Science Sunday: falling through the earth (and Giveaways!)

By: Meradeth Houston on 9:47 AM

Hi everyone! Welcome back to Science Sunday. Just as a note, I have TWO giveaways going on now: one for a copy of A PERFECT DAY (just leave a comment here), and another for SOCIAL MEDIA JUST FOR WRITERS (tons of ways to gain entries here). Please stop by the links to enter :)

Okay, so today's topic comes from the movie Total Recall, the remake, that hubby and I watched this last week. I actually kind of enjoyed the movie, if only because this version didn't involve Arnold (his name must be said with a seriously nasal accent :). Okay, so there's all kinds of hokey science in this, although the implantation of memories is something that I doubt is *all* that far off.

There was one aspect that had hubby chuckling, and that was a feature of the movie called The Fall. This was basically a means of traveling to the other side of the globe through traveling through the (near) center of the earth. This was basically the avoid traveling through contaminated areas (even though apparently they have the ability to fly through them anyhow, as demonstrated later in the film...). So, yeah, this was amusing to hubby, as during the middle of the trip, there was a moment of weightlessness as gravity was "reversed" and the passengers started traveling to the opposite side of the planet. This moment plays a part in the plot of the movie even!

This doesn't work this way. I mean, okay, yeah, there's lot of problems with the movie, but I thought I'd hit on this one today because it's so flawed when it comes to the rules of gravity that it's painful. So what would happen if there were a big hole through the center of the earth? (Assuming, of course, that it were possible to dig such a hole, rather than just, ya know, clean up the contamination...)

The ride in Vegas on top of the Space Needle.
I watched this go up & down while in Vegas this week
and seriously never want to try it!

If someone where to drop through this hole, what would happen is that they would experience free-fall, and the weightlessness that is associated with it, the entire time. Not just at the center of the earth. This is similar to what you might feel if you happened to be on one of those free-fall rides at an amusement park (one of the rides you'll never find me on, thankyouverymuch!). Ever hold out a penny in your hand while you fall? It'll float. Same thing would happen while falling through the earth.

It would be free-fall not just until one reached the center of the earth, too, but until you reached the opposite side of the earth. There, something would have to catch you, or you'd go shooting off into the air like the earth was spitting you up :) If nothing caught you, well, then you'd eventually be subject to gravity again, and then fall back to the earth again (and right back through the hole to the other side...). Actually, you could end up falling through the earth, from one side to the other, over and over again.

Crazy, right?

Anyhow, that's your physics lesson for the day. Anyone out there feeling up to attempting to tell me how long it would take to go from one end of the earth to the other? (Assuming the diameter of the earth is 12,756.2 kilometers).

A little hint: Force due to Gravity: F=GmM/r^2

Just for laughs!