Uranus - Science topic

The Earth's tilt is responsible for the change in seasons; a 33.5 degree tilt would result in greater temperature extremes during the seasons. Uranus' tilt is likely due to an ancient impact. If Earth was like Uranus, seasons would be extreme! The summer Sun would be up 24 hours a day, leading to a scorching climate, while the winter hemisphere would be in freezing darkness. The north and south magnetic poles, which affect things like navigation, drift and even switch places back and forth over time. Earth's other kind of pole is the axis around which the planet physically spins. This axis has also slightly shifted over time.

Dear Christopher Gerard Yukna ,

CGY: Whether Earth is not an ideal black body or not will not change the fact that all the planets mentioned "emit" , "glow", "shine" more energy than they receive. ... They contradict the conservation of energy.

No, they do not contradict the conservation of energy. There are however several effects to take into account.

CGY: "there is a very small amount of energy that comes from radioactive decay inside planets, so small that for heat balance calculations it is usually ignored."

For the overall heat budget for most planets, that is true, the Solar input is significantly greater than other sources.

CGY: Gentlemen the above statement is at odds with a number of things.

The stored heat from formation depends on the volume, the rate of loss depends on the surface area so larger planets can retain heat for longer. For a small planet like Mercury or Mars, the residual formation heat has almost entirely been lost, for Earth and Venus there is still a small amount and for gas giants it is dominant. At the time of formation, the gas giants with much greater gravity also generated more heat from accreting other bodies, but at present they are also farther from the Sun, have a lower surface temperature and so lose heat more slowly (the Stephan-Boltzmann Law).

For a rocky planet with a molten interior, a significant amount is released as Alfred says by the phase change on solidification. Rocky planets also have a much higher proportion of heavy metals and therefore radiogenic heat. There are few radioactive isotopes of hydrogen and helium but phase changes in the gas will also play a part.

For smaller bodies like the Moons of Jupiter, you also have to take tidal heating into account.

When it comes to calculating the surface temperature however, the input from the Sun dominates the overall balance. You can calculate the temperature as if the planet were a black body but none are even close to that. You have to apply an emissivity factor which depends on wavelength. If the atmosphere allows optical wavelengths in from the Sun but is reflective to infrared then the surface temperature must be higher than you would expect for a black body in order to radiate the same total energy as it receives from the Sun, from stored formation heat and radiogenic sources. That adds some tens of degrees for Earth but has a huge impact on Venus.

No, there is no clash but the topic is complex and needs careful and detailed modelling.

Thomas Jüstel ,

Please accept my belated thanks for your answer to my Research Gate discussion thread question "Why do Venus and Uranus rotate on their axes [and] or spin in a clockwise direction?" Currently, I have just completed and returned galley proofs for my article on "Darwinian Ideas and Marxian Idealism in Austen, Twain, Yeats, Camus, and Ishiguro" in the Routledge Companion to Literature and Class and also for my Elsevier chapter on "Artificial Intelligence for Heavy Vehicle Technology: Subtextual AI/HVT Imagery, Cultural Ethos, and Legal/Ethical/Moral Standards in The Long, Long Trailer. Currently, I am compiling a list of galley proof corrections for my chapter on "Toward a Quantum Theory of Cognitive Affect from Poe to Robotic Helpers: Newton, Arousal, and Covalent Bonding, which is scheduled for publication in Artificial Intelligence and Computing Logic: Cognitive Technology for Business Analytics, forthcoming in 2022.

In case you may be interested, I would also like to let you know that, only hours ago, a second answer arrived at this Research Gate discussion thread, contributed by a new scientific researcher whose principal scientific research linguistic areas are in German and Russian, I believe, with English as a third area. It would be of interest to me if you might be in agreement with the perspective he has presented on this RG discussion thread as an expert in the field.

Thank you very much!

With my best regards,

Nancy Ann Watanabe, Ph.D.,

Literature, Film, and Science

The problem with pebble accretion is it has to be gentle as there is no mechanical strength until the object gets big enough to be gravitationally stable. If you look at small asteroids, their gravity is negligible, but they have craters which implied an impact with enough energy to melt silicates. Impacts could have quite high energies, and even moderate ones would scatter pebbles, like the result of a collision on a snooker table. The evidence is that the initial maximum sizes of the dust is about 4 μm. How does this form strong pebbles? I have nothing against pebbles, but there has to be something stronger holding them together, and mhy answer to that comes from chemistry. Chemistry, after all, is the the science of the interactions of matter, but astronomers and physicists seem strangely reluctant to consider it, probably because what is required for this problem is relatively obscure.

https://www.youtube.com/watch?v=BED-ZQeFCiY

This short video, released in 2017, appears like a Neo-Genesis narrative in which Carl Sagan speaks as a voice located in the future as he looks back nostalgically to a time when humanity lived happily on a legendary planet named Earth.

It's complicated. Some would argue that Apollo was never about scientific exploration and achieved its goal as soon as the Apollo 11 crew returned to Earth on 24 July 1969: that it was, in other words, a Cold War exercise in soft power. There's no doubt that it was primarily geopolitical in motivation. NASA itself had doubts about Apollo's continuation, for lunar exploration was risky, with every new mission offering many chances for catastrophic failure that would undo the prestige gains previous missions had achieved. I think it can be argued that 14 and 15 were flown to restore prestige lost through Apollo 13 and that 16 and 17 were flown to undermine prestige the Soviet Union gained through robotic rovers and sample returners. Some within NASA wanted to shift to Earth-orbital space stations; that is, to get back to the track the agency had plotted out for itself in 1959. As part of that, the Administrator at the time traded away two Apollos (18 and 19) in the hope of obtaining support for a Station/Shuttle Program. Then there was Nixon's desire to end the Democratic JFK/LBJ Apollo Program and put his stamp on the space program, and intercenter rivalries, mainly between Marshall in Huntsville, with its evolutionary Apollo Applications Program (which became Skylab), and Johnson in Houston, with its revolutionary Shuttle Program (which killed 14 astronauts in 135 flights). There's a lot more to it, of course, and this does not address (except indirectly) why we've never created an opportunity to resume lunar exploration using crews. I think that, after Apollo, it became abundantly clear that the whole Solar System needs exploration and that Minovitch's work on gravity assist made the whole Solar System economically accessible to robots. More here:

David SF Portree