<p>Earth loses more mass as gases (especially Hydrogen and Helium) escape the atmosphere. Also, the numbers you mention as well as the mass of the air that is lost likely has large error bars associated with them.</p>

<p>Edit: For example see <a href="http://www.bbc.co.uk/news/magazine-16787636">here</a> or <a href="http://gizmodo.com/5882517/did-you-know-that-earth-is-getting-lighter-every-day">here</a>.</p>

CC BY-SA 3.0
2015-03-03T23:55:55.187Z
Thanks for the response Stali. Great points. Before marking an answer like this correct, I would like to see the numbers for weight loss and gained over time and our sources for this. Cheers
Brian M. Hunt
CC BY-SA 3.0
2015-03-04T02:14:13.010Z
I have added some links. But again, without error bars the numbers don't mean much.
stali
CC BY-SA 4.0
2023-05-21T14:08:47.097Z
The problem with this is if the earth were more massive then, dinosaurs couldn't possibly exist. In fact they shouldn't have been able to exist under current conditions.
JSON
CC BY-SA 3.0
2015-03-03T23:02:32.080Z
2015-03-04T02:14:03.453Z
2015-03-04T02:14:03.453Z
stali
<blockquote>
<p>I gather, but may be wrong, that the mass of earth at present increases by around 10<sup>8</sup>kg/day. All else being equal, one would expect the earth to have gained a mass, since 75 million years ago, of:</p>
<p><span class="math-container">$$ 75^6 \times 365 \times 10^8 kg = 6.496 \times 10^{21} kg $$</span></p>
</blockquote>
<p>First off, that should be <span class="math-container">$75\times10^6$</span>, not <span class="math-container">$75^6$</span>. That alone makes your estimate high by a factor of 2373. Correcting this error, the mass gain is only <span class="math-container">$2.7\times10^{18}$</span> kg, rather than <span class="math-container">$6.5\times10^{21}$</span> kg.</p>
<p>Secondly, I've never seen anywhere close to that magnitude of mass gain. The article you cited in a comment gives a range of 5 to 300 metric tons per day. Your value of <span class="math-container">$10^8$</span> kilograms per day is 100000 metric tons per day, which is high by at least a factor of 333 (and up to 20000). With this, the mass gain is between <span class="math-container">$1.5\times10^{14}$</span> and <span class="math-container">$8.2\times10^{15}$</span> kg. This seems big, but it's tiny compared to the mass of the Earth.</p>
<p>Thirdly, you are ignoring atmospheric losses. Almost all of the atmospheric losses are in the form of hydrogen and helium. Most of the lost hydrogen results from water vapor that makes its way from the surface of the Earth into the stratosphere and is dissociated. Most of the lost helium results from radioactive decay in the Earth. Both forms of atmospheric loss represent a decrease in the mass of the Earth. Estimates on this mass loss also vary widely, from 100 to 300 metric tons per day.</p>
<p>Putting these widely varying estimates together means the mass of the Earth is increasing by as much as 200 metric tons per day (+300 mass gain, -100 mass loss), or decreasing by as much as 300 metric tons per day (+5 mass gain, -300 mass loss, and since the numbers vary so widely, that's just -300). Either way, it's small potatoes, even over the course of 75 million years. This means <em>g</em> was between <span class="math-container">$13\times10^{-9}\,\text{m/s}^2$</span> smaller than it is now and <span class="math-container">$9\times10^{-9}\,\text{m/s}^2$</span> larger than it is now. Both of those numbers are very small.</p>

CC BY-SA 3.0
2016-02-08T21:10:31.520Z
The estimated mass for Earth is $5.972 \times 10^{24} \text{ kg}$ (after [quick check](http://www.wolframalpha.com/input/?i=mass+of+earth)). The mass gain (or loss) gets even proportionally smaller.
carnendil
CC BY-SA 3.0
2015-03-04T15:06:34.390Z
I have marked this as correct, but it would improve this answer to include citations for atmospheric loss (noting though those by @stall below). Cheers
Brian M. Hunt
CC BY-SA 3.0
2015-03-04T14:34:06.580Z
2015-03-04T14:34:06.580Z
2020-06-18T08:25:19.090Z
David Hammen
<p>Is there a significant difference in the mass of the Earth between now and the time of the dinosaurs (250 - 75 million years ago)? I was just wondering if the force of gravity on dinosaurs would have been significantly less when they were around.</p>

<p>I gather, but may be wrong, that the mass of earth at present increases by around 10<sup>8</sup>kg/day. All else being equal, one would expect the earth to have gained a mass, since 75 million years ago, of:</p>

<p>$$ 75^6 \times 365 \times 10^8 kg = 6.496 \times 10^{21} kg $$ </p>

<p>The current mass of Earth according to Wikipedia is 5.972<sup>24</sup>kg, so if my math is correct, the change since the time the dinosaurs went extinct would be less than 0.1%.</p>

<p>Is my math correct here? If it is, would the change in the mass of the Earth over this period of time have had any noticeable effect on weight from its gravity?</p>

CC BY-SA 4.0
2020-11-19T05:05:28.900Z
Your calculations have a flaw, they assume a constant rate of accretion over 75 million years. The rate of accretion would have decreased over time.
Sean
CC BY-SA 4.0
2023-05-21T14:04:54.763Z
This is a very interesting question.  Animals the size of dinosaurs should not have been able to exist under the planets current gravitational influence. They should have not been strong enough to support their own weight. As muscle mass increases by n^2, strength increases by n. This doesn't include bone mass etc.  It is a pardox.
JSON
CC BY-SA 3.0
2015-03-03T20:00:32.490Z
Meteorites, perhaps?
Gimelist
CC BY-SA 3.0
2015-03-03T21:48:30.543Z
@SabreTooth - Google, but I lost the original link. In looking for it again though I did find this topical page: http://www.universetoday.com/94392/getting-a-handle-on-how-much-cosmic-dust-hits-earth/
Brian M. Hunt
CC BY-SA 3.0
2015-03-04T11:32:17.880Z
Your mass-increase calculation is given incorrectly. The number on the left shouldn't be $75^6$, it should be $75 \times 10^6$. And please cite a source for your daily increase of $10^8$ kg
410 gone
<geophysics><earth-history><gravity>
Change in earth mass since the time of the dinosaurs
Brian M. Hunt
# Change in earth mass since the time of the dinosaurs

(Asked by: username_0 on 2015-03-03)

Is there a significant difference in the mass of the Earth between now and the time of the dinosaurs (250 - 75 million years ago)? I was just wondering if the force of gravity on dinosaurs would have been significantly less when they were around.

I gather, but may be wrong, that the mass of earth at present increases by around 108kg/day. All else being equal, one would expect the earth to have gained a mass, since 75 million years ago, of:

$$ 75^6 \times 365 \times 10^8 kg = 6.496 \times 10^{21} kg $$

The current mass of Earth according to Wikipedia is 5.97224kg, so if my math is correct, the change since the time the dinosaurs went extinct would be less than 0.1%.

Is my math correct here? If it is, would the change in the mass of the Earth over this period of time have had any noticeable effect on weight from its gravity?

**Tags:** geophysics, earth-history, gravity

> **Comments:**
> **username_3**: Meteorites, perhaps?  
> **username_0**: @SabreTooth - Google, but I lost the original link. In looking for it again though I did find this topical page: http://www.universetoday.com/94392/getting-a-handle-on-how-much-cosmic-dust-hits-earth/  
> **username_4**: Your mass-increase calculation is given incorrectly. The number on the left shouldn't be $75^6$, it should be $75 \times 10^6$. And please cite a source for your daily increase of $10^8$ kg  
> **username_1**: Your calculations have a flaw, they assume a constant rate of accretion over 75 million years. The rate of accretion would have decreased over time.  
> **username_2**: This is a very interesting question.  Animals the size of dinosaurs should not have been able to exist under the planets current gravitational influence. They should have not been strong enough to support their own weight. As muscle mass increases by n^2, strength increases by n. This doesn't include bone mass etc.  It is a pardox.  

---

## 2 answers

### Answer by username_6 on 2015-03-04. Score: 18 | Accepted answer

> I gather, but may be wrong, that the mass of earth at present increases by around 108kg/day. All else being equal, one would expect the earth to have gained a mass, since 75 million years ago, of:
>
> $$ 75^6 \times 365 \times 10^8 kg = 6.496 \times 10^{21} kg $$

First off, that should be $75\times10^6$, not $75^6$. That alone makes your estimate high by a factor of 2373. Correcting this error, the mass gain is only $2.7\times10^{18}$ kg, rather than $6.5\times10^{21}$ kg.

Secondly, I've never seen anywhere close to that magnitude of mass gain. The article you cited in a comment gives a range of 5 to 300 metric tons per day. Your value of $10^8$ kilograms per day is 100000 metric tons per day, which is high by at least a factor of 333 (and up to 20000). With this, the mass gain is between $1.5\times10^{14}$ and $8.2\times10^{15}$ kg. This seems big, but it's tiny compared to the mass of the Earth.

Thirdly, you are ignoring atmospheric losses. Almost all of the atmospheric losses are in the form of hydrogen and helium. Most of the lost hydrogen results from water vapor that makes its way from the surface of the Earth into the stratosphere and is dissociated. Most of the lost helium results from radioactive decay in the Earth. Both forms of atmospheric loss represent a decrease in the mass of the Earth. Estimates on this mass loss also vary widely, from 100 to 300 metric tons per day.

Putting these widely varying estimates together means the mass of the Earth is increasing by as much as 200 metric tons per day (+300 mass gain, -100 mass loss), or decreasing by as much as 300 metric tons per day (+5 mass gain, -300 mass loss, and since the numbers vary so widely, that's just -300). Either way, it's small potatoes, even over the course of 75 million years. This means *g* was between $13\times10^{-9}\,\text{m/s}^2$ smaller than it is now and $9\times10^{-9}\,\text{m/s}^2$ larger than it is now. Both of those numbers are very small.

> **Comments:**
> **username_0**: I have marked this as correct, but it would improve this answer to include citations for atmospheric loss (noting though those by @stall below). Cheers  
> **username_7**: The estimated mass for Earth is $5.972 \times 10^{24} \text{ kg}$ (after [quick check](http://www.wolframalpha.com/input/?i=mass+of+earth)). The mass gain (or loss) gets even proportionally smaller.  

---

### Answer by username_5 on 2015-03-03. Score: 6

Earth loses more mass as gases (especially Hydrogen and Helium) escape the atmosphere. Also, the numbers you mention as well as the mass of the air that is lost likely has large error bars associated with them.

Edit: For example see [here](http://www.bbc.co.uk/news/magazine-16787636) or [here](http://gizmodo.com/5882517/did-you-know-that-earth-is-getting-lighter-every-day).

> **Comments:**
> **username_0**: Thanks for the response username_5. Great points. Before marking an answer like this correct, I would like to see the numbers for weight loss and gained over time and our sources for this. Cheers  
> **username_5**: I have added some links. But again, without error bars the numbers don't mean much.  
> **username_2**: The problem with this is if the earth were more massive then, dinosaurs couldn't possibly exist. In fact they shouldn't have been able to exist under current conditions.  

---

