Jun 11th: Close Passes & Tilted History


Podcaster: Dr. Al Grauer
Travelers in the Night Digest: 295 & 296: Close Passes & Tilted History

Organization: Travelers in The Night

Link : Travelers in the Night ; @Nmcanopus

Description: Today’s 2 topics:

  • Rose Matheny is at it again! This time she’s discovered 4, count ’em 4 close approaching asteroids. Luckily they’re small, from 15′ to 60′ in diameter.
  • Human migrations in the distant past were helped by land bridges and corridors of plant life which were produced by small cyclic changes in the tilt of Earth’s axis of rotation.

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Bio: Dr. Al Grauer is currently an observing member of the Catalina Sky Survey Team at the University of Arizona.  This group has discovered nearly half of the Earth approaching objects known to exist. He received a PhD in Physics in 1971 and has been an observational Astronomer for 43 years. He retired as a University Professor after 39 years of interacting with students. He has conducted research projects using telescopes in Arizona, Chile, Australia, Hawaii, Louisiana, and Georgia with funding from NSF and NASA.

He is noted as Co-discoverer of comet P/2010 TO20 Linear-Grauer, Discoverer of comet C/2009 U5 Grauer and has asteroid 18871 Grauer named for him.

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295 – Close Passes
During a recent 3 night observing run my Catalina Sky Survey teammate Rose Matheny discovered 4 asteroids which can come to less than one half the Moon’s distance from us. Interestingly one of them passed about 25,000 miles over the South Pole 2 days after Rose discovered it. Rose’s four close approaching asteroids are small ranging in size from 15 to 60 feet in diameter. None of them are big enough to reach the Earth’s surface and make a crater. However, the largest is about the size of the one whose air blast shock wave injured nearly 1500 people when it exploded over Chelyabinsk, Russia in 2013 .

A space rock like one of the smaller of Rose’s discoveries enters the Earth’s atmosphere every few years, explodes at about three times the height airliners fly, and sometimes rains pieces on the ground for meteorite hunters to discover. Most of the time a 3 to 10 foot diameter meteoroid enters our atmosphere over the ocean or during the day so you have to be lucky to witness the light show it produces. Very rarely humans see a rock fall from the sky and are able to locate some fragments of it which reach the ground. This process has been made easier by using Doppler Weather Radar to track the dark fragments from a meteor when it explodes high above the Earth.

Asteroid hunters are working hard to improve their equipment and software so as to be able to track small asteroids which are on a collision course with planet Earth. Our goal is to be able to warn people to stay away from doors and windows should a small space rock be about to explode over a populated area.

296 – Tilted History
Seasons are created by the fact that the Earth’s axis of rotation is currently tilted 23 1/2 degrees relative to our path around the Sun. The slight out of roundness of the Earth’s orbit combined with a 41,000 year cycle in its 3 degree axis of rotation wobble can cause the Earth’s climate to change on very long time scales. Turns out that these astronomical cycles are likely to be the drivers of where you are from and where you live.

Recently Dr. Axel Timmermann and Dr. Tobias Fredrich from the University of Hawaii published an article which analyzed human migration over the past 125,000 years in the prestigious journal Nature. These researchers used a series of computer models guided by archeological data and the location of human fossils to follow our ancestors as they migrated across planet Earth. They found that tiny bidirectional waves of human migration happened every 20,000 years or so when the wobble in the tilt of Earth’s axis of rotation opened up green corridors of plant life between Africia and the eastern Mediterranean as well as Africa and the Arabian Peninsula. This research indicates that Homo Sapiens arrived more or less simultaneously in China and Europe about 80 to 90 thousand years ago. The human wave out of Africa that occurred 50,000 years ago apparently led to the eventual human occupation of the rest of the world. Along the way human wanderers were helped by land bridges and corridors of plant life which were produced by small cyclic changes in the tilt of the Earth’s axis of rotation.

End of podcast:

365 Days of Astronomy
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