Shark skin doesn't look like normal fish skin. It's made of microscopic diamond shaped scales with rough edges, called "denticles". These are thought to share an evolutionary origin with teeth - indeed, they have much more in common with teeth than with scales. Like teeth, they consist of a central cavity made of pulp surrounded by dentine and enamel.

The flexible but irregular surface is impossible for barnacles and other micro-organisms to cling to, as well as decreasing drag and turbulence.

So just when you thought sharks couldn't get any scarier, it turns out that their entire bodies are literally COVERED with teeth. ...

Roll cloud over Uruguay. This low, roll cloud formation occurs when sinking cold air causes warm, moist air on the planet's surface to climb to higher altitudes, where the moisture condenses into cloud form. Roll clouds aren't dangerous in themselves, though, and many roll clouds form in relatively calm weather as a result of sea breezes.

The Amazonian giant centipede is the largest centipede alive, reaching lengths of 30 centimeters. They are carnivorous and feed on lizards, snakes, mice, and even bats. While their venom is not enough to kill an adult human, it may cause reactions with the skin.

I've been following the war in Syria quite a lot. It's overwhelming to see how little media coverage there is on what's really happening there. This video is most accurate according to my own research. Take a few minutes to watch it...

The medication is designed to be injected right after a traumatic experience. It targets Oprl1, a receptor that researchers believe is responsible for attaching fear to traumatic memories.

Post-traumatic stress disorder is caused by many things, such as surviving an accident or exposure to violence. There are genetic risk factors, but many people who acquire the disorder had no predisposition. Symptoms include debilitating flashbacks and hallucinations of the event, avoiding close relationships, angry or violent outbursts, and an inability to return to the location where the traumatic experience occurred, among many others.

The earliest evidence of ancient dentistry we have is an amazingly detailed dental work on a mummy from ancient Egypt that archaeologists have dated to 2000 BCE.

A manned mission to Mars will inevitably consist of a few people living in incredibly close quarters in a constantly stressful environment.

Starting next summer, Mars Society will be conducting a mock Mars mission in the Canadian Arctic. Six participants will live in a facility 7.6 meters tall (25 feet) and 8.3 meters wide (27 feet). For one full year, they will perform a great deal of geological experiments similar to work that would be done on Mars. Spacesuits will be worn to help simulate Mars-like conditions.

Though similar studies have been done in the past, this is the most stressful and will be more true to actual conditions on Mars. The goal of the experiment is to determine leadership structure and what equipment will be necessary. ...