How fast is Earth growing?

[h4tt3n]

As far as I know it's a commonly accepted fact that the earth is gaining 100 to 200 tonnes of mass / day because dust and small meteorites hit our planet. This happens mainly because it "gets in the way" and is scooped up by our planet like snow on the front side of a driving car, rather than beeing sucked in by the earths gravity.

Since earth apparently grew much faster in its earlier stages, billions of years ago, I suppose the growth rate has been slowly descending as our solar system has been sucked clean by Jupiter and the other planets.

 

But how fast has it been growing over - say - the last billion years? Was earths gravity notably smaller in cambrium or the cretaceous than it is now?

 

regards,

Michael

[jackson33]

i should research some figures, but the earth is really a heavy place. i do feel you figures are a little high and what reaches the ground is maybe a ton a year. now, quite a few meteors are made up of ice and rock combinations. these burn up quickly and add some to the atmosphere, hydrogen, oxygen and carbon by products from the burn.

 

the addition to the overall weight of earths mass, over a billion years may be one percent, of what was then. your gravity notion was one i put up for a possible cause of dinosaurs extinction 65 million years back. this was based more on a felt, missing component to gravity, than mass to create gravity.

to me a spices that thrived well over a 100 million years, continental shifts, what should have been a good deal of volcano activity, asteroid and comet hits, plus total dominance over life, would die off so suddenly or could have been from all it had previously survived.

 

i do not, but some have suggested the moon was formed from earths matter some time back. you are probably correct in that more mass was collected in the first billion or two years, but even there the totals would be limited, to allow a cooling of the planet. Jupiter has over 300 times our mass, we know gets hit often and is still in the gaseous state.

[[Tycho?]]

Quick calculation:

 

Assume the earth has been adding 200 tons of mass every day, for say 200 000 000 years. This is a mass of 1.46x10^16 kg. This amount wouldn't affect the radius of the earth by a large amount, so we will take that to be constant. This results in 0.15m/s^2 difference back 200 million years ago. Current acceleration due to gravity at sea level is 9.8m/s^2, so thats a change of about 1.5%. Which is pretty large actually. I'm going to go look up some numbers on how much mass the earth gains to see if this number is actually accurate.

[[Tycho?]]

i should research some figures, but the earth is really a heavy place. i do feel you figures are a little high and what reaches the ground is maybe a ton a year. now, quite a few meteors are made up of ice and rock combinations. these burn up quickly and add some to the atmosphere, hydrogen, oxygen and carbon by products from the burn.

 

It doesn't matter if it burns up or not, its still adding mass to the earth.

 

And are you saying you think the extinction of the dinosaurs had something to do with a change in earth's gravity?

[Mokele]

your gravity notion was one i put up for a possible cause of dinosaurs extinction 65 million years back. this was based more on a felt, missing component to gravity, than mass to create gravity.

to me a spices that thrived well over a 100 million years, continental shifts, what should have been a good deal of volcano activity, asteroid and comet hits, plus total dominance over life, would die off so suddenly or could have been from all it had previously survived.

 

Yes, you put it forth and I smacked it down as utterly ridiculous and flatly contradictory of all known data.

 

But how fast has it been growing over - say - the last billion years? Was earths gravity notably smaller in cambrium or the cretaceous than it is now?

 

Doesn't the earth also lose mass to space, with the gasses at the top layer of the atmosphere evaporating into space?

 

Mokele

[swansont]

;311948']Quick calculation:

 

Assume the earth has been adding 200 tons of mass every day' date=' for say 200 000 000 years. This is a mass of 1.46x10^16 kg. This amount wouldn't affect the radius of the earth by a large amount, so we will take that to be constant. This results in 0.15m/s^2 difference back 200 million years ago. Current acceleration due to gravity at sea level is 9.8m/s^2, so thats a change of about 1.5%. Which is pretty large actually. I'm going to go look up some numbers on how much mass the earth gains to see if this number is actually accurate.[/quote']

 

Check your calculation again, of you would. The earth's mass is 6x10^24 kg, so the increase is less than a part in 10^8, and the acceleration changes linearly with the mass, for constant radius.

 

Actual mass gained is a little less than 100 tons/day (<25,000 tons/year) according to http://www.talkorigins.org/faqs/moon-dust.html

[Klaynos]

Check your calculation again, of you would. The earth's mass is 6x10^24 kg, so the increase is less than a part in 10^8, and the acceleration changes linearly with the mass, for constant radius.

 

Actual mass gained is a little less than 100 tons/day (<25,000 tons/year) according to http://www.talkorigins.org/faqs/moon-dust.html

 

In summary then, yes it makes a difference but the difference is SO amazingly small it is completely trivial.

[[Tycho?]]

Check your calculation again, of you would. The earth's mass is 6x10^24 kg, so the increase is less than a part in 10^8, and the acceleration changes linearly with the mass, for constant radius.

 

Actual mass gained is a little less than 100 tons/day (<25,000 tons/year) according to http://www.talkorigins.org/faqs/moon-dust.html

 

Thanks for seeing the mistake. I thought 1.5% seemed big, but I didn't get around to checking the numbers (or checking the math).

[h4tt3n]

Actual mass gained is a little less than 100 tons/day (<25,000 tons/year) according to http://www.talkorigins.org/faqs/moon-dust.html

 

Ok, lets assume this is our best estimate.

 

The trouble with all above calculations is that they assume a linear growth, and that's pretty impossible. I mean, how long would it take to form the earth if mass gain was just ~ 25,000 t/yr? The universe isn't even that old!

 

So, the question is what equation describes the rate of growth at a given time?

Lets set X as time and Y as growth rate. Since Earth probably grew much much faster in the early days, I suppose our graph would look Y = 1/X^2 -ish, beeing very high at x ~ 0 and panning out towards zero in our time, where X is very large.

 

Can we make an equation that gives a rough estimate of Earths radius and gravity at a given time?

 

Ideas Anyone?

[swansont]

Ok, lets assume this is our best estimate.

 

The trouble with all above calculations is that they assume a linear growth, and that's pretty impossible. I mean, how long would it take to form the earth if mass gain was just ~ 25,000 t/yr? The universe isn't even that old!

 

 

 

One might conclude that this was not the method by which the earth formed. The implicit assumption was that the earth already existed. The formation method did include gravity, so far as the model tells us, which was explicitly ruled out in the OP.

[h4tt3n]

Swansont,

 

I didn't rule out the possibillity that gravity has helped forming the earth to begin with, just that it doesn't help much at present time. Why? Because dust and meteoriets often move at speeds very much higher than earths escape velocity. I'm not completely ruling gravity out, I'm just saying it can't make much difference.

In the early years of the solar system, material was probably spread out in a disc with very little difference in speed between rocks orbiting at the approx. same distance from the sun. In such an environment gravity plays a much larger role when it comes to forming larger bodies from smaller ones.

 

oh, and if we assume a slow start the curve would be sinusoid rather than exponential.

[[Tycho?]]

Woah, why sinusodal? I rather doubt the mass of the earth would change periodically.

 

I think it would be hard to just make up a non-linear function for the growth of the earth in very early days. You'd have to know a fair amount about how planets actually formed to be able to estimate these things. I dont know if anyone has such details on the early formation of the earth.

[swansont]

Swansont,

 

I didn't rule out the possibillity that gravity has helped forming the earth to begin with, just that it doesn't help much at present time. Why? Because dust and meteoriets often move at speeds very much higher than earths escape velocity. I'm not completely ruling gravity out, I'm just saying it can't make much difference.

In the early years of the solar system, material was probably spread out in a disc with very little difference in speed between rocks orbiting at the approx. same distance from the sun. In such an environment gravity plays a much larger role when it comes to forming larger bodies from smaller ones.

 

oh, and if we assume a slow start the curve would be sinusoid rather than exponential.

 

Yes. Which has little to do with dust falling to the earth — they are two separate phenomena.

[h4tt3n]

;312049']

Woah' date=' why sinusodal? I rather doubt the mass of the earth would change periodically.

[/quote']

 

Rofl Tycho! Hopefully no-one in their right minds would suggest something as silly as that! X-D

Of course I'm talking about an S-shaped curve like the ones you see here. I believe such curves are also called sinusoid or sinusoidal, correct me if I'm wrong.

 

 

;312049']

I think it would be hard to just make up a non-linear function for the growth of the earth in very early days. You'd have to know a fair amount about how planets actually formed to be able to estimate these things. I dont know if anyone has such details on the early formation of the earth.

 

True. I'm fully aware that this is somewhat of a fools errand. I was just hoping that someone here'd know about it and shed ligh on the subject. The subject can only be discussed in general terms and with loosely estimated values, so I'd suggest we keep it there and dont argue too much over details.

[h4tt3n]

Swansont,

 

Yes, the early gravitational pull that initiated the formation of earth and the "scooping up" of dust happening today are two separate phenomena, but they both work in the same direction: making our planet grow, which is the topic of this thread. Even if there were even more phenomenons causing a gain in earths mass, they could probably still all be summed up in a single curve.

[jackson33]

Yes, you put it forth and I smacked it down as utterly ridiculous and flatly contradictory of all known data.

 

 

 

Doesn't the earth also lose mass to space, with the gasses at the top layer of the atmosphere evaporating into space?

 

Mokele

 

there were many arguments from several people. i will admit i learned a few things from those post but have not eliminated gravity from the equation. as i have told many with your attitude, i offer opinion and have never suggested otherwise. also i seek opinion and if just wanted opinions from people with letters after their name id do more googling and less of this...

 

i am sure your a very smart person and are able to smack down many opinions. the problem here is, your limiting those with opinions to express them with out fearing such face slappings. you are also aware that known data changes on a daily basis. accepted universal size, changed last week. a dog and cat cannot have an off spring changed a few days ago and the spin of black holes confirmed at 1000 times per second also last week.

[jackson33]

;311949']It doesn't matter if it burns up or not' date=' its still adding mass to the earth.

 

And are you saying you think the extinction of the dinosaurs had something to do with a change in earth's gravity?[/quote']

 

 

i said i suggested it and me-myself-my mind, is not convinced this is not a possibility. my response was to a hypothetical post inferring gravity change was a possible event over time.

 

if your saying all that burns up in space stays there, maybe we should revisit the global warming nonsense with 100 or 200 tons of potentially very damaging materials and discount the non-harmful 98% of atmosphere that is; nitrogen and oxygen.

[ParanoiA]

Are you all considering the 21 grams of mass lost by people who die? That is unrecoverable mass. Perhaps you should calculate the number of dead in the world and subtract that from your growth rate.

[insane_alien]

paranoia that is a myth. the scales used had an accuracy of +/- 100 grams. 21 grams is as good as zero on them.

[[Tycho?]]

i said i suggested it and me-myself-my mind, is not convinced this is not a possibility. my response was to a hypothetical post inferring gravity change was a possible event over time.

 

if your saying all that burns up in space stays there, maybe we should revisit the global warming nonsense with 100 or 200 tons of potentially very damaging materials and discount the non-harmful 98% of atmosphere that is; nitrogen and oxygen.

 

What in the world are you talking about? I never said anything stays in the atmosphere.

[[Tycho?]]

Are you all considering the 21 grams of mass lost by people who die? That is unrecoverable mass. Perhaps you should calculate the number of dead in the world and subtract that from your growth rate.

 

21 grams lost by people who die? ....what? The mass couldn't possibly be lost. If it were converted into energy it would be like a fusion bomb going off. Even if you got the number wrong, how can any mass just be lost?

[jackson33]

;312493'']What in the world are you talking about? I never said anything stays in the atmosphere.

 

then what burns up in space and becomes mass, either falls as acid rain or exits earths atmosphere and is lost mass. the those altitudes I'll pick the latter.

[[Tycho?]]

then what burns up in space and becomes mass, either falls as acid rain or exits earths atmosphere and is lost mass. the those altitudes I'll pick the latter.

 

Is english not your native language? You make very strange gramatical mistakes in your posts, it makes me think I am not understanding you.

 

If a meteor burns up in the atmosphere, the mass is not lost. Most of it will fall to the earth (as dust, not as acid rain). A tiny amount will remain in the atmosphere. Either way, no mass is "lost". It all contributes to the mass of the earth.