Recent comments in /f/askscience

seeriktus t1_j38d4cu wrote

Reply to Why do some diseases cause a loss of appetite? by Fragrant_Novel_3907

Satiety and hunger are controlled by hormonal circuits. If something interferes with the ability to release those hormones, or the bodies ability to respond to those hormones, then they will be impacted. See circuits for Ghrelin, Leptin. For example if an autoimmune disease targets cells holding ghrelin receptors in the hypothalamus then you might get anorexia (as well as brain damage).

A major thing that goes on during viral infections is the bodies release of interferon, which has the side effect of reducing hunger. https://pubmed.ncbi.nlm.nih.gov/?term=interferon+hunger&filter=pubt.review

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Butiwouldrathernot t1_j38af3e wrote

Reply to Could aquifers be actively recharged? by smontanaro

Deep groundwater takes decades to infiltrate. You can pump water underground, but the aquifers that have been depleted are porous formations and there's significant evidence in central California that aquifer depletion has resulted in sinkage, which means that space may no longer be available.

Fracking is the result of injecting liquid underground which fractures the porous formation and releases held oil or gas. These are different, and usually much deeper, formations than the formations that can hold potable aquifers.

Similarly, CO2 sequestration is done in very deep formations (typically around 2km below surface in my experience). This deep earth activity does not simulate subsurface potable water aquifers due to the difference in strata and pressure.

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aspheric_cow t1_j38aco0 wrote

Reply to comment by fliguana in How do you optimize a rocket or space vehicle liftoff? by seriousnotshirley

Also, you want a larger nozzle at higher altitude (lower ambient pressure). An engine + nozzle optimized for low altitude would be very inefficient at high altitude, so you might as well drop it and switch to the high altitude engine. The Shuttle is an exception as you say, but actually the solid rocket boosters provided about 2/3 of the thrust at liftoff.

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ForeverInQuicksand t1_j386kr9 wrote

Reply to comment by [deleted] in How much do water molecules move around within a stationary body of water? by KpgIsKpg

What if you took a 2ft pipe, that can be capped at both ends, and placed a valve you could open and close in the middle. Then you could place a small valve that allows a drop at a time to fall on both ends.

If you filled the left side with pure deuterated water, and the right side with pure water made with only normal hydrogen-1, and then opened the valve in the middle, while simultaneously collecting and isolating single drop samples of the water at each end of the tube over time.

By testing the samples in a mass spectrometer, wouldn’t it be possible to measure the deuterated water composition of each drop to see how long it would take both sides of the tube to release drops of the same d2O/H2O composition.

If the water molecules are distributing at a rate of 500m/s, there would be near instantaneous mixing of the two water types, as soon as the two samples touched.

I don’t think that would be the case.

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