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Author Topic: Lunar temp a few decimal points in the wrong place ?  (Read 820 times)
bxman
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« on: June 19, 2017, 10:55:08 AM »

 During a lunar eclipse when the Moon moves into the Earth's shadow, the surface temperature of the Moon can drop around 500 degrees Fahrenheit in less than 90 minutes.      from
http://www.bbc.co.uk/programmes/articles/1nnbBxFzw5BxqvpshGhfJmD/nine-out-of-this-world-facts-about-the-moon

what do you think folks
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todthedog
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« Reply #1 on: June 19, 2017, 01:29:19 PM »

The average temperature on the Moon (at the equator and mid latitudes) varies from -298 degrees Fahrenheit (-183 degrees Celsius), at night, to 224 degrees Fahrenheit (106 degrees Celsius) during the day.

http://coolcosmos.ipac.caltech.edu/ask/168-What-is-the-temperature-on-the-Moon-

Similar on
https://www.spaceanswers.com/space-exploration/how-did-lunar-astronauts-survive-the-extreme-temperatures-on-the-moon/

Probably right then?
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bxman
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« Reply #2 on: June 19, 2017, 02:08:31 PM »

So when the astronauts were romping about up there they were being subjected to these type of  temperature ext reams ?

or did they spend their entire time bathed in sun light

Is there a simulation anywhere 

At the moment I can not get my mind around this situation 

thanks Patrick
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todthedog
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« Reply #3 on: June 19, 2017, 02:36:23 PM »

Have a look at the second link Patrick.
I think it will help a bit. Still pretty mind boggling.
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bxman
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« Reply #4 on: June 19, 2017, 04:30:52 PM »

Thanks 
I do not think I will be volunteering then
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desperate
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« Reply #5 on: June 19, 2017, 06:54:48 PM »

Remember though that a Lunar day last and Earth month, so for a few earth days you could be in the dawn or evening sun thus navoiding the extremes. Temperature also has a very different meaning in a hard vacuum, if you are in direct sunlight it would be searingly hot but in the shadow of something quite small it's freezing snow

Desp
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Nickel2
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« Reply #6 on: June 19, 2017, 11:58:13 PM »

The surface temperature bit is true. A vacuum has no substance, therefore cannot be hot or cold. Ipso facto, space is not cold, it just does not contain things that can be warm. An item placed in a vacuum cannot be hotter or colder than it's surroundings. The item, (moon, asteroid etc), can only have a body temperature reference to absolute zero, ie Kelvin. Your personal temperature, (without a space suit) will depend upon the amount of heat you generate internally, and how much you absorb and re-radiate from a local source. (the sun) The surface of the moon temperature will depend on how much heat it has absorbed during exposure to the sun, then how much it has lost when radiating that heat to space.
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desperate
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« Reply #7 on: June 20, 2017, 06:20:50 PM »

The surface temperature bit is true. A vacuum has no substance, therefore cannot be hot or cold. Ipso facto, space is not cold, it just does not contain things that can be warm.[quote] An item placed in a vacuum cannot be hotter or colder than it's surroundings.
The item, (moon, asteroid etc), can only have a body temperature reference to absolute zero, ie Kelvin. Your personal temperature, (without a space suit) will depend upon the amount of heat you generate internally, and how much you absorb and re-radiate from a local source. (the sun) The surface of the moon temperature will depend on how much heat it has absorbed during exposure to the sun, then how much it has lost when radiating that heat to space.
[/quote]

Err?? it feels quite hot here on Earth at the moment, planet earth is in a vacuum, in fact all the planets are of course and they have a very wide range of temperatures.
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Nickel2
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« Reply #8 on: June 20, 2017, 07:10:50 PM »

... planet earth is in a vacuum, in fact all the planets are of course and they have a very wide range of temperatures. ...
The bit of earth I'm on has atmosphere, i.e. the presence of matter. The higher you go in the atmosphere, the sparser the air molecules are, and their ability to hold heat reduces.
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« Reply #9 on: June 20, 2017, 09:37:31 PM »

B ut Mercury and the moon for that matter have almost no atmosphere, but they do have widely varying serface temps, which in my mind somehow doesn't sit well with your statement I highlighted earlier.

I think??

Desp
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Nickel2
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« Reply #10 on: June 20, 2017, 11:36:53 PM »

... The surface of the moon temperature will depend on how much heat it has absorbed during exposure to the sun, then how much it has lost when radiating that heat to space. ...
As there is no atmosphere on the moon, there is no air to absorb heat. As solar radiation impinges on the surface, the surface temp will rise. The heat that is not conducted inwards through the surface will re-radiate out to space. If you were to put a Stevenson screen on the moon, the surface temperature of the moon could be +200c, but the wet(?) / dry temperature within the screen could be -200c. The measuring equipment would only receive heat by re-radiation from the wooden slats of the screen inwards. (There is no convection in a vacuum).
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« Reply #11 on: June 21, 2017, 07:23:03 PM »

So a body in a vacuum can be hotter or colder thaqn its surroundings wackoold

Desp
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Nickel2
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« Reply #12 on: June 21, 2017, 10:14:04 PM »

Yep.
Consider vacuum brazing of flat plate heat exchangers for instance. You load up a stack of stainless and copper components, put them in the chamber and pull a vacuum. Induction heaters the raise the temp to the melting point of the copper; the bits get red hot and the copper alloys to the stainless, the inside of the chamber only gets radiant heat from the process. No gas = no convection, no contact = no conduction. A bit like getting seriously burnt at the top of a mountain in -40c.
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« Reply #13 on: June 21, 2017, 10:40:09 PM »

So it can and it can't ............. faint

Desp
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Nickel2
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« Reply #14 on: June 21, 2017, 11:29:13 PM »

It's surroundings have no mass, (vacuum), therefore cannot absorb, conduct or radiate heat. If you introduced a small amount of gas into the vacuum, (i.e. the planet/moon/etc atmosphere), those molecules can be made more active by the addition of heat, and their relative temperature will increase. Space will always have matter in it everywhere, due to all those stars exploding, planets colliding etc, so is not a true vacuum, it just doesn't have much in the way of stuff there to absorb heat. Space is comparatively almost empty, although there are areas that appear to have a temperature above 0 K. As there is not a lot of mass floating around in space, anything that does go bang will emit hot particles, from lumps of broken planet, to bits of broken atoms. Some of them have traveled for billions of years to get here, losing nothing of their high energy level, provided they didn't hit anything on the way. Space is a very hostile place, not a benign emptiness. All this nastiness comes from all directions.
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