Recent comments in /f/askscience

LORD_HOKAGE_ t1_ja87tsq wrote

Reply to just curious, but how does a lightning form? by iamded2401

Static electricity ionizes air molecules in clouds/upper atmosphere

Tiny pockets, or strings, or tethers of the ionized air floats down to the earth invisibly in all kinds of random lighter than air floating patterns, and when it eventually touches the ground it creates a temporary circuit and the ionized static energy in the clouds transfers to the ground and you can see the weird random pattern the ionized air molecules drifted to the ground in, in the shape of the lighting bolt. That’s why lighting bolts all look different and completely random weird shapes.

Think if you dropped a feather or leaf from high up and traced its pattern downward. It would be random and flowy and chaotic every time. Same with the ionized air that creates lightning, flowing to the ground.

Lots of thin invisible ionized air tendrils pretty much hanging from clouds and the upper atmosphere, and when one of them manages to touch the ground a transfer of energy can occur along that least resistant ionized trail

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hixchem t1_ja828a8 wrote

Reply to Is there any difference between water boiled in a pot in the stove, in an electric kettle, or in the microwave? by strangecargo

There is no difference in boiling water from different methods. They all boil by transfer of heat into the system, causing increased motion of the molecules.

Electric kettle and pot on the stove both just use convection to heat it up. Microwaves use electromagnetic radiation to transfer the energy and heat it up.

The differences may be due to people using these different containers for things OTHER than water, and then not properly cleaning them out. Or it could be metals/minerals in the containers.

But no, the water itself is the same. It boils at 100°C (+/- based on air pressure, but generally)

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NatashOverWorld t1_ja8286a wrote

Reply to Is there any difference between water boiled in a pot in the stove, in an electric kettle, or in the microwave? by strangecargo

Some particles do get in, which is why copper pots are popular. This has links to the copper benefits that's backed by science: https://www.scmp.com/lifestyle/health-wellness/article/3185935/why-you-should-drink-water-stored-copper-jug-or-pot

But comparing stove boiling versus electric kettle or microwave ... Could you taste the difference? I certainly can't, unless the microwave was odourful.

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iayork t1_ja80u83 wrote

Reply to Is there a genetic disease where the heterozygote has more severe disease symptoms than the homozygote? by Altranite-

Maybe.

In sheep and pigs, there’s a complex scenario (“polar overdominance”) in which only heterozygotes with a particular mutation show the phenotype:

> A single nucleotide polymorphism in the DLK1-DIO3 imprinted gene cluster alters gene expression … muscle hypertrophy only occurs in heterozygous animals that inherit a normal maternal allele and the callipyge SNP on the paternal allele (+/C).

—New insights into polar overdominance in callipyge sheep

The details of how this works don’t seem to be well understood and I’m not going to try to summarize the complicated tentative explanations. In sheep and pigs, the muscular hypertrophy phenotype is at least somewhat desirable, but in humans there may be a similar mutation that, in heterozygotes, is associated with severe obesity.

> In a study sample of 1025 French and German trio families comprised of both parents and extremely obese offspring we found a single nucleotide polymorphism (rs1802710) associated with child and adolescent obesity. Analysis of the allelic transmission pattern indicated the existence of polar overdominance, an unusual mode of non-mendelian inheritance in humans previously known from the callipyge mutation in sheep.

—Preferential reciprocal transfer of paternal/maternal DLK1 alleles to obese children: first evidence of polar overdominance in humans

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Busterwasmycat t1_ja80g88 wrote

Reply to How is radioactive dating used to determine historical greenhouse gas levels and temperatures? by pog_irl

The dating is not used to define the temperature or other chemistry. It is used to put the sample into a time context. Most dating using radioactive decay as a "stopwatch" has a window of time where it works, and only works if the radioactive element and its daughters get captured at the time the mineral, rock, or organic residual got made, and any changes after formation to concentration of those atom types in that sample is only because of decay).

The date we would get from measurement and calculation refers to the date that the measured component got created. Dating the age of a mineral derived from erosion of an igneous rock will yield the age of the igneous rock, not the age of the sediment, so sediments tend to be more difficult to date by radioactive means. Some minerals do form in the sediments at (about) the time of sediment deposition, and dating those minerals, when possible, will give a decent age for the sedimentation. Generally speaking, radioactive dating is used to put date limits on sequences (using some cross-cutting relationships with datable units like dikes or sills; younger than that 5 million year old rock but older than this 3.2 million year old rock). Ash layers from volcano eruptions are actually really good for that, because the ash layer is a distinct layer and a fixed time and covers a very large area, and the age of the ash is the age of the sediment it is in, so it can be a very good marker unit for a lot of different places in the area.

Some fossils are actually pretty good for dating, but short time windows tend to rely on microscopic fossils like foramnifera that are a lot of work to find and ID). Carbon dating (which only works on fairly young materials, like 60,000 years old or less, about) isn't actually dating the sediment either, but the age of the piece of wood or plant leaf or whatever is going to be the same (to the precision we can measure) as the sediments it got buried by and within.

Mostly, though, we either use other non-radioactive methods to date the sediment or material. Ice ores are dated sort of the same way as trees using tree rings. The rings (layers) get counted. It isn't always counting right from surface, sometimes the section or the sample is compared to other sequences already counted and matched to a window of time without counting all the way back until today in that one sampling program.

The point here is that dating is not the same analysis as the measurements used to define chemical conditions of atmosphere and oceans. There are lots of ways to measure temperature and chemistry, some of which are very direct (when you can get an actual, real sample of preserved atmosphere in some ice and analyze it) and some are indirect (using stable isotope equilibrium among different species to define the temperature of equilibration (=formation) assume the minerals formed from sea water did so in equilibrium with that sea water and thus with each other). Similar things respecting ocean chemistry is revealed by major and trace element contents of minerals formed from that sea water. So we can get a pretty decent idea, within certain windows or ranges (small error limits), about what ocean chemistry and temperature was at the time of the deposition of sediments in that ocean.

It isn't just one thing and "POOF" the conditions are known for a given time. It is a lot of work involving measurement from a lot of samples from a lot of different places and times, and fitting all the data into how things have changed (or stayed the same) through time.

We keep doing sampling and analysis of different sediments, or ice, or whatever we can get our hands on, from different places and different times, and adding that data to what we already know, and this allows us to know more precisely, better, what actually happened. The more information we have, the more certain we can be in our understanding of things. It takes time and lots of work by lots of different people though.

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Of-Lily t1_ja7yvtq wrote

Reply to If the fuel that goes in car engines is extracted from hydrocarbons, which consist of only Hydrogen and Carbon, and those hydrocarbons react with Oxygen in the air (combustion reaction), to produce CO2 and H2O, why do we get a bad smell from car exhaust fumes if both gases are odorless? by Protoflare

Combustion of hydrocarbon is a fairly fractious process. (pun intended!) The parent hydrocarbons have various structures and each one of those multiple pathways to break down.

The noxious odors come from primarily smaller hydrocarbons with various structures and and nitrogen oxides. carbon monoxide is odorless but is also produced and incompletely converted. It is a particularly harmful byproduct.

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Skarr87 t1_ja7wzw7 wrote

Reply to comment by Thundahcaxzd in How is radioactive dating used to determine historical greenhouse gas levels and temperatures? by pog_irl

This is the correct answer. I would also like to add that O18 will precipitate out of the atmosphere faster as the temperature cools so as the temperature gradient decreases the ratio favors O16 more and more. So taking samples from all over we can get gradients for the temperature around the world at a particular timeframe.

Corals and animals with shells in the ocean make it out of calcium carbonate or silicon dioxide. The concentration of O18 to O16 in shells is dependent on the temperature of the water do to biological and chemical processes. So this is another check to corroborate ice core values.

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