Naked Science Forum
General Science => General Science => Topic started by: neilep on 09/03/2012 18:55:56
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Dearest Peeps who know stuff ?
The sun eh ?...it's like well hot yes ?...even hotter than a light bulb and that's hot !
Now as ewe know the Sun is a big candle flame a really long long away......about as far from UK to USA and that's really really far !!...LOL !!...someone told me that it was like even further away than that but then I showed them the sun in the sky and they agreed that it did not look that far !..ha ha ha ha ha 93,000,000 miles my derrier !!
Anyway...here is a representation of the Sun and Earth....
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The Sun And Earth Just Moments Ago
and as ewe can see the sun is quite hot ....and between the Sun and Earth it's really really cold...so...where does the heat come from when it has travelled through chilly space !! ? Why Can We Feel Heat When Space Is So Cold Between Sun And Earth ?
Hugs and shmishes
mwah mwah mwah
Neil
HaiKu To Sun
Oh Sun
You're bloody hot !
Thanks A lot !
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The sun transfers its heat via electromagnetic radiation, and we named the modeled process "black body radiation." The amount of radiation received and absorbed depends on the material composition of the body and the cross-sectional area of the body perpendicular to the path of the radiation. As spacecraft travel to the inner solar system, the heat management becomes an immense problem. To counter the higher energy, the spacecraft are coated in reflective materials to deflect the heat and/or coated in materials that can absorb the heat, but not transfer the heat into the body of the spacecraft.
Where things get really interesting in spacewalks. In the sunlight, temperatures can reach as high as 250 deg F, while plunging to -250 deg F in the shade. (Thanks, NASA: http://www.nasa.gov/audience/foreducators/spacesuits/facts/facts-index.html)
Even though it is cold between the Sun and Earth, if you put a body there, it will heat up due to absorbing the radiation from the sun. It is only cold, because it is empty space without a physical body there to absorb the energy. I promise, if the Earth magically moved to Venus' orbit, the surface would be much, much hotter!
Attached is the spectral output of the sun based on black body radiation (thanks, wikipedia). Notice how the power output of the sun at around 5,800 Kelvin, is nearly even across the visible spectrum. Which is why sunlight breaks into a nice even rainbow out a prism.
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Neilep what makes you think that space between the sun and the earth is really cold? (And Cheese for that matter?)
If there were absolutely nothing in it, it could not have any temperature at all.
But there is just a tiny bit of stuff -- mostly hydrogen and a little dust -- and that is quite hot!
It simply is not cold in space between the sun and the earth -- little heat stored there because there is little matter, but the temperature of the bit that there is is quite high!
Mind you, this has nothing to do with the answer.
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The sun transfers its heat via electromagnetic radiation, and we named the modeled process "black body radiation." The amount of radiation received and absorbed depends on the material composition of the body and the cross-sectional area of the body perpendicular to the path of the radiation. As spacecraft travel to the inner solar system, the heat management becomes an immense problem. To counter the higher energy, the spacecraft are coated in reflective materials to deflect the heat and/or coated in materials that can absorb the heat, but not transfer the heat into the body of the spacecraft.
Where things get really interesting in spacewalks. In the sunlight, temperatures can reach as high as 250 deg F, while plunging to -250 deg F in the shade. (Thanks, NASA: http://www.nasa.gov/audience/foreducators/spacesuits/facts/facts-index.html)
Even though it is cold between the Sun and Earth, if you put a body there, it will heat up due to absorbing the radiation from the sun. It is only cold, because it is empty space without a physical body there to absorb the energy. I promise, if the Earth magically moved to Venus' orbit, the surface would be much, much hotter!
Attached is the spectral output of the sun based on black body radiation (thanks, wikipedia). Notice how the power output of the sun at around 5,800 Kelvin, is nearly even across the visible spectrum. Which is why sunlight breaks into a nice even rainbow out a prism.
Wonderful response and thanks for the great information Cheese2001. Love the graph too !!
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Neilep what makes you think that space between the sun and the earth is really cold? (And Cheese for that matter?)
If there were absolutely nothing in it, it could not have any temperature at all.
But there is just a tiny bit of stuff -- mostly hydrogen and a little dust -- and that is quite hot!
It simply is not cold in space between the sun and the earth -- little heat stored there because there is little matter, but the temperature of the bit that there is is quite high!
Mind you, this has nothing to do with the answer.
Thanks Damocles...I just figured that if I was in my spaceship and wound down the window that apart form being blown out I'd freeze to death too !
Can I ask...how can you have no temperature at all ?
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"Temperature" is a quantity that determines which direction heat energy flows in. The energy always flows from something that is hotter to something that is colder. If there is no material present, then there is nothing that can either emit or absorb heat. Another definition of temperature relates it directly to the average kinetic energy of the atoms present. No atoms present = no temperature. Heat energy is always associated with a material that is present to "own" the energy.
In the inner part of the solar system there is a nearly complete vacuum: a zillion times fewer atoms per cubic metre than in the Earth's atmosphere. But there are still a million times more atoms per cubic meter than in interstellar space.
The equilibrium temperature of the inner solar system is derived theoretically from the black body radiation equations. It works out at -20°C at the same distance from the sun as the Earth. But the steady state/actual temperature is much higher because of the "solar wind" -- high energy particles that continuously stream outward from the sun, which are very hot indeed! Crudely, you could think of it as the "smoke" from the sun's fires.
By the way, if you put any sort of "thermometer" in space in the inner solar system, then even in the absence of any interplanetary medium or solar wind, it would be heated by the sun's radiation, and cooled by its own emission of radiation ("black body" type radiation), and reach the equilibrium temperature mentioned above.
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As a pilot, I have noticed that temperature decreasses about 2 degrees centigrade for each 1,000 feet of altitude. How long that continues I do not know. I have never been much higher than 25,00 feet. Thanks for comments. Joe L. Ogan
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Joe,
You're absolutely right. You're describing the Standard Atmosphere (the creation of which was pretty interesting history in itself). The model uses a standard lapse rate up to 36,152 ft MSL. Above which, the temperature is a constant -70 deg F until 82,345 ft MSL. NASA has a high school level description of the standard atmosphere at http://www.grc.nasa.gov/WWW/K-12/airplane/atmos.html.
Every assumption made by an aerodynamicist in designing your airplane inherently relies upon the standard atmosphere.
It may or may not be interesting that's why so many jet liners want to fly around 36,000 ft MSL. As you go higher, the density continues to decrease, but the temperature stays the same. It is effectively the "sweet spot" for turbine powered aircraft.
But, we're completely off topic for space...
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As a pilot, I have noticed that temperature decreasses about 2 degrees centigrade for each 1,000 feet of altitude. How long that continues I do not know. I have never been much higher than 25,000 feet. Thanks for comments. Joe L. Ogan
Obviously the detail of the temperature structure of the atmosphere varies with latitude, season, and time of day. The general structure is always similar though. It is quite complicated! I will quote figures typical of mid-latitude autumn/spring daytime.
In the troposphere -- surface to around 11-12 km (38,000 ft) -- temperature falls with increasing height from 15°C (59°F) to –65°C (–85°F).
In the stratosphere -- 12 km to 50 km (165,000 ft) temperature rises with increasing altitude from –65°C (–85°F) to around 0°C (32°F)
In the mesosphere -- 50 km (30 mi) to 85 km (53 mi) temperature falls with increasing altitude from 0°C (32°F) to –85°C (–121°F)
In the thermosphere -- 85 km to 650 km (400 mi) temperature rises with increasing altitude from –85°C (–121°F) to around 1700°C (3100°F)
In the exosphere -- 650 km to 10,000 km (6,000 mi) temperature falls from 1700°C (3100°F) to around 300°C (570°F).
The interplanetary medium in the neighbourhood of the Earth's orbit has a temperature which could be defined, calculated, or measured in several different ways, with results ranging from –20°C to 300°C.