If I were standing on a giant neodymium magnet the same diameter and mass of the Earth and dropped a rubber ball, would it fall at the same rate as it would on Earth?

It really is a matter of photoreceptor cells that evolved in a pit rather than flat on the surface. The "pit" allowed for a directional sensation.

Lack of sanitation, lack of population willing to protect each other with propylactic hygiene such as masking, distance, washing, vaccinations/antibiotic regimes. Vulnerability due to population concentration, travel, malnutrition, leadership not taking it seriously, science-deniers, alternate facts, illiteracy, substandard sanitation. So many factors go into the math, along with the robustness of the causitive organism, lethality and longevity of the infection.

Something to keep in mind: in the creatures eyes began evolving in, you aren't talking about generations spanning 20 years or something. Generations were on the order of a few weeks, and evolution was rather rapid fire by comparison to today. We have a nice stable planet, with stable weather and stable chemistry. When life was evolving basic forms of biology, that was not quite the case.

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Beyond that, there is more than 1 path to creating an eye.

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How is the distance of stars determined? Clearly you don't have two angles to do this

Why is the solar system on such a flat plane? Shouldn't it be more of a sphere with the sun in the middle?

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if you cross 2 incredibly long lines next to each other which both rotate clockwise and counterclockwise the point at which they cross increases exponentially. can the crossing point exceed the speed of light? if so does this mean you can essentially send information faster then the speed of light?

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Iron is the heaviest element you can get in a stars core when it does nuclear fusion before it collapses on itself

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Scientists talk about things "warping spacetime," like the way light is "bent" near a large mass--except it's traveling along a curve in spacetime. While that is helpful to visualize, it always leaves in my mind the impression that spacetime is something other masses are on or in, like a stapler inside jello.

But I keep wondering if spacetime is also, for lack of a better word, in everything? Does an atom displace spacetime? Is spacetime between the nucleus and the electrons? Or is it also inside the nucleus?

Maybe a bigger example. Is Earth in but separate from spacetime? Or is spacetime right beside me when I'm sitting in my living room?

^ This is the correct answer. If you look at the amount of DNA we share with other primates, like, say, the Bonobo, it is clear humans could be re-classified to more accurately reflect our close genetic ties to them.

But, here is the thing: It is we humans who define the categories into which we group genus/species, etc. And we really love to think of ourselves as extra special. So, the idea of including ourselves with a group of non-human animals goes against the grain of society, no matter how genetically accurate it would be.

There were at least a few dozen other Homo species. Homo sapiens, considered "modern humans", lived along side 8 other species at one point. They are all extinct now. Part of the reason is because of how well we adapted to a rapidly changing earth in the ice age. What seems like simple accomplishments now were monumental then, making ranged weapons, tighter fitting clothing, and being omnivores helped us dominate. The most famous cousin to us was Homo neanderthalensis, which were specialized in hunting big game. This hunting practice may of made them less adaptive and they had to travel great distances just to eat, which may of lead to their demise.

>Those "prions" in the paper you are referencing are yeast proteins that have distinct conformations that can propagate like human prions.

Thanks, I missed that they were only roughly analogous to prions. That's an important distinction.

And to address my other point myself, it looks like only a few groups of mammals are vulnerable to them, so evolution hasn't had billions of years to work on this, more like tens of millions, I think.

There was approximately 15 other Homo type species ranging from Neanderthals to Homo-Erectus etc... we either wiped them out or they came much earlier than us. Homo-sapiens-sapiens (us), were the last to leave Africa and settle around the world. There were numerous others that did this in the hundreds of thousands of years before us, so we either got there and killed them off / outcompeted them or they did that to themselves.

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This is addressed quite comprehensively in an existing FAQ.

There is a fantastic visualization of this on the show Cosmos (the Neil Degrasse Tyson version) on the evolution episode (how molecules work was the name of the episode if I recall)

Sorry I can't give you a great scientific answer but if you're looking for a surface level explanation it should help.

Yes, but. Reactivities depend greatly on physical conditions. In a cloud that's 100K, the molecular composition will be totally different than a cloud that's 1000K or one that's 10K. To predict which molecules form, you need a good census of how much gas is in each phase. We can actually tell that pretty well in galaxies by looking at various molecular and atomic emission lines.

The limit is actually in our knowledge of the chemistry, though. While we have good models to predict simple molecules, like CO, CO2, H2O, etc., we have a hard time with more complex molecules because the chemical reaction networks get very complicated, and in many many cases, the reaction coefficients are unknown. For example, our knowledge of Sulfur-containing molecular chemistry is very poor - there are too many reactions that haven't been measured in the lab, so we don't know what to predict. There is a lot of work left to be done in astrochemistry!