10 ms·

This is a very naive question, but is there some distance from the sun at which it would heat an object in space to a temperature that we would consider comfort

This is a very naive question, but is there some distance from the sun at which it would heat an object in space to a temperature that we would consider comfortable? I guess the obvious answer would be "the distance which the Earth is at," but what I really mean is could you be floating around in a spacesuit or some object with minimal shielding and you would neither overheat nor freeze to death.

DoreenMichele 8y ago
As a wild guess, probably further out then the Earth. The atmosphere here plays an important role in keeping us comfy. Even so, the tropical sun can be too much. Heat waves can be too much. Desert heat can be too much. Etc.
- Groxx 8y ago
  A brief google informs me that the sunny side of the Moon is around 127˚ Celsius, while Phobos goes up to about -4˚. So somewhere most of the way to Mars probably?
  - DoreenMichele 8y ago
    For other half-asleep Americans, 127 C is about 260 F. (100C is the boiling point. 0C is freezing.)
    - Monory 8y ago
      At 1 atmosphere of pressure. Important to remember when we are talking about Moon and such.
      - DoreenMichele 8y ago
        I had to think about that for a bit. I've tried to Google it to better understand it. I am not immediately coming up with an elucidation. Anyone got a link to a quick and dirty explanation of how the vacuum of space would impact this?
        Groxx 8y ago
        Air pressure on earth literally squeezes the water together, preventing it from turning into a gas until it's at a higher temperature. More generally: practically all phase-changes depend on both temperature and pressure. Lower pressure almost behaves like higher temperature... within certain ranges (and it varies for every material). E.g. for water, note that there are three major regions in its phase diagram[1]. At human-normal scales (the red horizontal line is 1 atmosphere) we see water boil/freeze at 100 and 0 celsius. If you lower the pressure though, you'll see there's a spot where all three phases meet, and below that there's no liquid phase separating solid and gas. When it's in near vacuum, you literally can't have water - ice evaporates (sublimates) directly into a gas, with no intermediate phase. Given the diagram, this seems to happen somewhere around -60c in a serious vacuum. So in space or on the surface of the moon (without an atmosphere / something pressurizing it) you simply can't have liquid water - a portion of it will evaporate almost immediately, which steals energy from the remaining portion, causing it to freeze. After that, the solid portion just sublimates away (because the sunny side is 127c, well above the temperature needed to turn it into a gas). [1]: https://en.wikipedia.org/wiki/Phase_diagram#/media/File:Phase_diagram_of_water.svg https://en.wikipedia.org/wiki/Phase_diagram#/media/File:Phas...
        DoreenMichele 8y ago
        Thank you. What I am trying to figure out specifically -- to mental model -- is what impact this has on human comfort, per the original question. So I have lived in very hot and humid places -- like Georgia, where it is often around 100F in summer -- and I have lived in even hotter places with a much dryer climate -- like the Mojave Desert, where it can get to 115F and I would wait until nightfall to go for walks for exercise at 99F and no sun. Humidity does make a big difference in how uncomfortable a temperature is. If it is hot and dry, you can stay reasonably comfortable if you get enough fluids and electrolytes into you and stay out of direct sunlight. I'm trying to fit this into a mental model of that sort. Like is a boiling temperature going to burn you? Or, you know "It's a dry heat, man!" only "It's in the vacuum of space, man!" Thanks to anyone who replies to this.
        8y ago
Gravityloss 8y ago
Earth's average temperature without the atmosphere and the greenhouse effect would be quite cool. Guess depends very much on the spacecraft design, how you absorb and radiate.
dTal 8y ago
A human in a spacesuit (or indeed anywhere) generates about 100W of heat. In the vacuum of space, the only way for this energy to escape is through radiation. The amount an object radiates depends on its temperature, its surface area, and its 'emissivity', which is simply 1-reflectance. Back of the envelope, a human sized object (2 m^2) with an emissivity of 0.12 (polished aluminum), generating 100W, will stabilize at almost exactly 20C - room temperature. So, you don't need the sun at all! Make your spacesuit small and shiny and you can enjoy balmy temperatures deep in the inky blackness of the interstellar void, for as long as your food and oxygen lasts (food and oxygen ultimately being the fuel for your 100W). Citations: https://en.wikipedia.org/wiki/Thermal_radiation https://en.wikipedia.org/wiki/Thermal_radiation and typing '100 Watt = 0.12 × (5.6704W⋅(10^−8)/(m^2⋅K^4)) × 2 m^2 × x^4 to celsius' into Qalculate

DoreenMichele 8y ago

As a wild guess, probably further out then the Earth. The atmosphere here plays an important role in keeping us comfy. Even so, the tropical sun can be too much. Heat waves can be too much. Desert heat can be too much. Etc.

Groxx 8y ago
A brief google informs me that the sunny side of the Moon is around 127˚ Celsius, while Phobos goes up to about -4˚. So somewhere most of the way to Mars probably?
- DoreenMichele 8y ago
  For other half-asleep Americans, 127 C is about 260 F. (100C is the boiling point. 0C is freezing.)
  - Monory 8y ago
    At 1 atmosphere of pressure. Important to remember when we are talking about Moon and such.
    - DoreenMichele 8y ago
      I had to think about that for a bit. I've tried to Google it to better understand it. I am not immediately coming up with an elucidation. Anyone got a link to a quick and dirty explanation of how the vacuum of space would impact this?
      - Groxx 8y ago
        Air pressure on earth literally squeezes the water together, preventing it from turning into a gas until it's at a higher temperature. More generally: practically all phase-changes depend on both temperature and pressure. Lower pressure almost behaves like higher temperature... within certain ranges (and it varies for every material). E.g. for water, note that there are three major regions in its phase diagram[1]. At human-normal scales (the red horizontal line is 1 atmosphere) we see water boil/freeze at 100 and 0 celsius. If you lower the pressure though, you'll see there's a spot where all three phases meet, and below that there's no liquid phase separating solid and gas. When it's in near vacuum, you literally can't have water - ice evaporates (sublimates) directly into a gas, with no intermediate phase. Given the diagram, this seems to happen somewhere around -60c in a serious vacuum. So in space or on the surface of the moon (without an atmosphere / something pressurizing it) you simply can't have liquid water - a portion of it will evaporate almost immediately, which steals energy from the remaining portion, causing it to freeze. After that, the solid portion just sublimates away (because the sunny side is 127c, well above the temperature needed to turn it into a gas). [1]: https://en.wikipedia.org/wiki/Phase_diagram#/media/File:Phase_diagram_of_water.svg https://en.wikipedia.org/wiki/Phase_diagram#/media/File:Phas...
        DoreenMichele 8y ago
        Thank you. What I am trying to figure out specifically -- to mental model -- is what impact this has on human comfort, per the original question. So I have lived in very hot and humid places -- like Georgia, where it is often around 100F in summer -- and I have lived in even hotter places with a much dryer climate -- like the Mojave Desert, where it can get to 115F and I would wait until nightfall to go for walks for exercise at 99F and no sun. Humidity does make a big difference in how uncomfortable a temperature is. If it is hot and dry, you can stay reasonably comfortable if you get enough fluids and electrolytes into you and stay out of direct sunlight. I'm trying to fit this into a mental model of that sort. Like is a boiling temperature going to burn you? Or, you know "It's a dry heat, man!" only "It's in the vacuum of space, man!" Thanks to anyone who replies to this.
        8y ago

Gravityloss 8y ago

Earth's average temperature without the atmosphere and the greenhouse effect would be quite cool. Guess depends very much on the spacecraft design, how you absorb and radiate.

dTal 8y ago

A human in a spacesuit (or indeed anywhere) generates about 100W of heat. In the vacuum of space, the only way for this energy to escape is through radiation. The amount an object radiates depends on its temperature, its surface area, and its 'emissivity', which is simply 1-reflectance. Back of the envelope, a human sized object (2 m^2) with an emissivity of 0.12 (polished aluminum), generating 100W, will stabilize at almost exactly 20C - room temperature. So, you don't need the sun at all! Make your spacesuit small and shiny and you can enjoy balmy temperatures deep in the inky blackness of the interstellar void, for as long as your food and oxygen lasts (food and oxygen ultimately being the fuel for your 100W). Citations: https://en.wikipedia.org/wiki/Thermal_radiation https://en.wikipedia.org/wiki/Thermal_radiation and typing '100 Watt = 0.12 × (5.6704W⋅(10^−8)/(m^2⋅K^4)) × 2 m^2 × x^4 to celsius' into Qalculate