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Not quite true. The true blind-spot is a little off-axis from the centre of vision.

What you describe is the effect that dimmer stars may seem to "disappear" when you look straight at them because the centre of vision, the fovea (while having higher resolution and colour) is less light-sensitive.

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The same amount of dark matter, with the same basic properties, can explain galaxy rotation curves, galaxy cluster dynamics, large scale structure, the CMB anisotropies, and the primordial abundances of chemical elements.

"Something is wrong with the measurements" has none of that predictive power, and even more quantitative ways of stating that (e.g. modified Newtonian dynamics) cannot explain the data as well as dark matter does.

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Even if it were true in general that at absolute zero there were no thermal motion of atoms, that wouldn't make things infinitely rigid.

When you push on something, your outer electrons are repelling the electrons of the other object (whether this repulsion happens because of the Pauli exclusion principle or electromagnetism or both is irrelevant for this reasoning).

Anything with mass, like an atom, doesn't move instantaneously when a force is applied. Instead, it accelerates. Therefore, it takes some finite amount of time to move the first layer of atoms back to their equilibrium position (i.e. how far away from your hand, or tool, or whatever, they would be if the two surfaces were just in contact). Similarly, it takes some finite amount of time to move the row of atoms, and the row after that, and the row after that. This is entirely independent of random thermal fluctuation of the atoms.

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It's called your persistence of vision, or retinal persistence. It is not even across your visual field. It is also not the same for all individuals. Some people can detect a pulsing light source at higher frequencies than others.

Your brain is faking all of it. The actual visual stimuli from your eye has far less bandwidth than you would think. Your brain builds a 3 dimensional internal representation of the world around you and is continuously updated part by part from your visual input. It's nothing like a computer monitor where all the pixels are being refreshed every single time.

In fact your ears will update the internal representation as well as your eyes. Your brain processes the sounds, directions, and timing of the sounds to help update your location within that representation.

Just how well your visual cortex understands the complex interaction of light on surfaces is truly amazing. There is a particular optical illusion that demonstrates how strong this knowledge of how light should work can influence what you believe is true.

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https://en.wikipedia.org/wiki/Checker_shadow_illusion

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Your brain INSISTS that A and B are different shades, because the rest of the checkerboard follows a consistent pattern, and part of it must be in shadow. It is one of those optical illusions that is nearly impossible to "turn off" because your visual cortex simply does this processing 100% of the time automatically.

Sacculina It's a crustacean that injects a small amount of cells into a crab. The cells grow tendrils into the crabs body and reproductive area and compells it to help spawn more sacculina.

Even if it infects a male crab the crab will still behave like a female.

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Makes sense from evolutionary point of view. Oh there is enough food? Then we can go into this major growth, that requires a lot of energy. Oh there is not enough food? Let’s wait another year or two and hope that the situation is better then.

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This was what i learned concerning this topic. The rate of producing the hormone was just slightly higher than the clear rate. Eventually it hits the concentration tipping point and begins the process. I vaguely remember it relating to how puberty starts, but it was so long ago I learned it the field probably moved to a different or more accurate understanding

There is a cutoff time. As the 99mTc decays, more and more of it becomes useless. There are several reasons it becomes useless (begins to lose its tag to whatever chemical it’s tagged to, decays and the amount of radiation left is too small to use, oxidizes, etc). There is an expiration time on each dose we receive and there are strict limits to how much and how little radiation we can give a patient depending on the type of scan we are doing. I’m a nuclear medicine tech, so I deal with this stuff all the time.

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Thank you! I really do appreciate it and will step off from here and investigate further. You’re the best!

Decent answer :)

The only thing I'd add (and I'm simplifying a lot here) is that if you imagine that the cells in the body are constantly signalling to each other, at various tipping points, one (or more) signal becomes more dominant than the other which in turn can trigger new behaviours.

So, the absolute trigger isn't often evident as it is the result of systemic change in cell function.

Just adding to your reply. I found this paper outlining different, competing hypotheses, and parasite hypothesis is only one of them:

The evolution of IgE-mediated type I hypersensitivity and its immunological value

Balloons aren't precise enough to try to capture something at 65k feet.

They control their direction via wind currents.

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