81
I have actually stuck a knife into a toaster, and I can confirm that yes, it is very definitely electrified. Please, Please, Please, don't do this. The only reason I'm still alive is because of a good fusebox / safety switch and the fact that my hand spasmed in such a way that I let go of the knife.
59
The toaster is going to have heating elements of a type of wire that has very high resistance, usually nichrome wire. When electricity is applied to the wire, it becomes hot enough to toast bread.
You'll notice if you look closely that the wire is supported by some form of non-conducting brackets, sometimes ceramic. This prevents the wire from following a ...
27
See this article: Digital History: The Rise of Hollywood and the Arrival of Sound.
It refers repeatedly to "movie houses", and uses the term "wired for sound". these are certainly what the Variety extract is referring to.
Note: I've also seen it hyphenated "movie-house", and contracted "moviehouse".
18
The first thing to remember is that the naming of eras such as the Stone Age or the Bronze Age is never done by those living during the period. It was always done by others much later.
To a certain degree, the reason why bronze was the first important alloy was luck. For whatever reason, design or mistake, someone at some stage during antiquity mixed copper ...
17
This is very common misunderstanding. When we look a a road, we see few centimeters thick layer of bituminous surface, and we think about "the road" as "the asphalt/tarmac."
It's not.
When you look how a road is build (or rebuilt), you can see that "the road" is actually over half a meter (or more) deep, consists of layers of sand and gravel and has ...
16
Yes. Especially considering gold and platinum prices as of today, Pt costs less than Au. - but let's earn much more with more modern solution and simultaneously slowly murder the king in a very nefarious plot:
Gold is 40 $\$/g$ at 19.3 $g/cm^3$
Platinum is 39 $\$/g$ at 21.45 $g/cm^3$
Depleted Uranium is about 6 $\$/g$ at 19.1 $g/cm^3$ (1)
[sorry for the ...
15
The device for taking horizontal and vertical angles that you mention is called a theodolite. Theodolites only started being phased out as the main surveying tool in the 1980s when total stations where introduced. Below is a Soviet theodolite from 1958, (ex Wikipedia).
Theodolites were analogue devices and the angles measured had to be written in a notebook....
13
How could they possibly sell a consumer-oriented product like that which zaps its users if they happen to touch the interior slightly as they stick a knife into the piece of toast bread to get it out from the toaster when it inevitably gets stuck sometimes? Or is too hot to use your fingers?
Consider your own perspective. This sentence shows an expectation ...
13
they mean wired for sound. Previously movies were accompanied by a pianist or organ player.
10
Yes, you are correct that there are different definitions of Systems Engineer that vary by company. In fact, different business units of the same company may even use the term differently.
A job posting on Stack Overflow Careers from Booking.com has a Senior Systems Engineer - Systems Architecture role. This role has responsibilities such as taking "...
10
The earliest CRT displays were in fact round. However, that was more due to manufacturing tradeoffs of making large glass envelopes with vacuum inside than a desire for the display area to be round.
Rectangular makes more sense than round for a variety of reasons:
It's what people want to look at. We use rectangular pieces of paper. Photographs are ...
10
Check this book out; it seems to be talking about that particular grade of steel used for reinforcement.
The choice of main bonded reinforcement is based on its high tensile strength and interaction between it and concrete, resulting in higher bond length and an improved degree of crack control. A considerable experimental work has been carried out by ...
10
Why would they have the metal parts responsible for pressing against the bread and keep it in place be having electricity going through it?
They don't. The metal parts responsible for pressing against the bread are not electrified.
The electrified parts are behind the wires which press against the bread. You can see them, touch them, burn yourself on them, ...
9
The transistor
The transistor was the revolutionary replacement of the vacuum tube, which had been at the heart of computers for the first half of the 20th century. Vacuum tubes themselves had only two main problems: They were power-hungry and they were relatively big. Relative to their replacements, that is. They also had a tendency to burn out or leak ...
8
You mean going back to cobblestone roads? Many sidewalks are often paved with pavers.
One of the challenges is maintaining a level surface. Asphalt holds itself together like a sheet and a dip in the surface below will pull on the sides delaying the onset of potholes. while separate parts will start moving under the vibration and frost heaving.
Once the ...
8
I'm still confused about what you mean by "engineering advances". To me, things like vacuum tubes, transistors and ICs are technologies, and engineering is all about applying those technologies to real-world problems, such as building computers.
Engineers have typically taken each available technology to its practical limit — to the point where other ...
8
Meet Vladimir Shukhov, a Russian architect who first developed hyperboloid structures. He was born in 1853, died in 1939, and created over 200 hyperboloid structures in the intervening years. He was the reason hyperboloids gained the popularity that they did. His first design, the first hyperbolic structure ever, was the Shukhov Tower in Polibino, pictured ...
8
Using the values of metals in 287 BCE – 212 BCE, could it be cost effective for the crown maker?
Of the metals known and used in antiquity (copper, gold, silver, lead, iron, tin, mercury, zinc), gold is by far the densest, at $19.30 \text{ g/cm}^3$; mercury is in second place at $13.53 \text{ g/cm}^3$. Platinum may have been known, but it certainly wasn't ...
7
The Oak Ridge National Laboratory had an experimental thorium reactor in the 1960s, but the program was terminated in the 1970s.
This can be partially be attributed to the needs of both the military and businesses, at the time. Unlike $^{235}{U}$, thorium is not naturally fissile, it needs to be bombarded with slow neutrons to ultimately produce $^{233}{U}$,...
7
Before the extremely accurate machines were made, they first had extremely accurate measuring devices.
I'll use the "first lathe" as an example. The bed of the lathe needs to be very flat, as the rest of the machine can be calibrated with it. One way it can be made that way is by putting the not-straight bed up against a much flatter surface plate, and ...
7
I don't believe there is any conflict but variation in how Human Resource choose to define system engineer positions within specific organizations.
It is my opinion that System Engineer has a broad definition mostly related to the specific industry. In my experience system engineer is an interdisciplinary professional of engineering as describe in your ...
6
In ancient times roundhouses were constructed and are still constructed in predominantly lesser developed countries.
One issue with roundhouses is, once constructed they can't be extended laterally and retain the same shape. Rectangular buildings can be easily extended and most of the original structure can remain - knock down one wall and extend while the ...
6
Systems Engineering pre-dates IT.
The classical Systems Engineering has roots in aerospace industry (for better, or for worse). Projects were were getting multidisciplinary, and complex, and required multiple contractors to complete. So appeared a need for a kind of engineer to keep track of various aspects (such as weight, for example) on a relatively ...
6
I think that there are a few things that you aren't considering.
Subgrade
Most roads have at least 12 in (300 mm) of compacted aggregate (rock) under the actual pavement. If the existing soil is very weak, then this depth of aggregate subbase can be increased. Sometimes the soil needs to be strengthened by mixing in cement.
This means that just removing road ...
6
This was an actual thought process that was spoken out loud by Feynman in his famous paper There's plenty of room at the bottom, in 1959.
Here's the related part:
A hundred tiny hands
When I make my first set of slave "hands" at one-fourth scale, I am going to make ten sets. I make ten sets of "hands," and I wire them to my original ...
6
If you could truly indefinitely keep a line open for anyone who calls you, by simply not hanging up on your end, the potential for abuse is endless.
That's the way the POTS (plain old telephone system) worked. The caller controlled the line.
This "feature" was exploited by criminals who called the police stations from phone boxes and ripped the handsets ...
6
Yes, and no. When the toaster is actually toasting, then obviously there's electricity running through the elements, which need to get hot (and will be seen to glow). Once it's turned off, but still plugged into the mains, electricity is not flowing through the elements. If it was, they'd still be glowing.
However, poking anything inside may touch something ...
5
I'm going to answer my own question because just before posting it I found an answer.
The Otto Lilienthal Museum has a comprehensive list of Lilienthal's designs. One is listed as the "small wing-flapping machine." It didn't use a propeller (or jet engine, of course!) but instead used a small engine weighing about 22 pounds when fully fueled. Its wingspan ...
5
I'd like to add to what @Fred said.
Bronze wasn't the first. Before the Bronze Age, there was a comparatively brief Copper Age [also this]. Copper is comparatively abundant, and it sometimes naturally occurs in pure state (nuggets), as well as ores.
In some places, polymetallic ores were used for producing copper. Early metalworkers noticed that the ...
5
HDE 226868 already mentioned the transistor in detail, so I will add many, many technological advances and theoretical backgrounds for the evolution of the computer.
Metallurgy
For the mass-market you need cheap and reliable methods to produce the desired electronic elements. For mass production you need integrated circuits and that means, especially if you ...
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