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Are Other Planets Tilted Like Earth?
You have seen drawings of how Earth is tilted on its axis, or perhaps you’ve spun a globe and noticed how it doesn’t rotate around points that are straight up and down. Most of the other planets are also tilted, some further than others.
The planet Mercury doesn’t seem to be tilted at all. It sits perfectly straight with its North Pole exactly on the top and its South Pole exactly on the bottom.
Venus is tilted only 3 degrees, but in the opposite direction that Earth is tilted. The other planets are tilted in the same direction as Earth, but different amounts.
Mercury, 0°
Venus, -3°
Earth, 23.4°
Mars, 25.2°
Jupiter, 3°
Saturn, 26.7°
Uranus, 98°
Neptune, 28.3°
Pluto, 122.5°
Notice that Uranus and Pluto lean so far over that their equators would go around from top to bottom, instead of around the middle like a belt.
Pluto and Neptune Appear to Be on Collision Course
Looking at a drawing of the planetary system, you might think that because of Pluto’s elliptical orbit, Pluto and Neptune have the opportunity to smash into each other in an interstellar demolition derby, but don’t start camping out with your telescope waiting for the fireworks to begin. Although Pluto’s orbit is longer and narrower than Neptune’s circular path, the tilt of Pluto’s course keeps them from ever coming close to each other.
Imagine Neptune’s orbit as a hard plastic bracelet—the kind little sisters like for playing dress-up. Now think about Pluto’s path following the same shape as a rubber band, a wide oval. If you held the bracelet parallel to the floor and slipped a large rubber band through the bracelet, pivoting the rubber band at an angle so that one end is above the bracelet and the other end is below the bracelet, you can see how the two paths could not possibly intersect.
Because of its unique orbit, Pluto is sometimes the furthest object in our solar system, and sometimes it is closer to the Sun than Neptune is. However, Pluto’s orbit is always far beyond the orbit of Uranus.
“Houston, we’ve had a problem here.”—Jack Swigert (Because this statement was repeated by Jim Lovell, the quote is often attributed to Lovell.)
“The massive bulk of the Earth does indeed shrink to insignificance in comparison with the size of the heavens.”
—Nicolaus Copernicus
“Praise the Lord. Praise the Lord from the heavens, praise Him in the heights above. Praise Him, all His angels, praise Him, all His heavenly hosts. Praise Him, sun and moon, praise Him, all you shining stars. Praise Him, you highest heavens and you waters above the skies. Let them praise the name of the Lord, for He commanded and they were created. He set them in place for ever and ever; He gave a decree that will never pass away.”—Psalm 148:1-6
How Far Away?
An “Astronomical Unit” (AU) is the measurement used for the distance between the Earth and the Sun, 93 million miles. Earth’s distance from the Sun is called 1 AU. Neptune’s distance is more than 30 AU.
Heliopause is the name given to the boundary between our solar system and the nearest star system, Alpha Centauri, which consists of three stars: Alpha Centauri A & B, and Proxima Centauri. The Alpha Centauri system is nearly 271,000 AU away from our solar system, which is why astronomers refer to distances of that magnitude in light-years, instead of AU.
How far is it to the nearest star? The distance to Proxima Centauri is approximately 4.2 light-years. Remember, space fans, a light-year is the distance a beam of light would travel in one year, and light travels at 186,000 miles per second! Therefore, if humans could travel at the speed of light (which we can’t… yet), we could journey to the next star in a little over 4 years and 2 months. However, recent space shuttle missions averaged a speed of 17,500 miles per hour, orbiting the Earth every 1½ hours, and the Apollo missions to the Moon hit a maximum speed of 25,000 miles per hour. Therefore, traveling at the speed of a space shuttle, the nearest star could be reached in 160,704 Earth-years. The top speed of an Apollo mission would cut that journey down to 112,493 years. The Voyager unmanned exploratory spacecrafts travel at 35,000 miles per hour and could reach Proxima Centauri in a mere 80,352 years. But that still doesn’t include a return trip home.
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