Video Notes from selected NOVA ScienceNow Segments

Dark Matter (13:50) - June 25, 2008

o    explains why physicists think dark matter exists - stars within galaxies and galaxies within galaxy clusters move faster than expected and, rather than flying apart, they stay in orbit together. However, there is not enough visible matter present to account for the gravitational pull required to hold these units together. Hence, if the laws of gravity are right, there must be an elusive substance (i.e., dark matter) responsible for the necessary gravitational force.

o    describes dark matter by what it is not, rather than what it is - it's invisible; doesn't glow; isn't composed of atoms; and doesn't create electric or magnetic fields.

o    suggests that dark matter may be made of a yet-to-be-identified particle, and that where there is ordinary matter, there is dark matter.

o    theorizes that after the Big Bang, dark matter acted like glue, pulling stars together to form galaxies, and that, without dark matter, galaxies would probably not have formed.

o    reports that dark matter maps reveal that galaxies are enveloped by giant clouds of dark matter.

o    describes a super-sensitive detector designed to "catch" dark matter particles. It is made of germanium, a superconducting crystal, that is kept at 50 thousandths of a degree above absolute zero (460 degrees below zero Fahrenheit).

o    explains that if dark matter strikes a super-cooled germanium crystal, the collision produces a minute amount of heat, which can be detected.

o    notes that because the detector is so sensitive, many things can set it off. Therefore it is located in an abandoned mine one-half mile underground.
 

First Primates (13:04) - July 9, 2008

o    explains that primates appear in the fossil record around 55 million years ago (mya), when a mouse-sized mammal with full primate characteristics appears.

o    describes key primate characteristics - the ability to leap, long fingers, specialized teeth, and hands uniquely designed for grasping.

o    introduces paleontologist Jonathan Bloch, who reconstructed three complete mouse-like skeletons, plesiadapaforms, that date well before 55 mya.

o    notes that plesiadapaforms have a hallmark characteristic of primates - a nail-like structure rather than claws. This marks the earliest such nail ever discovered, suggesting that plesiadapaforms may be the first primate.

o    introduces Mary Silcox, an evolutionary anthropologist who analyzed the plesiadapaforms bone fragments using a computed tomography (CT) scanner.

o    explains that Dr. Bloch, Dr. Silcox, and primate anthropologist Dr. Sargis devised an algorithm that compares, contrasts, and analyzes animal characteristics and generates possible family trees showing relationships between groups of animals.

o    reports that the plesiadapaforms data produced a single family tree that connects it directly to primates. The surprising fact that the algorithm did not suggest links to other modern groups of animals strongly suggests that plesiadapaforms are primates.

o    theorizes that after dinosaurs became extinct, plesiadapaforms developed a co-evolutionary relationship with plants - plants evolved to produce tasty, nutritious fruits filled with seeds and primates evolved characteristics enabling them to gather the fruits efficiently, which in turn helped the plants spread their seeds.
 

Killer Microbe (8:29) - July 9, 2008

o    introduces A. baumannii, named for microbiologist Paul Baumann, who studied it in 1968. At that time, it was relatively harmless. But it has now transformed itself into a drug-resistant killer.

o    explains that bacteria pass genes in two ways: through mitosis and through conjugation. In conjugation, two bacteria form a physical connection, and DNA passes from one bacterium to the other.

o    hypothesizes that A. baumannii received genes from two kinds of dangerous bacteria: one was fatal to humans and the second was resistant to antibiotics. This combination makes A. baumannii dangerous in two ways.

o    describes the work of a microbiologist researching drug-resistant A. baumannii who determined that new genes inserted at just one DNA location conferred resistance to 45 drugs.

o    states that soldiers of the Iraq War infected with A. baumannii bring the bacteria home, leading to its spread.

o    points out that until scientists better understand A. baumannii, the best way for the public to combat infection is through better hospital hygiene, good medical care, and good personal hygiene.