVor](https://boards.straightdope.com/u/LordVor)\ **Post date:** [May 10, 2003, 4:47pm UTC](https://boards.straightdope.com/t/how-can-the-earth-gain-or-lose-weight/174249/19 "2003-05-10T16:47:49Z")
[Turns bathroom scale upside down] Hmmm… [Places bathroom scale upside down on top of glass table] The Earth weighs 3 pounds! -lv ---
**Author:** ![matt](https://avatars.discourse-cdn.com/v4/letter/m/a6a055/32.png) [@matt](https://boards.straightdope.com/u/matt)\ **Post date:** [May 10, 2003, 8:04pm UTC](https://boards.straightdope.com/t/how-can-the-earth-gain-or-lose-weight/174249/20 "2003-05-10T20:04:10Z")
**I’m not the one nitpicking here as I think the sense of the OP comes across just fine whether saying mass or weight.** Oh, I agree! It’s **bugg** and me who are nitpicking. Personally, it’s because I’m more machine than man now, twisted and evil. I don’t know what his excuse is. On the other hand, **LordVor** is also correct. In the incredibly feeble gravitational field of his bathroom scale, the Earth does indeed weigh 3 pounds. **Achernar’s** point about solar radiation is interesting. I didn’t believe it at first, but my trusty back-of-the-envelope came up with 173 tonnes, which is close is enough. Makes me wonder how much mass is being lost by the Earth’s molten innards cooling down, and its rotation rate slowing. Brings home the reality of mass-energy equivalence, anyway! [Next page](https://boards.straightdope.com/t/how-can-the-earth-gain-or-lose-weight/174249.md?page=2)