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Comment Re:Several reasons... (Score 1) 660

True story (from the U.S.): My mom's husband once went through the aisle at a Target (cheap department store) and bought a couple bags worth of stuff with a credit card. After the cashier rang him up, he waited in the aisle, looking puzzled, until the cashier asked him what was the matter. He said, "You never gave me my card back."

She: "Oh yes, I did."

He: "No you didn't. It's in your front breast pocket."

And without a word, she took it out and handed it back to him. Presumably her thought was that because he was elderly, he would assume he'd made a mistake. He wouldn't have time to double-check, though, until he made it back to his car with his hands full of shopping bags. That would give her more than enough time to copy down all his card information, and when he came back to say his card really was missing, she could pretend she had found it on the floor.

Comment Re:Cash never fails. (Score 1) 660

I had a card with no raised numbers on it. I think they did it to make the card look cool/important. (This is a thing in the U.S. lately -- is not it true elsewhere?) They must have rethunk it, though, because when the card eventually expired, the replacement that came in the mail had raised numbers again.

Comment Rahm can go fuck himself. (Score 1) 399

At a time when the city and state are in dire financial straits, this asshole decides to pull a stunt that's going to waste millions in litigation before the court gets around to telling him that social engineering is not his fucking job.

If a kid earns a diploma, you fucking give it to him. Their plans after they get it are none of Rahm's goddamned business.

-jcr

Comment Re:I'm no math jeanyus, but... (Score 4, Insightful) 89

Actually no, it's not a straightforward calculation. That's why they want to conduct the test.

It's not a simple collision like we learned about in physics class, with the change in the asteroid's momentum coming entirely from the impactor. The impactor will hit at extremely high velocity (by earth standards), meaning that it will carry a lot of kinetic energy (one half mass times velocity squared) in a small volume. This kinetic energy will vaporize and blow off part of the asteroid, which because of the asteroid's small size, will completely escape.

The mass of the ejecta will greatly exceed the mass of the impactor, so even though it may move much more slowly than the impactor it will carry away considerably more momentum (mass times velocity). The momentum of this ejecta will have most of the effect on the asteroid's trajectory.

But it's unknown exactly how much momentum will be carried away by the ejecta as this depends on the makeup of the asteroid, its density, porosity, how quickly the impactor stops and releases its energy, etc. So that's why they want to try it.

A similar effect was at play in the JFK assassination that helped cause the counter-intuitive "back and to the right" motion of his head that had so many people incorrectly thinking there was a second shooter.

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