Yes, blood is toxic to neurons. We have a blood-brain barrier that only lets some things through (either passively if they're small enough like oxygen or alcohol, or actively for bigger molecules).

The brain sits in cerebrospinal fluid (CSF) rather than blood.

As for the actual mechanisms that blood will damage the brain -- first, if you've got a brain bleed, it'll increase intracranial pressure and make it harder for new oxygenated blood to get in, which will kill your neurons from simply lack of oxygen. Second, even a small bleed will kill neurons, because things like the sodium concentration in your CSF will get messed up, and then when the blood dies in your brain it'll leave behind a bunch of iron from hemoglobin which will also kill your neurons.

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Honestly, this made me think of the emdrive from a few years ago. Interesting phenomenon.

The medium plays a part in the momentum transfer, yes.

The net force on a spherical body isn't zero for a single beam because the beam changes shape moving through it, so the refractive details are different on either side.

But for two counterpropagating beams, which is what I used, the left–right forces do balance out, leaving an internal tensile load that stretches a compliant medium. You don't notice this in everyday situations with macroscale objects because they're stiff and the light is weak.

So when the light speeds up when it leaves the medium, where does that come from? The medium? So the net force on the medium is 0 because if gives it back up to the light when it leaves?

Neurons, especially in the CNS (brain/spinal cord), are quite sensitive, and are usually kept in a sheltered environment separated from the blood by the blood-brain barrier. Astrocytes and other glial cells provide a controlled environment for the neurons. They do take nutrients from the blood, but they act as a filter to only let through the right things and in the concentrations that neurons prefer.

Even in other tissues, blood isn't usually supposed to leave the blood vessels, and can cause trouble if it does. Perhaps the easiest to understand is coagulation - if everything's clotted up, that will disrupt whatever else is supposed to be happening in that tissue. There are also immune molecules which tend to get activated and cause inflammation when outside blood vessels. Inflammation generally interferes with regular tissue function, and CNS neurons are particularly sensitive to it.

Blood also contains higher concentrations of stuff like iron that would damage neurons.

Thank you for the detailed reply and follow up! It's unfortunate none of us will be around in 5 million years to see how the islands continue to change.

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No one thing is decelerating or accelerating. The photon–matter interaction propagates slower than c.

See the discussion here and the links within, for example.

Yep, it's even got a name, Maui Nui and included Kaho‘olawe as well (and some bits that are no longer islands). The general concept has been around for a while (e.g., Stearns & Macdonald, 1942) and there's been a variety of efforts to "reconstruct" what this island would have looked like (e.g., Price & Fisk, 2004). In detail, the Price and Fisk reconstruction suggests that Maui Nui at its maximum extent was actually larger than the "Big" Island is today.

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This answer got me wondering, if a photon could somehow enter an atmosphere, pass through water, then head back into the vacuum of space, does it “re-accelerate” to “full” lightspeed? How does that work?

from the bathymetry is it conceivable that the maui/moloka'i/lana'i trio was once a single island that eroded/subside into separate features?

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As I recall, the energy is split between absorption, reflection, and refraction. The frequency of the light wave stays the same; its speed changes. Remember that we’re talking about light interacting with matter, rather than lone photons in a vacuum.

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Thank you! I always forget to escape the parentheses on Reddit.