Riddle me this...

If a large meteor or something of the like were to come along and smack the FE at an angle, what do you figure would happen?

There would be a loud sound.

The earth is so big it would have to be very large in order for it to have any kind of noticeable impact on us.  But if such an object does indeed exist somewhere outside the observable part of the universe it could very well spell doomsday for us all.

We've been hit by some pretty large objects in the past, and if we're accelerating upward at around 1-g wouldn't it cause a big wobble (for lack of a better word)?  Possibly causing the water to spill over the "ice wall"

We've been hit by some pretty large objects in the past, and if we're accelerating upward at around 1-g wouldn't it cause a big wobble (for lack of a better word)?  Possibly causing the water to spill over the "ice wall"

That all depends on how thick, wide and massive the Earth is.

We've been hit by some pretty large objects in the past, and if we're accelerating upward at around 1-g wouldn't it cause a big wobble (for lack of a better word)?  Possibly causing the water to spill over the "ice wall"

In fact, by conservation of momentum it would start the Earth turning, or tipping over. Unless there is some kind of self-righting mechanism, the Earth should be doing (admitedly very slow) flips.

The bigger the Earth, the slower the flips, but they should be happening.

Quote from: Paizuri on September 11, 2008, 03:13:58 PM

We've been hit by some pretty large objects in the past, and if we're accelerating upward at around 1-g wouldn't it cause a big wobble (for lack of a better word)?  Possibly causing the water to spill over the "ice wall"

In fact, by conservation of momentum it would start the Earth turning, or tipping over. Unless there is some kind of self-righting mechanism, the Earth should be doing (admitedly very slow) flips.

The bigger the Earth, the slower the flips, but they should be happening.

I almost want to say it would spin out control like a top, but I'm not quite clear enough on the subtleties of FET.

Kinda like spinning a plate on a stick.  If you hit it with a tennis ball, the plate will be knocked off of its axis of spin at the center, causing the mass that we stand on to continue its acceleration.  since we are all being acted on by this acceleration, we will slide off, because, (as any FE'er will tell you, gravity doesn't exist.)

So in some misterious way the DE doesnt affect the meteor?

Might be that the meteor is moving more slowly than the Earth, and it is beyond the sun and moon which obscure it.

Over a long period of time there would be an equal number of collisions on each side of the flat Earth, so as long as the FE is massive enough to ride out each impact long enough for another few to occur the effects would cancel out (assuming nowhere on Earth is a 'favoured' impact site).

I can't believe I'm arguing for FE these days.

It happens to the best of us Matrix. 

OK, I've done some calculations based on the Chicxulub impact. I've assumed the Earth to be a uniform disk 40 000 km across, 1 000 km thick and having a density of 3 000 kg/m. This gives a total mass of 3.77*10²⁴ kg. I've used the statistics here in my calculation.

After this impact, the Earth would be tipping end-over-end with an angular speed of ω = 8.83*10^-13 s^-1.

This may not sound fast, but the Earth would be upside-down after 113 000 years. Put another way, the Earth will have completed 287 full rotations since the Chicxulub impact.

Conclusion: We would have fallen off the Earth ages ago. FET fails.

NB: If you disagree with my estimates for mass of the Earth, then feel free to do your own calculations. Angular velocity scales linearly with Earth's mass, so you can take my result and multiply it by the ratio of your mass to my mass.

Over a long period of time there would be an equal number of collisions on each side of the flat Earth, so as long as the FE is massive enough to ride out each impact long enough for another few to occur the effects would cancel out (assuming nowhere on Earth is a 'favoured' impact site).

I can't believe I'm arguing for FE these days.

It would take impacts of the exact same size and strength (possibly stronger to counter the damage the acceleration had already done to the trajectory of the earth) to keep us on the same path.  I'm just making this up as I go, but that's what FET is all about.

Over a long period of time there would be an equal number of collisions on each side of the flat Earth, so as long as the FE is massive enough to ride out each impact long enough for another few to occur the effects would cancel out (assuming nowhere on Earth is a 'favoured' impact site).

There haven't been enough giant impacts for them all to average out. Suppose that right before the Chicxulub impact, the Earth was still and level (this in itself is a big assumption, as there had been many giant impacts before this).

Then, the meteor hits Earth. Now the Earth is rotating.

We now have perhaps, say, 10 000 years to completely undo the effects of the Chicxulub impact and bring the Earth back to level because after 10 000 years the Earth is tilting at such an angle (16°) that the atmosphere will have fallen off. Seeing as giant impacts happen every few hundred million years, this is immensely unlikely.

Seeing as there is still life on Earth, FET seems to be lacking an explanation.

OK, I've done some calculations based on the Chicxulub impact. I've assumed the Earth to be a uniform disk 40 000 km across, 1 000 km thick and having a density of 3 000 kg/m. This gives a total mass of 3.77*10²⁴ kg. I've used the statistics here in my calculation.

After this impact, the Earth would be tipping end-over-end with an angular speed of ω = 8.83*10^-13 s^-1.

This may not sound fast, but the Earth would be upside-down after 113 000 years. Put another way, the Earth will have completed 287 full rotations since the Chicxulub impact.

Conclusion: We would have fallen off the Earth ages ago. FET fails.

NB: If you disagree with my estimates for mass of the Earth, then feel free to do your own calculations. Angular velocity scales linearly with Earth's mass, so you can take my result and multiply it by the ratio of your mass to my mass.

Did you assume that the impact was on the edge of the ice wall, or did you do the calculation based on the correct longitude of the Chicxulub impact site? Your argument does also assume (as you later point out) that the Earth was not slowly counter-rotating from previous impacts to which this one was playing its part in counter-acting.

Otherwise, your analysis could be considered good contributing evidence for calculating a lower bound on the thickness of the Flat Earth.

Did you assume that the impact was on the edge of the ice wall, or did you do the calculation based on the correct longitude of the Chicxulub impact site? Your argument does also assume (as you later point out) that the Earth was not slowly counter-rotating from previous impacts to which this one was playing its part in counter-acting.

I assumed the impact was at the correct latitude (not longitude, easy misake though) for the Chicxulub impact. It was at ~21°N, which translates to (90-21)/180 = 0.38 of the way from the centre to the edge. I also accounted for the fact that the impact was at a 45° angle.

If the Earth was slowly rotating before the impact, it would be unimaginably unlikely that the impact would be in the right place and be of the right size to exactly counterbalance it's effects. Even if it cancelled out the rotation to 1 part in 10, the Earth would still be upside-down after a bit more than 1 million years, and will have performed nearly 30 full rotations since then. We would have no atmosphere and no water by now.

Otherwise, your analysis could be considered good contributing evidence for calculating a lower bound on the thickness of the Flat Earth.

Unfortunately, I assumed the Earth was a relatively thin disk. In order for the Earth to be massive enough to remain stable it would need to be more like a long cylinder.

I assumed the impact was at the correct latitude (not longitude, easy misake though) for the Chicxulub impact. It was at ~21°N, which translates to (90-21)/180 = 0.38 of the way from the centre to the edge. I also accounted for the fact that the impact was at a 45° angle.

If the Earth was slowly rotating before the impact, it would be unimaginably unlikely that the impact would be in the right place and be of the right size to exactly counterbalance it's effects. Even if it cancelled out the rotation to 1 part in 10, the Earth would still be upside-down after a bit more than 1 million years, and will have performed nearly 30 full rotations since then. We would have no atmosphere and no water by now.

Unfortunately, I assumed the Earth was a relatively thin disk. In order for the Earth to be massive enough to remain stable it would need to be more like a long cylinder.

Yeah sorry, my bad with the lat/long thing... just wanted to check what assumptions had been made. There are many smaller impacts in addition to the big ones.  My hunch would be that the average impact energy over any given area should be uniform (there's no reason to assume a preferred impact site).  Sadly for RE, the kinetics of big impacts do not disprove the FET since all they can do is place a lower bound on the thickness and diameter (strictly the product of thickness and diameter) of the FE.

I agree that it is immeasurably unlikely to exactly counter-balance any previous rotation, but I wanted to caution against making too many unfounded assumptions when trying to make quantitative arguments.

Yeah sorry, my bad with the lat/long thing... just wanted to check what assumptions had been made. There are many smaller impacts in addition to the big ones.  My hunch would be that the average impact energy over any given area should be uniform (there's no reason to assume a preferred impact site).  Sadly for RE, the kinetics of big impacts do not disprove the FET since all they can do is place a lower bound on the thickness and diameter (strictly the product of thickness and diameter) of the FE.

I agree. My assumption here was the size of the Earth, which no FET hasn't been able to agree on.

However, I don't think the statistical "averaging out" argument is valid here. As we've seen (assuming the Earth is within a few orders of magnitude of the size I think it is) that even a single impact is important.

The reason things generally become uniform over time is that individual fluctuations become small compared to the size of the whole.

This is not the case here -- no matter how many impacts came before it, a single impact is still going to have the same effect on the Earth.

I've operated under the assumption (barring any kind of giant turtle involvement) that the earth would need to be shaped like a large top in the FE model.  The acceleration leads me to believe that the largest mass of the earth would be directly in the middle and likely come to a point at the bottom.  Which now that I'm thinking about it, also leads me to believe that over time we would also be losing mass and leaving a trail of debris below us as we travel. 

I agree. My assumption here was the size of the Earth, which no FET hasn't been able to agree on.

However, I don't think the statistical "averaging out" argument is valid here. As we've seen (assuming the Earth is within a few orders of magnitude of the size I think it is) that even a single impact is important.

The reason things generally become uniform over time is that individual fluctuations become small compared to the size of the whole.

This is not the case here -- no matter how many impacts came before it, a single impact is still going to have the same effect on the Earth.

My point was, if there are two smaller impacts in, say, China over the next few years, the rotation rate would not be entirely as fast as that lone impact - equally you could argue there could be more small impacts in the US which would speed up the rotation more.  If I were arguing an FE perspective, I could argue that the anthropic principle allows us to take accurate impact models as evidence for determining a bound on the product of diameter and thickness for the FE.  After all, the Earth still has an atmosphere/layer, does it not, and therefore no previous impact or series of impacts has caused the Earth to flip over.

After all, the Earth still has an atmosphere/layer, does it not, and therefore no previous impact or series of impacts has caused the Earth to flip over.

Or ... The Earth may not be flat, as previously suspected. 

Or ... The Earth may not be flat, as previously suspected. 

It may not be.  This evidence does nothing to sway the argument either way - that was the key to my post.

If I were arguing an FE perspective, I could argue that the anthropic principle allows us to take accurate impact models as evidence for determining a bound on the product of diameter and thickness for the FE.  After all, the Earth still has an atmosphere/layer, does it not, and therefore no previous impact or series of impacts has caused the Earth to flip over.

I mostly agree.

However, you are not quite correct in saying it would put a lower bound on the product of thickness and diameter. It would put a lower bound on Earth's moment of inertia about an axis perpendicular to the axis of the cylinder, i.e. it would put a lower bound on I_x, which is given by



For those who believe the FE is rotating on the z-axis, it would also put an upper bound on the rotation speed, because if it was rotating too fast the edges would fly off. When I have time, I'll pull some statistics on the tensile strength of rock and give you some figures.

I mostly agree.

However, you are not quite correct in saying it would put a lower bound on the product of thickness and diameter. It would put a lower bound on Earth's moment of inertia about an axis perpendicular to the axis of the cylinder, i.e. it would put a lower bound on I_x, which is given by



For those who believe the FE is rotating on the z-axis, it would also put an upper bound on the rotation speed, because if it was rotating too fast the edges would fly off. When I have time, I'll pull some statistics on the tensile strength of rock and give you some figures.

Yes, it's not a direct product but those two variables are all you need to calculate the moment of inertia (if you assume uniform density, which is most likely an invalid assumption). I didn't have the inclination to look up the MOI of a cylinder since I am at work and am doing all this from memory, with an occasional quick forage for images

You take my point though - impact evidence can be used to set limits on these parameters, which combined with the mean inclination of the surface of the Earth will most likely make them extremely large.

You could even argue that it is evidence for the infinite plane model rather than a finite disc model.

Quote from: ghazwozza on September 12, 2008, 06:08:32 AM

I agree. My assumption here was the size of the Earth, which no FET hasn't been able to agree on.

However, I don't think the statistical "averaging out" argument is valid here. As we've seen (assuming the Earth is within a few orders of magnitude of the size I think it is) that even a single impact is important.

The reason things generally become uniform over time is that individual fluctuations become small compared to the size of the whole.

This is not the case here -- no matter how many impacts came before it, a single impact is still going to have the same effect on the Earth.

My point was, if there are two smaller impacts in, say, China over the next few years, the rotation rate would not be entirely as fast as that lone impact - equally you could argue there could be more small impacts in the US which would speed up the rotation more.  If I were arguing an FE perspective, I could argue that the anthropic principle allows us to take accurate impact models as evidence for determining a bound on the product of diameter and thickness for the FE.  After all, the Earth still has an atmosphere/layer, does it not, and therefore no previous impact or series of impacts has caused the Earth to flip over.

So why haven't the impacts on the earth shot the earth off it's orbit? Or started it spinning at odd rates or angles? The Flat earth is massive like the RE. Throw a baseball at bull elephant, how much did it move? There is more of a difference than that in size.

You take my point though - impact evidence can be used to set limits on these parameters, which combined with the mean inclination of the surface of the Earth will most likely make them extremely large.

You could even argue that it is evidence for the infinite plane model rather than a finite disc model.

Extremely large indeed. If we allow gravity into our model (fixing the thickness of the Earth to 5000 - 10,000 km) I'd imagine the Earth would have to be many orders of magnitude larger than the habitable region within the ice wall. Maybe 1000 times larger.

Extremely large indeed. If we allow gravity into our model (fixing the thickness of the Earth to 5000 - 10,000 km) I'd imagine the Earth would have to be many orders of magnitude larger than the habitable region within the ice wall. Maybe 1000 times larger.

Perhaps the infinite plane model is more plausible in that case, since a larger, finite Earth would have had more impacts at latitudes further over the Ice Wall which would impart more angular momentum than impacts near the centre.  That is, of course, assuming that the habitable region is near the centre!

Perhaps the infinite plane model is more plausible in that case, since a larger, finite Earth would have had more impacts at latitudes further over the Ice Wall which would impart more angular momentum than impacts near the centre.  That is, of course, assuming that the habitable region is near the centre!

Not quite. As the Earth gets larger, mean angular momentum imparted by an impact is propotional to R (R = radius of Earth) but moment of inertia is proportional to R². The infinite Earth is the limiting case R -> infinity.

*adopts FE stance*

Statements of fact:

The earth is an infinite plane.

Actually, there seems to be some debate within the FE community on the true size of the FE.  Some FE models say infinite plane, others say finite disc.  Since no FE'er has been to the wall to see if the FE continues beyond it, this question remains unresolved.