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Could Earth be shrinking?

by brainstorm
Tags: earth, shrinking
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Aug15-10, 10:33 AM
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Quote Quote by airbourne View Post
A few posts in here have raised a a question (simple curiosity).

Does anyone have information of the volume of matter entering earth annually (dust etc) compared to the volume of matter we've put into orbit/sent permanently into space? I would assume much more mass is leaving the earth than entering it at present.
That seems counter-intuitive. Things fall down into a gravity well easier than they find their way out of it. Plus, it's not as though the satellites put into orbit are leaving Earth; they're just gaining a lot of altitude on it.

edit: Loseyourname, I tried googling the issue of molten metal density/expansion and there was nothing simple and straight-forward enough for my feeble non-engineer mind. I would think this would be standard knowledge, like the fact that water expands when it freezes, but no one has chimed in with it.
Aug19-10, 01:04 AM
P: 334
Here is some interesting info:

.....the Earth's total mass increases by one tenth of one millionth, or one one-hundred-thousandth of a percent, over the entire 4.5 billion years]
Aug19-10, 04:44 AM
P: 274
Quote Quote by loseyourname View Post
If you want to isolate volume changes due to cooling effects, just figure out what the mantle is made of, find the coefficients of volumetric thermal expansion for each, and figure out the volume change expected from temperature decrease.
This, regretably, is oversimplified to the point of uselessness. You have completely ignored the phase changes in which significant changes of mineral composition or structure occur in response to ambient temperature and pressure. The net result of a decrease in temperature may be to promote a change to a less dense mineral, or mineral suite. This could result in an increase, decrease, or zero change in overall volume. Only a very sophisticated finite element analysis, based upon several questionable suppositions could hope to approach any sort of a meaningful answer.
Aug19-10, 04:51 AM
Borek's Avatar
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Dust/meteorites mean mass increase, at the same time Earth is losing some of the mass as the atmospheric gases escape.

Quote Quote by brainstorm View Post
BTW, what evidence demonstrates how many days were in a dinosaur year anyway, Flintstones calendars?
See for example
Aug22-10, 01:20 AM
P: 8
Thanks for the link Radrook. At least the amount of mass added per year is calculable.
Aug22-10, 03:17 AM
P: 5,462
Maybe, maybe not but how about this?
Oct16-10, 02:04 AM
P: 9
Quote Quote by mgb_phys View Post
The earth's core temperature hasn't gone down very much since the first life.
The average diameter of the earth is measured extremely accurately (0.1mm levels by VLBI) and doesn't change much.

The length of the day has been increasing as the Earth's rotation slows (due to the moon) the years was 450-500 days long in the days of dinosaurs. This has a slight change on the gravity at the equator
Whether or not the earth is growing or shrinking in diameter could be diagnosed with why many Dinosaurs structures were so immense. Interjecting with the physics of biology, I am pondering how the bone structure etc. of immense dinosaurs could be related to this topic. The relative mass of the Earth may have remained unaltered, yet the displacement of the density of elements it consisted of may have changed.

If the dinosaurs were larger because gravitation towards the earth was weaker, then we could assume either the crust of the earth was farther away from the center of the earth(larger diameter), or the earth was spinning much faster and lessened the effect of gravitation (i'm not too sure if increased rotation speed would lessen gravitation; info please).
Or the dinosaurs bones and other structures developed in such a way because they had to be able to repel greater gravitation, of which we could say the crust was closer to the core of the Earth bach then(smaller diameter). The latter would assume that the rotation speed of Earth was rotating Even faster due to conservation of momentum. (not sure again if the effects of rotation would equalize the increased gravitational force)

Quote Quote by brainstorm View Post
Also, how do you know that the greater number of days wasn't due to the year being longer because Earth was further from the sun, for example?
I'm quite compelled with whether or not the earth was further away from the sun 200 million or more years ago as well, because this also would have affected the length of year! Was the orbit of the earth longer, which in effect would compensate for a faster rotation and exposure to temperature and pressure from the sun? The different convective currents inside the Earth due to this would alter the maleability of mantle and crust.

If so, how might radiation pressure from the sun have affected the saturation balance between solid, liquid, and gas on the surface of the Earth as well as temperature(displacing the true diameter of solid Earth) and thus the distribution of masses of these phases (as Ophiolite states) through this timescale?
Oct19-10, 01:50 AM
P: 9
"Even at the Earth's present subdued rate of rotation, at the equator, the rotation is still fast enough to help propel rockets into space with up to 13 percent less fuel, which allows heavier payloads. Just imagine the heavy payloads that could have been launched in the past when the planet was spinning much faster.
The Sea Launch Company currently launches its commercial satellite delivery missions from a floating platform at the equator. The rocket is able to carry heavier payloads into Earth orbit by taking maximum advantage of greater angular momentum in the equatorial region of the planet."

Quote Quote by brainstorm View Post
Is the Earth growing in diameter then?
"In the past, when the Earth was younger and spinning faster, the stronger angular momentum caused the Earth to assume a more pronounced oblate spheroid shape much greater than the twenty-seven miles it is today. A 15% increase in the equatorial circumference of the faster rotating young planet, relative to its present rotation, could produce approximately 3600 more miles of surface around the young planet's equatorial zone."

Quote Quote by brainstorm View Post
Would Earth's volume shrink as it cools and settles? If so, how much would its diameter have decreased since, say, the first life appeared? Also, how much variation would this cause in gravity at sea level and the length of a day/night cycle?
So the Earth's circumference could have decreased by ~3600 miles since the dinosaurs. Precambrian life, although, evolved about 1.8 billion years Earlier compared to dinosaurs.
The effects on gravity and sea level at the poles would have been respectively stronger and shallower; at the equator, weaker and deeper.
Water of the oceans would have gravitated towards the equator creating shallower depths at the poles. This would explain the abundance of life in a dense and moist equalateral atmosphere and even more so for the precambrian life that evolved in the oceans, when the Earth may have been rotating even more frequently;
Sediments of these early epoc's are found up to 6000m or more thick, meaning the evolution of life affected the displacement of chemical and physical elements. And coal was formed after the carboniferous period.

"Plankton and algae, proteins and the life that's floating in the sea, as it dies, falls to the bottom, and these organisms are going to be the source of our oil and gas. When they're buried with the accumulating sediment and reach an adequate temperature, something above 50 to 70 C they start to cook. This transformation, this change, changes them into the liquid hydrocarbons that move and migrate, will become our oil and gas reservoir."

Quote Quote by brainstorm View Post
How much more could it shrink by the time the core is completely cooled?
With the contraction of the equator due to less angular momentum, I would think it could create a denser, hotter core because there are generally greater equal parallel forces and less geological activity to release internal pressure and create perturbative effects.
The significant effects then would be due to precession, solar activity and location of the entire solar system, creating changes of the convective currents inside and on the surface of the Earth (since momentum must be conserved).

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