Hath in these last days spoken unto us by his Son,
whom he hath appointed heir of all things,
by whom also he made the worlds;
Hebrews 1:2
"Uranus has an axial tilt of 98 degrees, giving it the appearance of a bulls-eye as it revolves around
the sun. Its moons revolve comfortably around the planet’s equator. This unusual arrangement, unique in the solar system, has challenged planetary scientists since its discovery. A new model accounts for it through a series of gentle bumps from impacts as the planet was forming from dust and gas, but how would one ever test such an idea?
Previous theories used a single giant impact to explain the tilt. Uranus, though, has lower orbital eccentricity than the other gas giants save Neptune, and lower orbital inclination than the other gas giants. It would seem strange such a collision would not have greater effect on the planet’s orbit or moons, which have relatively circular orbits in the orbital plane of Uranus.
Science Daily noted that problem for the single-impact theory, saying, “the moons of Uranus should have been left orbiting in their original angles, but they too lie at almost exactly 98 degrees.” What to do?
This long-standing mystery has been solved by an international team of scientists led by Alessandro Morbidelli (Observatoire de la Cote d'Azur in Nice, France), who is presenting his group's research at the EPSC-DPS Joint Meeting in Nantes, France.
Morbidelli and his team used simulations to reproduce various impact scenarios in order to ascertain the most likely cause of Uranus’ tilt. They discovered that if Uranus had been hit when still surrounded by a protoplanetary disk – the material from which the moons would form – then the disk would have reformed into a fat doughnut shape around the new, highly-tilted equatorial plane. Collisions within the disk would have flattened the doughnut, which would then go onto form the moons in the positions we see today.
Problem: the model makes the moons end up in retrograde orbits, requiring additional tweaks to the model. Adding two more impacts yielded a “higher probability of seeing the moons
orbit in the direction we observe.”
Problem 2: “This research is at odds with current theories of how planets form, which may now need adjusting.” If planets formed by accreting small material, the way textbooks have claimed for decades, then “They should have suffered no giant collisions,” Morbidelli said like a worried umpire.
Calling three strikes on Uranus will end the game: “So, the standard theory has to be revised,” he said – as if the planet-maker team was on base already.
But the multiple collisions necessary to create the Uranus we see appear so finely-tuned in his model, they appear almost miraculous (again). If so, it’s doubtful that anything has been gained scientifically by the exercise except that Morbidelli can add another published paper, miracles and all, to his curriculum vitae." CEH
"When I teach medical students, they're more interested in the rare people who are born with birth defects, They want to understand embryology so they understand how things go awry, but I'm more interested in the fact that for everyone sitting in my classroom—all 200 of those medical students and dental students—it went right! And every one of them has a heart on the left side and every one of them has two kidneys, and how the heck do you do that?" 
