There is a compound in garlic called allyl methyl sulfide (AMS). It is a gas which gets absorbed into the blood when you are digesting the garlic (and onions and shallots). From the blood it is transferred to the lungs where it is then exhaled. A big part of flavor reception is through the nose so you get that lingering taste that way. Some of the AMS compound is also released through the skin.
Tuesday, 29 March 2016
ELI5: Why do flavors like garlic and onion stick around in the taste buds so much longer than others?
ELI5:How come people can't be cryogenically frozen safely as the ice crystals destroy the cell membranes, but sex cells such as sperm are kept frozen for long periods of time yet remain functional?
I work in a lab where we freeze down cells all of the time. We freeze our cells in a medium that contains 5% DMSO, which among other things can be used as a cryoprotectant. However, DMSO is also toxic to cells at the concentrations necessary for cryoprotection. Consequently, when you freeze cells in DMSO, you add the DMSO medium at ice-cold temperatures and don’t allow the cells to warm up. When you later thaw the cells, you have to dilute out the DMSO as quickly as possible without causing osmotic shock, which can pop the cells. Such restrictions on freezing and thawing would basically be impossible to control at the level of a complete organism.
However, to contradict a lot of previous posts, individual cells can be recovered from freezing with high viability. When performed properly (and this varies quite a bit by cell type), you can expect >90% of cells to be alive following thaw.
The chemicals that allow cells to survive freezing are toxic to the body. Keeping the cells cold minimized the damage that this chemical does to the cells. With single cell solutions, adding the chemical at ice-cold temperatures and immediately diluting it out when you thaw the cells can keep 90% of the cells alive. There’s no way to do this with an intact body.
It’s also worth noting that this is probably not the only reason that this technique doesn’t scale to organisms.
Wednesday, 23 March 2016
ELI5: Does a sonic boom only occur at the moment you break the sound barrier or is it constant and if it is does it get louder the faster you go?
It is constant.
A sonic boom is a shock wave that travels outward from the plane. It follows the plane wherever it goes. When the plane flies by a person on the ground, the shock wave will hit that person (and be heard as a “boom”) shortly after. Since the boom moves at the speed of sound, and the plane is moving faster than that, a cone shape develops, with the plane at the point of the cone. Here’s an example image.
As for speed vs. loudness, it’s actually the opposite of what you’d expect. The faster the plane, the skinnier and pointier the cone. As a result, the energy of the shock wave gets spread out over a longer distance. Additionally, super-fast aircraft tend to fly at much higher altitudes, meaning the boom travels through a lot more air before it reaches the ground, dissipating it. So sonic booms actually get quieter the faster the plane flies.
Saturday, 19 March 2016
ELI5: Why is charcoal so effective in fire places/pits/barbeque stands if the most of the wood/fuel has been used up?
Wood burns in two stages: the hydrogen stage and the carbon stage. In the hydrogen stage, hydrocarbon molecules are broken and oxidise. In the carbon stage, the carbon oxidises.
The carbon stage burning is a hotter and cleaner chemical reaction than hydrogen stage burning.
Charcoal is made by burning wood in the hydrogen stage (hence removing the hydrocarbons) but not allowing the carbon stage (by limiting the amount of oxygen).
ELI5: Why did old school TVs have a "layer" of static that sat on the screen? You could even "wipe it off" and it would be gone for a while then come back.
Old cathode ray tube (CRT) televisions have an electron gun which fires electrons at the back of the screen. And the screen is coated with phosphors which emit light whenever struck by an electron. The side-effect of this process is that each electron increases the static charge of the screen, and over time as the image on the TV changes it increases the charge. Meanwhile, rubbing your hand, which has a slight negative charge, across the screen will remove some of this built-up static.
Wednesday, 16 March 2016
ELI5: Why does having general anesthesia feel like you blink and you're in the recovery room when normal sleep feels like time passed?
No one really knows. Seriously we do not understand how it works. An anaesthetised unconscious state is not like sleep at all but more like a coma, though the exact details of what happens remain a mystery so far. Obviously the parts of the brain that are responsible for creating a sense of time having passed when we sleep are also prevented from working or prevented from recording it for a while.
Monday, 14 March 2016
ELI5: Why is it still so difficult to definitively determine the source of major rivers like the Nile and Yellow River?
Because hundreds of rivers merge to form these big rivers. So technically there are numerous sources. Which creek, drainage, stream or other water source is the river and which is just a feeder? Lot of options to debate there.
ELI5: What happens inside of a USB flash drive that allows it to retain the new/altered data even when it's not plugged in?
When you charge a battery it retains the charge for a long time even though it is not plugged in. Think of a flash drive like a collection of billions of microscopic tiny batteries. Some of them are charged up (and contain a “1”) and others are not (containing “0”).
ELI5: Why is growling such a common way to show aggression in the animal kingdom?
Growling in dogs isn’t a show of aggression. It is a show of unease - you’re invading its space or you represent a threat and (s)he wants you to back off.
It’s actually a sign the dog would prefer for this to not evolve into conflict.
Aggressive dogs attack without any growling.
Saturday, 12 March 2016
ELI5: Why do colleges accept students who excel in sports while having bad academic merits?
Money. College football and basketball generate a lot of money and donations from alumni. Especially if you have really wealthy alumni like T. Boone Pickens. He paid for a lot of new athletic buildings. There are lots of former college players with degrees that can barely read or write but were able to run fast with a ball. Several colleges have been busted for enrolling their athletes in phantom classes where they never had to show up and still earned A’s. My best friend’s cousin played football at a college in Texas and wouldn’t have to turn in assignments or take exams in most classes.
Thursday, 10 March 2016
ELI5: Why is marijuana "impossible" to overdose on?
Bluntly put, the median lethal dose (LD50) of THC (the active ingredient in marijuana) is so high and the methods of intake so dilute that you would have to do absolutely impossible feats to have it occur. While there are a couple of different and conflicting sources, one estimate placed it at 40,000 times as much as the dose needed to get high. This is contrasted with alcohol, where five to ten times the amounted needed to get you drunk can kill you. To extrapolate, With pot brownies you’d die of sugar poisoning long before the THC got you. With smoking, you’d have to smoke something like 1,500 pounds of weed in a period of 15 minutes.
To actually manage a THC overdose you’d have to spend a lot of effort to first purify a sizable quantity of THC and then ingest it rapidly. This would never happen accidentally.
ELI5: Why did Iraq invade and annex Kuwait in 1990? How could they have not anticipated that much stronger countries allied to Kuwait would intervene and drive them out?
Iraq invaded Kuwait for financial reasons mostly. Kuwait supported Iraq during the war with Iran. After the war Iraq was in debt to Kuwait for something like $15 billion. Kuwait refused to debt relief. Kuwait was over prducing oil when there was already a glut. This drives the price of oil down which is bad for Iraq because they are really far in debt not just to Kuwait but to many countries around the world to the tune of $60 billion. Also Iraq accused kuwait of slant drill across the border into Iraq and pumping oil from Iraqi oil fields.
Now, how does Iraq invade Kuwait and not expect retaliation from the U.S. and other? Iraq at the time was the most powerful military in the region and the U.S. and Russian had just wound down the cold war. Iraq calculated we wouldn’t be able to stomach another conflict with Vietnam and Afghanistan in our rearview mirror.
Another reason they thought the U.S. wouldn’t get involved was a matter of mixed signals from the U.S. ambassador. Statements such as “ we have no opinion on Arab-Arab conflicts” and that the U.S. did not intend to “start an economic war against Iraq”. This was said while Iraqi forces were forming on the border with Kuwait. These statements and others, said and not said, was seen as a go ahead for invasion.
The U.S. didn’t think Iraq was really going to annex Kuwait. The U.S. believed it was just posturing by the Iraqis to put pressure on Kuwait for debt relief and lower oil prduction. I’ve heard that Saddam was surprised by the response from the U.S.
Wednesday, 9 March 2016
ELI5: if matter can't be created or destroyed, how does matter currently exist? Isn't the existence of matter already breaking that law?
Matter can definitely be created and destroyed. Mass-energy, however, is preserved. Now if you want to go further with “then how was mass-energy created?” you’re getting into “Beginning of the universe” stuff and we don’t know how that functioned.
Bear in mind that a physical law doesn’t mean “Mother nature has to obey the speed limit” it means “We pretty much always see Mother Nature obey the speed limit.” It is an observation of how we see the universe functioning, not a limit we put on how the universe can function.
ELI5: Why is dead weight (unconscious person) so heavy when the person's weight doesn't change?
When a person is alive and with-it, they “participate” in being held by making sure weight is distributed to your core. Getting a floppy body to have its weight distributed to your core muscles is hard and this makes balancing difficult and causes you to engage relatively weak muscles.
Even young children will do this instinctively, making them much easier to carry.
ELI5:How do terrestrial ant colonies survive torrential downpours without flooding in and drowning them?
Water does flood in. However, ants usually dig colonies at least a foot deep. That creates a lot of surface area relative to the tiny entrance hole, so the dirt absorbs the rain quickly. Ants also build chambers at the top of upward sloping tunnels, so water can’t flow in.
As a last-ditch effort, some species will form living rafts that can float on top of floodwaters.
Tuesday, 8 March 2016
ELI5:Why do airline passengers have to put their seats into a full upright position for takeoff? Why does it matter?
You’re most likely to have some sort of accident during takeoff and landing. This is also why your tray tables have to be up and you can’t have laptops during these times: ease of evacuation. If your seat is back, and something happens and the plane needs to be evacuated quickly, you just made it harder for the person behind you to get out.
Extra: I’ve gotten this message lots of times, and as has been beautifully explained, your window thing has to be up so, in the event of an emergency, emergency personnel can see into the plane/you can see a fire, should there be one.
Sunday, 6 March 2016
ELI5: If the age of the universe is about 14 billion years old how come the diameter of the universe is 93 billion light years?
Because space itself can expand faster than the speed of light.
The speed of light is the fastest anything can move through space. Space itself, however, doesn’t have that limitation in expansion.
Also worth mentioning that is only the observable universe that is 93 billion light years in diameter. No matter where you are in the universe, you can only observe the 93-billion-light-year sphere centered at your location. Move beyond that edge, and your sphere just has a different center. You’ll never observe the entire universe. As such, we have no reason to believe the universe has a edge at all. It may be much MUCH wider than 93 billion light years, or it may be truly infinite.
Tuesday, 1 March 2016
ELI5: Why does putting a mug of water in the microwave keep bread from getting soggy when heated?
The water acts as a ‘dummy load’ when you have it in the microwave with bread. So it reduces the amount of energy going to the bread. Think of it in terms of cranking down an energy knob. The higher the energy the faster it heats up which means it gets soggy. If you have less energy and cook it slowly and evenly it won’t get soggy.
It’s assumed the bread is frozen. Why is the bread frozen? It stays fresher longer. Good for when you’re living by yourself and don’t go through food as fast. As a poor graduate student who knows the struggle lol.
Can I lower the power for the same effect? Yes, basically it will do the same thing. Lowering the amount of energy reduces the amount of 'work’ used to heat the bread. You’ll have a lower temperature and this will allow for the heat to dissipate evenly throughout the bread.
Wait a minute, what happens if I heat room temperature bread? If you heat it the moisture from the bread will be released and moisten the bread. If you do this with water that water will be 'added’ to the atmosphere in the microwave and may condense to make the bread wet on the outside. Of course if you heat it long enough it will dry out or burn.
Why does bread get soggy? At room temperature for example the bread is saturated with moisture, kind of like a damp sponge that has been sitting out for a couple hours. If you heat it up it softens the pores of the material and you get that 'soggyness’. When heating frozen bread at high temperatures it can be concentrated in certain areas and the heat may not be able to spread out. If you lower that temperature the heat can spread out and let the vapor escape.
I worked in a bioenergy lab for a year with some people who studied pyrolysis with domestic and industrial microwaves. We had a metal 'mixer’ to mix up the wood pellets or other biomass. We used water as a dummy load so that the microwaves would not be reflected back and damage the magnetron.
