1. JohnJones

    JohnJones New Member

    I think you will find that my description of the interaction of radiation with matter is in line with contemporary quantum theory.

    In the kinetic theory of gases, the temperature of a gas is defined as the average kinetic energy of the particles making up that gas. The atoms and molecules in the thermosphere being at a high temperature consists in the fact that they're travelling at high velocities. The only opportunities these particles have to convert their kinetic energy to radiative energy occur during collisions with other particles, which are rare due to their long mean free paths.

    You have formed the impression that the solar radiation in the thermosphere is particularly intense. But we can actually measure the intensity of solar radiation at the top of the atmosphere, where it's about 1.36 kW/m2, and compare it with the intensity of the solar radiation on the Earth's surface, where at midday it's about 1 kW/m2. (The Wikipedia article on "Solar Constant" is an accessible source for this.) That's not that big a difference, so it would be surprising if the radiative equilibrium temperature of a black body at the top of the atmosphere were much different than the equilibrium temperature of the same body at the Earth's surface.

    It would be interesting if you could answer Trailblazer's question about what makes the thermosphere special. Would you agree that the solar flux in the thermosphere is about the same as it is on the surface of the Moon, for example? If you think it's significantly higher, what do you suppose causes that?
     
  2. Hevach

    Hevach Senior Member

    For the thermosphere's temperature I've always liked the oven metaphor. Inside an oven at 400 everything is 400°. The air is uncomfortable but not particularly dangerous. The cake you just baked is too hot to handle but safe to touch for a few seconds at a time. The pan you baked it on will give you third degree burns almost instantly. The three do not transfer heat into your hand uniformly.
     
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  3. JohnJones

    JohnJones New Member

    This metaphor is helpful, but perhaps slightly misleading. Inside the oven, the radiative equilibrium temperature of a black body would be 400°, and if you stayed in the oven long enough, you would also be at 400° and get cooked. In the thermosphere, the radiative equilibrium temperature of a black body would be just above freezing point, and you could stay there as long as you liked.

    Our experience with the oven reflects the fact that air is a poorer conductor than cake, which in turn is a poorer conductor than the cake pan. But the anomalously high temperature of the gas molecules in the thermosphere has nothing to do with their conductivity, rather with the fact that, as isolated particles, they have no way to convert their kinetic energy into thermal radiation.
     
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  4. F. Serby

    F. Serby New Member

    I haven't read all of these, but has anyone mentioned the fact that the satellites also spend some time out of the sun's incoming radiation, when they are in the shadow of the earth? I don't know if all polar orbits (pole to pole) have an orientation that keeps them out of the sun's radiation--that would depend on what angle the orbit's plane is to the incoming rays--but geostationary orbits around the equator should have them in the shadow for a good percentage of the time they are in orbit, depending on the season.
     
  5. Layman research

    Layman research New Member

    This topic has interested me a long time. And this webpage just opened up my understanding exponentially. Thanks to all above for your input! Both skeptical and explanative! I'm taking all this great discussion about vacuums, radiative heat, relflectivity, it's great.

    The reason I started looking at this tonight is saw SpaceX Tesla roadster floating in space on YouTube, and opened the live stream chat... About half the chat comments were "fake.. It's fake." Then I also saw the rubber tires of the car, and thought "how can those not melt right up???"

    So I just found this website which states the average continuous temperature in space near the Earth is 248 degrees. Outer space, not the Thermosphere or Exosphere.

    I'm not someone who generally accepts everything I'm told, but I think through information and come to my own conclusions. So for things like flat Earthism or "all space flight and space exploration is a hoax" I disagree and tend to say... If you already are married to a conclusion, you'll probably keep finding reasons to keep together with that conclusion. (funny how that same mentality also drives climate change denial.)

    So here's the website, and I accept for now that satellites and Hubble and ISS are constructed with proper shielding and materials that can survive balancing out at around 250 degrees.

    https://sciencing.com/temperatures-outer-space-around-earth-20254.html

    Above near Earth outer space temperature is too simplified. Here's a fuller explanation from the referenced website :

    "
    "
     
    Last edited by a moderator: Feb 11, 2018
  6. Trailblazer

    Trailblazer Moderator Staff Member

    Again, space doesn't really have any temperature. Individual objects in space have an equilibrium temperature that depends on their distance from the sun and their reflectivity (albedo), plus any other effects (e.g. planetary atmospheres).

    For instance the Earth, with no atmosphere but the same albedo it has now, would have an equilibrium temperature of about zero degrees Fahrenheit (–1°F in fact). The fact that it has an atmosphere with a greenhouse effect makes the actual equilibrium temperature about 60°F higher than that.

    The tyres of the Roadster have a lower albedo than Earth, but they also have no atmosphere to warm them up. They won't "burn up", but the harsh unfiltered UV light will probably degrade the rubber pretty quickly.
     
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  7. Laser

    Laser Member

    It may help to point out that cosmic rays with temperatures of millions of degrees are hitting your body constantly, but you don't melt because there are just such a tiny number of them that they can't heat you up enough to melt you before their heat dissipates.

    Another example is that you can wave your finger quickly through a candle flame and not get burnt. The candle is plenty hot enough to burn you, but not enough of the hot molecules in the flame are able to touch your skin to heat it up in the short time your finger is in the flame. It's true that a satellite stays in the heat plenty long, but there are vastly many fewer hot particles per volume in the thermosphere than in the candle flame. The thermosphere is so thin that it's kind of like waving one small hot candle under your spacecraft once every ten minutes and letting the heat dissipate in between.

    The high "temperature" radiation from the sun, such as UV and X-ray radiation is a different but similar story. If you look at all the radiation from the sun from all wavelengths, most of the total is from the visible and infrared radiation. Again there is just not enough UV and X-rays to heat an massive object in earth orbit up very much before the energy dissipates. Indeed, if you had some kind of filter that would block all the visible, IR, and lower "temperature" radiation from the sun from hitting your spacecraft, and only the high "temperature" radiation could warm your craft, not only would your craft not melt, it would get very cold because of the small amount of energy coming in from the high "temperature" radiation. I put the quotes around temperature because electromagnetic radiation doesn't really have a temperature, even though it may have a relatively high energy per photon.

    Some satellites can't naturally dissipate as much of their heat energy as they would like, and thus tend to overheat. In those cases radiators may be used. But sometimes even a plain radiator can't radiate enough heat away in the form of infrared radiation. So for extra cooling it may be necessary to use something like air conditioning. A refrigerating fluid is compressed, causing it to heat up. Then the hot fluid is pumped through the radiators to dissipate the heat energy by infrared radiation out to space. Because the refrigerant is hotter than the craft, it can radiate much more energy through a small radiator area than the craft at it's average temperature could. When the refrigerant is allowed to uncompress after dissipating much of its energy to space, it gets very cold and can be used to absorb the excess heat and cool the spacecraft.
     
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  8. MvK

    MvK New Member

    I would like to post a comment that seems contradictory to what has been stated about how objects can find an equilibrium between the amount of radiation an object absorbs and which can potentially heat it, and the amount of radiation it radiates which could potentially cool it and therefor remains at a constant relatively cool temperature.
    This view seems to be contradictory to what NASA itself claims on it's on website, especially since it is viewed that any object is nothing more than a collection of molecules or atoms, so why can't these atoms themselves achieve this 'state of equilibrium'?

    Any thoughts on this?
     
    Last edited: Oct 12, 2018
  9. Mick West

    Mick West Administrator Staff Member

    Satellites are not a collection of atoms. They are a collection of linked atoms (i.e. molecules). It's the links that are important for absorption and radiation. .

    Molecules are atoms linked together. They can vibrate because of these links. This vibration is what causes absorption and radiation of heat.

    The more links, the more possible vibrations. CO2 absorbs more than atmospheric O2 (or N2) in part because it can vibrate in more ways. Atomic O and N don't vibrate, so don't absorb or radiate heat. Solid objects have way more links (lots more atoms per molecule), so are very good at absorbing and radiating heat.

    See:
    https://scied.ucar.edu/molecular-vibration-modes
    [​IMG]
     
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  10. MvK

    MvK New Member

    Thank you for your reply,
    So if I understand it correctly then atomic 'O' and 'N' don't vibrate and therefor have no inert heat, and are also not able to get heated?
     
  11. Mick West

    Mick West Administrator Staff Member

    They have translational temperature (kinetic energy from moving) but not vibrational or rotational temperature (kinetic energy from atoms in a molecule vibrating and rotating relative to each other). So they can be heated.

    There's also the electronic component of temperature, the kinetic energy of free electrons, more of a factor in the ionosphere.

    Remember the thermosphere and ionosphere are very thin. They hold vastly less heat than solid matter, so comparing them to a spaceship isn't that useful.
     
  12. MvK

    MvK New Member

    Thank you for your reply.

    Can I maybe return another time to NASA article, they stated:
    In your answer you said:
    Could there then be a second way the atomic 'O' and 'N' can absorb heat?
     
  13. Mauro

    Mauro New Member

    Another example could be the Sun: its surface is at about 6000 °K, while its corona has a temperature above one million degrees. But we only feel the heat radiated from the 'balmy' sun surface, we are not roasted by the corona because it's very rarified and its total heat output is low, notwithstanding the staggering temperature.
     
  14. deirdre

    deirdre Moderator Staff Member

    it sounds like they are saying the molecule absorbs heat (then splits, which might make more heat.. ??) , but then once they are atoms they don't have the ability to radiate this heat that was absorbed by the molecule.
     
  15. Mick West

    Mick West Administrator Staff Member

    When NASA refer to the "the heat from this absorption." The are talking about the heat the O and N absorbed when it was O2 and N2 and able to absorb radiation.

    When it splits, some of the energy is converted to chemical potential energy. The O wants to recombines into O2.

    This isn't really relevant to satellites though, as satellites are made of solids, molecules, which all absorb and radiate heat just fine (some more than others), and all reach an equilibrium.

    And again, satellites are designed with heat management in mind.
     
  16. Z.W. Wolf

    Z.W. Wolf Active Member

    A fairytale to sort out the difference between heat and temperature; and equilibrium as well:

    Preface
    Heat = the total amount of water in the land
    Temperature = the amount of water in one elf-bucket


    The land of Thermosphere was vast but there was one city, the City of Satellite. The elves in the City of Satellite were so numerous that they were packed together. The floor of the city couldn't hold them all so they stood on each other's shoulders, thousands and thousands of elves high, and shoulder to shoulder as well. Not an uncomfortable thing for the elves, because they loved company and often linked arms.

    Every elf in the land of Thermosphere had a water bucket. But there was a problem in the City. It rained in the Land of Thermosphere but only the outermost elves on the very edges of Satellite could gather the water in their own little bucket. The bucket would grow full and then that generous little elf would pass his water to the next, and that little elf to the next. But when the passing was done, there were so many elves in Satellite, each elf only had a little water in his bucket. There was a lot of water, but not much for each elf bucket.

    King Elf devised a plan. He would send for help from the Wild Elves who lived out in the vast spaces of Thermosphere. There were many of the Wild Elves but Thermosphere was so vast that one Wild Elf only came across another on occasion. The buckets of the Wild Elves were usually full, because each one could roam about gathering rain. They hardly ever passed water to each other because each one's bucket was full. And the bucket was so heavy that these delicate little Wild Elves couldn't dump the bucket out. Most of the rain in the Land of Thermosphere thus fell straight through and was lost to the Lands Below. Only a small amount was ever gathered by the Wild Elves or the City Elves.

    When the Wild Elves heard the call for help from the King Elf they said, "We are wild and free folk and won't work for you city folk. But if on our wanderings we happen to come across the edge of the City of Satellite you can take as much water from our bucket as you can manage."

    So it was. The occasional Wild Elf that came across the edge of the City of Satellite allowed his water to be taken out of his bucket, where it was again passed from bucket to bucket to every Elf in the City. The amount of water in each City Elf's bucket thus grew, but alas, only a tiny amount; for there were so few Wild Elves coming across the City with a full bucket and so many empty buckets within the City.

    And, alas, the tale grows sadder. For the City Elves were strong but clumsy. The City Elves on the edge of the city would sometimes accidentally spill their bucket out into the vastness of The Land of Thermosphere. Then the generous elves of the interior would pass their water toward the edge of the city. Thus, try as they might, the total amount of water within the City of Satellite stayed much the same.

    So ends the tale of the total amount of water in the Land of Thermosphere, the full buckets of the Wild Elves, and the almost empty buckets inside the City of Satellite.


    Postface:

    Heat = the total amount of water in the land... or the city
    Temperature = the amount of water in one elf-bucket
     
    Last edited: Oct 13, 2018
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  17. MvK

    MvK New Member

    Thank you for your reply.
    And although it could be feasible, the NASA article stated:
    i.e. that the splitting of the molecules is what created the heat.

    As for the satellites being of molecules and they will reach an equilibrium, then I would like to get into that after the completion of this first section, going by them one by one if that's ok?

    Any thoughts about the atom part?
     
  18. Mick West

    Mick West Administrator Staff Member

    No. Satellites are not made of gases, or ionized gases, or plasmas, or clouds of electrons. They are solid objects. So if you want to discuss how satellites maintain thermal equilibrium, then the only really relevant topic is how solid objects absorb and radiate electromagnetic radiation.
     
  19. MvK

    MvK New Member

    I'm sorry if I misunderstood the problem, from what I understood of thermodynamic equilibriums is that they mostly don't exist in reality except on extreme small scale, or are assumed to exist only on a very small scale, and that most, if not all objects are in fact thermodynamic nonequilibriums, and that these are then observed from a very small scale so these small parts can be assumed equilibriums and we are then able to come close to a solution for the nonequilibriums.

    [off topic material removed]
     
    Last edited by a moderator: Oct 13, 2018
  20. Mick West

    Mick West Administrator Staff Member

    If conditions are kept constant then a system will reach an equilibrium.

    Just consider the worst case for a satellite, which is quite simple really. It's in sunlight, with the same side facing the sun. The amount of incoming solar radiation is constant. The satellite will heat up until it is radiating as much heat as it is taking on.

    You do not need to understand the atomic and sub-atomic level mechanism of radiative heating and cooling. That's irrelevant to the point. The point is that it happens. Increased radiation with increased temperature is something that is empirically observed, measured, and quantified.
     
  21. deirdre

    deirdre Moderator Staff Member

    that's not what your quote says. your quote says
    molecules are made up of atoms.

    try the Khan Academy. it's free and online and teaches science stuff.
     
  22. MvK

    MvK New Member

    I assume you mean that the warmer an object is, the more heat it will radiate off, if so, then that is something we can agree upon.
    And it pleased me that you mentioned this part: "empirically observed, measured, and quantified" because this is what science has be to all about, emperics and not philosophy. And I was actually thinking about this before, but I wanted to get into later, but as long as we have gotten to it then this it:
    Are there any empirical evidences that prove that this equiblibrium state will occur and that the object will not get as hot as some believe it will get?
    I envisioned it as inserting a sheet of some metal, or a satellite itself for that matter, or something close to it, into a vacuum chamber, or a near vacuum, and then exposing it to the same light and radiations conditions (or something close to it) as in the thermosphere and measure it's temperature. It would be interesting to know the results.
     
  23. Mick West

    Mick West Administrator Staff Member

    That's what NASA does with their satellites. They have a thermal vacuum chamber to test various extremes.
    https://www.nasa.gov/mission_pages/NPP/news/npp-testing.html
    With a more detailed explanation here:
    https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20020053654.pdf
    (Edit: although that second on is for re-entry conditions)
     
    Last edited: Oct 13, 2018
  24. MvK

    MvK New Member

    As for the quote then it was the second part, the second scientist that was mentioned that was ment, but the article was seen as off topic so I won't go into it any further.
     
  25. MvK

    MvK New Member

    Thanks, I will look into that, but there is no real-life footage right?

    *edit*
    F.W.I.
    I noticed this discussion is in the "Flat Earth" topic, and I just want to see that I believe that the Earth is round, there is no doubt what so ever about it, and not round like a perfect sphere, but round as a more compressed sphere with it's height being lesser then it's width, that's what I believe.
     
    Last edited: Oct 13, 2018
  26. Mick West

    Mick West Administrator Staff Member

    You can just stick a thermometer in a there. The thermometer itself being the object.


    Source: https://www.youtube.com/watch?v=-hTAr2GkhpM


    When he removed the air it initially cools the chamber and the thermometer and so the temperature drops. But where he full evacuates the chamber it (the thermometer) gets into thermal equilibrium from the room's thermal radiation.So it warms up.
     
  27. Mechanik

    Mechanik New Member

    Apologies in advance if I’m butting into a technical conversation with non-technical observations.

    I’m reminded of a video by Chris Hadfield, the Canadian astronaut, in a YouTube video. Here’s the video URL


    Source: https://youtu.be/t6rHHnABoT8
    .

    and the piece I’ll reference is the first item in the video. He says he’d like to debunk space myths and starts with what would happen to the unprotected human body in space (I’ll use quotes, but this is not an exact transcription): “The myth is that you will immediately fry to a crisp by the unfiltered, unadulterated solar radiation in space if you get sucked out an airlock. In truth, it’s much worse than that. “

    He points out that the part of you in sunlight will burn at 250 degrees (as compared to the OP’s 2500 degree number), while your shady side freezes at at the -250 degree shady temperature. Not relevant to the OP but no less horrific is your air being pushed out of your body and the boiling off of your blood gasses in the low pressure. Think of the bends times 1000.

    Back on topic, the reason parts don’t melt is a) the heat imparted by radiation is not hot enough to melt the metals used in satellites and b) satellites are designed to bleed the heat into the cold side to keep them from getting too hot.
     
  28. MvK

    MvK New Member

    A nice experiment, thank you.
    Some points I saw in this experiment:
    The equilibrium it was said to reach was 14.9C, then at the end of the video it went up to 15.9C.
    How nice would it would be if he would have put like a 500 Watt incandescent light bulb next to it, to simulate some what of the effects the sun could have on an object like this thermometer.
    Any thoughts?
     
  29. Mick West

    Mick West Administrator Staff Member

    Give it a go yourself. You could do it for under $200. Report back.
     
  30. MvK

    MvK New Member

    Thank you, I thought you might be in contact with the person that performed these experiments so you could maybe ask him.

    Know that I'm trying to find the truth right here and I'm not trying to just put forward a case, I'm actually trying to sift out between what I've studied about orbits, space flights and cosmological events, and the doubts others come with, and these are doubts that made some of them refute scientific empirically established truths which cannot be doubted about at all, as if they are doubting that the sun heats up the car. So I'm trying to go by these doubts one by one, debunking or affirming, trying to rely as good I can on only empirically observable truths so no one can deny them.

    The doubt concerning the heat of the thermosphere and the impossibility of a satellite or object being able to be over there seems to be far fetched after this small research, while I still have some points remaining that I mentioned in posts before the last ones and in the last ones, while at first it seemed their strongest point.

    Following up I have some other scientific topics about satellites I would like to research, but I'm not sure this topic suits them, the one I would like to discuss firstly is about the satellites in the exosphere, or near to it, the geostationary satellites. Does this topic suits it, or does a new topic has to be created?
     
  31. Mick West

    Mick West Administrator Staff Member

    It's not really clear what you want to discuss. But it sounds like a different topic. Check out the posting guidelines. It might not really be a Metabunk type thing.