Recent comments in /f/askscience

ECatPlay t1_ja6pex2 wrote

Reply to comment by KingSpork in 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

Oh, yes. In particular, some refineries blended extra aromatics in with the gasoline to increase the octane: benzene, xylenes, and alkylates. And before catalytic converters and emission standards limited unburnt hydrocarbons in the exhaust, these could give it an almost pleasant odor, especially when it was running rich. (After all, benzene compounds get the name “aromatic” because of the type of odor they have.)

But only if the engine was burning clean and not also burning oil. That made the exhaust smoky. Now days engines are manufactured to closer tolerances and you seldom have to add oil. But back in the day it was routine to check your oil every time you stopped for gas, because there was always a little bit of oil making it past the rings and getting burned in the cylinders.

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Pandarmy t1_ja6lpux wrote

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

The other reply has some great info but I can add a bit. Another way we know it hasn't melted is radioactive dating. I'll use carbon dating as the example since I'm most familiar with it. Carbon-14 is radioactive (half life 5700 years) and naturally present at a rate of 1 ppt. If a substance has gas exchange with the atmosphere, it will keep that 1ppt amount of carbon-14. If not, that number will fall as the carbon decays. Since the ice sheet has a much lower percentage of C-14 (or other radioactive element they are testing) it means the ice must have been there for a long time.

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Welpe t1_ja6lj14 wrote

Reply to comment by 8myself in Is there any possible relation between the recent earthquakes in Turkey/Syria, Japan and Papua New Guinea? by Corvid-21

Fortunately/Unfortunately, IQ doesn’t work like that, gaining knowledge shouldn’t increase IQ theoretically or IQ fails to measure intelligence. Knowledge isn’t intelligence. I of course say “shouldn’t” because IQ tests are already flawed and this is veering off-topic but I really wish we wouldn’t conflate IQ score and knowledge or educational attainment (Or even intelligence for that matter, but that’s a whole ‘nother rant).

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ShadowDV t1_ja6jrpx wrote

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

The ice sheet is up to 3 miles deep. Antarctica is also a desert getting less than 2 inches of precipitation a year. Also, the glacial ice flows out. Imagine pouring something very viscous, like honey on top of a bowling ball. That kind of like how continental glaciers flow.

So as the ice flows out, the annual sheet accumulation thins out, to where 1 year’s worth of accumulation can be like 1mm thick. And those layers can be read like tree rings for the age in an ice core.

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Origin_of_Mind t1_ja6hsnb 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

When you start the car, the engine is cold. In this situation, there is much more unburned fuel which passes into exhaust. The catalytic converter is also still too cold to do anything. This is called cold-start emissions.

What you smell particularly strongly at that time is aromatic compounds from the gasoline. In chemistry, they were named "aromatic" precisely because they smell. A representative aromatic compound that is responsible for the exhaust smell during the cold start is benzene, although many of its derivatives are also present.

Incidentally, in many countries gasoline is called benzin/benzine.

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Sammy81 t1_ja6ej2y wrote

Reply to comment by parikuma in How old is the ISS REALLY? by gwplayer1

I was not familiar with TAI until your question, but I googled it. It looks to me like TAI is the most accurate GPS time. The problem with GPS time is that it is not “earth time”. By that I mean GPS time is independent of the position of the earth. Since the earth rotation is slowing over time, GPS time deviates from it, running ahead of it as the earth slows. UTC time takes this into account. Leap seconds slow GPS time to align with “earth time”, or the time it takes the earth to rotate one time. Since satellites are often concerned with observing earth, or communicating with earth, it’s important for them to stay aligned with the actual earth rotation, so UTC time is more useful. One of my first assignments was making it easy for ground control to upload deltaUT1 and leap seconds to our satellite (Calipso) so that it’s science data was accurately tied to the ECEF reference frame.

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