Along with dolphins, California sea lions have been part of the US Navy's Marine Mammal Program, which employs animals for a wide range of military purposes, for decades. They have long been used to retrieve objects lost or fired underwater, but, in the last few years, the Navy has placed sea lions on more active duty, employing them as sentries for military ships and piers. The animals can apprehend and detain divers, who could be enemy combatants or saboteurs, by placing a special clamp around the divers' legs attached to a line. Once the diver has been immobilized, human operatives can then reel the diver in. Their training in object retrieval has also made them ideal agents for locating and identifying underwater mines.

There are currently just 28 sea lions in the Navy's ranks (along with 80 bottlenose dolphins and a Beluga whale), but one team is about to get a permanent posting. The Navy has just announced that a team of sea lions will defend the Kitsap-Bangor base in Washington State, patrolling for divers, looking for explosives, and participating in naval exercises.

But how long will it be before the sea lions team up with the dolphins and use all that military training to overthrow their human masters?

US use sea lions in terrorism fight [Telegraph via Popular Science]

On August 22, 1924, the Earth was 55,777,566 km from the Red Planet during the Mars opposition, offering ideal conditions for receiving radio signals from Mars — if anyone happened to be sending them. Amherst College professor David Todd persuaded both the US Army and Navy to listen for messages from Mars. In the telegram above, Edward W. Eberle, the Chief of US Naval Operations, informs Naval stations of the possibility of Martian communications, and instructs them to report any unusual phenomena. For three days, the stations listened for unusual transmissions, but came up empty handed.

[Letters of Note]

According to an article in the most recent issue of Physics World:

The "stealthiest" ship that currently exists is Sweden's Visby Corvette. Apart from being painted in grey dazzle camouflage and made of low-radar reflectivity materials, it also does not use propellers, which are the noisiest part of a ship. The vessel also has the lowest "magnetic signature" of any current warship.

But the next generation of warships could be truly invisible by exploiting "metamaterials" - artificially engineered structures first dreamt up by physicist John Pendry at Imperial College, London. Metamaterials are tailored to have specific electromagnetic properties not found in nature. In particular, they can bend light around an object, making it appear to an observer as though the waves have passed through empty space.

About the research, Chris Lavers writes, "If optical and radar metamaterials could be developed, they might provide a way to make a ship invisible to both human observers and radar systems, although the challenges of building a cloak big enough to hide an entire ship are huge."

Future Navy ships will use electric drive propulsion, making the electric-powered railgun possible. The railgun sends current along parallel rails, creating an electromagnetic force so powerful, it can shoot a metal projectile at record-breaking speeds. Photos by AP/U.S. Navy, John F. Williams [Gizmodo]