GASP! Bad Science on the History Channel!

tags: , , , , ,

This streaming video is a short presentation of a theoretical physics exercise to demonstrate Newtonian physics and the Shell Theorem [1:58].

Okayyy .. what's wrong with the er, "science" in this video?

More like this

tags: humor, class warfare, streaming video This is a bit of British-style humor to get you started on your work day, starring David Letterman. [1:58].
tags: parrots, politics, humor, behavior, streaming video This streaming video is a CNN report about a parrot that .. er, parrots .. Barack Obama's slogan, "Yes we can". But it also includes some other parrots .. the one that says "Whateverrrr" is my favorite [2:31].
tags: the world's most deadly animal, streaming video Do you know what the world's most deadly animal (for humans) is? The grizzly bear? Or wolves? Or maybe the humble hippopotamus? There is a streaming video below the fold that answers this question. [1:58] The females of most mosquito species…
This parody of The Lord of the Rings is from the MTV Movie Awards. It depicts how The Fellowship was set up in the first film. It is absolutely funny, but it is a bit er .. bawdy .. or, er .. suggestive .. as well (not that I disapprove; just warning you). . tags: streaming video, satire, parody,…

They assume a perfectly frictionless tunnel, and that gravity is the only force acting on the traveller. That's not the only difficulty in realizing such a scheme, though...the heat and pressure deep inside the earth makes tunnel construction, shall we say, problematic?


The video says that it would take 42 minutes "regardless of the path you take".

This is obviously garbage. (To see why without math, consider the path that goes from LA to Tokyo... via another city.)

(In fact, it has to be a straight line path. (Assuming the various idealised conditions, of course.)

They didn't mention that the Earth would have to be perfectly spherical and uniform density. Also, there's coriolis forces if the tunnel isn't directly on the north and south pole.

It's just the History Channel, cut them some slack :P

The answer is _always_ 42.

Surely I can't be the _only_ reader of Douglas Adams around here who is profoundly DISTURBED by this?

By Emory Kimbrough (not verified) on 19 Jun 2008 #permalink

Disturbed? Why, it makes perfect sense. How else would the Earth unit fulfil its proper function, simian?

If the cities are not antipodal, the time can always be made less than 42 minutes using a curved path. What curve gives the shortest time? This is the famous brachistochrone problem, which led to the development of the calculus of variations in the eighteenth century. If the cities are close enough that the curvature of the earth can be neglected, the optimal curve is a cycloid.

GrrlScientist, what bit most annoys you on this. Without doing the math myself, it seems like a perfectly typical 'ignore all the complicating realworld factors' toy problem. Yeah, they definitely should include the 'simplified case' caveat... but constructing a straight tunnel thousands of miles long through a flowing mantle (much less the core) already puts it out of the realm of 'realistic'.

Lots of mistakes, all down to the use of an oversimplified model - but this is an exercise in mathematics, not engineering, so I consider them acceptable simplifications.

Except for one - the ommision of rotational considerations. Chris pointed that out - any elevator would have a bumpy ride that involves a lot of crashing into the tunnel wall.

Conveniently for any occupents, the effect would actually provide them with some 'gravity' effect. I have no idea how much, but even a small amount of apparent gravity would make the trip more comfortable.