maybe off topic, but i recently found out that the earth is expanding also. a nice theory from what i heard, it accounts for what we see as continental drift, and why the dinosaurs were so <snip> big (lower gravity)

 

That is off topic for this thread - http://forum.allaboutcircuits.com/showthread.php?t=50136&page=5

Can you provide a link to this source?

 

The expansion of the earth doesn't affect the gravity in an analogue fashion. Gravity is a function of mass and distance from the center fo gravity. The mass of the earth has remained the same, and if the planet indeed expanded, the gravity would be greater when the earth's surface was closer to its core.

 

If the earth is expanding, Increased centripetal/centrifugal force and decreased density would cause the gravity to decrease over time, not increase.

Unless you mean expanding in the sense that mass is being added and coating the earth, then I'm not sure.

 

well to be honest, it's just something which i heard word of mouth. i'll ask for links when my source returns.

the way i see it: earth was much smaller with a pangaea super-continent, not bunched into a clump on one side of the world, but surrounding much of it.. plus some ocean and some other land masses. gravity is less, lifeforms are big. large objects, a wave of objects perhaps, collide with the earth, much of which is absorbed into the globe. most of the biosphere is obliterated by the impacts, climate changes and so on. the super continent splits apart as the core of the planet heats up the new material and expands. conditions then favour the smaller lifeforms who continue to evolve whilst the larger ones die off.
something like that.

 

I don't think a change of size is needed for tectonics theory. We have a thin crust with a rapidly spinning interior of molten iron. It is amazing we have a solid crust at all, the fact it moves is no big stretch.

 

ah.. so yeah, cosmic material adding mass.
but i guess that changes to the earth's spin from impacts could affect gravity also

 

Not really, there are a lot of schemes for antigravity, they haven't panned out.

What made the dinosaurs and giant insect possible was a really high oxygen content in the atmosphere, I'm not sure of the number but I think it was about double what we have today.

 

bribri, either you 're trolling or you seriously need to get your geology down.

 

 

ah.. yes that's what i mean.
it just seems a more intuitive process if the globe is growing.

but, here's a link to the dinosaur guy:
http://www.dinox.org/q&a.html
and there's a wiki-page.

bribri, either you 're trolling or you seriously need to get your geology down.

pretty standard models of planetary formation require expansion and accumulation of mass for planets to exist in the first place. i really don't recall there being any need for such processes to just stop. planets could increase or decrease size and mass over time through various mechanisms, that's pretty well established is it not?

trolling?
it's just a theory. i really don't think that it particularly challenges plate-tectonics and seafloor spreading models... could provide a mechanism, or maybe not. no big deal. it's not like it's really challenging anyone's fundamental belief-systems or world-views or anything.

 

Accumulation of mass when the solar system is in gas form and the planets are formed by condensed clouds of gasses. In that scope sure. But after the solar system is comprised by discrete bodies, I don't think that the size of the planets changes significantly.

As for what your second .gif displays, who said that when Pangaia existed, there where no oceans?

 

But after the solar system is comprised by discrete bodies, I don't think that the size of the planets changes significantly.

jupiter is said to be shrinking at a rate of 2km/year. it is also said to be a kind of cosmic hoover, capturing objects (and therefore adding them to its mass). such an event has been witnessed within our lifetime.
depends on what you mean by significant, but changes happen.
the most popular theories of how our moon formed involve a giant object impacting the earth; and research which suggests that we had some kind of second moon is out there (the earth's L4 and L5 triangular Lagrange points could once have hosted objects as is the case with other planets).

As for what your second .gif displays, who said that when Pangaia existed, there where no oceans?

well it wasn't very accepted 50 years ago, but i thought that the existence of Panga is pretty well established now. the oceans would have been there and could have grown over time.

 

As for what your second .gif displays, who said that when Pangaia existed, there where no oceans?

I was wondering the same thing, why is the amount of water on the planet increasing?

 

I was wondering the same thing, why is the amount of water on the planet increasing?

i don't know.
rocks? atmosphere?
colliding protoplanets from solar-system's outer asteroid belt maybe?

 

Sounds like an assumption there. Just because there was one land mass does not mean there was more or less water. I would suspect there were configurations before Pangia that we will never know.

It also sounds like you are confusing the early solar system when everything was coalescing with the more or less final construct. Given the shear size of Jupiter the number you named is truely insigificant, the heat death of the universe is likely to occur before any real change to Jupiter's mass is noticable at that rate of change (by the way, source of your info please). The Sun's death will cause much more dramatic changes.

If the changes you claim were still happing life would be extinct, or would never have occurred. This solar system has been static enough over time for us to wonder about it. Above all, life requires stability, the mass extinctions puntuate that soundly. A fair enough argument all by itself.

 

Sounds like an assumption there. Just because there was one land mass does not mean there was more or less water. I would suspect there were configurations before Pangia that we will never know.

yes i agree.

It also sounds like you are confusing the early solar system when everything was coalescing with the more or less final construct.

no, not at all. but therein lays another assumption: that no relatively significant changes are possible since initial planetary formation... or in this case, the last 100 million years or so.

Given the shear size of Jupiter the number you named is truely insigificant, the heat death of the universe is likely to occur before any real change to Jupiter's mass is noticable at that rate of change (by the way, source of your info please). The Sun's death will cause much more dramatic changes.

source: http://en.wikipedia.org/wiki/Jupiter#Mass
it is noted that a "small" rise in Jupiter's mass would cause the planet to shrink dramatically.

If the changes you claim were still happing life would be extinct, or would never have occurred. This solar system has been static enough over time for us to wonder about it. Above all, life requires stability, the mass extinctions puntuate that soundly. A fair enough argument all by itself.

...BUT... life will adapt just fine to slow enough changes and, it seems, can adapt to quicker ones. mass extinctions themselves point to periodic and relatively fast changes of some sort.
has earth's size, mass, and gravity significantly changed in the past 1/4 billion years? i don't know... like i said before, i just think that there's a kind of intuitive sense to it.

 

source: http://en.wikipedia.org/wiki/Jupiter#Mass
it is noted that a "small" rise in Jupiter's mass would cause the planet to shrink dramatically.

What your source actually says is this:

Source=http://en.wikipedia.org/wiki/Jupiter#Mass
Theoretical models indicate that if Jupiter had much more mass than it does at present, the planet would shrink.[25] For small changes in mass, the radius would not change appreciably, and above about 500 M⊕ (1.6 Jupiter masses)<snip>

...BUT... life will adapt just fine to slow enough changes and, it seems, can adapt to quicker ones. mass extinctions themselves point to periodic and relatively fast changes of some sort.
has earth's size, mass, and gravity significantly changed in the past 1/4 billion years? i don't know... like i said before, i just think that there's a kind of intuitive sense to it.

Here's a much simpler explanation:

John

 

You know, compared to what is documented and theorized your idea is pretty tame, but I've never heard it before, it accounts for not facts (but does create problems). Intuition is not science. Lets go over some real theories, the kind that account for facts.

Our solar system is less than 5 billion years old. The sun has burned less than ¼ of its fuel, but is middle age. As the remaining hydrogen is fused, it will turn into a red giant, in about 5 billion more years. It will grow big enough it will eat the inner planets, including earth. It will not be gaining mass to speak of, as it already has 99.89% of the total mass of the solar system. Most of the remaining mass (99% of that) is split between the gas giants, which may survive the red giant phase. In the end it will become a minor nova and collapse into a white dwarf, probably about the size of our moon. The latter is speculation by me, who would know? The outer gas giants will still be there.

http://en.wikipedia.org/wiki/Sun

The moon is thought to have been created by collision with a mars sized planetiod with the Earth. The results were a moon very close to Earth, which was spinning much, much faster. At this point the masses were fixed, they don't change much. However, the tidal coupling with the moon as slowed down the earths spin, and has moved the moons orbit much further out. Given time, the moon will eventually decouple and wander off, but the sun will get involved before happens.

http://en.wikipedia.org/wiki/Earth

http://en.wikipedia.org/wiki/Moon

Most of this I get from simple reading of science, and science shows on TV. But let's get down to the silliness you propose.

A typical dinosaur killer was around 1 mile across. Much bigger and life will not survive, except the single celled stuff. There isn't enough time to recreate everything back in the time left on earth, the sun is middle aged. The history of life shows that it has taken the full time to get where we are now, and the concept "life will survive" is basically a dream.

A 1 mile asteroid is tiny. Every year about 10 tons of material rain down on earth, mostly ash from burning up in the upper atmosphere. This translates out to about 10^6Kg. The mass of the earth is shy of 6^27Kg. So in a billion years you will have added 10^12kg. This number is suspect, but go with it for a moment. The mass of the earth will have increased by less than a trillionth. If the circumference of the earth increased by that amount (10^-15) you will have grown less than a mm. Much less. In a billion years.

The problem, my friend, is you have no sense of scale.

The history of life offers some clear records. Fortunately for us large asteroid collisions are relatively rare, measured in 10s if not 100s of millions of years.

So we have the moon slowly moving further and further out, causing the length of the day to slowly change. This is documented.

We have a number for how much material comes in on the earth. It is a pittance.

And we have the moon and earth actually moving inside the sun as the sun grows to a red giant. Documented not, but pretty good science with lots of observational background.

What we don't have is the earth growing in size. Why? Because it is a true planet. It is already so big the amount of material that would have to come in to make a difference would kill everything, and it is one of the smaller planets.

Jupiter protects us. It eats much more material than the Earth. And it isn't growing or shrinking either, though the storms in it's atmosphere may last for thousands of years caused by the asteroids.

 

A typical dinosaur killer was around 1 mile across. Much bigger and life will not survive, except the single celled stuff. There isn't enough time to recreate everything back in the time left on earth, the sun is middle aged. The history of life shows that it has taken the full time to get where we are now, and the concept "life will survive" is basically a dream.

This is the one part with which I cannot agree.

First, if any liquid water is left on earth after such a cataclysmic collision, even sequestered in rocks, complex life forms will also be left. Even without liquid water, spores, viruses, and other non-vegative life forms can survive.

Second, the single-celled organisms of today are as highly evolved as are the multi-cellular organisms of today. Evolution in single-cell organisms did not cease when multi-cellular organisms developed. For example, the earliest organisms or proto-organisms are thought to have had only RNA as genetic material. Some people claim that proteins may have preceded RNA. While some life forms with only RNA or proteins still exist (e.g., viruses and prions, respectively), all single-cell organisms today contain DNA too.

Third, unlike in the beginning, DNA is everywhere today. A large percentage of DNA found in the mid-oceans cannot be identified to any specific organism. Some people put that percentage at >90%.


Thus, even if all vertebrates were to become extinct, enough genetic history remains to reboot their evolution in a much shorter time. There is no guarantee, of course, that vertebrates would ever re-evolve. As you know, past performance does not guarantee future performance -- just ask your stockbroker. There may be no need for vertebrates in that new world, and maybe next time, there will be fewer mistakes.

John