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  • 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.
    Battles are dangerous affairs... Wang Hsi

    Comment


    • 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??

      Comment


      • 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...
        Battles are dangerous affairs... Wang Hsi

        Comment


        • 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.
          "Put guards on all the roads, and don't let the men run to the rear."
          Major General John Buford's final words on his deathbed.

          Comment


          • 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.

            Comment


            • 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

              Comment


              • 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.

                Comment


                • 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

                  Comment


                  • Originally posted by G David Bock View Post
                    Hopefully that is so.
                    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).
                    27,300 - 4,200 = 19,100 miles error from their first guess

                    Twice the Earth's diameter is 15,834 miles, so they were slightly worse than my speculation.

                    Good thing the latest number is the more accurate one...
                    Battles are dangerous affairs... Wang Hsi

                    Comment


                    • Originally posted by G David Bock View Post
                      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.
                      Like you pointed out in your post 262 NASA and the major observatories are calling for it to miss earth by more than 27,000 miles. Well outside their (now more refined) margin of error.
                      "Put guards on all the roads, and don't let the men run to the rear."
                      Major General John Buford's final words on his deathbed.

                      Comment


                      • The Asteroid That Killed the Dinosaurs Caused Catastrophic Climate Change

                        https://www.seeker.com/earth/climate...climate-change

                        Comment


                        • Originally posted by G David Bock View Post
                          The Asteroid That Killed the Dinosaurs Caused Catastrophic Climate Change

                          https://www.seeker.com/earth/climate...climate-change
                          would it have broken up slightly into many pieces?

                          Comment


                          • Originally posted by Moulin View Post
                            would it have broken up slightly into many pieces?
                            Maybe, but net effect could have been the same to slightly less. There are many variables to consider.

                            Generally speaking, anything over about 2-3 miles size can and could cause significant biosphere damage that could take centuries to millenia for Nature to recover from.

                            "broken up slightly" depends upon the mechanics/math of such. ...

                            ... If broken into smaller pieces and on a horizontal axis, roughly same impact time range, one might defuse overall destructive level while spreading such over a larger area, circle of impact.

                            Alternatively one might get a staggered imapct area~time range like in case of Shoemaker-Levy9 https://en.wikipedia.org/wiki/Comet_...E2%80%93Levy_9 which could result in larger and greater destruction zones.

                            Lots of variables involved but my studies to date suggest a single impact event is usually better over a larger impact event and deflection away from Earth is Best yet.

                            Comment


                            • Originally posted by G David Bock View Post
                              Maybe, but net effect could have been the same to slightly less. There are many variables to consider.

                              Generally speaking, anything over about 2-3 miles size can and could cause significant biosphere damage that could take centuries to millenia for Nature to recover from.

                              "broken up slightly" depends upon the mechanics/math of such. ...

                              ... If broken into smaller pieces and on a horizontal axis, roughly same impact time range, one might defuse overall destructive level while spreading such over a larger area, circle of impact.

                              Alternatively one might get a staggered imapct area~time range like in case of Shoemaker-Levy9 https://en.wikipedia.org/wiki/Comet_...E2%80%93Levy_9 which could result in larger and greater destruction zones.

                              Lots of variables involved but my studies to date suggest a single impact event is usually better over a larger impact event and deflection away from Earth is Best yet.
                              Amoung the timing and placement variables, consider the Tunguska Event of just over a century ago. Had this happened a few hours later (and maybe a few degrees lower in latitude) and had the object been "busted up" into several impactors, the results may have had a major set-back to global history in the destruction that might have occurred to Europe.

                              https://en.wikipedia.org/wiki/Tunguska_event
                              ...
                              The Tunguska event was a large explosion that occurred near the Stony Tunguska River in Yeniseysk Governorate (now Krasnoyarsk Krai), Russia, on the morning of 30 June 1908 (N.S.).[1][2] The explosion over the sparsely populated Eastern Siberian Taiga flattened 2,000 km2 (770 sq mi) of forest yet caused no known human casualties. The explosion is generally attributed to the air burst of a meteoroid. It is classified as an impact event, even though no impact crater has been found; the object is thought to have disintegrated at an altitude of 5 to 10 kilometres (3 to 6 miles) rather than hit the surface of the Earth.[3]

                              The Tunguska event is the largest impact event on Earth in recorded history. Studies have yielded different estimates of the meteoroid's size, on the order of 60 to 190 metres (200 to 620 feet), depending on whether the body was a comet or a denser asteroid.[4]

                              Since the 1908 event, there have been an estimated 1,000 scholarly papers (most in Russian) published on the Tunguska explosion. In 2013, a team of researchers published analysis results of micro-samples from a peat bog near the center of the affected area showing fragments that may be of meteoritic origin.[5][6]

                              Early estimates of the energy of the air burst range from 10–15 megatons of TNT (42–63 PJ) to 30 megatons of TNT (130 PJ),[7] depending on the exact height of burst estimated when the scaling-laws from the effects of nuclear weapons are employed.[7][8] However, modern supercomputer calculations that include the effect of the object's momentum find that more of the energy was focused downward than would be the case from a nuclear explosion and estimate that the airburst had an energy range from 3 to 5 megatons of TNT (13 to 21 PJ).[8]

                              The 15 megaton (Mt) estimate represents an energy about 1,000 times greater than that of the atomic bomb dropped on Hiroshima, Japan — roughly equal to that of the United States' Castle Bravo (15.2 Mt) ground-based thermonuclear detonation on 1 March 1954, and about one-third that of the Soviet Union's Tsar Bomba explosion on October 30, 1961 (which, at 50 Mt, was the largest nuclear weapon ever detonated).[9]
                              It is estimated that the Tunguska explosion knocked down some 80 million trees over an area of 2,150 square kilometres (830 sq mi), and that the shock wave from the blast would have measured 5.0 on the Richter magnitude scale. An explosion of this magnitude would be capable of destroying a large metropolitan area,[10] but, due to the remoteness of the location, no human fatalities were officially documented. Several reports have indicated that two people may have died in the event, however these deaths remain unofficial.[11][12][13][14] This event has helped to spark discussion of asteroid impact avoidance.
                              ...
                              https://en.wikipedia.org/wiki/Tunguska_event

                              Comment


                              • Originally posted by G David Bock View Post
                                Amoung the timing and placement variables, consider the Tunguska Event of just over a century ago. Had this happened a few hours later (and maybe a few degrees lower in latitude) and had the object been "busted up" into several impactors, the results may have had a major set-back to global history in the destruction that might have occurred to Europe.

                                https://en.wikipedia.org/wiki/Tunguska_event
                                ...
                                The Tunguska event was a large explosion that occurred near the Stony Tunguska River in Yeniseysk Governorate (now Krasnoyarsk Krai), Russia, on the morning of 30 June 1908 (N.S.).[1][2] The explosion over the sparsely populated Eastern Siberian Taiga flattened 2,000 km2 (770 sq mi) of forest yet caused no known human casualties. The explosion is generally attributed to the air burst of a meteoroid. It is classified as an impact event, even though no impact crater has been found; the object is thought to have disintegrated at an altitude of 5 to 10 kilometres (3 to 6 miles) rather than hit the surface of the Earth.[3]

                                The Tunguska event is the largest impact event on Earth in recorded history. Studies have yielded different estimates of the meteoroid's size, on the order of 60 to 190 metres (200 to 620 feet), depending on whether the body was a comet or a denser asteroid.[4]

                                Since the 1908 event, there have been an estimated 1,000 scholarly papers (most in Russian) published on the Tunguska explosion. In 2013, a team of researchers published analysis results of micro-samples from a peat bog near the center of the affected area showing fragments that may be of meteoritic origin.[5][6]

                                Early estimates of the energy of the air burst range from 10–15 megatons of TNT (42–63 PJ) to 30 megatons of TNT (130 PJ),[7] depending on the exact height of burst estimated when the scaling-laws from the effects of nuclear weapons are employed.[7][8] However, modern supercomputer calculations that include the effect of the object's momentum find that more of the energy was focused downward than would be the case from a nuclear explosion and estimate that the airburst had an energy range from 3 to 5 megatons of TNT (13 to 21 PJ).[8]

                                The 15 megaton (Mt) estimate represents an energy about 1,000 times greater than that of the atomic bomb dropped on Hiroshima, Japan — roughly equal to that of the United States' Castle Bravo (15.2 Mt) ground-based thermonuclear detonation on 1 March 1954, and about one-third that of the Soviet Union's Tsar Bomba explosion on October 30, 1961 (which, at 50 Mt, was the largest nuclear weapon ever detonated).[9]
                                It is estimated that the Tunguska explosion knocked down some 80 million trees over an area of 2,150 square kilometres (830 sq mi), and that the shock wave from the blast would have measured 5.0 on the Richter magnitude scale. An explosion of this magnitude would be capable of destroying a large metropolitan area,[10] but, due to the remoteness of the location, no human fatalities were officially documented. Several reports have indicated that two people may have died in the event, however these deaths remain unofficial.[11][12][13][14] This event has helped to spark discussion of asteroid impact avoidance.
                                ...
                                https://en.wikipedia.org/wiki/Tunguska_event
                                Point being that efforts to deflect and/or reduce composition of a potential impactor could result in even worse Impact Event than originally in line for.

                                Comment

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