# Blue Hour (DD-574)

> The blue hour is the period of twilight just before sunrise or just after sunset, when the Sun is a few degrees below the horizon. Only indirect sunlight reaches the ground, and ozone absorption and scattering leave mostly blue wavelengths of the visible spectrum, so the sky and landscape take on a deep blue tint. How long it lasts depends on season and geographic location. The footage, credited to eastern_european_aesthetic, shows a snowy street at dusk.

- Department: Science (also Nature)
- First published: 2025-05-18
- Last updated: 2025-05-18
- Permalink: https://detailenjoyer.com/case/blue-hour/
- Author: Marcus Easterling (DetailEnjoyer), The Detail Department

## Quick facts

- **DD-574-F01**: Twilight. _(Write-up · Exhibit A (When))_
- **DD-574-F02**: Below horizon. _(Write-up · Exhibit B (Sun))_

## Write-up

The blue hour comes just before sunrise and just after sunset. Indirect sunlight paints everything blue.

1. **When**: Twilight.
2. **Sun**: Below horizon.
3. **Light**: Indirect.
4. **Color**: Blue wavelengths.
5. **Length**: Varies with location.

## Reel vs. record

- **Note**: None needed.

## Video: Blue Hour: The Blue Hour Comes Just Before Sunrise and Just After Sunset

- Duration: 21.3 s · Published: 2025-05-18
- File: https://detailenjoyer.com/assets/videos/DJzcM1IxfEA.mp4

### Transcript

[...] is a short [...] or just after [...] takes on [...] indirect light [...] visible spectrum, [...] The Blue Hour [...] geographic location [...] NOW YOU KNOW!

## Questions & answers

**Q: When?**  
A: Dawn and dusk. _(Source: Write-up · Exhibit A (When) · Wikipedia: Blue hour)_

**Q: Sun position?**  
A: Below. _(Source: Write-up · Exhibit B (Sun) · Wikipedia: Blue hour)_

**Q: Light type?**  
A: Scattered. _(Source: Write-up · Exhibit C (Light) · Wikipedia: Blue hour)_

**Q: Dominant color?**  
A: Name. _(Source: Write-up · Exhibit D (Color) · Wikipedia: Blue hour)_

**Q: Length depends on?**  
A: Latitude. _(Source: Write-up · Exhibit E (Length) · Wikipedia: Blue hour)_

## Sources

- [Wikipedia: Blue hour](https://en.wikipedia.org/wiki/Blue_hour)

## Cite this case file

Easterling, Marcus. "Blue Hour." The Detail Department (DetailEnjoyer), case file DD-574, last updated May 18, 2025. https://detailenjoyer.com/case/blue-hour/