Nature sets a hard limit on how precisely position and momentum can both be known

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Nature sets a hard limit on how precisely position and momentum can both be known

the gist

The uncertainty principle says that some pairs of properties of a particle cannot both be known precisely at the same time. Position and momentum are the best-known pair, and the more accurately one is measured, the less accurately the other can be known. This is a built-in limit of quantum mechanics, not a flaw in our instruments. Werner Heisenberg introduced the idea in 1927, and Earle Kennard and Hermann Weyl soon gave it a precise mathematical form. The principle applies to many other pairs, including energy and time, which is why quantum states have blurred energies.

how it works

In quantum mechanics a particle's wave-like nature means it has no single sharp position and momentum at once. Narrowing the spread of position widens the spread of momentum, and the product of these spreads has a minimum set by Planck's constant. The limit comes from the mathematics of waves, not from clumsy measurement.

so what

The principle is why atoms do not collapse and why electrons occupy shells, and it underpins technologies like lasers and electron microscopes. It also reshaped how physicists think about measurement itself.

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 ↗