Caffeine keeps you awake by blocking adenosine, the chemical that signals tiredness

the gist

Caffeine is a stimulant that is the most widely consumed psychoactive drug in the world, mostly through coffee and tea. Its molecule has a shape similar to adenosine, a chemical that builds up during the day and makes you feel sleepy. Caffeine fits into adenosine receptors and blocks them, so the sleep signal cannot take effect, and it also increases the release of acetylcholine, which supports alertness. Regular use leads to tolerance and mild dependence, with withdrawal causing headaches and drowsiness. Research supports modest benefits such as faster reaction times, and the safe daily intake for most adults is around 400 milligrams.

how it works

Adenosine builds up in the brain as you stay awake and binds to receptors that slow nerve activity. Caffeine has a similar shape, so it occupies the same receptors without triggering the slowdown. The brain responds by making more receptors, which is why regular users need more caffeine over time.

so what

Caffeine is one of the most studied substances in the world, and knowing how it works explains why it helps alertness, why it disrupts sleep, and why stopping can cause headaches. It is also a useful example of how drugs act by copying natural molecules.

fun fact

Caffeine is chemically related to the adenine and guanine bases found in DNA and RNA.

Hampi was once one of the world's largest cities, until its Vijayanagara capital was destroyed in 1565

the gist

Hampi is a UNESCO World Heritage Site in Karnataka, India, with more than 1,600 surviving remains spread over 4,100 hectares. It was the capital of the Vijayanagara Empire from 1336 to 1565. Travellers from Persia and Portugal described it as a prosperous, wealthy and grand city with temples, markets and farms along the Tungabhadra River. By 1500 it was estimated to be the world's second-largest city after Beijing, and probably India's richest at the time. In 1565 a coalition of Muslim sultanates defeated the Vijayanagara Empire, its capital was conquered and destroyed, and the city was left in ruins. Hampi remains a religious centre, with the active Virupaksha Temple at its heart.

how it works

The city was built around a fortified core with temples, markets and water structures along the river, supplied by an extensive network of roads and waterworks. When the empire fell, the city was not rebuilt, so its stone monuments were left standing.

so what

Hampi shows how quickly a great city can vanish after a military defeat, and how a ruined capital can remain sacred. Its ruins give historians a view of medieval South Asia that few other sites can match.

fun fact

The name Hampi comes from Pampa, an old name for the Tungabhadra River.

From Wikipedia, the free encyclopedia · text CC BY-SA 4.0

Image: Wikimedia Commons

source: Wikipedia ↗

2 min

politicsshortCNA2:01

False allegations about Singapore’s hand in Indonesia’s markets and a made-up meeting

from CNA

CNA Verify has found close to 400 posts pushing falsehoods tying Singapore to Indonesia’s stock market rout and to a secret meeting that never took place. Together, they drew nearly 12 million views, and some were circulated by accounts that appeared to be working in concert, across multiple social media platforms.

Here’s how the disinformation campaign targeting Singapore was uncovered.

on YouTube: CNA ↗