Stories tagged navigation

Mar
07
2013

Good day sunshine: Scientists have found a sunstone on a sunken ship, similar to the devices believed to help Vikings navigate the seas on cloudy days.
Good day sunshine: Scientists have found a sunstone on a sunken ship, similar to the devices believed to help Vikings navigate the seas on cloudy days.Courtesy ArniEin
One legend connected to the Nordic Vikings got a strong jolt of reality with the discovery of a possible "sunstone" on a shipwreck off of Great Britain. Viking lore claimed that the sailors used such a stone to determine the position of the sun, even on cloudy days or when the sun had dropped below the horizon.

The stone is an Icelandic spar about the size of a pack of cigarettes that has a crystal appearance. Due to its shape and material, the sunstone can diffract light into two distinct rays which can be used to determine the position of the sun. This particular stone was found on a ship that sank in 1592 and was found close to other navigational equipment. The theory is that the stone would have been used as a back-up to a conventional compass on the more modern ship.

Why have no Viking sunstones been found? The strongest theory is that the stones were shattered in the cremation rituals given to dead Vikings. Researchers will now be able to tinker with the newly found sunstone to learn more about how Vikings possibly used them.

Descent of Jacques Garnerin with a parachute (1797)
Descent of Jacques Garnerin with a parachute (1797)Courtesy trialsanderrors
On October 22, 1797, André-Jacques Garnerin made the first parachute jump from a balloon floating 2,230 feet above the Parc Monceau in Paris, France.The 23-ft. diameter silk parachute lacked an air vent at the top of the parachute, which resulted in violent oscillations during his descent. As a result, Garnerin also has the dubious honor of the first person to have suffered from airsickness.Diagram of a Parachutist's Wind Cone
Diagram of a Parachutist's Wind ConeCourtesy Chris Rumell
Parachutists of the Marine Corps's 1st Force Reconnaissance Company jump from the back of a C-130
Parachutists of the Marine Corps's 1st Force Reconnaissance Company jump from the back of a C-130Courtesy United States Marine Corps

For several years, parachute jumping was never a precision mission. But now, in 2011, a laptop manufactured by General Dynamics provides an avionics navigation system for HAHO/HALO (High Altitude-High Opening/High Altitude-Low Opening) military parachutists. The software, called GlideLine, calculates the variables of a pre-jump mission and helps the parachutist stay on target as he drops in elevation. GlideLine was designed by the firms Nanohmics Incorporated in Austin, Texas and Complete Parachute Solutions, Inc. in Deland, Florida. On the application, a display shows concentric circles, representing what parachutists call a wind cone. If the parachutist veers outside of the wind cone, he is not going to make his drop zone. When you're parachuting, there is no good way to tell if you're outside of the wind cone ... until now.

GlideLine reads a signal from a GPS device worn by the parachutist and, using latitude/longitude coordinates of the desired landing zone, the software program displays a visualization of the wind cone and the parachutist's relationship to it. This way, the parachutist can can concentrate on the mission on hand, which is not the jump, but the tasks needed to be accomplished once the parachutist reaches the ground.

Later this afternoon, the US Army Corps of Engineers is going to lower the water level of the river by two feet in the area of the bridge collapse.

After the initial investigation is done, the Corps will open the roller gates at the Ford dam (i.e. Lock&Dam #1), dropping the level of the pool and giving emergency workers and investigators better access to the wreckage.

The silver lining of our recent drought is that the Mississippi is flowing at only 15% of normal. That means the river is shallower than it would otherwise be, and the debris in the channel isn't creating a massive dam.

May
05
2005

Every winter Monarch butterflies head south to Mexico to avoid cold temperatures.

monarch butterfly on a branch
Want to learn more about Monarchs and other butterflies? Visit the Science Museum's Monarchs and Migration website

But how in the world do they know how to get there? Well, they don't follow Highway 35, that's for sure. It turns out that monarchs can detect the sun's ultraviolet (UV) rays even when it's cloudy out. (UV rays are the part of sunlight that causes sunburn.)

Up until now we didn't know how butterflies used this UV information to fly south. Researchers led by Steven Reppert at the University of Massachusetts Medical School ran some monarchs through a flight simulator and discovered their secrets. It turns out that monarchs' eyes are very sensitive to UV light. They synch this UV information up with a natural clock in their brain. By combining these two bits of information, monarchs are able to determine the angle of the sun and always head due south. Sailors used a similar method (a sextant) to navigate around the world before the invention of compasses. Monarchs can do the trick all by themselves, though.

Do you think you could walk due south, from Minnesota to Mexico even on a cloudy day?

Some tagged monarchs have travelled more than 265 miles in a single day! Not bad for an insect...

Journey North and Monarchs in the Classroom also have cool websites (complete with projects and "Citizen Science" opportunities) about the annual Monarch butterfly migration.