07 November 2008

Friday Collection

First, WHAT is this? There's a metal detector forum, over at Treasurenet.com, where metal detector enthusiasts can post photos of things they've found and can't identify, and one of those unidentifiable things is seen in the photo here. If you know what it is, head on over to the forum (there are more pictures there, too), and give them a shout out.

Second, my brother Carl didn't believe the video of a plane landing with one wing to be a true, un-messed-with, actual video of a plane landing with one wing, and Snopes doesn't either. This will be a sad piece of news for the ex-fighter pilot who sent me the clip. He loves that video.

Third, a friend has pointed me to a new ancient religion, Tarvuism, "the world's fastest growing religion," which holds octopuses as sacred (cause the deity was saved by one), and fosters the belief that we should all be nice. I'm just passing this along. That the whole octopus-deity conjunction sorta reminds me of Cthulu is my problem completely, and should in no way be connected to Tarvuism.

Fourth, the president-elect has a website -- change.gov -- where we can go to find out what's happening, see what we can get involved in, give our opinions, comment on the agenda.


CarlBrannen said...

The reason that the model airplane could pull off the "flying on one wing" stunt is because of its very large ratio of thrust to weight.

What is going on here is that you have to replace the wings, as a lifting body, with the fuselage. I really don't think that this is possible with a full scale aircraft.

Aircraft slow down before landing by putting out their flaps and increasing their angle of attack. Putting out your flaps increases your wing surface area. Losing a wing and switching to the fuselage as a lifting body severely decreases your lifting area and therefore greatly increases your landing speed. The result is that you hit the ground very hard. This would damage the aircraft more than was shown.

A model airplane is built very lightly so its landing is much easier. The model airplane footage shows that the airplane was built so lightly that a wing fell off. This doesn't happen very often to real aircraft. In addition, strengths do not scale properly with size. Small objects are stronger relatively speaking, than big objects. You can set your pocket watch upside down on concrete without damaging it. If you do the same thing with your automobile (which is designed for a concrete world) you will total it.

And thanks for the mystery link.

Pandora said...

Yes, this all makes sense to me. I like especially the part about small and strength; this was an explanation I heard once in the long ago as to why giant lobsters the size of Godzilla can't exist.

CarlBrannen said...

Engineers have drilled into them that large objects are inherently weak. Sometimes when I talk to non engineers I realize that a failure to understand this is behind a lot of weird beliefs.

People's understanding of concrete and steel is that of unyielding objects of infinite strength. But if you make something big enough from it, it will be very delicate. Big enough, and it will fall apart easily (like the World Trade Center buildings), largely as a consequence of its own weight.

This is because you can break a beam by cutting through any cross section area (square of length), but the weight of the beam goes up as the volume (cube of length).

So delicacy is proportional to length (a cube over a square). The human intuition is that strength is proportional to length. Bigger things are stronger.

CarlBrannen said...

The recent physics excitement has started a fight over the question of whether or not some of the data was leaked to a theorist or two, who published papers that predicted the effect a couple days before the paper came out.

Part of the reason this is funny is that the experimental paper was signed by something like 100 people. Keeping something like that secret would be uttery impossible even in a totalitarian country. So if you want to read the accusations and claims of innocence, there you are.