What is the difference between atoms and molecules

✓ Accepted Answer

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 bintambodj3380 · 82 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 oliveredwards3713

The immune system is your body's defence network against pathogens — bacteria, viruses, fungi, and parasites. It operates on two levels: innate immunity (fast, non-specific) and adaptive immunity (slower, highly specific). The innate system responds immediately to anything recognised as foreign. Skin is the first barrier. If pathogens breach it, immune cells like neutrophils and macrophages attack using inflammation — redness, swelling, and heat are signs of this response working. The adaptive system is slower but devastatingly precise. When the innate system flags a threat, specialised white blood cells called T cells and B cells are activated. B cells produce antibodies — proteins specifically shaped to bind to that particular pathogen and neutralise it. T cells directly destroy infected cells. Memory cells remain after infection resolves, enabling faster response to the same pathogen years later. This is how vaccines work — they trigger this memory formation without causing the disease itself. Autoimmune diseases occur when the immune system mistakenly attacks the body's own tissues — conditions like rheumatoid arthritis, lupus, and type 1 diabetes.

by ayeshaqureshi