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How has childhood mortality changed, and what do historical estimates miss?

Records of births and deaths, burial evidence, and later statistical systems offer different windows on childhood survival. Their estimates cannot be compared casually if one counts deaths before age five and another before fifteen. Historical progress becomes more meaningful when the population, age cutoff, and uncertainty remain visible.

3–7 min

Questions you could explore

  • Which two estimates could be compared on the same basis?
  • Whose lives might be missing from the surviving records?

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Health and the body

Daylight and the body's clock

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3–5 min

Daylight and the body's clock

Health and the body3–5 minEven in a room with no clocks, your body follows an internal roughly 24-hour schedule of sleepiness, hunger, and alertness. Those internal daily rhythms respond to outside cues, with morning and evening light helping reset and coordinate the body's master clock.

Health and the body

How vaccines build immune memory

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4–5 min

How vaccines build immune memory

Health and the body4–5 minThe first time the immune system encounters an unfamiliar antigen, building a response takes time. Vaccines help develop recognition and memory before a later encounter with a pathogen. Different types introduce antigens or instructions for making them in different ways, offering a starting point for exploring how immune memory works.

Health and the body

Antibiotics and the viruses they cannot treat

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2–3 min

Antibiotics and the viruses they cannot treat

Health and the body2–3 minAntibiotics can treat certain bacterial infections, but they do not treat the viruses that cause a common cold. Because bacteria are living cells with their own metabolic machinery and viruses are tiny genetic packages that hijack your cells, an antibiotic that disables bacteria has no matching target in the viruses that cause a cold.

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