questioner121 wrote:

Weaver wrote:
Are you claiming that the Earth's orbit has existed in it's current form for billions of years? What is the basis of this claim, if so?

Lovely strawman you've erected here ... be a shame if something happened to it.

Life is billions of years old so I'm assuming the conditions were pretty similar.

Actually life evolved on a verry different planet then the one we have now. For an example look up snowball earth. A combination of the earth's orbital variation the suns weak output in deep time and a lack of greenhouse gasses in the atmosphere basically froze all of the earth from pole to pole with maybe part of the equator free of ice.

hackenslash wrote:You just wouln't believe how mind-bogglingly huge...

lucek wrote:

But I think the answer to the question you are trying to ask is, Space is big.

Looking at the impact craters on the moon it seems like there have been numerous collisions all with big impacts. The impact on Jupiter by the comet shoemaker was huge. The coronal mass ejections if the sun can be seen to huge even relative to the size of the sun.

If there is molten iron flowing around the earth the earth has to be providing some resistance to in order for the earth to keep on "spinning" as has been claimed.

questioner121 wrote:

lucek wrote:

But I think the answer to the question you are trying to ask is, Space is big.

Looking at the impact craters on the moon it seems like there have been numerous collisions all with big impacts. The impact on Jupiter by the comet shoemaker was huge. The coronal mass ejections if the sun can be seen to huge even relative to the size of the sun.

If there is molten iron flowing around the earth the earth has to be providing some resistance to in order for the earth to keep on "spinning" as has been claimed.

Impact rates vary over time.

I don't understand the point yu make about the core.

questioner121 wrote:

lucek wrote:

But I think the answer to the question you are trying to ask is, Space is big.

Looking at the impact craters on the moon it seems like there have been numerous collisions all with big impacts. The impact on Jupiter by the comet shoemaker was huge. The coronal mass ejections if the sun can be seen to huge even relative to the size of the sun.

OK now you are just ignoring my posts,

Again impacts are due to the fact that perturbations due to larger objects causes 2 orbits to cross close enough. For earth this is a minor effect changing earths relative position in the solar system minutely over billions of years.

But this is again kinda strange. I already pointed out that the perturbation due to the other planets results in ~1% chance that the earth will collide with one of our neighbors. But again this is a long process. The thing is we're talking a process that'll take another ~3.3 billion years.

questioner121 wrote:If there is molten iron flowing around the earth the earth has to be providing some resistance to in order for the earth to keep on "spinning" as has been claimed.

The core goes faster then the surrounding mantle. The core is breaking not the mantle.

You are making one mistake in you're phrasing. Nothing has to keep it spinning something has to break it like the moon does.

lucek wrote:

questioner121 wrote:

lucek wrote:

But I think the answer to the question you are trying to ask is, Space is big.

Looking at the impact craters on the moon it seems like there have been numerous collisions all with big impacts. The impact on Jupiter by the comet shoemaker was huge. The coronal mass ejections if the sun can be seen to huge even relative to the size of the sun.

OK now you are just ignoring my posts,

Again impacts are due to the fact that perturbations due to larger objects causes 2 orbits to cross close enough. For earth this is a minor effect changing earths relative position in the solar system minutely over billions of years.

But this is again kinda strange. I already pointed out that the perturbation due to the other planets results in ~1% chance that the earth will collide with one of our neighbors. But again this is a long process. The thing is we're talking a process that'll take another ~3.3 billion years.

questioner121 wrote:If there is molten iron flowing around the earth the earth has to be providing some resistance to in order for the earth to keep on "spinning" as has been claimed.

The core goes faster then the surrounding mantle. The core is breaking not the mantle.

You are making one mistake in you're phrasing. Nothing has to keep it spinning something has to break it like the moon does.

So the huge impact craters seen on the moon should have no effect on it's orbit?

questioner121 wrote:
So the huge impact craters seen on the moon should have no effect on it's orbit?

The effect is of the same order as that of a bug hitting your windscreen whilst doing 80mph down the motorway.

campermon wrote:

questioner121 wrote:
So the huge impact craters seen on the moon should have no effect on it's orbit?

The effect is of the same order as that of a bug hitting your windscreen whilst doing 80mph down the motorway.

I'm sure there's something to be said about things going through minds that seems doubly appropriaie in this particular thread...

Edits: feckin' smartphone.

campermon wrote:

questioner121 wrote:
So the huge impact craters seen on the moon should have no effect on it's orbit?

The effect is of the same order as that of a bug hitting your windscreen whilst doing 80mph down the motorway.

In deed, Lets look at "huge" impact creator and the impactor that made them.

Chicxulub crater is 180 kilometers in diameter and 20 in depth. The asteroid that made it was 10 km. The largest creators on the moon from after it's formation (impacts from other moonlets may have created some of what we think of as maria) are about twice that size. So yeah compared to the size of earth and the moon. . .

questioner121 wrote:
So the huge impact craters seen on the moon should have no effect on it's orbit?

They do but the effect is small. Are you familiar with Newton's second law?. Think about the mass of the Moon compared to the mass of the impactors.

If the earth is spinning so fast that it completely rotates once each day, why don't we go flying off into space from the centrifugal force? Why aren't we subject to horrific wind all the time?

Don't go talking to me about this thing "gravity." As far as I can tell that is some magical force Newton invented to explain all this but what it seems to consist of is the earth reaching out with unseen hands and holding me in place.

Frank Merton wrote:If the earth is spinning so fast that it completely rotates once each day, why don't we go flying off into space from the centrifugal force? Why aren't we subject to horrific wind all the time?

Don't go talking to me about this thing "gravity." As far as I can tell that is some magical force Newton invented to explain all this but what it seems to consist of is the earth reaching out with unseen hands and holding me in place.

Don't be silly. Invisible pixies are holding us in place.

klazmon wrote:

Frank Merton wrote:If the earth is spinning so fast that it completely rotates once each day, why don't we go flying off into space from the centrifugal force? Why aren't we subject to horrific wind all the time?

Don't go talking to me about this thing "gravity." As far as I can tell that is some magical force Newton invented to explain all this but what it seems to consist of is the earth reaching out with unseen hands and holding me in place.

Don't be silly. Invisible pixies are holding us in place.

Of course. I intended to get to that but had to build a base first.

campermon wrote:The effect is of the same order as that of a bug hitting your windscreen whilst doing 80mph down the motorway.

A while ago, I calculated what would happen to the orbit of the Earth if an asteroid the size of Mars would hit us. For a typical impact velocity of 16 km/s, the orbital eccentricity of the Earth would change to about 0.08. So even something as big as Mars would hardly have an impact on our orbit.

Here's the calculation:
http://physics.stackexchange.com/questions/68306/mars-just-collided-with-earth-a-question-of-eccentricity

That would be a great addition to the equations thread if we can get LaTeX working again...

If Mars or the equivalent were to collide with the earth, just think of the ecological damage!

It would certainly leave a nasty mark.

questioner121 wrote:

2. Shouldn't a plane which flies in an opposite direction to the spin of the Earth move faster relative to the land mass below it?

NASA actually launches space shuttles to the east to take advantage of the rotation of the earth .