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How does daylight set the body’s clock?

Feeling sleepy at night involves more than counting the hours since you woke up. Internal daily rhythms respond to outside cues, with light helping coordinate the body's sense of time.

3–5 min

Questions you could explore

  • How does information from the eyes reach the body's timing system?
  • What changes when the light-dark cycle shifts across time zones?

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Health and the body

How does a vaccine give the immune system a memory?

The immune system can respond differently to something it has encountered before. Vaccines make use of recognition and memory, though different vaccine types introduce the relevant information in different ways.

4–5 min

How does a vaccine give the immune system a memory?

Health and the body4–5 minThe immune system can respond differently to something it has encountered before. Vaccines make use of recognition and memory, though different vaccine types introduce the relevant information in different ways.

Health and the body

Why won’t an antibiotic treat a viral cold?

The word infection covers illnesses caused by very different organisms. An antibiotic that helps against certain bacteria has no matching target in the viruses that cause a cold.

2–3 min

Why won’t an antibiotic treat a viral cold?

Health and the body2–3 minThe word infection covers illnesses caused by very different organisms. An antibiotic that helps against certain bacteria has no matching target in the viruses that cause a cold.

How does the ear turn vibration into a signal the brain can use?

Health and the body4–5 minThe sound of a voice reaches the ear as vibration, yet the brain receives nerve signals. The eardrum, small bones, fluid-filled cochlea, and sensory hair cells take different parts in that conversion.

How does daylight set the body’s clock? | Speech Topic | speaking.app