# Universal Sizing (DD-546)

> The observable universe spans about 93 billion light-years. Its oldest light has traveled about 13.8 billion years, but expansion has carried those regions much farther away since. The Milky Way is about 100,000 light-years wide with an estimated 100 to 400 billion stars, and the observable universe holds hundreds of billions to perhaps 2 trillion galaxies. The footage, credited to explainingtheuniverse, shows a zoom out through space.

- Department: Space
- First published: 2025-04-17
- Last updated: 2025-04-17
- Permalink: https://detailenjoyer.com/case/universal-sizing/
- Author: Marcus Easterling (DetailEnjoyer), The Detail Department

## Quick facts

- **DD-546-F01**: About 93 billion ly. _(Write-up · Exhibit A (Diameter))_
- **DD-546-F02**: 13.8 billion years. _(Write-up · Exhibit B (Age of light))_

## Write-up

The observable universe is about 93 billion light-years across. Light from its edge left 13.8 billion years ago.

1. **Diameter**: About 93 billion ly.
2. **Age of light**: 13.8 billion years.
3. **Milky Way**: About 100,000 ly.
4. **Stars**: 100-400 billion.
5. **Galaxies**: Hundreds of billions to ~2 trillion.

## Reel vs. record

- **Note**: The Reel says 'over 2 trillion galaxies'; that 2016 estimate has since been revised downward by some studies to a few hundred billion.

## Video: Universal Sizing: The Observable Universe Is About 93 Billion Light-Years Across

- Duration: 28.6 s · Published: 2025-04-17
- File: https://detailenjoyer.com/assets/videos/DIjCuPIRzM9.mp4

### Transcript

Did you know, the universe is incomprehensibly vast, with the observable portion stretching about 93 billion light years across, meaning light from the farthest regions has taken over 13.8 billion years to reach us, but due to the universe's expansion, those regions are now much farther away. Our galaxy, the Milky Way, is about 100,000 light years wide, and contains an estimated 100 to 400 billion stars, while the observable universe contains over 2 trillion galaxies, each with billions of stars and potentially even more planets. NOW YOU KNOW!

## Questions & answers

**Q: Diameter?**  
A: Expansion. _(Source: Write-up · Exhibit A (Diameter) · Wikipedia: Observable universe)_

**Q: Milky Way width?**  
A: Disk. _(Source: Write-up · Exhibit B (Age of light) · Wikipedia: Observable universe)_

**Q: Stars in Milky Way?**  
A: Estimate. _(Source: Write-up · Exhibit C (Milky Way) · Wikipedia: Observable universe)_

**Q: Age of oldest light?**  
A: Big Bang. _(Source: Write-up · Exhibit D (Stars) · Wikipedia: Observable universe)_

**Q: Why bigger than 13.8 billion ly?**  
A: Space stretches. _(Source: Write-up · Exhibit E (Galaxies) · Wikipedia: Observable universe)_

## Sources

- [Wikipedia: Observable universe](https://en.wikipedia.org/wiki/Observable_universe)

## Cite this case file

Easterling, Marcus. "Universal Sizing." The Detail Department (DetailEnjoyer), case file DD-546, last updated Apr 17, 2025. https://detailenjoyer.com/case/universal-sizing/