Well, sort of. It was discoverd in the course of a deliberate search for substances that would effectively kill bacteria, though.
If it were not for this, submariners not be allowed to eat their toast in the torpedo tubes.
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Although the full visual field of the human eyes encompasses a visual angle of something like 100º, foveal vision, the central, high acuity region of the visual field where all discernment of fine detail and most color perception takes place is only about 2º across, equivalent to about the size of your thumbnail held at arm’s length. Peripheral vision is not good for very much except detecting movement in the periphery, so that we can turn our eyes (saccade) toward whatever is moving, so as to bring it into foveal vision and check out what it actually is.
On average, human eyes make a saccade, a rapid, purposeful “flick” of movement, about three times every second (only a minority of them are toward sources of motion in the visual periphery), and several other types of eye movement also very frequently occur. It has been plausibly claimed that most human behaviors, the majority of our actions, are movements of the eyes.
One of the pioneers of eye movement research was Charles Darwin’s father, Robert.
" The ENIAC was big. It weighed 30 tons and took up 1800 square feet of floor space. The entire machine contained over 17,000 vacuum tubes, 70,000 resistors, 10,000 capacitors and 6,000 manual switches. It cost almost $500,000, and required six full-time technicians to keep it running."
On ENIAC’s fiftieth anniversary, Popular Science ran a few articles. One said ‘Today, a chip to do the same calculations would be the size of a dime and cost about a quarter’
The next time you have a kettle boiling, look closely at the lip of the spout. Between the lip and the point where steam actually condenses and becomes visible as a cloud, you will be able to see the hot vapor issuing from the spout.
Aside from the hydrogen, just about every atom that makes up your body was created by an exploding star (the hydrogen was created by an exploding universe). We are all–literally–stardust.
You mean the little gap where there’s no visible steam? Doesn’t that exactly prove what Machine Elf said?
If you can see the “steam”, then you’re seeing tiny droplets of condensing liquid water. Water vapour is invisible. You might be able to see a kind of “shimmering” in the air, but that’s just because of the heat changing the refractive index of the air, same as a heat haze.
Sperm from one family of fruit fly is also notable for being the largest sperm of any organism- 6cm long in one species (over 2").
Sex sucks worse for bed bugs, due to the phenomenon of ‘traumatic mating’, which is possibly even worse than it sounds- the males actually puncture their own holes in the side of the females to inject sperm. Mating with several males can actually kill the females outright.
Ahh, what the hell, one more freaky animal sex fact, why not.
An Australian marsupial mouse, the antechinus (there are several species), has males which only live for 11.5 months. The entire male population goes suddenly sex crazed at the exact same time, and basically dedicate the whole rest of their lives to having as much sex as is physically possible- they’ll mate for up to 12 hours in a go, until every single male drops dead of sheer exhaustion about 2 weeks later. For the next few weeks, the whole antechinus population is comprised of pregnant females.
So far as I know, scientists haven’t yet tried introducing some of the males to WoW to see if this will prolong their lives.
There was a time when the freezing point of water was exactly 0 °C (32 °F). Today we are not sure what it is.
You see, before 1954, the freezing point of water (also called the ice point of water) was defined to be exactly 0 °C. After 1954 we abandoned the freezing point of water as a defined temperature standard and used the triple point of water instead (exactly 0.01°C). Since the freezing point of water is no longer a defined temperature, we are not sure what it is exactly.
An attempt was made by NIST in 1995 to construct an ice water bath that matched the attributes of an ideal bath as closely as possible. All equipment was repeatedly rinsed with pure, analytical-grade water over the course of many days, and measures were taken to minimize airborne contamination. After performing numerous differential temperature measurements between the ice bath and a water triple point cell, it was concluded an ideal ice water bath has an ITS-90 temperature of around 0.000089 °C. (Give or take a few microkelvin. Remeber… we don’t know *exactly *what it is.) Ambient pressure and hydrostatic head corrections were taken into account when calculating the temperature.
The value of 0.000089 °C (± a few μK) for the ice point of water is primarily an academic curiosity. For virtually all applications, the temperature of an ideal ice water bath may be assumed to be precisely 0 °C.
If work in a lab, or do precision measures in a production environment, and you measure the mass of something using a precision balance (such as a Mettler analytical balance), the value it gives you will probably be wrong.
And it’s not because the balance is faulty or inaccurate. The balance could be *perfectly *accurate, and the mass value it reports will *still *be wrong in all likelihood.
Why? Because the balance assumes that whatever you are placing on the pan is made of pure stainless steel.
If the specimen you place on the pan is constructed of pure stainless steel, the reported mass value will be accurate. If it is plastic specimen, for example, the value reported by the balance will be less than the actual mass of the specimen.
So in the science and analytical world, all measured mass values are “effective” values, not real, actual mass values. This is not a problem in most applications, since all you usually care about is relative changes in mass or differences in mass between different specimens. But it can be a serious issue in some applications, such as chemical reactions and chemical mixtures. I recall a case where a drug manufacturer was adding an incorrect amount of a drug to a capsule because they thought the values reported on their analytical balance were the actual mass of the drug and not the “effective” mass.
Ask an electrical engineer, “What are the charged thingies that constitute electric current?” and 99% will say, “Electrons, of course!”
But this is only true is *some *things. Like metals. And semiconductors. (Even “hole” current is really made of mobile electrons.) But is *not *true in electrolytic solutions. Such as current through a battery. Or current through your body if you’re electrocuted. In those cases, there is very little (if any) current due to mobile electrons. Almost all of the current is due to mobile ions.
So it is incorrect to say, “Electric current is made of mobile electrons.” You should instead say, “Electric current is made up of mobile charges.”
Under the influence of an electric field, of course.
People refer to the electricity available at your wall receptacle as “alternating current” (AC), e.g. “The coffee maker needs to be plugged in to an AC outlet.” But IMO, it should not be called AC. It should be called AV (alternating voltage). Because that’s what it is; the polarity of the voltage is constantly alternating between the hot and neutral conductors. It is an alternating voltage regardless of what’s plugged in to the receptacle (unless the breaker is off or it’s a complete short, obviously). And it’s an alternating voltage even when *nothing *is plugged in to the receptacle.
The *current *at the receptacle is a totally different story. It might be periodically changing direction when something is plugged in to the receptacle. And it might not be periodically changing direction when something is plugged in to the receptacle. And it might be zero, which is the case when nothing is plugged in to the receptacle.
In other words, the current at the receptacle can be just about anything… alternating, direct, zero, intermittent, crazy, weird, etc. The voltage, on the other hand, is very “strict”… it is alternating, dammit. All the time. Regardless of anything else.
Could you expand on that? Why should the material make any difference to the mass? Balances are calibrated using standard masses, yes, which are generally made out of stainless steel, but that’s not the same thing at all.
Because of atmospheric buoyancy. a 1-kilogram mass specimen of plastic has more volume, and therefore will displace more air, than a 1-kilogram mass specimen of stainless steel, resulting in less total downforce on the balance, despite having the exact same actual mass. For high-precision mass measurements, the difference really does matter.
Let’s say you have 1 meter of *stranded *12 gauge wire and 1 meter of *solid *12 gauge wire. Since both are 12 gauge, both wires have the exact same cross-sectional area (3.31 mm[sup]2[/sup]). (Note that this is the cross-sectional area of just the copper. Which means the overall diameter of the stranded wire will be slightly larger than the solid wire due to air gaps between the strands.)
Will both wires have the same resistance, then?
No. The stranded wire will have slightly higher resistance.
Why? Because the 1 meter of stranded wire is really longer than 1 meter. The real length is probably around 1.03 meters or so. This is because the strands in stranded wire are twisted.
To understand why, imagine manufacturing the stranded wire by first laying the strands out straight and then bundling them together. Next, grab each end and put a twist in the bundle of 180 degrees or so. When you do this, the two ends will come closer together, and the entire bundle of will have a slight, overall “corkscrew” shape. When you untwist the strands, the bundle will lengthen to its original length, and the corkscrew will disappear.
So if you were to take the 1 meter of stranded wire, remove the insulation, and untwist the strands (so that all strands are straight and parallel), the two ends of the wire will move slightly farther apart, to around 1.03 meters or so. Since the real length of 1 meter of stranded wire is slightly longer than 1 meter of solid wire, the former will have slightly higher resistance.
I’m probably going to regret asking this, but how can the density of the material to be measured affect the reading of its mass? Unless it’s something wildly esoteric like a lower density material distributes the same mass such that the center of mass is farther from sea level affecting the accuracy of the balance. Just what precision are we talking about here?
EDIT: I don’t regret asking but I regret asking without previewing first Question answered.
