mass of planet earth

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StoneRoad
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mass of planet earth

Post by StoneRoad » Thu Jun 03, 2010 9:33 am

I am curious enough to wonder about this question.


Is the mass of the earth increasing, staying the same, or decreasing?? Timescales both short term (human generations) and long term as in goelogical time??

Personally, in terms of a single human gneration (50 - 100 years) I would say that it remains the same, but then .....

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Amir
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Re: mass of planet earth

Post by Amir » Thu Jun 03, 2010 9:59 am

i think it doesn't change; i can't think of any reason which can increase or decrease the mass of earth. there are, of course meteorites, etc. but they are almost nothing compared to the mass of earth. considering meteorites as an increase to earth's mass is like you throw a grain of sand at a mountain each day, and say I'm increasing it's mass.
interesting question though, i would like to know of any way that earth's mass could increase or decrease. if there is any.
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Chris Peterson
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Re: mass of planet earth

Post by Chris Peterson » Thu Jun 03, 2010 2:27 pm

StoneRoad wrote:Is the mass of the earth increasing, staying the same, or decreasing?? Timescales both short term (human generations) and long term as in goelogical time?
It is losing mass in the form of gas and water to space. It is gaining mass via meteoritic material. Right now, the latter is dominant, but eventually we'll lose our magnetic field and the mass loss from our atmosphere will be greater than the mass received from space dust. There must be an effect from the long term heat balance as well.

Of course, all of these are very tiny with respect to the actual mass of the Earth. Effectively, the mass can be seen as unchanging.
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Re: mass of planet earth

Post by Amir » Thu Jun 03, 2010 6:43 pm

Chris Peterson wrote:It is losing mass in the form of gas and water to space.
i can't understand. how?
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Chris Peterson
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Re: mass of planet earth

Post by Chris Peterson » Thu Jun 03, 2010 8:09 pm

Amir wrote:
Chris Peterson wrote:It is losing mass in the form of gas and water to space.
i can't understand. how?
Some gas in the upper atmosphere is always diffusing away into space. That is probably why Mars doesn't have much of an atmosphere anymore- with its lower mass and lack of magnetic field, the atmosphere was lost much quicker.
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Re: mass of planet earth

Post by Amir » Thu Jun 03, 2010 8:33 pm

i see. and what's the role of magnetic field in this?
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Re: mass of planet earth

Post by Chris Peterson » Thu Jun 03, 2010 9:05 pm

Amir wrote:i see. and what's the role of magnetic field in this?
The Earth's magnetic field creates a bubble around the planet called the magnetosphere, which extends several Earth diameters. This deflects the solar wind. Without that, the solar wind would literally blow the upper atmosphere into space (and eventually nearly all the atmosphere).
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Ann
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Re: mass of planet earth

Post by Ann » Fri Jun 04, 2010 1:33 am

Speaking of the mass of the Earth, I have managed to learn that the mass of the Sun is about 300,000 times the mass of the Earth, but I have never managed to learn a number for the mass of the Earth. How much is it in metric tons?

Speaking of large numbers, I can't seem to learn the distance to Apha in kilometers. And if that is ridigulously large anyway, I'd like to learn how much longer it is compared with the distance to the Moon (which is the longest distance that humans have ever travelled in a spaceship) or compared with the distance to the Sun. (Of course I know that the distance to the Moon is generally 1.5 light second and the distance to the Sun is about 8 light minutes, but I can't seem to divide 4.2 light years by 1.5 light seconds or 8 light minutes.)

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Re: mass of planet earth

Post by BMAONE23 » Fri Jun 04, 2010 3:05 am

Light travels at 186000mps or 300000kps.
300000 kilometers per second
450000K to the moon
x 60 = 18,000,000 kilometers per minute
x 60 = 1,080,000,000 kilometers per hour
x 24 = 25,920,000,000 kilometers per day
x 7 = 181,440,000,000 kilometers per week
x 4 = 725,760,000,000 kilometers per month (Feb)
or x 52 = 9,434,880,000,000 + 1.25 days (9,467,280,000,000) kilometers per year (365.25 days)
At 4.2 LY Alpha lies approx 397,625,760,000,000 kilometers away

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Re: mass of planet earth

Post by Ann » Fri Jun 04, 2010 7:41 am

Thanks, BMAONE23! I'll try to remember it. The distance in kilometer to Alpha Centauri is approximately 400 followed by twelve zeros!

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Re: mass of planet earth

Post by BMAONE23 » Fri Jun 04, 2010 4:55 pm

Any time...WOW 400 trillion kilometers. At 450 trillion kilometers you would be a million times the distance to the moon

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Re: mass of planet earth

Post by StoneRoad » Sat Jun 05, 2010 11:15 pm

A further thought...

if some mass is converted into energy ...
(example; a fossil fuel burnt to provide heat, some of which is radiated and more is used to generate electricity, some of which is converted into radio waves, some of which is transmitted into space)
... is this lost from the mass of the earth??

or am I imagining this....

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Chris Peterson
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Re: mass of planet earth

Post by Chris Peterson » Sun Jun 06, 2010 12:18 am

StoneRoad wrote:if some mass is converted into energy ...
(example; a fossil fuel burnt to provide heat, some of which is radiated and more is used to generate electricity, some of which is converted into radio waves, some of which is transmitted into space)
... is this lost from the mass of the earth??
Yes, but chemical conversion of mass to energy is so inefficient that the mass loss associated with it is pretty insignificant.
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Re: mass of planet earth

Post by alter-ego » Sun Jun 06, 2010 1:49 am

StoneRoad wrote:A further thought...

if some mass is converted into energy ...
(example; a fossil fuel burnt to provide heat, some of which is radiated and more is used to generate electricity, some of which is converted into radio waves, some of which is transmitted into space)
... is this lost from the mass of the earth??
The fundamental answer to your question is yes - radiative energy loss has an equivalent mass loss. But the mass conversion rate is so low that this process is likely the lowest of all the contributors. Thermodynamically, the process of energy conversion always has a component of heat, which is utimately radiated away. Even if the Earth equilibrates (rate of heat input = rate of heat loss) to a higher temperature, the radiative loss component will also increase (proportional to T^4) and still lead to an equivalent mass loss. Note that the Sun is a heating source, and because it is external to the Earth system (like meteoric material), the Sun's light also can increase Earth's mass, albeit only as long as the Sun flux does not stop. I mean it comes down to the balance of rates - radiative heating verses radiative cooling in this case. Simply put, if an external heat source raises the Earth's overall temperature, there is an equivalent mass increase associated with the absorbed energy. You've asked a great question, and althought it is legitimate to use mass - energy equivalence here, the disuccusion is really only academic.

As an interesting bookend, if the Earth were to absorb 100% of the Sun's radiation for 1000 years, and with no radiative cooling (way, way wrong), the fraction increase of Earth's mass would be 1 part in 10^14. Conversely, the total deposition rate of meteoric material is somewhere around 25,000 metric tons per year. Over 1000 years, the acquired mass would amount to 1 part in 10^15. The former estimate is clearly overestimated by a large factor which I can't guess (>1000 times too big), but the latter is probably a reasonable estimate over the near-term. In any case, you can see how small an effect these components have on the Earth's mass!
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Re: mass of planet earth

Post by StoneRoad » Sun Jun 06, 2010 4:28 pm

Thanks for the answers and discussion,
I had no idea just how much meteoric mass was added per year. I know now that compared to the mass of the Earth even 25,000 metric tons is insignificant, however, a large piece of that lot could really spoil your day!

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