← Back to the archive★ Support my pages
DD-574Sciencealso NatureFiled Last updated

Blue Hour

Short answer: 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.

VideoWrite-up1 sources
More like this★ Support my pagesCite this file

What should you know about Blue Hour?

Quick facts. Each one stands alone and has a stable ID you can cite.

  1. Twilight.

    DD-574-F01 · Write-up · Exhibit A (When)

  2. Below horizon.

    DD-574-F02 · Write-up · Exhibit B (Sun)

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

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

Burned-in captions, read frame by frame (see transcript.md) · 21.3s Reel ·

Video coming soonBlue Hour · Instagram Reel
Blue Hour: The Blue Hour Comes Just Before Sunrise and Just After Sunset Instagram Reel · · 21.3s

The write-up

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

  1. Exhibit A

    When

    Twilight.

  2. Exhibit B

    Sun

    Below horizon.

  3. Exhibit C

    Light

    Indirect.

  4. Exhibit D

    Color

    Blue wavelengths.

  5. Exhibit E

    Length

    Varies with location.

Questions people ask about Blue Hour

When?

Dawn and dusk.

Source: Write-up · Exhibit A (When) · Wikipedia: Blue hour

Sun position?

Below.

Source: Write-up · Exhibit B (Sun) · Wikipedia: Blue hour

Light type?

Scattered.

Source: Write-up · Exhibit C (Light) · Wikipedia: Blue hour

Dominant color?

Name.

Source: Write-up · Exhibit D (Color) · Wikipedia: Blue hour

Length depends on?

Latitude.

Source: Write-up · Exhibit E (Length) · Wikipedia: Blue hour

Test Your Knowledge

All quizzes →

5 questions, all from this case file. Answers are revealed instantly.

  1. When?

    1. Twilight
    2. Noon
    3. Midnight only
    4. Eclipse only
    Show the answer

    Answer: A. Twilight Dawn and dusk. Source: Write-up · Exhibit A (When) · Wikipedia: Blue hour

  2. Sun position?

    1. Just below horizon
    2. Overhead
    3. Behind clouds only
    4. Rising fast
    Show the answer

    Answer: A. Just below horizon Below. Source: Write-up · Exhibit B (Sun) · Wikipedia: Blue hour

  3. Light type?

    1. Indirect
    2. Direct
    3. Artificial
    4. Laser
    Show the answer

    Answer: A. Indirect Scattered. Source: Write-up · Exhibit C (Light) · Wikipedia: Blue hour

  4. Dominant color?

    1. Blue
    2. Red
    3. Green
    4. Yellow
    Show the answer

    Answer: A. Blue Name. Source: Write-up · Exhibit D (Color) · Wikipedia: Blue hour

  5. Length depends on?

    1. Location and season
    2. Wind
    3. Tides
    4. Clouds only
    Show the answer

    Answer: A. Location and season Latitude. Source: Write-up · Exhibit E (Length) · Wikipedia: 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/

Permalink: https://detailenjoyer.com/case/blue-hour/ · Last updated

Markdown version

Cite a single fact by its ID, for example DD-574-F01 → https://detailenjoyer.com/case/blue-hour/#DD-574-F01