What is a " Gerstenkorn event"?

Something to do with the Earth-Moon (and I assume other orbiting bodies) system. Wikipedia has nuthin’ and a Google search didn’t turn up anything explanatory.

This Google Books result explains it pretty well, I think. Gerstenkorn theorized that the Moon may have a captured body whose trajectory was such that it put it initially in a retrograde (opposite the way it goes now) orbit around the Earth. This retrograde orbit would have cause it to get closer to the Earth as tidal friction acted on the system. At some point, as the orbit’s inclination (tilt) passed 90 degrees, the orbit would become prograde and tidal friction would cause the Moon to drift away again, as it still does today. The hypothetical Event is when this orbital changed was thought to have occurred, and would have coincided with the Moon’s closest approach to Earth under his theory.

It has been since discredited.

What was the significance of the event? Would anything have changed on Earth?

I bet if you raised your arms up over your head and yelled “Whoo!” it would have been a lot more fun.

Also true with getting a prostate exam.*

*(Note: Not true.)

Well…imagine crust-melting friction-generated heat combined with thousand-foot tides and earthquakes that make the strongest ones we get today look like mere hiccups. This would have lasted many hundreds (if not thousands) of years until the Moon once again receded far enough to diminish the tidal effects. Fortunately, at the time, life hadn’t yet evolved here because it would have been thoroughly unpleasant for any living things.

According to the G-book you referenced, Horst conjectured that the G.E. happend some 1-2 billion years years ago, and life might have existed at that point, but since his idea has been discredited (e.g. we now believe it never happened) that’s a bit of a moot point.

To hijack my own thread: IIUC, current theory is that the Moon was created when a large (Mars-sized) object struck the then new Earth and splattered a large (Moon-sized, duh) chunk of material into orbit which then became the Moon. Is that correct?

And to get back to Horst & his Event. I understand (I think) why tides cause the orbiting object to move in, but what causes the inclination of the orbit to increase? That seems counter-intuitive (“there’s nothing for it to push on” :)).

Basically correct, yes. We don’t know precisely what happened, of course, but it’s believed the object struck Earth a glancing blow, shattering itself into a bajillion (that’s the precise number ;)) pieces and completely melting the young Earth. All the crap spewed forth from this, the largest impact in our planet’s history, eventually coalesced to form the Moon we know and love today.

A retrograde Moon will slowly approach the Earth because the tidal bulge it pulls up beneath it will be dragged in the direction of the planet’s rotation and lag behind the Moon, pulling on it due to its intrinsic gravity and slowing it in its orbit. A slower orbiting velocity means a lower altitude orbit. A prograde Moon, on the other hand, will have a bulge which leads it in its orbit, pulling it around faster. A faster orbital velocity, naturally, results in a higher altitude orbit.

As for the orbital inclination shift, this is a natural consequence of the incoming object not approaching exactly along a diameter. If it passes slightly above or slightly below the exact centerline, it will have an orbit whose inclination will rotate slowly around. I’m not sure what forces were theorized to have acted to stop (or at least dramatically slow) this inclination rotation, but I’d imagine it’s similar to the mechanism which acts to cause the Moon to drift away; that is, feedback via gravitation from the tidal bulge.