Star Talk: Think small to grasp immensity of solar system, universe

Want to get a sense of perspective for our place in the universe? Start with a grapefruit as the sun

The immensity of the universe can be intimidating to some, exhilarating to others. Distances across the cosmos can be daunting, the sizes of celestial objects gargantuan and the numbers that quantify these parameters overwhelming. We can set these astronomical quantifiers into perspective — a cosmic perspective — that will give us a sense of our place in the universe.

We are part of a solar system, the space family of the star named Sol, our sun. Recognized members of this stellar unit include eight planets, more than 150 known moons, millions of rocky objects (asteroids) between two of the planets, as well as many thousands of small, icy solar system objects beyond the last recognized planet, Neptune, and, of course, one star.

To begin our cosmic perspective, we can shrink our solar family downward by a factor of 10 billion by applying this conversion to both the sizes and distances between objects in our solar neighborhood.

With this new point of view, the sun would be reduced to merely the size of a grapefruit and Earth would become the size of the ball at the tip of a ballpoint pen. This tiny ball representing Earth would have to be placed 50 feet from the solar “grapefruit” to indicate Earth’s average 93 million mile distance from the sun.

3 specks and a grapefruit

Between Earth and the sun are only two objects of any significance, the planets Venus and Mercury. Since Venus is slightly smaller than Earth and Mercury about one-third its size, both these planets would be smaller than Earth’s ballpoint. Therefore, the inner solar system would be represented by three tiny objects placed at 20 feet, 35 feet and 50 feet from the grapefruit sun with essentially nothing else between. Space is a big and empty place. (That’s why we call it “space”!)

On this 10 billion to 1 reduction scale, the moon would be simply a fourth the size of Earth’s ballpoint. Its quarter of a million mile distance from Earth would be reset to an inch and a half. Earth, moon — which is the most distance place that humans have ventured — and its path around our planet would all fit into the palm of your hand.

Farther out in the solar system, Jupiter, the largest object in our solar family after the sun, would reduce to the size of a marble while the small solar system object, Pluto, about the size of our moon, would also be rescaled to a quarter of a pen’s ballpoint. Resetting Pluto’s 3.5-billion-mile distance from the sun on our reduction model would relocate it to a third of a mile from the solar grapefruit.

Fly Me to the Moon

A further perspective on the distance to the sun or moon can be appreciated by substituting the remarkable speeds attained during space flight with ordinary, everyday speeds. It took the Apollo program astronauts three days to reach the moon traveling at speeds in excess of 3,000 mph. If it were possible for us to drive to the moon at 55 mph, it would take almost six months to reach the lunar surface. To travel to the sun using our vehicle at that speed would take almost 200 years!

We could increase this speed by almost 10 times by boarding an imaginary jet airliner that could fly through the near vacuum of space. Flying at a speed of 500 mph to reach the moon would nonetheless take us about 20 days. Crossing the distance to the sun on our pretend airplane would require us to keep our seat belts fastened for 20 years before the flight arrived at its truly stellar destination.

As we move away from the solar system and out into our Milky Way galaxy, we would have to travel an enormous amount to reach the nearest star, even with our 10 billion to 1 downgrade. The nearest star, Proxima Centauri, is a member of a stellar collection of three mutually orbiting stars. Called the Alpha Centauri star system, it is more than 25 trillion miles away, but the 10 billion to 1 reduced distance scale would place it on the West Coast with the sun’s grapefruit on the East Coast. Using this cosmic perspective, humans have only journeyed an inch and a half of the 2,500 miles to the West Coast.

The cosmic perspective gives us the opportunity to grasp the large and the small of the universe in the same thought. Perhaps most of all, the cosmic perspective is humbling. Our minute planet is an insignificant cosmic object, yet it is a remarkable oasis of life. We are not the center of the solar system, of our galaxy, or of the universe as was once thought. We are children of the universe who have the ability to comprehend and embrace the grand cosmic perspective.

October Sky

October is the month that the two brightest planets return to the early evening sky. One is already conspicuous by midnight; the other will slowly become evident as the month advances.

The first of these bright planets is Jupiter. This planet will come into view over the eastern horizon about an hour and a half after sunset during the last week of September. Jupiter’s rise time will then narrow to almost an hour after sundown by the second week of October. During the last week of October, Jupiter will be rising just as the solar disk sets.

For the past year, Jupiter has been at its closest distance to Earth in nearly a half century. In 2011, Jupiter will be at its absolute closest to us on Oct. 27. Jupiter’s mammoth globe combined with its relative nearness will make it shine at its most intense for the next eight weeks. Watch for the moon to the left of Jupiter on Oct. 13.

The other bright planet is Venus. As October opens, Venus may be difficult to see without using binoculars, because it comes into view less than an hour after sunset. Although Venus is more than twice as bright as Jupiter, its brightness will be diminished by its position very low in the west within the dusk sky. Venus will, however, be blazing as the evening star this winter. Look for the crescent moon to the upper left of Venus soon after sunset on Oct. 28.

Richard Monda is an astronomer living in the Capital Region.

Categories: Life and Arts

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