Ferrofluids
A ferrofluid is a colloidal solution of nanoparticles in a carrier fluid. A colloid is a "mixture" of certain extremely small particles that are equally distributed inside a fluid, and in this case, the particles are a few nanometres across and are ferromagnetic (i.e., attracted by and magnetizable by magnets).
When an external magnetic field is applied across this ferrofluid, the nanoparticles begin to clump together because they become magnetized and the magnetic force begins to draw them together. In order to "declump" the particles once the field is switched off, the particles are given a thin coating of a surfactant (like sodium citrate).
With precisely controlled fields, ferrofluids assume beautiful formations and arrangements in space. The primary use of this fluid is in two industries:
- X-ray spectroscopy - The principle purpose of this device is to resolve high-energy electromagnetic radiation, and for that, it must be remain extremely stable during operation. Refrigerators built with ferrofluids are called adiabatic demagnetization refrigerators (ADR) and their working temperatures are between 0 K and 100 mK, and provide the low temperatures required for stability.
- Armour - Battle tanks have moved on from possessing just one thick layer of metallic armour to two layers sandwiching a second material. This material is a ferrofluid. During an explosion in the immediate surroundings of a tank, the first layer presses down on the ferrofluid. Because of the increased pressure, the nanoparticles in the fluid clump together and increase the density and the viscosity of the fluid (the more viscous a fluid is, the less easily it flows). This makes it more hardy and imparts an increased resistance to let the shockwaves from the blast penetrate the second layer of metal.
Once the pressure subsides, the fluid becomes less viscous and, more importantly, less dense. This decrease in density is important for the vehicle to retain its working brake-horsepower.
Technical illustrations
Illustrating for science is tricky business. At first glance, the proportions have to be precise; I've known whole projects that had to be abandoned because someone got the metric wrong by 5% or less. Once you begin to scrutinize the images, it also becomes evident that the generation of a visual stimulus has to be carefully manipulated in order to evoke certain associations.
For example, consider three objects, A, B and C, within a frame. If A and B are considered to be more important than C is, then using the same colour to highlight A, B and C would make that distinction harder to grasp. Of course, the demarcation could be invoked using other methods, but why bother when colour is so easily represented and accessible? Using blue for A and B and grey, a slightly more muted colour, for C establishes distinction, significance and association all in one.
My last comment is on the object itself: if A is a kind of lizard, then showing it from the top or the side won't make the same impact as would its depiction in a characteristic pose, like preparing itself to lunge at prey.
[caption id="attachment_20186" align="aligncenter" width="357" caption="Association by posture, hue and position (Source: Wikimedia Commons)"]
[/caption]Large Hadron Collider
According to the Standard Model of particle physics, the Universe is composed of leptons, hadrons, gluons, bosons and quarks. Leptons are light, hadrons are heavy, gluons are sticky, bosons are bossy and quarks are weird. At least, those were what physicists thought necessary until Einstein came along and asked, "What makes things heavy?" A clever mathematician by the name of Peter Higgs (amongst others) solved Einstein's equations for general relativity and in his solutions, proposed an elementary, hypothetical particle called in his honour today as the Higgs boson, and said it "gave" everything mass.
When the Big Bang happened all those years ago, the Higgs boson is thought to have formed as a result of the extreme pressure and temperature. Because of its unstable nature, it quickly decayed, but not before mediating the gravitational force between the other particles that were beginning to form, thereby giving them mass.
The Large Hadron Collider (LHC) at CERN is the largest science experiment in history, and has been built for the sole purpose for recreating the conditions of the Big Bang so that another Higgs boson may form. Since each particle has a distinct decay pattern, detectors, censors and other data acquisition devices have been mounted over certain sections of the LHC to quickly capture the energy signature of a decaying Higgs. If that happens, the only thing particle physics will have left to explain is dark matter.
These sections where the detectors are mounted are where the protons (or, Hydrogen nuclei) are going to be smashed together 40 million particles per second at speeds approaching that of light. In fact, data has emerged that speeds of 0.99c have been attained, which means the particles were each traveling at 296,794.5 km/s. That's 11 times around the earth in a second. At such speeds, the mass of the particles climbs monstrously, and the temperatures at the time of the smash beat the temperature of a billion suns.
Awesome.
Tsar Bomba
Tsar Bomba is the strongest man-made nuclear weapon to be detonated in the history of mankind. Imagine the amount of energy released by every bullet, missile, grenade, bomb, shell, flamethrower, chemical and reaction in World War II (incl. Little Boy and Fat Man), sum them up, and understand that Tsar Bomba's yield beat it by 10 times.
Conceptualized by scientists and constructed by engineers of the Soviet Union through 1960 and 1961, the bomb was originally supposed to have a yield of 100 MT. However, during the testing phase, it was found that any suitable site that would be exposed to such a fallout was populated by Soviet citizens. Consequently, the yield was reduced to 50 MT, and is considered to have been the cleanest explosion in history (relative to its yield).
Tsar Bomba was a 3-stage explosive:
- The first stage was a fission reaction. During a fission reaction, the nucleus of an atom splits into smaller parts, release free neutrons, photons and gargantuan amounts of energy. Inside a cavity within the fissioning material, the second stage is placed.
- The second stage was a small fusion reaction. During a fusion reaction, two or more nuclei fuse to form a larger nuclei, releasing such amounts of energy as to dwarf a fission reaction. The fusion reaction releases energy when the participating nuclei have individual masses less than the atomic mass of iron, and absorbs otherwise. Inside a cavity within the fusing material, the third stage is placed.
- The third stage was a large fusion reaction. Identical in every way but in quantity to the second stage, the third stage contained larger numbers of nuclei waiting to fuse. As the first stage went off, nuclei in the second stage become heated and compressed to a tortuous extent, generating the critical mass required for the first, smaller fusion reaction to commence. As that happened, the energy from it generated the critical mass for the final stage to go off.
In order to reduce the yield from 100 MT to 50 MT, a reexamination of the fusion tampers was required. Between the first and second stages and the second and third stages, something called a tamper was used to accelerate the fission process. As the fission reaction subsided and the first fusion stage took off, free neutrons released would collide with the tamper, made of uranium-238, and set of a fast fission reaction. This result was provided for to enhance the yield of the bomb. When reducing the yield became necessary, engineers removed the uranium tamper and replaced it with one made of lead.
The lead trapped the free neutrons. Fusion reactions took over. Fast fission became prohibited. Game over.
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