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Uranus' orbit is 20x further from the Sun than Earth, which means it only gets 0.25% as much sunlight. Not sure what exactly that means for human eyesight, but

Uranus' orbit is 20x further from the Sun than Earth, which means it only gets 0.25% as much sunlight. Not sure what exactly that means for human eyesight, but it's probably less spectacular out there than we'd hope.

kridsdale1 3y ago
Human vision is strongly exponential in terms of brightness sensitivity. In photography we talk about “stops” which are powers of two of light intensity. Consumer digital cameras around 2005 could see maybe 9 stops for a single exposure. Now they can do maybe 10-14 (which means they’re ~30x more capable of a range of light values). Human vision can handle adapting to a much wider range because we don’t see with a single exposure. The iris adjusts, we saccade around the scene collecting data and mentally aggregating it. A good approximation is the iPhone’s panorama mode. It’s really recording video and adapting the dynamic range window as you pan, so the sun tends not to blown out the rest of the image. The main point I want to make is that outdoor sunlight on earth is indeed a million times more intense in terms of lux, lumens, candelas, or watts, than interior living (say lit by a nightlight or candle). This works out to 20 stops. - 100,000 lux outdoors on earth - 0.1 lux finding your seat in a theater So we can see already when the light is 0.0001% the power of “Earth, noon”. We could see Uranus. Sunlight on earth is extremely intense! You feel it direct on your skin like being 2 feet from a fire. It damages your cells. It evaporates the sea and propels hurricanes. I’d we hadn’t evolved to live with it, we’d find it quite intolerable.
jl6 3y ago
For comparison, daytime on Earth is about 100,000 lux while a typical moonlit night is 0.1 lux[0]. Uranus gets 350 lux[1], which is similar to the light level at sunrise on Earth. So quite dim but not dark. [0] https://academic.oup.com/astrogeo/article/58/1/1.31/2938119 https://academic.oup.com/astrogeo/article/58/1/1.31/2938119 [1] https://oikofuge.com/same-sun-other-skies/ https://oikofuge.com/same-sun-other-skies/
jetrink 3y ago
You'd be surprised by the dynamic range of the human eye. I happen to have my camera on my desk, so I used it to take a couple measurements just now. It's a bright, sunny day. Pointed out the window[1]: 1/2000th The interior of my office[2]: 1/30th My office feels brightly lit to me, but the ambient light level is only about 1-2% of what it is outdoors. I estimate that 0.25% is roughly how bright it is indoors on an overcast day or outdoors at twilight on a clear day. It's dim, but people with unimpaired vision have no trouble seeing in that light level and the planet would still look spectacular. 1. Grass and trees with no sky in frame. 2. Shades open, light grey walls mostly. Same ISO and aperture.

kridsdale1 3y ago

Human vision is strongly exponential in terms of brightness sensitivity. In photography we talk about “stops” which are powers of two of light intensity. Consumer digital cameras around 2005 could see maybe 9 stops for a single exposure. Now they can do maybe 10-14 (which means they’re ~30x more capable of a range of light values). Human vision can handle adapting to a much wider range because we don’t see with a single exposure. The iris adjusts, we saccade around the scene collecting data and mentally aggregating it. A good approximation is the iPhone’s panorama mode. It’s really recording video and adapting the dynamic range window as you pan, so the sun tends not to blown out the rest of the image. The main point I want to make is that outdoor sunlight on earth is indeed a million times more intense in terms of lux, lumens, candelas, or watts, than interior living (say lit by a nightlight or candle). This works out to 20 stops. - 100,000 lux outdoors on earth - 0.1 lux finding your seat in a theater So we can see already when the light is 0.0001% the power of “Earth, noon”. We could see Uranus. Sunlight on earth is extremely intense! You feel it direct on your skin like being 2 feet from a fire. It damages your cells. It evaporates the sea and propels hurricanes. I’d we hadn’t evolved to live with it, we’d find it quite intolerable.

jl6 3y ago

For comparison, daytime on Earth is about 100,000 lux while a typical moonlit night is 0.1 lux[0]. Uranus gets 350 lux[1], which is similar to the light level at sunrise on Earth. So quite dim but not dark. [0] https://academic.oup.com/astrogeo/article/58/1/1.31/2938119 https://academic.oup.com/astrogeo/article/58/1/1.31/2938119 [1] https://oikofuge.com/same-sun-other-skies/ https://oikofuge.com/same-sun-other-skies/

jetrink 3y ago

You'd be surprised by the dynamic range of the human eye. I happen to have my camera on my desk, so I used it to take a couple measurements just now. It's a bright, sunny day. Pointed out the window[1]: 1/2000th The interior of my office[2]: 1/30th My office feels brightly lit to me, but the ambient light level is only about 1-2% of what it is outdoors. I estimate that 0.25% is roughly how bright it is indoors on an overcast day or outdoors at twilight on a clear day. It's dim, but people with unimpaired vision have no trouble seeing in that light level and the planet would still look spectacular. 1. Grass and trees with no sky in frame. 2. Shades open, light grey walls mostly. Same ISO and aperture.