Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: Eric A. Taylor on 15/01/2010 02:15:40
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When I was growing up my father worked part time as a flight instructor. He also owned a share in a Cessna. One of the jobs of us kids was to watch out for other aircraft, mainly because mid air collisions tend to be really bad thing. He told us you can instantly tell if another aircraft was on a collision course with ours if it didn't appear to move agents the background.
Would the same be true of an asteroid on a collision course with Earth? If so could it be distinguished from the stars?
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Same for boats. If you see a boat on a constant angular position relative to your boat, it means, if neither of you change direction or speed, you are on a collision course. I think the only case where this is not true is if the other vessel is heading in the same direction as you and at the same speed.
In the case of an asteroid it is more complicated because the earth is not going in a straight line but is in orbit around the sun and is also rotating. Looking against the star background is the way to do it. As it gets closer its position will be moving laterally relative to the stars.
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Unfortunately the most likely method of discovering a large (bigger than say 100 meters) asteroid that is going to collide with Earth is by the glow caused by atmospheric entry. In this case all you can do is say "Oh sh-" before you die.
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A blink comparator was a viewing apparatus used by astronomers to find differences between two photographs of the night sky shot using optical telescopes such as astrographs. It permitted rapidly switching from viewing one photograph to viewing the other, "blinking" back and forth between the two taken of the same area of the sky at different times. This allowed the user to more easily spot objects in the night sky that changed position.
In photographs taken a few days apart, rapidly moving objects such as asteroids and comets would stand out, because they would appear to be jumping back and forth between two positions, while all the other fixed stars stood still.
http://en.wikipedia.org/wiki/Blink_comparator
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The constant relative bearing assumes of course that both objects are moving in a straight line with a constant velocity. all objects in space including the earth are moving in orbits which are neither straight lines nor a constant velocity so that theory does not apply until the object is so close that their mutual approach approximates to a straight line of constant velocity.
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If an asteroid were on a collision courae with Earth
... we can always call Bruce Willis..... : )
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Anything on a collision course with Earth would have to follow a curved path and not a straight path, so we would see it move against the background.
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If an asteroid were on a collision courae with Earth
... we can always call Bruce Willis..... : )
Nothing ageist Mr. Willis, he's a great actor....well okay he's a good actor.....Fine! He's a okay actor. But he's the last guy I'd call to save the Earth. I wonder what old Stanislav Yevgrafovich Petrov is up to these days? I'd call him considering he has experience REALLY saving the Earth in real life even though his experience is in something totally different.
What's really amazing is every single person on the planet has him to thank for being alive and hardly anyone has heard of him or his very courageous deed that saved everyone living in the western world, if not the ENTIRE world.