There are about 155 species of voles. There are species in Europe, Asia, North Africa and North America. The closest relatives of voles are the lemmings and muskrats, which are in the same subfamily.
Adult voles, depending on the species, are 7.5 to 17.5 centimetres (three to seven inches) long. They eat seeds, grass or other plants, and insects.
Many animals hunt voles, for example owls, hawks, coyotes, foxes, weasels, cats and snakes.
The average life of the smaller vole species is three to six months. These voles rarely live longer than 12 months. Larger species, such as the European water vole "Arvicola", live longer. They usually die during their second winter. As many as 88% of voles die during the first month of life.
Isthmus
An isthmus is a narrow strip of land, with water on either side, that connects two bigger landmasses. For example, the Isthmus of Panama connects the continents of The Americas. Separating two water bodies and joining two land bodies, an isthmus is the opposite of a strait.
Rodent
Rodents are a very successful group of mammals. They form the order Rodentia.
They have no more than 2 incisors. These keep growing, and must be kept worn down by gnawing (eroding teeth by grinding them on something hard); this is the origin of the name, from the Latin "rodere", "to gnaw", and "dent", "tooth".
Most rodents are small. Examples of commonly known rodents are mice, rats, chipmunks, and squirrels. Some other small rodents sometimes kept as pets are Guinea pigs, hamsters, and gerbils.
Examples of larger rodents are porcupines, beavers, and the largest living rodent, the capybara, which can grow to between 105 and 135 cm (40-55 in) in length, and weigh 35 to 65 kg (75-140 lbs).
Almost half of all mammal species are rodents. More examples of rodents are voles, prairie dogs, groundhogs, and chinchillas.
Rabbits, hares, and pikas are sometimes called rodents, because they also have teeth that keep growing. But in 1912 biologists decided to put them in a new, separate order, Lagomorpha, because they have two extra incisors in their upper jaw.
Shrews are sometimes called rodents, because they look like mice, but that is not correct. They are in the order Insectivora.
There are more families than these. The list includes the more common families.
Titan (moon)
Titan (Ancient Greek: "Τῑτάν") is one of Saturn's moons. It was found by Christiaan Huygens on 25 March 1655. Titan is a unique moon because it is the solar system’s only moon to have an atmosphere.
Titan is the largest moon of Saturn and the second largest in the Solar System. Titan is larger than the planet Mercury. Its equatorial diameter (wideness at the equator) is 5,150 km. It orbits 1,221,865 km away from Saturn.
Titan is the only moon known to have an atmosphere and it more thicker than Earth’s. But humans could not breathe it as it's very cold, and also poisonous. The air is made of nitrogen and methane. Titan is the only place in the Solar System, except Earth, that has lakes and much liquid on its surface. But the liquid is methane, not water.
Titan was discovered on 25 March 1655 by Christiaan Huygens, an astronomer from the Netherlands. Earlier, in 1610, Galileo Galilei had discovered four of Jupiter's moons. This inspired Huygens: he also wanted to discover new moons. Because Huygens had also improved the telescopes of the time, making them a lot better, he thought he might be able to discover a new moon.
Christiaan and his brother, Constantijn, started to build their own telescopes in 1650. Using the first telescope he ever built, Christiaan Huygens was able to see Titan. At first he called it "Luna Saturni", which means "Saturn's moon" (he did not know there was more than one). Through the years, lots of other moons have been discovered and today the moon is known as "Titan" or as "Saturn VI". The name "Titan", and all the names of Saturn's other moons, are from the Greek legends.
Titan is the only moon in the Solar System that has a thick atmosphere (the gases that surround a planet or moon). After the spacecraft Voyager I visited the moon on 12 November 1979, it showed that Titan's surface (the ground level) is hidden under an atmosphere that is 900 km thick. Before this, everyone thought that Titan was the biggest moon in the Solar System. Now we know that it is the second biggest, after Ganymede, one of Jupiter's moons.
Even though it is smaller, Titan is close in size to Ganymede. It is also close in size to the slightly smaller Callisto, another of Jupiter's moons. Not only is Titan a big moon, it is even bigger than the planet Mercury, but it only has half as much mass (it is much lighter). Because Titan does not have a lot of mass, scientist think that Titan is made of matter that is not very heavy, specifically frozen water and ammonia. Some scientists think that there is a lot of liquid water and ammonia underneath the surface, enough to fill an entire ocean. These scientists think that there might be a form of life inside this ocean.
At its centre, Titan has a rocky core that is about 3400 km thick. This core is made up of silicates and metals. The gravity (the force that keeps everything attached to the ground) is a lot weaker than here on earth. If you could jump 1m high on the Earth, you would be able to jump 7m high on Titan.
It takes Titan 15 days and 22 hours to orbit (travel) around Saturn. This is almost the same time it takes Saturn to rotate or spin around its own axis - one full spin. This is known as "synchronous rotation", which means that the same side of Titan is always pointed to Saturn.
The path in which Titan moves, its orbit, is very close to a circle, but not quite. We use the word "eccentricity" to describe the path that a moon or planet travels in. An image with an eccentricity of 0 (zero) has a path that is a perfect circle. If the eccentricity is more than 0, the path is less round (see image below). Titan's eccentricity is 0.028, very close to zero.
On July 1, 2004, the Cassini-Huygens probe entered into orbit around Saturn. On December 25, 2004, the Huygens probe separated from the Cassini probe and started to move towards Titan. It landed on Titan's surface on January 14, 2005. It landed on a dry surface, but it confirmed that large bodies of liquid exist on the moon. The Cassini probe continued to gain data of Titan and a number of the icy moons. It found evidence that the moon Enceladus had water erupting from its geysers. Cassini also proved in July, 2006 that Titan contained hydrocarbon lakes, located near its north pole. In March, 2007, it discovered a large hydrocarbon lake the size of the Caspian Sea near its north pole. The lake of liquid methane has been named Kraken Mare. In 2009, Nasa showed a photograph showing the sunlight reflecting off the surface of the lake. This was the first ever picture of liquid on another world.
In 2012 researchers at NASA discovered that Titan is giving off a faint glow of light. This is believed to be caused by complex chemical reactions occurring in Titan's atmosphere. This kind of light is called an airglow.
Computer number format
A computer number format is the way that computers and calculators represent numbers. Most computers use a system of binary which is composed of ones and zeros.
Other systems in use are the octal (0,1-7) or the hexadecimal (0,1-9,A,B,C,D,E,F) systems.
So we can use codes, which the computer understands only, as well as other number systems.
1550
Columbus, Georgia
Columbus is the third largest town, in the U.S. state of Georgia. Coca-Cola and RC Cola (Royal Crown Cola) were first made here. It is south of Atlanta. It is about one hour and thirty minutes to two hours away from Atlanta.
Carthage
Carthage is an ancient city-state in what is now Tunisia. It began as a Phoenician colony. Carthage at the height of its power was the foremost power in the Mediterranean Sea, controlling parts of Spain, Sicily, North Africa, Sardinia, and the Balearic islands.