NOVA ScienceNOW Season 3 #301 1x53

DARK MATTER
Host Neil deGrasse Tyson reports from a half mile underground in an abandoned mine, where scientists are using special detectors to look for evidence of a ghostly substance that they believe makes up most of the matter of the universe: a hypothetical entity called dark matter. No one has yet seen dark matter, but theorists have good reasons to believe that it exists and that galaxies, stars, and planets would never have formed without the gravitational attraction that dark matter exerts on ordinary matter. In fact, this is how they know that dark matter must be out there: from the otherwise inexplicable effects that this unseen stuff has on galaxies and galaxy clusters. Since dark matter can supposedly pass through solid rock, a mine is a good place to set up experiments to detect it, well-screened from the ordinary cosmic radiation that pervades the universe. In the “Cosmic Perspective” that closes the program, Tyson points out that another unseen component of the cosmos — dark energy — is even more pervasive and more mysterious, meaning that the part of the universe we know about with certainty is very limited indeed.

ALZHEIMER’S/MEMORY MICE
The brain is an astonishingly complex organ that continues to surprise scientists with its hidden capabilities. NOVA scienceNOW reports on recent work that shows that mice — and maybe humans — could have previously unsuspected resources of memory. Researchers have found that mice with induced memory loss are able to retrieve memories by either being put into an enriched environment or by being given a drug that promotes beneficial gene activity in their brains. Such new insights may lead to a better understanding of dementia and other memory-impairment disorders. While scientists are still far away from extending this work to humans, it’s striking that many Alzheimer’s sufferers temporarily improve in an activity-rich environment, providing a tantalizing clue to further research on the possible mechanisms at work in the brain.

HANY FARID
Is seeing believing? In this age of easy photo manipulation, sometimes you have to call in a digital detective to be sure. Enter Hany Farid, professor of computer science at Dartmouth College. Farid got the idea for software that detects doctored photos from a celebrity shot that showed Angelina Jolie and Brad Pitt strolling on the beach early in their relationship. On closer inspection, Farid realized the lighting was different on the two figures and so “Brangelina” couldn’t have been together: at least not on that occasion. He went on to develop a program that can unmask photo tampering by analyzing light sources and other subtle features in an image: a service that turns out to be in high demand, not least during political campaigns when suspiciously incriminating photos often turn up. While Farid has become a respected maverick of mathematics, with awards from the National Science Foundation, the Howard Hughes Medical Institute, and the Sloan Foundation, he thinks of himself as an “accidental scientist”. An indifferent student in college, he didn’t find his calling until he took his mother’s advice to try a course in computer science. Moral: “Always listen to your mother”, he says.

WISDOM OF THE CROWD
Beware of fallacies in statistical reasoning! That’s the moral of this comical song about the famed British scientist Sir Francis Galton, who lived from 1822 to 1911. A proud aristocrat, he thought he was proving the ignorance of the masses in his observation about a country-fair competition in which entrants were asked to guess the exact weight of an ox. The correct answer was 1,198 pounds, and, understandably, none of the 800 contestants got it exactly. “See!” said Sir Francis. “Decisions should be left to higher classes” — or sentiments to that effect. However, Sir Francis failed to realize that graphing all the guesses and determining their median produces the right answer, and shows the “wisdom of the crowd”.