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Impact ~ NEO; Near Earth Objects

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  • G David Bock
    replied
    A THREE MILE wide asteroid is set to graze past Earth on Sept. 1 - and NASA says it's the largest to come this close since they began keeping track

    • NASA says asteroid that's 2.7 miles wide will make 'relatively close encounter'
    • Dubbed ‘Florence,’ the space rock will pass 4.4 million miles from our planet
    • This is the closest an object this large has come since NASA began NEO program
    • It hasn't come this close since 1890, and won't be this close again until 2,500

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  • G David Bock
    replied
    Originally posted by Moulin View Post
    well, if they can land something safely on an asteroid,--which I think is phenomenal-- I'll take it that they know where this thing is going pretty accurately
    Hopefully that is so.
    In the case of the landing on another asteroid, they had fairly good numbers for its orbital characteristics.
    In the case of this one; 2012 TC4, seems we don't have enough data and numbers to be certain. It's already shifted from 4,200 miles to about 27,300 miles away (from Earth's surface, not center ~ which would add another @4,000 miles).

    Wiki provides a good basic on orbits;
    https://en.wikipedia.org/wiki/Orbit

    The term is ephemeris;
    ...
    In astronomy and celestial navigation, an ephemeris (plural: ephemerides; from Latin ephemeris, "diary", from Greek: εφημερίς, ephēmeris, "diary, journal")[1][2][3][4] gives the positions of naturally occurring astronomical objects as well as artificial satellites in the sky at a given time or times. Historically, positions were given as printed tables of values, given at regular intervals of date and time. Modern ephemerides are often computed electronically from mathematical models of the motion of astronomical objects and the Earth. Even though the calculation of these tables was one of the first applications of mechanical computers, printed ephemerides are still produced, as they are useful when computational devices are not available.
    ...
    https://en.wikipedia.org/wiki/Ephemeris

    In posts above, offerring error on scale of 2-4 diameters of Earth, with Earth's diameter @8,000 miles we may be at hazarrd risk depending if the the low of 4.200 miles applies or not(less so?) if the 27,300 miles applies.

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  • Moulin
    replied
    well, if they can land something safely on an asteroid,--which I think is phenomenal-- I'll take it that they know where this thing is going pretty accurately

    Leave a comment:


  • G David Bock
    replied
    OK guys, long day and late night so I'm trying this visualization ...

    Lets take a sheet of paper and make the X and Y axis cross on such.
    Place the incoming rock/NEO at the center where the lines cross.
    Using one inch equals 4,000 miles (we're rounding here), make a mark one inch to the left on the X (horizontal) line; this locates the Earth's surface closest to the NEO.

    Now go another inch to the left on X and mark this point. With a drawing compass set for one inch radius and on this "two inch" point, draw a one inch radius/two inch diameter circle to represent Earth.

    Now from the X=0/Y=0 location of the NEO, set the compass for 4 inch radius circle and draw it. Four inches equals two Earth diameters (2 x 8,000 miles). Looks to me like Earth is within that circle, which is what Pirate-Drakk gave us.

    If we draw an eight inch radius circle from 0/0 we have a much large circle but one that still has Earth within it, this one from Widow-Maker.

    Looks to me like anything over a one Earth radius margin of error could place Earth in an impact zone.

    Of course the larger error factors could suggest it might pass by on the far side of Earth from where it is expected, missing by a long mile(s).

    BTW, at this scale the Moon is about 5 feet (59.5") further out on the X Axis from Earth.

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  • Widow Maker
    replied
    Originally posted by Pirate-Drakk View Post
    Perhaps twice the diameter of the Earth, which would put us in the target zone...
    more like four times Earth's diameter and they are already certain it will miss.

    We are not in the "target" zone this pass.

    Leave a comment:


  • Pirate-Drakk
    replied
    Originally posted by Moulin View Post
    but how far could they be off??
    Perhaps twice the diameter of the Earth, which would put us in the target zone...

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  • Moulin
    replied
    Originally posted by Pirate-Drakk View Post
    As per above, the trajectory is not "exactly" known. That is because the mass of the object is in question, as we didn't build it. To determine that, you have to track the object and use other "known" masses (and trajectories) like Sol, Luna, and Earth at the least.

    In the real world of science, every measurement has an error.

    The force of gravity goes as 1/r^2 so errors in measured position and trajectory result in unpredictable non-linear forces on the rock. We can do the math but small errors compound.

    How bad is their measurement error that gives them a calculated distance 4,200 miles from Earth?


    That is scary close but I have "some" faith in scientists.

    We could lose a satellite but the odds are very low (not zero) for that scenario.
    but how far could they be off??

    Leave a comment:


  • Pirate-Drakk
    replied
    Originally posted by G David Bock View Post
    [*]As it starts to approach Earth, telescopes will establish its precise trajectory[*]The observations are expected to help refine knowledge about its orbit[/LIST]

    As per above, the trajectory is not "exactly" known. That is because the mass of the object is in question, as we didn't build it. To determine that, you have to track the object and use other "known" masses (and trajectories) like Sol, Luna, and Earth at the least.

    In the real world of science, every measurement has an error.

    The force of gravity goes as 1/r^2 so errors in measured position and trajectory result in unpredictable non-linear forces on the rock. We can do the math but small errors compound.

    How bad is their measurement error that gives them a calculated distance 4,200 miles from Earth?


    That is scary close but I have "some" faith in scientists.

    We could lose a satellite but the odds are very low (not zero) for that scenario.

    Leave a comment:


  • Moulin
    replied
    I didn't know they had such power being that ''small''
    Russian 2013 meteor
    The bulk of the object's energy was absorbed by the atmosphere, with a total kinetic energy before atmospheric impact estimated from infrasound and seismic measurements to be equivalent to the blast yield of a nuclear weapon in the 400–500 kiloton (about 1.4–1.8 PJ) range – 26 to 33 times as much energy as that released from the atomic bomb detonated at Hiroshima.
    1500 people needed some type of medical aid?
    https://en.wikipedia.org/wiki/Chelyabinsk_meteor

    Leave a comment:


  • G David Bock
    replied
    Originally posted by G David Bock View Post
    30-metre asteroid skimming past Earth in October will test Nasa's doomsday 'planetary defence system'

    • Asteroid 2012 TC4 will pass 4,200 miles from Earth on October 12
    • Nasa is using the flyby to test its asteroid detection and tracking network
    • As it starts to approach Earth, telescopes will establish its precise trajectory
    • The observations are expected to help refine knowledge about its orbit


    Read more: http://www.dailymail.co.uk/sciencete...#ixzz4oTiJLrYN

    4,200 miles is dang close!
    Lunar distance averages about 239,000 miles and GEO is about 24,000 miles. This is a dang close shave here.
    Maybe not quite so close;
    EXCERPT:
    ...
    Paris (AFP) - An asteroid the size of a house will shave past Earth at a distance of some 44,000 kilometres (27,300 miles) in October, inside the Moon's orbit, astronomers said Thursday.
    The space rock will zoom by at an eighth of the distance from the Earth to the Moon -- far enough to just miss our geostationary satellites orbiting at about 36,000 kilometres, according to the European Space Agency (ESA).
    "It will not hit the Earth," said Detlef Koschny of ESA's "Near Earth Objects" research team. "That's the most important thing to say."
    The asteroid, dubbed TC4, first flitted past our planet in October 2012 -- then at about double the distance before disappearing. It is about 15-30 metres (49-98 feet) long.
    ...
    https://www.yahoo.com/news/asteroid-...155009565.html

    Leave a comment:


  • Moulin
    replied
    Originally posted by G David Bock View Post
    The variable is size of impactor. Anything a mile or larger could have significant effect in regional damage and weather changes.

    Tsunamis can travel far and many coastlines are populated.

    The impactor that wiped out the dinos and many other lifeforms 65 million years ago has been gauged at about 3 miles diameter.
    great points ...3 miles doesn't seem like much on an earthly scale...very telling
    ..but I thought perhaps volcanic activity was also a theory of the extinction--along with the impact
    ...however, what about Shoemaker hitting Jupiter with multiple hits?
    that would be devastating, yes?
    Last edited by Moulin; 01 Aug 17, 14:15.

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  • G David Bock
    replied
    Originally posted by Moulin View Post
    the damaging tsunami would have hit ''near'' populated areas
    75% of Earth is ocean....
    not a good chance of an asteroid doing ''major'' damage IMO
    thanks for link....I need and enjoy reading something other than Trump, etc
    The variable is size of impactor. Anything a mile or larger could have significant effect in regional damage and weather changes.

    Tsunamis can travel far and many coastlines are populated.

    The impactor that wiped out the dinos and many other lifeforms 65 million years ago has been gauged at about 3 miles diameter.

    Leave a comment:


  • Moulin
    replied
    Originally posted by G David Bock View Post
    Would have to hit a high population area to have significant and negative affect(impact). An ocean impact could set off damaging tsunami, many hardground impacts will send weather altering conditions, etc.

    Here's the NASA page on Asteriod Redirection Mission;
    https://www.nasa.gov/mission_pages/a...ive/index.html

    Here's an example of what happens if not near a high population area;
    https://en.wikipedia.org/wiki/Tunguska_event
    the damaging tsunami would have hit ''near'' populated areas
    75% of Earth is ocean....
    not a good chance of an asteroid doing ''major'' damage IMO
    thanks for link....I need and enjoy reading something other than Trump, etc

    Leave a comment:


  • G David Bock
    replied
    Originally posted by Moulin View Post
    is it worth it, though?
    what's the chances of a large enough asteroid hitting a populated area?--but they can't really test it against the real thing? will it work for sure?
    Would not have to hit a high population area to have significant and negative affect(impact). An ocean impact could set off damaging tsunami, many hardground impacts will send weather altering conditions, etc.

    Here's the NASA page on Asteriod Redirection Mission;
    https://www.nasa.gov/mission_pages/a...ive/index.html

    Here's an example of what happens if not near a high population area;
    https://en.wikipedia.org/wiki/Tunguska_event

    Leave a comment:


  • Moulin
    replied
    so it's a detection system only? ''part'' of a defense system?

    Leave a comment:

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