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Saturn was named after the ancient Roman god of agriculture. His counterpart in ancient Greek mythology was Cronus, the father of Zeus (the counterpart of the Roman god Jupiter). The planet Jupiter is Saturn’s nearest neighbor and the closest to it in size and composition. Like Jupiter, Saturn is a giant world formed mainly of hydrogen with no solid surface. It has a massive atmosphere, or surrounding layer of gases, with complex weather patterns. ESA/NASA/JPL/University of ArizonaESA/NASA/JPL/University of Arizona The planet’s extensive system of icy moons includes nine major moons and dozens of small ones. Some of the moons help create the rings and maintain their shape. Titan, the largest of Saturn’s moons, is bigger than the planet Mercury. It is the only moon in the solar system known to have a dense atmosphere.

The second planet from the Sun is Venus. After the Moon, Venus is the most brilliant natural object in the nighttime sky. It is the closest planet to Earth, and it is also the most similar to Earth in size, mass, volume, and density. These similarities suggest that the two planets may have had similar histories. Scientists are thus intrigued by the question of why Venus and Earth are now so different.

Uranus is the third largest planet in the solar system, after Jupiter and Saturn. Uranus is about four times bigger than Earth. Its diameter at the equator is about 31,763 miles (51,118 kilometers), as measured at the level of the atmosphere where the pressure is the same as at sea level on Earth. The planet is slightly larger than Neptune, but Neptune is about 1.2 times more massive. Uranus’ density is quite low—only about 1.3 times that of water, compared with 1.6 for Neptune and 5.5 for rocky Earth.

The planet that Voyager uncovered is a stormy, windswept world with a vivid blue hue. Its highly active atmosphere is surprising, since it receives so little sunlight to power its weather systems. Like the other giant outer planets, Neptune has no solid surface. It also has a system of rings and more than a dozen moons.

Neptune is the smallest of the four giant outer planets. The diameter at its equator is about 30,775 miles (49,528 kilometers), as measured at a level of the atmosphere where the pressure is 1 bar (the pressure at sea level on Earth). This makes it slightly smaller than Uranus but nearly four times as big as Earth. Neptune’s mass is about 1.2 times greater than Uranus’, however, and more than 17 times greater than Earth’s. It is the third most massive planet in the solar system, after Jupiter and Saturn. Like the other outer planets, Neptune has a low density—only about 1.6 times the density of water. However, it is the densest of the four, being roughly 25 percent denser than Uranus.

in timekeeping

3,600 seconds, now defined in terms of radiation emitted from atoms of the element cesium under specified conditions. The hour was formerly defined as the 24th part of a mean solar day—i.e., of the average period of rotation of the Earth relative to the Sun. The hour of sidereal time, 1/24 of the Earth’s rotation period relative to the stars, was about 10 seconds shorter than the hour of mean solar time.

In even earlier systems of timekeeping, an hour was 1/12 of a period of daylight or darkness—hence, variable in length with seasonal changes in the length of day and night. The custom of dividing the cycle of day and night into 24 periods seems to have originated with the ancient Egyptians.

1. Tears help us see. Starting with the most basic function of tears, they enable us to see. Literally. Tears not only lubricate our eyeballs and eyelids, they also prevent dehydration of our various mucous membranes. No lubrication, no eyesight. Writes Bergman: “Without tears, life would be drastically different for humans–in the short run enormously uncomfortable, and in the long run eyesight would be blocked out altogether.”

2. Tears kill bacteria. No need for Clorox wipes. We’ve got tears! Our own antibacterial and antiviral agent working for us, fighting off all the germs we pick up on community computers, shopping carts, public sinks, and all those places the nasty little guys make their homes and procreate. Tears contain lysozyme, a fluid that the germ-a-phobic dreams about in her sleep, because it can kill 90 to 95 percent of all bacteria in just five to 10 minutes! Which translates, I’m guessing, to three months’ worth of colds and stomach viruses.

3. Tears remove toxins. Biochemist William Frey, who has been researching tears for as long as I’ve been searching for sanity, found in one

"The origin of our time system of 24 hours in a day with each hour subdivided into 60 minutes and then 60 seconds is complex and interesting," says Dr Nick Lomb, consultant curator of astronomy, from the Sydney Observatory.

Our 24-hour day comes from the ancient Egyptians who divided day-time into 10 hours they measured with devices such as shadow clocks, and added a twilight hour at the beginning and another one at the end of the day-time, says Lomb.

"Night-time was divided in 12 hours, based on the observations of stars. The Egyptians had a system of 36 star groups called 'decans' — chosen so that on any night one decan rose 40 minutes after the previous one.

The planet is one of the brightest objects in the night sky, and even a small telescope can reveal its multicolored stripes. These stripes are bands of clouds being pushed around the planet by strong east-west winds. Jupiter is a world of complex weather patterns. Its most prominent feature is an orange-red oval called the Great Red Spot. The oval is a storm system that has lasted at least 300 years and is bigger across than Earth and Mars combined.

ARE YOU A SUPERTASTER? To find out, put blue food coloring on your tongue. Blue dye doesn't stick to taste papillae, so if your tongue doesn't get very blue, you're probably a supertaster. The bluer it gets, the greater the chance you are a subtaster. More hot sauce!

People who have a lot of papillae—the bumps on our tongue, most of which house our taste buds—often find flavors overwhelming. They're "supertasters," and as such they add cream to their coffee and order food mild instead of spicy. Subtasters, on the other hand, have low papillae density and prefer their chicken wings "atomic."

Most toxic plants taste bitter, and nomadic groups that came into contact with a variety of plants would have, over time, developed a variety of receptors. People from malaria-infested parts of the world tend to carry a gene that makes them less sensitive to some bitter compounds, specifically those that contain cyanide.

Nevertheless, the search for life on Mars continues, in part because it shows signs of having been wetter in the past. Water is necessary for all known forms of life. It is possible that microscopic life once existed on Mars. Today the surface is too cold and the air is too thin for liquid water to exist there for long. It is also bombarded with ultraviolet radiation from the Sun, which is very harmful to living things.