Mercury is therefore far closer to the Sun than Earth, which circles at an average distance of km (mi), or one AU. This distance is measured in kilometers (mi) – 0.98 to 1.017 AU. The Moon, which orbits around Earth at a distance of about 250,000 km (155,000 mi), also affects how close we are to the Sun during part of each year. When the Moon is full, it can be as close as 400,000 km (250,000 mi). But when it's new, it is farther away from us than that, about 240,000 km (150,000 mi).
Earth's mean radius is 6,371 km (3,917 miles), but due to its spherical shape, its area is only 4,852,885 km2 (1,807,265 sq mi), so it's fairly small compared with other planets in the solar system. It has a mass of 5.97 x 1024 kg (13.3 billion pounds), about a quarter of which is water. The rest is iron core with a thin layer of crust.
Venus is almost entirely covered by clouds made of sulfur dioxide gas. There may be oceans beneath the clouds, but they're too hot for life as we know it. Scientists think that most of Venus' atmosphere escaped over time into space.
Mercury is 0.4 astronomical units distant from the Sun at an average distance of 36 million miles (58 million kilometers). The distance between the Sun and Earth is measured in astronomical units (abbreviated as AU). It takes 3.2 minutes for sunlight to get from the Sun reach Mercury at this distance.
Thus, the time taken by Mercury to orbit the Sun is about 87 days.
The speed of light is 300,000 km/s. If we assume that Mercury travels in a straight line from the Sun, then its distance will decrease by 1/2 every 86 days or so. So in exactly one year it will have receded to half its current distance from the Sun. This means that it takes 38 hours 45 minutes 48 seconds for Mercury to make one full orbit around the Sun.
As far as I know, there are no significant forces acting on Mercury other than the Sun's gravity. Therefore, its orbit should be almost identical to that of Earth around the Sun; but because of its closer proximity to the Sun, it gets heated more intensely by it than we do. Also, because it moves faster through the Solar System than Earth, it gets swept out of its orbit and flung towards the Sun with enough energy to cause major problems for its surface.
These problems include intense heat that melts rock and causes volcanic activity, and also creates a magnetic field around the planet that protects it from some of this heat.
One astronomical unit is the mean distance between the Earth and the Sun, about 150 million miles (241 million km).
Thus, 0.4 AU is the distance between the Earth and Mercury averaged over a year. Because the orbit of Mercury is not exactly circular but rather elliptical, this distance will vary between approximately 58 million miles (93 million kilometers) when it is on the far side of the Sun and 47 million miles (77 million kilometers) when it is closest to us.
The average density of mercury is 4.5 grams per cubic centimeter, which means that it weighs about 115 pounds per cubic foot. At one astronomical unit from the Sun, its surface temperature would be -173 degrees Celsius (-280 degrees Fahrenheit). However, because mercury is almost entirely made up of atoms with atomic numbers 80 or above, most of these atoms are lost when it gets hot because they become ionized and can't absorb heat like neutral atoms can. So, assuming no other sources of heat, after 100 million years or so it would have melted completely into a globe-girdling ocean.
At an average distance of 92, 955, 807 miles, Earth circles the sun 100,000 times closer than the Oort Cloud (149, 597, 870 km). The distance between Earth and the sun is known as an astronomical unit, or AU, and it is used to measure distances across the solar system. Jupiter, for example, orbits the sun at 5.2 AU. Our own planet travels around the sun at 1.5 AU.
The solar radius is about 695,000 miles, or 10,921,500 kilometers. At this distance, a ball bearing one inch in diameter would travel around the sun once every 4 minutes 20 seconds.
The sun is our star and its energy drives life on Earth. It is also responsible for most of the damage we experience during a solar eclipse. During a total lunar eclipse, the moon passes through the shadow of Earth, which blocks out the sun's light and causes the eclipse.
Lunar eclipses are visible on half of Earth. When the eclipse occurs at night, it is called nocturnal. During a lunar eclipse, the Earth's atmosphere refracts light from the Sun that reaches it from beyond the Moon, causing a reddish hue to appear over certain areas. The color varies depending on how much dust or clouds are present in Earth's atmosphere at the time of the eclipse.
For example, if you were watching the sunset from Hawaii right now, you might see a red color reflected in the ocean.