Recent comments in /f/askscience

PeteyMax t1_j93sebp wrote

Reply to How do spider eyes work? by NoMoreMonkeyBrain

Most spiders have two main eyes similar to ours, each having a lens and a retina with multiple light sensing organs for detecting images. Unlike our eyes, however, it is the retina rather than the eye that moves in order to both focus and direct the view. Since the field of view tends to be quite narrow and spiders cannot move their heads, in addition to the two main eyes, spiders also have between four and six other simple eyes scattered around their heads. These eyes can detect motion so that the spider can orient itself towards the source of interest.

Here is a video showing a translucent spider where you can see the motion of its retina:

https://www.youtube.com/watch?v=gvN_ex95IcE

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Reliv3 t1_j93s6hd wrote

Reply to comment by ParanoidMaron in Was reading something related to Rock Salt mining. In places like the Himalayas where rock salt mining is done in cold temperatures, a lot of miners report burns. Why is it so that salt burns in a colder surroundings? Would it be the same reason why the salt ice challenge was so dangerous? by vvdmoneymuttornot

Yeah, I think molten is actually fine here. People are just used to using molten when describing melting materials which are solid at higher temperatures. Ice is a solid at much lower temperatures, so a state one may describe as "molten" will also exist at a much lower temperature.

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Interesting-Month-56 t1_j93ro1k wrote

Reply to comment by Recipe-Jaded in Was reading something related to Rock Salt mining. In places like the Himalayas where rock salt mining is done in cold temperatures, a lot of miners report burns. Why is it so that salt burns in a colder surroundings? Would it be the same reason why the salt ice challenge was so dangerous? by vvdmoneymuttornot

Just to add to this, not only is there less no convection with a solid (ice), it has a lower thermal conductivity (though not by much), and the surface area of water in contact with your skin is much higher.

Conductive heat transfer efficiency at an interface will be a function of the total area of contact between the two surfaces. Add in convection, where the heat is rapidly moved away from the skin by mixing of the water and water is a much better coolant than solid ice.

If you further add things like evaporative cooling into the mix, wet skin can be really dangerous.

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WiartonWilly t1_j93qz2a wrote

Reply to Why are fevers cyclical? by Key-Marionberry-9854

Your immune system has rhythms. There are a whole zoo of different immune cell types in your blood. The immune system is like a bunch of liquid organs, each with many cell types. Many cell types which are derived from bone marrow have a tendency to return to the bone during the day. They go home. Circulating cells found in a blood draw, such as neutrophils, can increase by 2 fold at night. At night more immune cells are on active duty.

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fack_yuo t1_j93qfy2 wrote

Reply to Why are fevers cyclical? by Key-Marionberry-9854

as your body fights off the virus the viral load drops, the fever reduces, the body becomes more hospitable for the virus again, the virus is reproducing in cells teh whole time, the cells burst, the viral load shoots up again, the body responds with more fever. I'm sure someone will explain it in more detail but as i understand it thats pretty much it. viral load goes up and down which causes symptoms to be cyclic.

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ParanoidMaron t1_j93q0ce wrote

Reply to comment by monsieurkaizer in Was reading something related to Rock Salt mining. In places like the Himalayas where rock salt mining is done in cold temperatures, a lot of miners report burns. Why is it so that salt burns in a colder surroundings? Would it be the same reason why the salt ice challenge was so dangerous? by vvdmoneymuttornot

>Molten means liquefied by heat.

... Ice melts thanks to heat.. into liquid water, ice is just solid water. Ergo, ice can become molten, as water and ice are the same material, just the same as aluminium is the same material molten or not.

It sounds wrong. It is not, technically speaking, wrong.

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monsieurkaizer t1_j93pgtj wrote

Reply to comment by LogicalMeerkat in Was reading something related to Rock Salt mining. In places like the Himalayas where rock salt mining is done in cold temperatures, a lot of miners report burns. Why is it so that salt burns in a colder surroundings? Would it be the same reason why the salt ice challenge was so dangerous? by vvdmoneymuttornot

It is because they can't be molten. Molten means liquefied by heat. Cheese can be molten, because it exists as cheese and melted cheese. Ice cubes just melt into water. So they're no longer cubes, and maybe that's why it irks you.

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johndburger t1_j93nt8z wrote

Reply to Is toxoplasmosis life long? by Angel_thebro

You may be confusing the infection with the resulting disease that some infected people develop. By some estimates as much as half the global population has been infected with the parasite Toxoplasma gondii, but many of those people never develop symptoms of the disease toxoplasmosis. And for those that do, many of them require no treatment.

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