Uranus up close: What proposed NASA 'ice giant' mission could teach us

[Admin]

A proposed NASA mission to Uranus would shed light on the mysterious ice giant as well as a type of exoplanet that's among the most common in the universe, researchers say.

Uranus up close: What proposed NASA 'ice giant' mission could teach us : Read more

 

[progan01]

I should be very interested in any theory that can explain how a single planetary collision could tilt not just Uranus but its rings and major satellites to the same precise degree. That's a billiard shot I'd pay a DOLLAR to see.

 

[billslugg]

The collision that turned Uranus on its side did not also tilt the existing rings and moons, it destroyed them and created a new set. Any off center hit would put a huge accretion disc around the planet which would catch any existing rings and moons that happened to be on a different orbital plane. During their orbit they would be forced to cross the new plane and would collide with it. Any gravitationally bound system of random items in orbit eventually forms a single plane.

 

[progan01]

The energy required to shift the rotational axis of a planet is considerably in excess of the amount of energy required to disintegrate the planet entirely, leaving a ring about the Sun that would, due to the effect of orbital harmonics, disperse to other stable orbits, likely colliding with other bodies already present, such as moons, and the planets themselves, leaving no Uranus whatsoever. No. The Solar System is not a billiards table with planets knocking into each other and bouncing away, nor do they change their orbital momentum post collision. It is now evident that Mars and Earth both suffered such collisions in their early history, transforming both planets, but not noticeably altering their rotational axes. We should be living on an entirely different world with radically different seasons if rotational axes could be altered so easily.

The 'Uranus collision' theory is intellectually bankrupt and needs to be discarded before we make any headway in understanding of the planet. For my money, it's much more likely that Uranus is a captured outer planet formed in the same stellar nursery around a different star, and ejected from its original orbit due to the effect of orbital harmonics among the planets of that other system. We have postulated that our Solar System lost a gas giant world due to the perturbations of the orbits of the forming planets. If we could lose a planet, could we not gain one in more-stable times after formation? We need to probe Uranus and determine its physical makeup, which I suspect is similar to that of the other planets but differing in some elemental isotopes not found here in the same proportions. I find this postulate far more convincing than the notion that a whack can change a planet's rotation axis AND destroy all its moons at the same time. Preposterous.

 

[billslugg]

Here is a simulation from NASA that shows an impact was sufficient to turn Uranus on its side and change its rotation without being powerful enough to even strip away its atmosphere.
Planet-Shifting Collision Shaped Uranus’ “Rolling” Rotation | NASA

Here is another article from NASA, one that posits the most likely origin for Uranus was formation around the Sun and then migration outwards
In Depth | Uranus – NASA Solar System Exploration

Do you have references for any of your claims?

 

[progan01]

Didn't you notice that the 'simulation' you posted showed only a two-dimensional animation of the potential impact, with no explanation for how or to what degree this would change the planet's rotational axis? Not to mention that nothing is said about the destruction of rings and moons and their miraculous 'resurrection' in the new 'tilted' system, as you insist happened. What do you think this example proves, other than your attempt to invoke the name of NASA to justify a physically impossible astrometric change?

I already cited the migration of the planets after formation, which this NASA blurb on Uranus mentions in passing, and in less depth than I have already provided. Not that there aren't better examples, but given your attempt to rely on inapt authority to carry your case, there's no point in bringing more and better evidence in.

You might refer to this LiveScience article on changing the Earth's rotational axis for the amount of force required to do so, which ought to give you an idea of the scale of energies involved:

Can a Nuclear Blast Alter Earth's Rotation?

Nuclear bombs are humankind's most powerful weapon, but can it alter the rotation of the earth?

www.livescience.com

We haven't yet seen the destruction of a planet, but we can calculate how much energy it would take to reduce, say, Earth to powder -- the energy equals three-fifths of the gravitational constant, times the mass of the planet squared, and divided by the radius of the planet. Or 2.25 x 10^32 joules. You may refer to this article and the accompanying Scott Manley video for how this determination was derived:

Watch: How Much Energy Does It Take to Blow Up a Planet?

The prospect of blowing entire planets to smithereens isn't exactly pertinent for us Earthlings, but Star Wars fans will know that in three of the seven films, a device capable of such destruction makes life very difficult for the protagonists.

www.sciencealert.com

But this would completely eliminate the gravitational binding energy of the Earth, erasing it utterly; reducing it to chunks would presumably take a good deal less. Much less than the energy required to change its axis. Your cited simulation provides no figures as to the energy released or recombined in the 'reconstructed' Uranian system, so I can't say that you've 'proved' anything other than a preference to use a big name to assert a conclusion you cannot yourself prove or justify.

I also note that you did not bother to counter the possibility that Uranus is a 'captured' world. I must therefore conclude that you agree it is as likely an event as the migration of the planets through orbital resonance. If you have actual figures and probabilities of any sort of planetary axial change, feel free to bring them. I can't find a one.

Mind, now, human beings have already altered the Earth's rotational axis through climate change and the loss of hundreds of billions of tonnes of polar ice. But not by 97.77 degrees. See this Guardian article on the issue: https://www.theguardian.com/environ...risis-has-shifted-the-earths-axis-study-shows

I look forward to receiving your data. If any.

 

[Mememe]

I should be very interested in any theory that can explain how a single planetary collision could tilt not just Uranus but its rings and major satellites to the same precise degree. That's a billiard shot I'd pay a DOLLAR to see.

Computer modeling shows that when a planet turns its rotational angle its moons eventually follow and turn to what you call the same precise degree. It has to with the centre of gravity which is strongest at a planet’s equator. The theory is completely plausible.

 

[progan01]

I take it you have never worked with a gyroscope, or owned so much as a toy one. Or you would have some personal experience of the amount of force required to change the direction in which a gyroscope, or any turning cylinder or ring, is rotating. This is what is meant by rotational energy, and it is by no means trivial. And it is certainly most difficult to change. I invite you to purchase a toy gyroscope, set it spinning, and then use a hammer to hit it to change the direction in which it spins. I daresay you will run out of both gyroscopes and hammers before you succeed.

I don't know what sort of computer modeling you have referenced, if any, but we have no examples in nature of any sizable astronomical body changing its spin axis, for the reason stated above. Or any orbiting bodies such as moons following suit. There simply is no physical law for an orbiting body to match the direction of spin of the primary object it orbits. Were this true, then long ago all the satellites launched into Earth orbits - even polar and westward-launched - would have settled into a west-to-east equatorial orbit and no other.

For these reasons, as well as the others I have stated, the postulate that some collision resulted in 'tilting' the spin of Uranus is entirely erroneous. I look forward to your results hammering your gyroscope. You may attempt the same experiment with a rotating car wheel, if you prefer. I expect the same results regardless.