Posted: May 09, 2019 12:27 am
by Calilasseia
zulumoose wrote:
"Just one example: billions of celestial bodies in perfect movement, why don't they crash into each other if there is no Creator to guide them?"

The result of "perfect" movement guided by an infallible Creator.


Apparently the individual you've alighted upon, has a short memory. Wind the clock back to 1994, and NASA was aligning the Hubble Space Telescope to take lots of lovely photos of Comet Shoemaker-Levy 9, as its various fragments slammed into Jupiter at 30 kilometres per second or so.

The principal reason we don't see this sort of pyrotechnic display more often, centres upon that decision by the International Astronomical Union, to include clearance of an object's neighbourhood as part of the definition of the term 'planet'. Basically, almost all of the big rocks engaged in their collisions a long time ago, indeed collisions of this sort are necessary for planetary accretion. But once those collisions have taken place, and a large accreted body has attracted other, smaller bodies to itself, taking them out of circulation, the frequency of subsequent collisions with leftover objects diminishes accordingly. Even so, Earth is itself subject to these collisions to this day, albeit with much smaller objects. Scientists have estimated that the Earth gains 1,000 tons of mass every year, courtesy of lots and lots of small rocks that fall through the atmosphere, and add their contents to the planet.

However, there are still enough decent sized rocks out there to be troublesome - the one that hastened the demise of the dinosaurs 65 million years ago was estimated to be 10 miles in diameter. This is a big rock by our everyday standards, but on the cosmic scale, it's a speck of dust, and there are numerous asteroids of comparable size still moving about on orbits that cross the orbit of Earth. There are around 400 of these listed in a nice little catalogue by NASA, and any one of those could potentially undergo an orbital perturbation leading to a collision with Earth, at which point it's "Game Over" for us in a big way.

Even a relatively small body such as 99942 Apophis, at just 0.185 km radius, could unleash a catastrophe if it collided with Earth. This is a body that occupies a volume about the same as a Nimitz Class nuclear supercarrier, but if it was perturbed onto a collision course with Earth, it would impact our planet at around 30 km/s. Its mass is around 6 × 1010 kg, and as a consequence would turn up with a lot of kinetic energy - 2.7 × 1019 J or thereabouts, a large amount of which would be liberated as heat pumped into the asteroid as it was brought to a halt. By comparison, the most powerful nuclear weapon ever detonated on Earth, the former Soviet Union's Tsar Bomba, liberated 2.1 × 1017 joules by comparison, so we're looking at a collision event liberating over 100 times the energy of the Tsar Bomba, if Apophis 99942 decides to play "Trick or Treat" with Earth.

There are bigger bodies in that catalogue, such as 5731 Zeus, which is somewhere between 2.1 and 4.7 km in diameter, which would, if it ever paid us a serious visit, trigger yet another extinction event, probably wiping us out in the process. 1866 Sisyphus is 7 kilometres across, making it comparable to the KT-event bolide in size.

Even on a more modest scale, does this individual not remember this little event from 2013?