Long-form guides for students: what each method really measures, the equations, numbers to check yourself and the assumptions that break.
THERMODYNAMICS
Sometimes yes, often no. Whether hot water "wins" depends on what you call frozen, on how you cool it, and on the random way each sample of water starts to turn into ice. Here is what careful experiments, including a 2026 study with 176 measurements, actually found.
PHYSIOLOGY · STUDENT GUIDE
A hiccup is not one event but two: a sudden pull of the diaphragm, then a slam of the vocal cords about 35 milliseconds later. What drives the rhythm, what sets it off, why nobody knows what it is for, and why home remedies and long-lasting hiccups deserve a careful look. For undergraduate and graduate students. Not medical advice.
HEALTH · ANIMAL PHYSIOLOGY
A purr is the larynx buzzing about 25 times a second. Cats purr when they are content, but also when they are hurt or frightened. And the popular claim that purring heals bones rests on a matching number, not on a healing study. The mechanism, the evidence and how to read a health claim. For undergraduate and graduate students.
ANIMAL BEHAVIOUR
Almost every dog eats grass, and the usual explanation is that it feels sick and wants to vomit. The largest owner survey says otherwise: only 8 % of plant-eating dogs often looked ill beforehand and only 22 % regularly vomited afterwards. Here is what the studies measured, what they did not, and when grass eating deserves attention.
THIN-FILM ELECTRICAL METROLOGY
A student guide to probe roles, the 4.532 factor, ohms per square and geometry limits. One calculation, checked step by step.
PHYSICS · ASTRONOMY
The Sun is about 400 times wider than the Moon and about 400 times farther away. The two factors cancel, so both span about half a degree in our sky. Here is the arithmetic, what it means for eclipses, and why total eclipses have an expiry date. For undergraduate and graduate students.
THIN-FILM DEPOSITION
Vacuum, argon, electrons, magnets and ion hits: what each step does, the numbers behind it, a worked example you can check yourself, and the one target that DC cannot sputter. For undergraduate and graduate students.
ASTRONOMY · METEOR SHOWERS
A shooting star is a sand grain, a meteor shower is a comet's dust stream, and the date is fixed by where Earth is on its orbit. With the numbers for the 17–18 November 2026 peak, a rate formula you can use yourself and how to watch. For students and curious observers.
SPACE PHOTOGRAPHY
The stars are there. A camera is set for the brightest thing in the frame, and one frame cannot hold the sunlit Moon and the faint sky at once. Here is the physics, with real numbers from NASA's Artemis II image data.
PHYSICS · GRAVITY AND ORBITS
Gravity does not switch off in orbit. Astronauts float because they, their spacecraft and everything inside are falling together. The numbers, the mechanism, and the word that misleads almost everyone. For undergraduate and graduate students.
SOLAR PHYSICS · STUDENT GUIDE
The Sun's surface is about 5,500 °C, yet the thin corona above it reaches about two million degrees. What we know, what Parker Solar Probe measures from inside, the two classic suspects, the 2026 dust idea, and why the probe does not melt. For undergraduate and graduate students.
SUPERCONDUCTIVITY · EPISODE 1
What a superconductor is, from the outside: the two signatures that define it, the experiments that showed them, the numbers you can check yourself, and why temperature decides where superconductors are used. For undergraduate and graduate students.
MATHEMATICS · POPULATION · STUDENT GUIDE
In 1960 the journal Science printed a paper titled 'Doomsday: Friday, 13 November, A.D. 2026'. It was not a prophecy but a curve fitted to two thousand years of population estimates. What the curve says, why it blows up on a finite date, how the real world broke away from it, and what it teaches about extrapolation. For undergraduate and graduate students.
SOLAR CELL MANUFACTURING
A freshly sawn silicon wafer reflects about a third of the light that hits it and cannot deliver any current. Six factory steps change that: texture, emitter diffusion, cleaning and edge isolation, a nitride coating, printed and fired contacts, and a light test. This guide follows one cross-section through the conventional aluminium back-surface-field (Al-BSF) route and asks, for each step, which loss it removes. For undergraduate and graduate students.
SOLAR CELL MEASUREMENT
A J–V curve tells you how much current a cell gives under the whole spectrum. A quantum-efficiency curve tells you where that current comes from, one colour at a time: which photons are lost at the front, which at the back, and which never had a chance. How it is defined, how it is measured, how to read it, how to turn it into Jsc, and the one thing it is not. For undergraduate and graduate students.
SOLAR CELL PARAMETERS
Two cells, same light, same Voc, same Isc, and one gives a quarter less power. The difference hides in two resistors that every real cell carries. Where they come from, which end of the I–V curve each one bends, how to estimate them and why the quick estimates mislead. For undergraduate and graduate students.
SOLAR CELL PHYSICS
Every electron that flows out of a solar cell was already in the silicon. Light only lifts it, the junction only sorts it, and the power is spent in the load. A step-by-step guide for undergraduate and graduate students, with numbers you can check yourself.
SOLAR CELL PARAMETERS
Forty milliamps and 0.60 volts do not make 24 milliwatts. A step-by-step guide to reading the two ends of an I–V curve, finding the maximum power point, computing the fill factor, converting the area, and getting an efficiency you can actually compare. For undergraduate and graduate students.
SOLAR CELL MEASUREMENT
Negative current, a voltage that is a few percent low, a curve with a flat shelf, a staircase that never settles, a dark curve that runs through zero: five things you will see the first time you put a solar cell on a source-measure unit, and what each one means. For undergraduate and graduate students.
THIN-FILM METROLOGY
What each tool really measures, the equation behind it, a number you can check yourself, and the assumption that most often breaks. For undergraduate and graduate students.