Elliott C. Back: In Aere Aedificare

I saw this physics interview question pop up on the internet, and thought it might be worth discussing:

A plane is standing on a runway that can move (some sort of band conveyer). The plane moves in one direction, while the conveyer moves in the opposite direction. This conveyer has a control system that tracks the plane speed and tunes the speed of the conveyer to be exactly the same (but in the opposite direction). Can the plane take off?

There are a number of forces here that apply: gravity, the force of the engines / airspeed / lift, and the drag of the wheels against the conveyor / the speed of conveyor. However, the wheels provide essentially a frictionless boundary between plane and ground; unlike car wheels, the wheels of an airplane spin freely in place. So, as the conveyor belt speeds up, the airplane stays in place, but its wheels spin at the same velocity. Furthermore, the lift of the airplane is relative to its airspeed, and its engines push against air. So, the airplane will accelerate forward and take off as normal.

The commenter “Max” has a nice summary as well: “A comparable example in my mind would be a car on a treadmill. If the car is being pulled along by a winch and the wheels are turning freely then the car is going to be pulled at an identical rate whether or not the treadmill is there or not (assuming as you did that the treadmill’s speed is inverse to that of the car).”

Reading about the poor MIT student who was recently arrested at submachine gunpoint on BoingBoing I saw a few comments that interested me enough to write a brief rebuttal. For example, comment #63 by Jacob Davis:

On another note, to everyone saying, “It’s obviously not a bomb, they should have known better!” : that’s really condescending. My mother doesn’t know what a breadboard is. My neighbors don’t. Several of my friends don’t. I’d wager the great majority of the US doesn’t know, for better or worse. Don’t pretend that everyone else knows what you know, especially when you are judging circumstances after being given all the facts at once in hindsight.

See the problem is that security personnel, if expected to guard against bombs and bombers, should be able to positively recognize bombs. Your mother and neighbors are not airport security officers, military police, or Boston police for exactly that reason; they don’t know what bombs look like.

Then there are comments #7 and #8, which feel like the police brutality (they arrested her outside the airport with force) is justified:

Wow, she sure put the “mor[on]” in sophomore! Maybe for her next art project she can run around the airport screaming “I’m Al Qaida! Look at me! I’m Al Qaida!”

I’d have wished the above moron had written “more[on] in sophomore;” it would have bee more funny. That said, there’s nothing wrong with a geeky girl wearing a hoodie with some blinking LEDs. As far as I know (and I think the statistics support me here) no one has ever died or been injured, directly or indirectly, by an LED. And, I fully support her right to voice her political opinions, even in the airport. Unfortunate the climate these days means wearing we will not be silent arabic / english t-shirts will probably get you detained.

I thought MIT students were supposed to be a bit more intelligent than the rest of us. Walking into an airport with an electronic device strapped to her chest ….. a very stupid action. She is lucky to just be in a cell, but I have a feeling a lot of people (including her) will never understand why, this time, the Boston Police are in the right.

This one is begging for me point out that 99.99998% of people walk around airports with iPods tucked around their chest or body somewhere… and I’m not even going to start counting people with pacemakers, who actually have an electronic device embedded in their chests! An electronic device isn’t a bomb, and if you think airport security can prevent terrorism, you’re wrong.

Finally, on a lighter note, Rob Cockerham’s comment #27 takes the cake, and eats it too:

I can’t believe NBC is promoting Bionic Woman like this. What a terrible idea.

I got the following message in my inbox from the kind folks at Expedia:

We have received an unconfirmed response on your reservation. This means that the airline has not acknowledged the flight and/or fare that you originally purchased. We have attempted to restore the original flights and have been unsuccessful. Without confirmation from the airline, we are unable to ticket this reservation.

Please call us at 1-800-EXPEDIA as soon as possible and refer to your itinerary number so that we can work with you to make alternate arrangements. Unless you call within 72 hours of receiving this e-mail, your reservation will automatically cancel.

If you have further questions, feel free to reply to this e-mail or contact Expedia customer services at 1-800-397-3342 and reference case ID xxxxxx. You can also visit the Expedia.com “Customer Support” page () for more customer service information.

I always thought when I bought plane tickets from Expedia that somewhere tickets, real tickets, would be issued to me, a seat reserved and noted, etc. Unfortunately, everything seems to operate in batch-mode, where airlines give blocks of seats to online vendors who match them together in strange ways that allow the possibility that the tickets they’ve resold may not represent spots on a plane:

I’m not the only one complaining about this practice. See:

• Expedia dot SCAM?
• Rate IT All Expedia
• Mouth Shut on Expedia
• Victims of Expedia

My bank account also looks quite cute, waiting for $3000 in refunds:

This isn’t to blame Expedia though. To their benefit, they are refunding the total amount over those two cancelled flights. Also, their customer service reps on the phone were extremely apologetic and kind. It’s more a flaw in the system of batch-time ticket booking. With a real-time synchronized process, this sort of thing could not happen.

Only two people are dead in a small fixed-wing plane crash which occurred earlier this morning on the Upper East Side. Yankees player Cory Lidle, 34, died while piloting with his flight instructor. According to the media, no one in the Belaire apartment building at 542 East 72nd at York Street was killed.

Breaking News: Helicopter Crash

Still, according the Chicago Tribune, terrorism was not ruled out at first:

Nonetheless, as a precaution North American Aerospace Defense Command (NORAD) scrambled fighter jets over several U.S. and Canadian cities minutes after the plane crashed into the midsection of the 50-story building at 2:45 p.m. Eyewitnesses said the plane smashed into the north face of the red brick building, producing a fireball that engulfed several apartments around the 30th floor and dropped debris into the street.

For those morbid souls, the Guardian Unlimited has a chronology of memorable planes crashing into NY buildings, starting with a B-52 lost in the fog in WWII.

Farecast now runs to over 55 different cities, and is no longer in private beta. They’ve also added a literal host of new features, including the following liberal trip planner:

You can input a number of cities, and within those five destination cities, your departure city, and a 30-day window, Farecast will find the cheapest place to visit. I can see this being useful for vacationing on the cheap!