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89

There's a lot of detail you could go into with regard to this question, as is done in the other answers and comments, but I think the answer itself is pretty simple. Imagine a surface that just barely surrounds your body, as if you shrink-wrapped a body in plastic. By the law of conservation of mass (valid in non-relativistic physics), the only way your body ...


66

Suppose current entering into this parallel circuit is $10A$ then almost all the current flows through poor small fish's body current through poor small fish's body = $10A \times \frac{1M}{1M+1} \approx 10A $ This is probably the large picture but I am just guessing. Hope its correct.


48

Essentially, losing of weight occurs by means of burning fuels precisely like your car does when it burns petrol and emits exhaust gases. The only difference is that for humans that fuel is to be found in the form of sugars. The fat is what you want to get ultimately rid off, of course, but sugars are more easily processed and so this is what you are ...


39

When you exercise, you "burn" more glucose, the simplified reaction for which (from Wikipedia) is: ${\rm C_6H_{12}O_6 + 6~O_2 → 6~CO_2 + 6~H_2O}$ So when you exhale, the carbon in the carbon dioxide, and the hydrogen and the oxygen in the water vapor, came from the glucose being burned, thereby removing that mass from the body.


39

I checked to make sure: The simple answer is that electric eels insulate their critical tissues with a layer of fat below the skin, preventing the shock from traveling through their body as the "path of least resistance". I may update with visuals and details if I can find good ones.


37

The following fact lies at the heart of this and many similar issues with sizes of things: Not all physical quantities scale with the same power of linear size. Some quantities, like mass, go as the cube of your scaling - double every dimension of an animal, and it will weigh eight times as much. Other quantities only go as the square of the scaling. ...


34

This question is sort of difficult to answer in an objective way, because it depends very strongly on your definition of "best." Natural selection favors traits which provide a reproductive advantage; no more, no less. Could our eyes be better by the standards of modern optical design, in terms of precision and features? Sure. I could easily design a camera ...


29

As others have pointed out, in metabolism you breathe in oxygen and exhale carbon dioxide with the net reaction being $$CH_2O + O_2 \to CO_2 + H_2O$$ The carbon dioxide gets exhaled, and the water is lost through some combination of other things. Let's think about whether this is a reasonable way to explain weight loss. A breath is maybe one liter of ...


29

Assume also that I have access to an immense amount of parallel computing processing power (I do). Unless you are an important person in the Chinese computational science world (using Tianhe-2), or you have access to secret government computers us mere mortals don't know exist (so they don't appear in rankings of the best supercomputers in the world), I ...


26

It is all about the loss of energy during each stride - the tendons store some energy, but not a lot. A kangaroo and a greyhound, for example, have far more efficient elastic storage in their legs / tendons, allowing them to achieve (and maintain) greater speeds with less effort. Key phrase from the abstract in that reference: elastic storage of energy ...


13

This is a common misconception -- evolution has not stopped a million years ago leaving all the creatures in the "best possible state"; it is a continuous pursuit of adapting to the current environmental conditions, with only aim in reproductive success. Moreover most of the population stays in even more suboptimal surroundings due to random mutations (the ...


13

[Updated to correct a couple of mistakes pointed out in comments. Thanks!] At my age, it's clear that there's room for at least one major improvement: more accommodation. Accommodation, in this context, means the ability of the eye to focus at different distances. This is accomplished by changing the shape, and hence the focal length, of the lens. The lens ...


13

No it's an urban myth. It's impossible for them to fly using a very simple and inappropriate model of wing behaviour - possibly closer to say that bumble bees can't glide like albatrosses


13

Yes, it's very much physics related: The perceived smallness of distant objects is a direct function of how many space dimensions we live in. Here's an example: For a one-dimensional or "string land" creature, what would be the apparent difference in size between a dot nearby and a dot many miles away? If you think about it a bit, the answer is "none" -- ...


12

This is an example of "scaling laws". Have a look at http://hep.ucsb.edu/courses/ph6b_99/0111299sci-scaling.html - for once Wikipedia doesn't have a good article on the subject. The strength of a muscle is roughly proportional to the area of a cross section through the muscle, so strength is roughly proportional to size squared. That's why I'm a lot ...


11

Moving at a constant velocity, no matter how close to the speed of light, has absolutely no effect on the person moving. In fact, it has no effect on the laws of physics. This is the fundamental tenet of special relativity - you cannot tell absolute motion, only relative motion between different things. The changes you are referring to are what someone ...


10

You can grow arbitrarily large as long as you are essentially flat. For example, one fungus covers several thousand acres; there's a grove of clonal aspen trees that may have higher mass. Scaling in three dimensions is much harder, though. The pressure on the bottom is proportional to the height--eventually that pressure is too great for tissue to ...


10

It may have something to do with the growth rate of sunflowers. During peak growing times sunflowers can grow inches in a single day, which likely results in them drawing more water out of the ground, allowing them to concentrate the radioactive materials through deposition in the plant matter at a faster rate than other plant organisms. I would suspect ...


9

This has been extensively studied in linguistics and acoustics. Humans and other primates predict speaker gender through a combination of fundamental frequency $F_0$ ("pitch") and Vocal-Tract-Length estimates ($VTL$) which are a proxy for body size. Sometimes "formant dispersion" is used for $VTL$. It is usually defined as ...


8

Insect flight is different than bird flight. With insects, the rapidly moving wings, which do a figure 8 sort of motion, generates a vortex tube over the wings. This vortex by Bernoulli principle has less pressure, which permits the larger air pressure underneath to lift the animal up. If one is trying to understand insect flight according to the mechanics ...


8

Strength Strength goes like area. Intuitively, the cross sectional area of a muscle counts the number of muscle fibers (actually, myofibrils). Thus, $S\propto A \propto L^2$. But mass goes like volume, $M\propto V\propto L^3$. Therefore strength is proportional to the $2/3$ power of mass, $$S\propto M^{2/3}.$$ This equation expresses the fact that an ...


7

This is obviously a very broad question, but here are a few thoughts that may be helpful. As dmckee points out in a comment, it's difficult to define consciousness. However, consciousness clearly requires computation, and computation is something that physics can address. There is a psychological arrow of time: we can remember the past but not the future. ...


7

The cochlea has a complex physical structure, with multiple membranes and fluid-filled chambers. Therefore to explain the separation of frequencies along the basilar membrane of the cochlea is complex to. Sure, there are a lot of very general descriptions (even the answer of theblackcat) and a lot never go into the actual physics of the system. This ...


7

There are two primary factors that allow the cochlea to isolate frequencies. These are generally referred to as passive and active properties: tl;dr version: The passive properties are due to the mechnical properties of one of the membranes in the cochlea, the basilar membrane, primarily the width and stiffness at a given point. The active properties are ...


6

Looks like neutrons can cause visual perception: Visual phenomena noted by human subjects on exposure to neutrons of energies less than 25 million electron volts, Science. 1971 May 21;172(3985):868-70, "Six subjects reported multiple starlike flashes and short streaks on exposure to neutrons of energies up to 25 million electron volts. The probable mechanism ...


6

Potentially yes it could. There are no noise-cancelling headphones to stop the U.S. Navy's 235-decibel pressure waves of unbearable pinging and metallic shrieking. At 200 Db, the vibrations can rupture your lungs, and above 210 Db, the lethal noise can bore straight through your brain until it hemorrhages that delicate tissue. If you're not deaf after ...


6

The basic answer is that mass scales with the cube of linear dimension and strength of things like legs scales with the square of the linear dimension. Note that large animals have therefore evolved comparatively thicker legs than smaller ones. Linearly scale up a dog to elephant size, and its legs would snap. Even more extreme, think of scaling a ant to ...


6

One simple approximation that you could make is to assume that the human body is made of water. Then you can reduce your question to: what happens to water molecules in a magnetic field. Consequently, you would have to ask how you can break the Van der Waals Bond in water with a magnetic field. I think here you would have to differentiate between a static ...


6

I would just like to add something here. These answers are great but I might have another answer. At first it was indeed a mystery how these insects were capable of flying, but thanks to high speed recordings they found something which investigators didn't concider. The wing motion has a sort of dubble lift feature. By twisting her wings over at the end of ...



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