How much more could the Earth shrink as it cools and the core completely cools?

[brainstorm]

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? How much more could it shrink by the time the core is completely cooled?

 

[mgb_phys]

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

 

[Evo]

BS, did you take into consideration how much additional material from meteorites is added to the Earth every day?

 

[brainstorm]

BS, did you take into consideration how much additional material from meteorites is added to the Earth every day?

So the added mass is responsible for the rotation speeding up? Is the Earth growing in diameter then?

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? BTW, what evidence demonstrates how many days were in a dinosaur year anyway, Flintstones calendars?

 

[Jim1138]

Tidal effects slow down the Earth's rotation and increase the orbital radius of the Moon. Eventually, the Earth will tidal lock with the Moon, the Moon's orbit will decrease over billions (and billions) of years and eventually re-merge with the Earth. http://en.wikipedia.org/wiki/Tidal_acceleration

 

[Evo]

So the added mass is responsible for the rotation speeding up? Is the Earth growing in diameter then?

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? BTW, what evidence demonstrates how many days were in a dinosaur year anyway, Flintstones calendars?

Did you mean to ask MGB?

 

[brainstorm]

Tidal effects slow down the Earth's rotation and increase the orbital radius of the Moon. Eventually, the Earth will tidal lock with the Moon, the Moon's orbit will decrease over billions (and billions) of years and eventually re-merge with the Earth. http://en.wikipedia.org/wiki/Tidal_acceleration

What is "tidal lock?"

Did you mean to ask MGB?

What is "MGB?"

 

[Evo]

What is "MGB?"

The member that you should have been responding to instead of me.

BS, do you pay any attention to what you respond to?

 

[buzzjig]

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? How much more could it shrink by the time the core is completely cooled?

If Earths core cooled down completely what would be the effects on the Formation of Earth?

I think that eventually, over millions of years, the enitre surface of the Earth would be covered in water, a huge ocean. There would be no new mountains being formed, and eventually errosion from rain would erode every protruding part of the Earth's surface until the surface was so flat the entire Earth would be covered by water. Similar to what Europa looks like, a big ball of ice.

Could that happen?

 

[brainstorm]

The member that you should have been responding to instead of me.

BS, do you pay any attention to what you respond to?

You called "BS" and suggested that mass-increase due to meteorites would be responsible for the rotation speed increase - or did I misinterpret your post?

Do I pay attention to what I respond to? More to the content than to the poster, honestly. I treat these forum discussions as open critical exchanges. I figure anyone is free to respond to anything anyone else says because its all public.

 

[Evo]

You called "BS" and suggested that mass-increase due to meteorites would be responsible for the rotation speed increase - or did I misinterpret your post?

BS=BrainStorm

And you did misinterpret my post. I asked if you had considered the mass from meteorites, nothing else.

 

[brainstorm]

BS=BrainStorm

And you did misinterpret my post. I asked if you had considered the mass from meteorites, nothing else.

Now I'm utterly confused by miscommunication. I thought you were disagreeing with the other poster with reference to meteorite mass addition. To answer you question, no, I did not in the slightest consider meteorites when posting. I was just thinking that the core could be shrinking as it cooled and that matter settles through time due to erosion and other entropic mechanisms.

What is your point with the meteorites? That they would add to the mass of the planet, the volume, or both? And with what implications/effects?

 

[Evo]

Cosmic "dust" adds to the mass of the earth.

You realize that if the Earth's core cooled, which I take to mean that it shuts down, that the fate of Earth would be similar to that of Mars. Do we have evidence of Mars shrinking when it's core shut down?

 

[brainstorm]

Cosmic "dust" adds to the mass of the earth.

I think you're right that everything that falls to Earth adds to its mass. I have no idea how much this is, how much it would affect the volume and mass over very long periods of time.

You realize that if the Earth's core cooled, which I take to mean that it shuts down, that the fate of Earth would be similar to that of Mars. Do we have evidence of Mars shrinking when it's core shut down?

What basis do you have for thinking that Mars was more similar to Earth at some point? Is there even any evidence that it had a molten core besides the assumption that it was formed in a similar way and around the same time as Earth? As for the shrinking, I tried googling molten metal density and nothing accessible to my feeble mind emerged. I assume for some reason that hotter molten liquid maintains lower density than if it cools. This is admittedly naive and based only on the hunch that heat results in pressure/motion. Water expands when it freezes but this is exceptional, I think.

 

[Evo]

What basis do you have for thinking that Mars was more similar to Earth at some point? Is there even any evidence that it had a molten core besides the assumption that it was formed in a similar way and around the same time as Earth? As for the shrinking, I tried googling molten metal density and nothing accessible to my feeble mind emerged. I assume for some reason that hotter molten liquid maintains lower density than if it cools. This is admittedly naive and based only on the hunch that heat results in pressure/motion. Water expands when it freezes but this is exceptional, I think.

Just going by what the current scientific belief is.

Earth's global magnetic field comes from an active dynamo -- that is, circulating currents at the planet's liquid metallic core. A similar dynamo once churned inside Mars, but for reasons unknown it stopped working four billion years ago. The patchwork fields we see now are remnants of that original magnetic field.

How do scientists know when the dynamo turned off? "Mars has been kind to us," explains Mitchell. "There are two large impact basins, Hellas and Argyre, about four billion years old that are demagnetized. If the dynamo was still operating when those impact features formed, the crust would have re-magnetized as they cooled. The dynamo must have stopped before then."

http://science.nasa.gov/science-news/science-at-nasa/2001/ast31jan_1/

 

[Janus]

What basis do you have for thinking that Mars was more similar to Earth at some point? Is there even any evidence that it had a molten core besides the assumption that it was formed in a similar way and around the same time as Earth?

Mars' surface is dotted with extinct volcanoes, lava plains and other evidence of being geologically active in the past.

 

[loseyourname]

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? How much more could it shrink by the time the core is completely cooled?

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. I think the main materials down there are iron, magnesium, and silicon in various mineral configurations. The inner core is solid, so it wouldn't expand or contract, but I guess the outer core and the entire mantle would.

 

[airbourne]

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.

 

[brainstorm]

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.

 

[Radrook]

Here is some interesting info:


Excerpt:
...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]

http://www.talkorigins.org/faqs/moon-dust.html

 

[Ophiolite]

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.

 

[Borek]

Dust/meteorites mean mass increase, at the same time Earth is losing some of the mass as the atmospheric gases escape.

BTW, what evidence demonstrates how many days were in a dinosaur year anyway, Flintstones calendars?

See for example http://gsabulletin.gsapubs.org/content/82/4/1085.short

 

[airbourne]

Thanks for the link Radrook. At least the amount of mass added per year is calculable.

 

[Studiot]

Maybe, maybe not but how about this?

http://www.theregister.co.uk/2010/08/20/moon_shrinking/

 

[sigma143]

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)

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?

 

[sigma143]

Interesting;
"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."

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."

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."

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).