Ultimately, once all processing is finished, the end result that comes out of the speaker can be thought of as a single sound wave. During the mixing process, all the individual waves from all the different instruments are compiled together into effectively a single, complex waveform.

There's more to it, of course - most speakers have more than one speaker element (one for highs, one for lows, or more) and then you are of course dealing with multiple sound sources all coming together at the point where your ears are. And your ears only have one membrane (the timpanic membrane) that oscillates back and forth, so again this feed to your brain and nerves can be considered a single "source".

Ultimately, the amount of detail you can perceive depends on the relative loudness and position of different external sources, and the quality of the audio mix.

That will probably be more to do with moisture being able to escape - with open windows, your house will be a lot drier than if you keep them closed for weeks at a time. You wouldn't need to open windows to get the UV effect, just your curtains.

The colour of an object is defined by the wavelengths of light it absorbs. When you add lots of colours together, the absorbtive characteristics of each are combined together and, generally speaking, the darker it gets the more colours you add. If you were to perfectly combine an equal ratio of cyan, magenta, and yellow (incidentally, CMY is the negative/inverse of Red/Green/Blue), you'd get black.

This is in contrast to coloured light, which selectively emits specific wavelengths, rather than selectively absorbing them. In the case of equally combining red, green, and blue light emissions, you end up with white.

However we do have several adaptations that are very well-suited to the endurance hunter lifestyle - the ability to sweat (quite rare in animals in general), hairlessness (which allows passive heat radiation as well as more effective sweat evaporation), a large surface-area-to-volume ratio (again, good for surface cooling), an upright stance allowing us to see greater distances than most prey animals, and bipedal locomation, which is not very fast but is extremely energy-efficient. We also have spectacularly well-adjusted physiology for the throwing of projectiles, which somewhat compensates for our lack of speed. Our combined torso and shoulder mobility is unparalleled in the animal kingdom.

I appreciate the response but it doesn't answer the question, just reiterates the premise. I'm interested in the biological pathways that cause "happy chemicals" to be released when in an oxygen-starved state.

I think the reason people talk about the body using up all its carbs before starting to munch on fat reserves is that sugar is the "fast" energy source. It is the easiest energy source for the body to use, because:

• it requires little to no processing/metabolism/breaking down before its chemical energy can be accessed, as it is a fairly simple molecule.
• it is stored primarily in the liver and in muscle cells, so it is always immediately accessible during the initial period of exercise.
• It is water-soluble, so readily dissolves into blood and is easy to transport around the body.

Fats are far more complex molecules than a sugar like glucose. They are made of the same atoms as sugars (C,H,O), so fat can be processed into sugar to replenish depleted reserves, but this requires a level of energy investment before the energy payoff is reached.

For the above reasons, I think it's pretty fair to assume that carbs and sugars will be used preferentially over fats and proteins, simply because of their ease of use and accessibility.

One thing I find really cool about weight loss is how the mass actually leaves the body. I don't remember the exact process, but ultimately it is mostly excreted via your lungs - all that carbon and oxygen is breathed out as carbon dioxide.

"Steam" is evaporated water - that is, water in gas form. It is colourless and invisible. What you see as a steam cloud is actually cooled, recondensed, liquid water droplets.

Sponges, especially large and thick ones, are extremely porous and have an incredibly high surface area. The more surface area there is, the more space bacteria has to grow - especially because a sponge likely has bits of food debris lodged in it to feed them. This also makes it difficult for detergent to fully penetrate every nook and cranny, and a high bacterial load, combined with the large amount of lipids typically present in food, will very rapidly "use up" all available detergent in the sink.

I wouldn't resort to cooking my sponges though - I don't like the idea of broken-down plastics and petrochemicals from synthetic sponges making it onto my plate. Letting a sponge completely dry out between uses is pretty effective at killing germs, and always make sure you use lots of detergent when washing your dishes. And yeah, regularly switch to a new sponge.

That's true. Most hand-and-body soaps are developed without detergents, and wash away bacteria cells rather than kill them - this is because detergents have the same effect on your skin cells as they do on bacteria, and repeated use for cleaning your body would cause injury over time.

I'll address your questions one at a time.

First, detergents are close to 100% effective at killing germs, but they can only be applied to exposed surfaces - any bacteria that have infected deeper tissue, or are hidden in nooks and crannies, cannot be reached by detergenty water, so other treatment is needed. Detergents cannot be applied internally - see the next part of my response for why. With that said, regular hand-washing is one of the most effective disease-control measures we have.

Second, detergent absolutely does have this effect on human tissue. Your skin cells in particular have evolved to be quite resilient, but detergent can and does kill them - fortunately your skin is made of many layers of cells, so damage is not immediately evident. Your skin also secretes oils to keep it soft and protected, and these oils use up a good amount of detergent before it can get to the cells themselves.
But wash your hands with strong dish soap many times a day, and after a few days you'll develop irritated, dry, cracking skin, with bleeding sores. This is also why the whole tide-pod thing was so dangerous - your internal tissue has not developed the same resilience as your skin has, and eating high-strength detergents can cause serious damage to your digestive tract.

Third, how can bacteria live on soap? Partly because of the reasons I mentioned in the previous paragraph, most body soaps have been developed to not so much kill bacteria and other cells, as dislodge them and allow them to be washed away. This causes minimal damage to your skin, but still cleans it - the bacteria have been washed off, rather than killed. Furthermore, those soaps and detergents that ARE lethal to cells (like dish soap) are only effective in the presence of water. See my original comment for more info there.

Honestly, I don't know - evolution is capable of producing some pretty incredible results - but I doubt it. It would require cells to either use something other than lipids to form their outer membrane, or to reinforce the layer to the point that the attractive molecular forces cannot break it. Such an adaptation would so fundamentally change the way cells currently operate, that any drift in that direction would probably be incompatible with life.

A suitable analogy might be to ask if vertebrates could evolve to be totally immune to fire. Like yeah, maybe, but the required physiological changes would be totally incompatible with life as we know it.

Well there ya go! Thanks

Australia. And I've just googled it, and I can't find it referred to as bilipid layer anywhere, so my best explanation is a little brain-fart that somehow mixed up the phrasing in my head and got stuck that way lol.

Thanks for catching it!

A bacteria cell consists of many different parts, but the relevant one here is called the "Bi-Lipid Layer", which is a layer of lipids that enclose the cell and essentially function as its skin.

Lipids are a group of compounds that include organic fats, oils, and waxes.

In general, most things are either hydrophobic (fat/oil soluble, but not water soluble) or hydrophillic (water soluble but not lipid soluble). Things are usually one or the other.

Detergents are somewhat unique in the fact that they are both hydrophillic and hydrophobic - they bind to both oil and water, and allow them to be bonded together in very close proximity, where they would usually very strongly repel each other.

So, you have a bacteria with its lipidous cell wall, immersed in water. The water is normally repelled by this layer, preventing the bacteria from dissolving into it. Enter a molecule of detergent. This molecule bonds strongly to the bacteria's protective lipid layer. This causes a very strong attraction to the surrounding water, while adjacent lipid molecules, which are not bonded to detergent, strongly repel the water. This bonding and attraction between a water molecule and the lipid molecule is now so strong that the bacterial cell wall rips and ruptures apart, thereby spilling its innards and killing the cell.

Edit: a commenter corrected my phrasing - the terminology is lipid bilayer, not bi-lipid layer.

Aren't tidal forces from our moon responsible for generating additional heat, as it stretches and compresses Earth in different directions?

If you were to fill your lungs with something with greater density than a human body (which is about the same as water on average) and then pull an extremely high-G manoeuvre, the heavier liquid would be more affected than your body. It'd essentially be trying to "sink" through you in the direction of the G force and probably crush something important.

Quick note - it is not the speed of sound in the gas that affects a person's voice, it is the density of the gas that affects resonance. Speed of sound usually correlates with gas density if the pressure remains equal, however, so it is easy to conflate the cause there.

Gas density will also affect how Bernoulli's principle causes your vocal cords to vibrate - a less dense gas will lessen the effect of Bernoulli's principle, which is responsible for pulling your vocal cords into the moving airstream - but this is counterbalanced by the fact that it also offers less physical resistance to your cords springing back and forth, and that it requires less effort for your diaphragm and lungs to expel. The result is that more gas volume will be expelled for a given amount of effort i.e. your lungs will push out the air faster if you do not consciously compensate, thereby increasing the effect of Bernoulli's principle. So these two effects more or less cancel out and the fundamental pitch and amplitude of a person's voice will remain basically consistent.

Rather, it is the resonant characteristics of your head and chest, which give your voice its unique timbre, and distinguish it from another person's voice (and indeed from a piano or violin), which will be noticeably affected.