(Pi quoting atheist Dave >>
Is David now reduced to ad hominem arguments? DaveB is a Baptist physics professor at a Christian university. David knows this. Last I checked, Baptists are not atheists.
The likelihood is NOT (as Pi said previously) "The physics favors Earth as a target by at least a factor of 5 just due to the surface area..... leave alone the 6 fold gravitational attraction the Earth has compared to the moon." Notice HE got it wrong in his guess (5x) about surface area.
David is correct.... I was wrong about the factor of 5. It should have been a MINIMUM of 13.45. Of course, David was estimating 3.66. So, which of us was closer?
Apparently Dave B had to point his error out to him.
Not quite true. I ASKED DaveB for his input. That's a big difference between IndyDave and I. When I'm getting in over my head, I seek out the advice of those who are true experts in physics.... often several of them. On the other hand, Indy gets his "technical support" only from the one whose work is being questioned. In more than 5 years, he has not once sought outside input.
Pi SHOULD have come clean to admit he too missed it LIKE I DID, but so far he has kept mum about HIS mistake, pointing it out AS IF it were only MINE.
Hey Indy.... what do you think this means?
So, we were both partly right and both partly wrong.
But I was much closer to Dave B in estimating the effect of gravity, and Pi should admit that too. He said it would be "SIX FOLD" more.
That is not correct. In fact, I pointed out that while Earth's gravity was 6x that of the moon, that is too much of an adjustment for gravity and immediately revised that downward.
I said it would have hardly any effect, especially for larger objects. Instead of 6-fold, Dave B said (for a speed of 16.82 km/s) the factor would take it from 13.435x to 19...
Notice, Indy is claiming his estimate (3.66x) was closer than mine.... which was 20x. His 3.66 multiplier, as it turns out is IMPOSSIBLE. Even then, it is off from the minimum by 72%. On the other hand, my 20x estimate was possible and was greater than the minimum by less than 50%. By any standard of measurement, mine was closer than his (impossible) estimate.
Of course, Dave will now claim I'm making a "big deal" of this by my response to his criticism. Hint: If Dave hadn't posted his criticism, I was done when I pointed out we were both "partly right and partly wrong" and went to the 13.5x multiplier. However, his comments created a whole new group of issues that need to be addressed in a fair and open discussion.
Also note that Dave B said that "when the asymptotic inbound speed is enormous for objects coming into the solar system from interstellar space, and the gravity difference between the Earth and Moon becomes irrelevant." I think DB misspoke to say "interstellar" since no one says stuff hits E or M from beyond the Solar Sytem (if you include the Oort Cloud...if it exists...as part of the SS)..... So I think my answer was FAR closer to reality than Pi's was, given that we BOTH messed up by not squaring the radius to get cross-sectional area.
It's pretty safe to say that material arriving at such velocities is not part of Brown's model as it would escape the solar system and never return to Earth under any circumstances. However, it is fair and reasonable to point out that DaveB was talking about only these super high velocities and not anything that approaches what would be expected in Brown's model. In fact, Indy even points out that
DaveB points out that the slower an object is moving relative to the Earth/Moon, the greater gravitational influence they will exert. In fact, DaveB's best estimate is that the Earth will be a 52x larger target due to its greater gravity and the relatively low relative velocities of material launched from Earth. Once again.... when compared to DaveB's estimate of a reasonable value (52x) which of us was closer.... me at 20x or Indy at 3.66x?
By any standard of measurement, my estimate was better than Indy's.
I think it should be noted, and I expect Dave B would agree that for Earth to have a gravity effect on something (rather than the Sun affecting it) coming from far out in the Solar System, the Earth would have to be STATIONARY, rather than moving around a large circular orbit around the Sun. How COULD the Earth move some object nearer to Earth's position in JUNE (when the hit takes place) when the object is far from Earth in DECEMBER and Earth is 186,000,000 miles to the other side of the Sun? I would BET that neither Oard nor Dave B have thought at ALL about that in doing their calcs. Earth's higher gravity than Moon would have negligible effects, especially at 17km/s.
Whether or not the Earth is stationary makes no difference. It looks like Dave ass-u-me(s) a distance object needs to be coming in from the opposite side of the solar system .... hence his comparison between June and December. Apparently he has not considered it is equally likely the object is coming in from the side of Earth opposite the Sun and has not traversed that 186,000,000 miles.
DaveB was pretty specific on the gravitational impact at 17 km/s. He said it would increase the effective target size of the Earth from 13.45x to 19x that of the moon. That's pretty significant.