Recent comments in /f/askscience

Glasnerven t1_j983sez wrote

Reply to When something is bent (a metal ruler for example) and returns to its original shape, what is happening on the molecular level? Where is the information of the original shape stored and what forces do the unbending? by JewNugget2525

Ah, a chance to put my material science classes to use!

When you bend something (and a metal ruler is a great example) and it can spring back, we call that "elastic deformation".

On an atomic level, metal is made of atoms in a crystal lattice. Each atom is spaced a certain distance away from its neighbors. The atoms stay at that particular distance because electromagnetic forces from their electrons and their protons add up in such a way that that distance is a low-energy configuration, like a ball sitting at the bottom of a dip in the ground. You can push and pull the atoms closer or farther apart, but to do that you have to put energy in, and they'll "want" to go back to that optimal distance.

Next, consider the shape of the ruler. Obviously, when it's straight, both sides are the same length. But, you can bend the ruler into a curve. When you do this, the two sides aren't the same length any more. The outer side of the ruler is now longer than the shorter side. It's the same principle as taking a corner in a car; the wheels on the outside have to go farther.

If you've stayed within the limits of elastic deformation, what's happened at the atomic level is that on the outside, you've pulled the atoms farther apart. The same crystal lattice structure is still there, but the atoms are now spaced farther apart than the lowest energy positions. On the inside, the opposite has happened: the metal is compressed, and the atoms are closer together than the lowest energy distances.

When you release the ruler, the atoms go back to their optimal distances. The long side shrinks and the short side expands.

So, the information of the original shape is stored in the crystal lattice structure. As long as you don't disrupt the lattice structure, the atoms "want" to go back to their original places. The forces that do the unbending are electromagnetism. (realistically, the only two forces you'll ever experience directly in your life are gravity and electromagnetism. If you are directly experiencing the effects of the nuclear forces, you're having a very bad day.)

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Pugzilla69 t1_j981evc wrote

Reply to Can doctors tell when cancer is caused by something specific, such as smoking or chemicals? by [deleted]

To some extent. Characterstic mutations in certain cancers can be associated with specific etiologies.

Angiosarcomas with MYC amplificaton are associated with radiotherapy and lypmhedema.

p16 positive carcinomas are almost universally caused by HPV.

Burkitt Lymphoma with EBER positivity is caused by EBV.

There are many more.

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Zestyclose_War7063 t1_j97sq4w wrote

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

As above people have discussed - I often tell parents this with their kids, to reassure them re swinging fevers- that’s it ok and it’s the immune system doing it’s job. However- I also say, and please correct me if I’m wrong- that from current trial evidence, when groups treated with anti pyretics vs no anti pyretics are compared- there is not a significant difference in length or severity of illness… anyone know if I am talking out of my rear here??

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