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Five Reasons We Think Dark Matter Exists

"Modifying the theory of gravity is no easy game. We have fantastically precise measurements of gravity’s influence on objects throughout our solar system which fit precisely within the current understanding of gravity from General Relativity (a fact that underpins the precision of modern GPS). If you want to change the theory of gravity, you have to preserve its behavior as we’ve already measured it in the solar system."

When you hear about dark matter, you very likely put it up there with string theory in the pantheon of “well, that’s a nice idea, now call me when you find it” style of scientific ideas. After all, direct detection of dark matter has proved elusive, despite many arduous experiments designed specifically to find it. Yet we continue to look, convinced that it exists. Why? Amanda Yoho has the top five reasons!

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“In 2002, having spent more than three years in one residence for the first time in my life, I got called for jury duty. I show up on time, ready to serve. When we get to the voir dire, the lawyer says to me, “I see you’re an astrophysicist. What’s that?” I answer, “Astrophysics is the laws of physics, applied to the universe—the Big Bang, black holes, that sort of thing.” Then he asks, “What do you teach at Princeton?” and I say, “I teach a class on the evaluation of evidence and the relative unreliability of eyewitness testimony.” Five minutes later, I’m on the street.
 A few years later, jury duty again. The judge states that the defendant is charged with possession of 1,700 milligrams of cocaine. It was found on his body, he was arrested, and he is now on trial. This time, after the Q&A is over, the judge asks us whether there are any questions we’d like to ask the court, and I say, “Yes, Your Honor. Why did you say he was in possession of 1,700 milligrams of cocaine? That equals 1.7 grams. The ‘thousand’ cancels with the ‘milli-’ and you get 1.7 grams, which is less than the weight of a dime.” Again I’m out on the street.”

“In 2002, having spent more than three years in one residence for the first time in my life, I got called for jury duty. I show up on time, ready to serve. When we get to the voir dire, the lawyer says to me, “I see you’re an astrophysicist. What’s that?” I answer, “Astrophysics is the laws of physics, applied to the universe—the Big Bang, black holes, that sort of thing.” Then he asks, “What do you teach at Princeton?” and I say, “I teach a class on the evaluation of evidence and the relative unreliability of eyewitness testimony.” Five minutes later, I’m on the street.


A few years later, jury duty again. The judge states that the defendant is charged with possession of 1,700 milligrams of cocaine. It was found on his body, he was arrested, and he is now on trial. This time, after the Q&A is over, the judge asks us whether there are any questions we’d like to ask the court, and I say, “Yes, Your Honor. Why did you say he was in possession of 1,700 milligrams of cocaine? That equals 1.7 grams. The ‘thousand’ cancels with the ‘milli-’ and you get 1.7 grams, which is less than the weight of a dime.” Again I’m out on the street.”