Recent comments in /f/askscience

PlutoniumChemist t1_j4qdvq8 wrote

Reply to comment by TerjiD in If nuclear fission in U-235 causes the atom to be split into 2 smaller atoms (such as Kr-92 and Ba-141) then how is it that U-236 is produced as waste since the U-235 was just split into smaller peices? by Ian98766

There are multiple types of radioactive decay, some make the atomic number go up, some make the atomic number go down, but it's correct to refer to them all as radioactive decay.

37

chcampb t1_j4qdn3k wrote

Reply to Does anybody have any good examples or uses of negative derivatives of displacement, such as absement, absity, and so on? Though it is easy to calculate, it’s hard to find use for it. by LunarSolar1234

"Negative Derivatives" -> Integrals? Is this a thing? I would just say the integrals of position, in the same way jerk is the derivative of acceleration. I have heard "anti-derivative" as well.

Pipe organs and other flow based instruments were the examples I remember from when I last looked up uses for absement. The volume is based on the position of a key, which allows flow to build up in a pipe, which is proportional to how far down the key is pressed (ie, the integral of key position).

This was posted in a similar question and has a lot of good info, except for the 2nd integral of position except to say that there is a two staged absement instrument (so, what would be the sound output actually controls the "key" for the next stage of the pipe...). It's pretty contrived.

8

PhiliFlyer t1_j4qc8fj wrote

Reply to What makes a fiber or fabric absorbent, wicking, breathable, or cooling? by DisenchantedAuD

Fibers such as cotton absorb a substantial amount of water. Clothes made from cotton can therefore transport water from your skin to the outside of a garment where it can evaporate. This cools your skin because the heat of vaporization of water is quite large.

Cotton is mostly cellulose, a polysaccharide. It has hydroxyl (alcohol) groups in the repeat units, meaning that a single polymer chain has thousands of hydroxyl groups. Hydroxyl groups form hydrogen bonds with water, and are mostly responsible for the water absorbency of cotton.

Synthetic fibers such as polyesters are often co-woven with cotton to improve the mechanical properties of the cloth. Polyesters absorb much less water than cotton. Cloth made exclusively from polyester fiber is uncomfortable for this reason. There are synthetic polyester fibers such as poly(lactic acid) that absorb water and are more comfortable. They are more expensive, and therefore have not been widely adopted.

11

tdgros t1_j4qbwij wrote

Reply to comment by mfb- in If nuclear fission in U-235 causes the atom to be split into 2 smaller atoms (such as Kr-92 and Ba-141) then how is it that U-236 is produced as waste since the U-235 was just split into smaller peices? by Ian98766

Are the shape of the curves (clean, a few spikes, lots of spikes, super clean from ~0.002MeV onward) related to some physical processes we know? is it just due to the scale of the plot?

2

d0meson t1_j4qb8l2 wrote

Reply to comment by taphead739 in Why does the existence of magnetic monopoles imply quantized electric charges? by Speterius

As an aside, Dirac's statement is so interesting because 1) the angular momentum carried by such a field configuration is independent of the distance between the electric and magnetic charge, and 2) it only requires one point magnetic charge to work.

So as long as there is at least one magnetic monopole somewhere in the universe, his argument works.* What if there's genuinely only one? It's an interesting scenario to think about in terms of the limits of the scientific method; for example, if that one monopole passed through an experiment and left our Solar System, never to return, that experiment would essentially be non-repeatable and therefore non-verifiable.

*in a classical universe; not sure whether GR or QFT impact this statement.

9

TerjiD t1_j4q996f wrote

Reply to comment by PlutoniumChemist in If nuclear fission in U-235 causes the atom to be split into 2 smaller atoms (such as Kr-92 and Ba-141) then how is it that U-236 is produced as waste since the U-235 was just split into smaller peices? by Ian98766

This is a really interesting explanation. Made me smarter.

I gotta ask though - is "decay" the correct term, when an element goes up in protons?

Only curious, just trying to get smarter.

18

NeverPlayF6 t1_j4q8mhj wrote

Reply to comment by AmphoraExplorer in If nuclear fission in U-235 causes the atom to be split into 2 smaller atoms (such as Kr-92 and Ba-141) then how is it that U-236 is produced as waste since the U-235 was just split into smaller peices? by Ian98766

Doppler broadening- the higher the temperature of the fuel, the faster the nuclei are vibrating. Nuclei can only absorb neutrons of a certain energy. If the nuclei were at rest, they would only be able to absorb a narrow range of neutrons based on the neutron's velocity/energy. Since the nuclei are in motion, the relative velocities/energies between the neutrons and the nuclei are spread out. The higher the temperature, the wider the spread. The wider the spread, the more likely that a neutron is to encounter a nuclei with the correct relative energy to absorb it.

Imagine that it is only possible to catch a baseball that is moving between 15 and 20 mph relative to the person trying to catch it. If you have 1,000 people standing still, then any baseball slower than 15 mph or higher than 20 mph cannot be caught. Now imagine that those 1,000 people are all walking around in random directions at 3 mph. It is now possible for a baseball thrown at 12 mph or 23 mph to be caught. If they're moving faster (the same as increasing the temperature of the fuel)- say 19 mph, it is possible for a baseball thrown between 1 mph and 39 mph to be caught.

47