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but a part of me wondered if the geometry of the earth and the typical inclination of solar system objects might favor some locations over others (or the concept that some parts of the planet have a slightly stronger gravitational pull than other parts.....but I suspect this is insignificant when compared to drawing in something from millions of miles away?)
Yes, the variations in Earth's gravitational field are far too small to cause any noticeable effect on meteor strikes. Meteor paths aren't affected as much by Earth's gravity as you might think, anyway, because they move so fast. Most meteors that hit Earth were not so much "pulled in", but rather the Earth simply got in their way. We can actually make that claim rigorous. We can calculate the "effective cross section" of the Earth, meaning the area of the target Earth presents for a potential impactor when we factor in its gravity (so it must be larger than the actual Earth itself.) To do that, we find the "impact parameter" (the minimum approach distance an asteroid would have if we ignored Earth's gravity) such that when we do factor in the gravity, it comes closer and ends up just grazing Earth's surface. Then the Earth's effective cross section is pi times the square of the impact parameter (just like finding the area of a circle whose radius is the impact parameter.)This page on spaceacademy
goes through the calculation and has a nice table summarizing these values for a given range of asteroid speeds (both the "far-away" speed, and the speed at impact). Intuitively, the greater the speed, the smaller the Earth's effective cross section is, because at higher speeds there is less time for Earth's gravity to have an effect on the path.Now let's check at what speed the effective cross section of the Earth is doubled. If the area is doubled, that means half the strikes happen because they would have missed but Earth's gravity pulled them in, and the other half would have hit anyway. According to the table, this happens when the "faraway" speed is between 10 and 15 km/s, or an impact speed of between 15 and 19 km/s. As it turns out, the area is exactly doubled when the "faraway" speed equal to Earth's escape speed, 11.18km/s. That gives an impact speed of 15.8km/s. But wait. The average impact speed of asteroids on the Earth is faster -- about 17km/s. And comets strike even faster still. That means for the average impact, Earth's effective cross section was less than double its actual cross section. Therefore there was a greater than 50% chance the impact would have happened even without Earth's gravity playing any role. Earth was simply in the way.
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(sort of like how some people are prone to getting hit by lightning because of their iron content.)
Where did you hear that? I am quite sure it is not true. At the very least, I have never seen any reputable study connecting lightning strike risk to iron in the body. And it would be almost impossible to determine from data, since there are so many other factors that matter more.
The amount of iron in a person is very small (a few thousandths of a percent), so I doubt that would play any significant role in our conductivity. But perhaps the more important lesson is that iron does not attract lightning, anyway. Lightning strikes are determined by what "sticks out" from the surrounding environment. (Something which is well described and visualized in this XKCD "What if?" comic
.) This is also a very general feature of electric arcs: they tend to form at sharp points on a conductor, because sharp points are where electric field is maximized. That's the basis of how lightning rods work, and also why we try to make conductors as smooth as possible when we want to prevent arcs from forming.
So don't worry about iron in your body when it comes to lightning. Worry instead about being in a vulnerable situation when there is lightning nearby. Basically, don't be the tallest thing around, or close to the tallest thing around.
It was from another science forum but I see the person was mistaken. I looked for research on body metal content and there is no research connecting it. As a matter of fact, there isn't even a connection between external metal content or proximity to metal objects and more of a likelihood of lightning strikes. It looks like lightning is most likely to seek tall pointy objects (of any composition, not just metal), which is a good reason not to shelter under a tree! There are certain occupations which may make lightning strikes more likely, just because of the amount of time spent outdoors and proximity to tall pointy objects like trees- Roy Sullivan is a case in point- he was struck by lightning 7 times.https://en.wikipedia.org/wiki/Roy_Sullivan
He met with a really sad ending
Did you read what happened to him?
Roy Cleveland Sullivan (February 7, 1912 – September 28, 1983) was a United States park ranger in Shenandoah National Park in Virginia. Between 1942 and 1977, Sullivan was hit by lightning on seven occasions and survived all of them. For this reason, he gained the nicknames "Human Lightning Conductor" and "Human Lightning Rod". Sullivan is recognized by Guinness World Records as the person struck by lightning more recorded times than any other human being.
1 Personal life
2 Seven strikes
4 See also
6 External links
Roy was born in Greene County, Virginia, on February 7, 1912. He started working as a ranger in Shenandoah National Park in 1936. Sullivan was described as a brawny man with a broad, rugged face, who resembled the actor Gene Hackman. He was avoided by people later in life because of their fear of being hit by lightning, and this saddened him. He once recalled "For instance, I was walking with the Chief Ranger one day when lightning struck way off (in the distance). The Chief said, 'I'll see you later.'"
On the morning of September 28, 1983, Sullivan died at the age of 71 from a self-inflicted gunshot wound to the head. Two of his ranger hats are on display at two Guinness World Exhibit Halls in New York City and South Carolina.
About the escape velocity research, I find that absolutely fascinating! So the asteroid faraway speed is just slightly more than earth's escape speed, but it's enough to show that impacts are more due to the earth getting in the way, which makes sense, because at that speed, the earth's gravity doesn't have enough time to influence the asteroid's trajectory. And I think you also showed before that the moon doesn't have much of an influence either in "deflecting" them away from us, except for whatever protection it can offer by "getting in the way." So it would only give us a marginal protection and wouldn't have influenced the start of life on Earth much in that way but moreso with its impact on the tides and allowing life to transition over to land.