<p>Earth is already pretty bright due to cloud cover, with a typical albedo of .3-.35 -- that is, it reflects about a third of the visible light that hits it.</p>

<p>That means it couldn't get more than about three times as bright even if it were perfectly reflective (albedo 1.0), which means about 1.2 magnitudes brighter.</p>

<p>Spotting Earth from a great distance with the naked eye is less an issue of brightness, more an issue of separation from the Sun. I can't run numbers at the moment to get actual magnitudes or angular separations.</p>

CC BY-SA 4.0
2019-08-07T18:45:40.410Z
If the Sun is the problem with visibility,  just wait until nighttime  (#itsajokedammit)
Carl Witthoft
CC BY-SA 4.0
2019-08-07T20:43:44.713Z
Max elongation is 3 deg. Stellarium estimates magnitude 3.5 at superior conjunction (full), 4.5 at greatest elongation (quarter phase); Sun magnitude -20.
Mike G
CC BY-SA 4.0
2019-08-08T08:05:55.647Z
@MikeG, thanks for the numbers! Is that from Uranus, today?
Simon Korneev
CC BY-SA 4.0
2019-08-08T19:21:28.933Z
@SimonKorneev Those are typical values from Uranus. A snow-covered Earth would be brighter, but you'd still need to hide the Sun with an occulting disk.
Mike G
CC BY-SA 4.0
2019-08-07T18:02:20.177Z
2019-08-07T18:02:20.177Z
jeffB
<p>The Earth likely <a href="http://www.astronomy.com/news/2019/04/the-story-of-snowball-earth" rel="nofollow noreferrer">froze over</a> almost completely about 700 million years ago. This increased its albedo significantly, and I wonder if that would have a considerable effect on its apparent magnitude from other planets. (The Sun was like 4% fainter, though.)</p>

<p>If so, would the Earth be naked-eye visible from farther away 700 mya than it is now? Maybe from Uranus's moons?</p>

<apparent-magnitude><magnitude><absolute-magnitude><albedo>
Snowball Earth brightness
Simon Korneev
# Snowball Earth brightness

(Asked by: username_0 on 2019-08-07)

The Earth likely [froze over](http://www.astronomy.com/news/2019/04/the-story-of-snowball-earth) almost completely about 700 million years ago. This increased its albedo significantly, and I wonder if that would have a considerable effect on its apparent magnitude from other planets. (The Sun was like 4% fainter, though.)

If so, would the Earth be naked-eye visible from farther away 700 mya than it is now? Maybe from Uranus's moons?

**Tags:** apparent-magnitude, magnitude, absolute-magnitude, albedo

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## 1 answers

### Answer by username_1 on 2019-08-07. Score: 8 | Accepted answer

Earth is already pretty bright due to cloud cover, with a typical albedo of .3-.35 -- that is, it reflects about a third of the visible light that hits it.

That means it couldn't get more than about three times as bright even if it were perfectly reflective (albedo 1.0), which means about 1.2 magnitudes brighter.

Spotting Earth from a great distance with the naked eye is less an issue of brightness, more an issue of separation from the Sun. I can't run numbers at the moment to get actual magnitudes or angular separations.

> **Comments:**
> **username_2**: If the Sun is the problem with visibility,  just wait until nighttime  (#itsajokedammit)  
> **username_3**: Max elongation is 3 deg. Stellarium estimates magnitude 3.5 at superior conjunction (full), 4.5 at greatest elongation (quarter phase); Sun magnitude -20.  
> **username_0**: @MikeG, thanks for the numbers! Is that from Uranus, today?  
> **username_3**: @SimonKorneev Those are typical values from Uranus. A snow-covered Earth would be brighter, but you'd still need to hide the Sun with an occulting disk.  

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