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Is the sky falling?

Local astronomy expert weighs in on recent events

March 16, 2013
By Ilsa Matthes - staff writer (imatthes@dailypress.net) , Daily Press

ESCANABA - Following the explosion of a meteor over Russia last month injuring more than 1,000 people, and an asteroid the size of a city block passing by Earth last weekend, some may be wondering if the sky is falling.

"The near miss last week by a large asteroid and the meteor explosion over Chelyabinsk reawakened fears in many people that the end of the world might be near," said Dan Young, vice president of the Delta Astronomical Society.

However, meteors are not uncommon. When meteoroids - space debris frequently left over from comets - enter the Earth's atmosphere they cause meteors.

Article Photos

Dan Young, center, vice president of the Delta Astronomical Society, adjusts a telescope to view June 2012’s Venus in transit near the waterfront in Escanaba. (Daily Press photo by Holly Richer)

"A 'meteor' is actually the bright flash of light that one sees when one of these rocks hits the Earth's atmosphere and burns up," said Young.

The meteors can be caused by everything from cosmic dust to mountain-sized rocks, known as asteroids. The asteroid which passed 604,500 miles from Earth on Saturday, known as 2013ET, was 262 feet wide. However, because the asteroid never entered the earth's atmosphere it is not considered a meteoroid.

"Generally, large meteors, like the 55-foot wide one that exploded over Chelyabinsk, (Russia) are very rare - Statistically, only about one that size is expected to hit Earth each century," said Young, adding the last known meteor in the 50 to 300 foot category exploded over Tunguska, Siberia in 1908.

To illustrate the emptiness of space, Young explained that the if our sun and the next closest star, the Alpha Centauri System, were each the size of a grain of sand they would be 15 miles apart.

"This scale holds roughly true on average for the universe as a whole. So, even though there are perhaps several million 50 foot wide rocks with orbits around the Sun that sometimes cross Earth's orbit, the chances of one of them being in the right place at the right time turns out to probably only happen once every hundred years," said Young.

Even rarer are meteoroids like the one that is believed to have killed the dinosaurs 65 million years ago. That meteoroid is believed to have been about 6 miles in diameter.

All meteorites - meteoroids which reach the Earth's surface - are rare, and because 71 percent of the planet is covered in water, most meteorites are lost in the ocean. However, according to Young, some meteorites are worth more than their weight in gold.

Part of the reason that meteorites are so rare is most meteoroids burn up when entering the atmosphere. Meteoroids that are basketball-sized or larger and with high iron content are more likely to reach the surface, but even dust which never reaches the surface will make meteor displays.

"Actually, hundreds of tons of dust hit our atmosphere each day, with slightly more hitting between midnight and 4 a.m., as that side of the Earth is facing into the direction of our planet's travel around the Sun," said Young.

Overall, Young believes that the because of the vastness of space, there is little chance of another incident like the Chelyabinsk meteorite explosion happening in the near future.

"Does that mean it won't happen again tomorrow? No. It just means it probably won't," he said.

 
 

 

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