# Tidal Locking

> Same side always faces star.

- Field: Astronomy
- Level: Advanced
- Qur'an passage: Quran 25:45
- URL: https://dailymuslim.org/quran-miracles/tidal-locking

In the Quran the moving shadow can stand still. Skeptics claim that whoever wrote the Quran made a mistake, a shadow can never stand still. Today astronomers confirm that planets can get tidally locked to their star with their same side always facing the star.

> "Tidal locking between a pair of co-orbiting astronomical bodies occurs when one of the objects reaches a state where there is no longer any net change in its rotation rate over the course of a complete orbit. In the case where a tidally locked body possesses synchronous rotation, the object takes just as long to rotate around its own axis as it does to revolve around its partner. For example, the same side of the Moon always faces Earth..."

— [Wikipedia, Tidal locking, 2024](https://en.wikipedia.org/wiki/Tidal_locking)

Tidal locking causes the same face of the moon to always face Earth. Do you remember the oceanic high tides and low tides? Well they are caused by lunar gravity. This figure teaches you how ocean friction transfers the kinetic energy of Earth's spin to the moon:

![Source diagram: ocean friction and the Moon’s recession.](https://dailymuslim.org/miracle-media/tidal-locking/speed-of-light-moon-recede.gif)

The tidal bulges transfer Earth's rotational kinetic energy to the moon; this causes Earth's spin to slow down. A time comes when the Earth is spinning at the same rate as the moon orbits Earth. In this case there is no more misalignment of tidal bulges and no energy is transferred to the moon. The same side of Earth always faces the moon.

This exact process also happens between Earth and the sun. Earth also transfers its rotational kinetic energy to the sun. But due to the larger distance to the sun this energy transfer is much weaker and takes much longer time for Earth to be tidally locked to the sun. But given enough time it will eventually be tidally locked to the sun. This was known recently however this was portrayed in the Quran 1400 years before it was discovered. The Quran says that the moving shadow can stand still:

## Qur'an passage · Quran 25:45

٤٥ أَلَمْ تَرَ إِلَىٰ رَبِّكَ كَيْفَ مَدَّ الظِّلَّ وَلَوْ شَاءَ لَجَعَلَهُ سَاكِنًا ثُمَّ جَعَلْنَا الشَّمْسَ عَلَيْهِ دَلِيلًا

*Do you not see how your Lord extends the shadow? Had He willed, He could have made it still. And We made the sun a pointer to it.*

The shadow can only stand still if the same side of Earth always faces the sun. Today we know what it is, this is tidal locking.

### Additional references

> Original article: Miracles of Quran. The Wikipedia excerpt and its translations are available under CC BY-SA 4.0. The explanations below are separate additions.

— [CC BY-SA 4.0](https://creativecommons.org/licenses/by-sa/4.0/)

### Additional evidence — summary

> NASA explains that the Moon takes the same time to spin on its axis and to orbit Earth. Ocean tides slow Earth’s rotation and help the Moon move away. However, the original article’s certainty that Earth will lock to the Sun is not an established prediction. NASA says Earth and the Moon would lock to each other in about 50 billion years, if they could survive the end of the Sun’s life. That condition matters.

— [NASA — Tidal Locking](https://science.nasa.gov/moon/tidal-locking/)

### Tafsir Ibn Kathir — 25:45

> Ibn Kathir connects the shadow with the time from dawn to sunrise and explains that Allah could have left it unchanged if He willed. The link with tidal locking is the original author’s modern interpretation. The verse gives no orbital model and does not say that Earth will lock to the Sun.

— [Tafsir Ibn Kathir — 25:45](https://quran.com/al-furqan/45/tafsirs/en-tafisr-ibn-kathir)

## Ponder

**How could an illiterate man who lived 1400 years ago have known about tidal locking?**

## Sources and further reading

- [Quran 25:45 · Quran.com](https://quran.com/25/45)
- [Wikipedia, Tidal locking, 2024](https://en.wikipedia.org/wiki/Tidal_locking)
- [Miracles of Quran](https://www.miracles-of-quran.com/tidal_locking.html)

— Miracle of Quran, Daily Muslim · https://dailymuslim.org/quran-miracles/tidal-locking