What is nuclear fission vs fusion

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Earthquakes occur when stress accumulated along geological fault lines is suddenly released. Tectonic plates — the massive sections of Earth's crust — are constantly moving, typically a few centimetres per year. Where plates meet, they grind against each other. Friction prevents smooth sliding, so stress builds up over decades or centuries until it releases catastrophically. The point underground where the earthquake originates is the hypocentre (or focus). The point on the surface directly above is the epicentre, which is what news reports refer to. Seismic waves radiate outward in all directions from the hypocentre. The Richter scale and more modern moment magnitude scale measure energy released. The scale is logarithmic — a magnitude 7 is about 32 times more energy than a magnitude 6. A magnitude 9 releases about 1,000 times more energy than a magnitude 7. Earthquakes are concentrated along plate boundaries: the Pacific Ring of Fire (Japan, Indonesia, Chile), the Alpine-Himalayan belt, and mid-ocean ridges. But intraplate earthquakes can occur far from boundaries and are often harder to predict.

by kojoboateng · 76 upvotes

Vaccines work by training your immune system to recognise a specific pathogen without causing the actual disease. The immune system has a remarkable memory — once it encounters and defeats a pathogen, specialised memory cells remain that enable a much faster, stronger response to future encounters. Traditional vaccines do this by exposing you to a weakened or killed version of the pathogen, or to a harmless protein from its surface. mRNA vaccines (like COVID-19 vaccines) take a different approach: they deliver genetic instructions that cause your own cells to temporarily produce the target protein, triggering the immune response. Herd immunity — when enough of a population is immune that the pathogen can no longer spread easily — protects vulnerable people who cannot be vaccinated. The threshold varies by how contagious a disease is. For measles, about 95% immunity is needed. For COVID, lower because it's less contagious. Vaccines are among the most impactful medical interventions in history. Smallpox is eradicated. Polio is nearly gone. Measles, diphtheria, and tetanus once killed millions annually.

by danaalamin97586 · 6 upvotes

Quantum mechanics describes how matter and energy behave at the subatomic scale, and it's deeply counterintuitive. Several principles will sound strange: Superposition: quantum particles can exist in multiple states simultaneously until measured. Schrödinger's famous thought experiment — a cat that's both alive and dead — illustrates this absurdity at everyday scales. Entanglement: two particles can become correlated so that measuring one instantly determines the state of the other, regardless of distance. Einstein called this "spooky action at a distance." It's now experimentally confirmed and forms the basis of quantum cryptography. Uncertainty principle: Heisenberg showed you cannot precisely know both a particle's position and momentum simultaneously. This isn't a measurement limitation — it's a fundamental feature of reality. These aren't abstract — they're why transistors (and therefore all computers) work, why MRI machines function, and how lasers operate. Quantum mechanics is the most precisely tested theory in all of science.

by papediallo59953