| Do you think space, or rather the vacuum, is cold? | | | | heat exchange between air and ground material |
| During my survey on the web during the past few | | | | molecules and part by what it absorbs itself directly. |
| months, it clearly showed that most people would | | | | The same principle is valid for glass and that's why |
| answer yes to that question. Fact is that only matter | | | | your car gets so hot inside, when it is parked in the |
| can have a temperature, which is the speed of its | | | | sun. Likewise the temperature in green houses rise |
| molecules... | | | | above surrounding air temperatures, as is the |
| Do you think space, or rather the vacuum, is cold? | | | | purpose of those. |
| During my survey on the web during the past few | | | | The warm atmosphere of the Earth radiates off heat |
| months, it clearly showed that most people would | | | | into space at a far lower frequency than what it |
| answer yes to that question. | | | | received from the Sun and this heat disperses into |
| Fact is that only matter can have a temperature, | | | | space, without "warming" it up. Space, the vacuum, |
| which is the speed of its molecules. The faster the | | | | cannot have a temperature and so the heat energy |
| molecules in a material move, the warmer that | | | | that the Earth's atmosphere radiates off, disperses |
| material is. Per definition, an absolute vacuum is a | | | | into larger and larger volumes of "nothingness". The |
| void, nothingness and therefore it cannot have any | | | | Earth is thus not cooled by any "cold" space, because |
| temperature. In as far as the space of the Universe | | | | that would require convection, which the vacuum |
| is an absolute vacuum, that space cannot have any | | | | cannot provide. |
| temperature and it is thus not "cold". | | | | Likewise, the distant planets are very cold, because |
| However, an absolute vacuum does not really exist; | | | | they receive very little energy from the Sun, not |
| there are molecules whirling around everywhere in | | | | because they are surrounded by "cold" space. Any |
| space. Actually, some recent theories say that all | | | | object in "dark" space, not receiving any heat, nor |
| these molecules whirling around, constitute more | | | | generating any itself, will become extremely cold, as |
| mass than all the visible galaxies contain together - it's | | | | it radiates off whatever little it still has. How cold, |
| called "dark matter". Even so, the density of these | | | | we'll see at the end of this article. |
| molecules is so incredibly low, that in practical terms, | | | | The average temperature of the Earth is determined |
| as far as space technology is concerned, | | | | by a balance between received and given off heat |
| interplanetary space behaves as an absolute vacuum. | | | | energy. The atmosphere's temperature stabilizes |
| Even the Moon, that actually does have an | | | | there where both amounts are the same. Hence, the |
| atmosphere in the sense that the density of its gas | | | | Earth gives off as much energy as it receives from |
| molecules is considerably higher than in "free" space, | | | | the Sun; nothing is "consumed", or "used" as many |
| can yet be seen as an absolute vacuum | | | | erroneously think. The same is valid for a |
| environment in practical terms for human activity | | | | green-house and you car parked in the sun; the inner |
| there. This means that the molecules that are there, | | | | temperature stabilizes at a value where energy |
| do not have a measurable contact (convection) heat | | | | balance is reached. |
| exchange effect with other materials around and | | | | Of course, not all the solar energy that hits the Earth |
| thus a Moon vehicle or base on the Moon can neither | | | | is absorbed by it. Much of it is reflected back into |
| be cooled, nor heated by these molecules. The same | | | | space. From the rest, the atmosphere absorbs a part |
| is valid for space vehicles traveling around in the Solar | | | | itself and lets through a part to reach the surface. As |
| System; they also have no measurable heat | | | | long as the properties of the atmosphere do not |
| exchange with the molecules moving in the vacuum | | | | change, the Earth's global temperature will not |
| around. | | | | change, but if we bring about noticeable changes |
| Even on Mars, that has a well defined atmosphere, | | | | with our emissions of whatever gases, anything can |
| such heat exchange effects would not have much | | | | happen. The Earth can become cooler or warmer. |
| significance for human activity there, though it would | | | | Today the talk is about global warming, but there are |
| be noticeable nonetheless. Surely, the air temperature | | | | scientists who argue for a risk of global cooling also. |
| on Mars can locally come up to plus 30 degr. C, but | | | | In the end, nobody knows for sure, because the |
| that doesn't mean you would "feel" it, the same as | | | | heat household of the atmosphere is a very |
| on Earth, because the Mars air is so much thinner. | | | | complicated system, with many unknown parameters. |
| The atmospheric pressure on Mars is just 6 mbar, | | | | However, if it ever would happen that we release so |
| compared to Earth's atmospheric pressure of 1000 | | | | much heat from fuels, that it becomes a noticeable |
| mbar. No industrial "vacuum" pump on Earth could | | | | part of the Earth's total energy household, we would |
| reach such a low pressure and it is yet called a | | | | indeed warm up Earth by it. I don't think that ever |
| vacuum pump. Hence, in technical terms, also Mars | | | | will happen, it's just a theoretical exercise, but we do |
| could be seen as a vacuum environment for | | | | cause heat-pollution locally, warming up waters around |
| astronauts, just not an absolute one, as it is on the | | | | large power plants that are cooled by them and it |
| Moon. | | | | affects the biological systems there. |
| This all means that space, the vacuum, is a perfect | | | | On Earth, cars, green-houses and whatever other |
| temperature insulator for convection heat. The only | | | | structures, are heavily cooled by the surrounding air, |
| heat exchange that can be done between bodies in | | | | especially if there is wind blowing around them. Not |
| the vacuum is through radiation, because the vacuum | | | | so on the Moon for example. If you see |
| lets electromagnetic energy pass through. Very | | | | science-fiction designs of huge glass cupolas on the |
| fortunate, so we can get light and warmth from the | | | | Moon and space-crafts with large glass windows all |
| Sun, all being electromagnetic radiation. The | | | | around, you are basically looking at ovens. If exposed |
| frequency of this radiation is a measure for how | | | | to sunlight, they would self-destruct by overheat, |
| much energy it transmits. The higher the frequency, | | | | unless practically all of the solar heat is reflected (not |
| the more powerful the radiation is and usually | | | | absorbed !) by such glass, or whatever transparent |
| penetrates deeper into materials. X-rays have a very | | | | material. Even then, such habitats are additionally |
| high frequency and are therefore powerful enough to | | | | heated by the body heat of people in there and by |
| penetrate our bodies, which for example is used in | | | | the power supplies to run technical systems (all |
| medical applications. Gamma rays are even more | | | | energy decays to heat at ambient temperature - |
| powerful and are generated by decaying atoms - | | | | Second Law of Thermo). All that heat must be |
| nuclear radiation. Heat radiation is called infra-red, | | | | radiated off also. |
| because the color red is the lower frequency limit of | | | | How cold can an object in "dark" space become? |
| what our eyes can see (violet the upper). | | | | Many say 3 Kelvin, which is the "temperature" of the |
| Infra-red has a too low frequency for our eyes to | | | | cosmic background radiation (actually 2.7 K). This |
| see and we feel it as heat instead. Its frequency | | | | radiation is assumed to be a remnant of the Big-Bang |
| relates to the temperature of the emitting body, the | | | | and its frequency corresponds with 3 Kelvin. Many |
| higher the frequency, the warmer that body is. This | | | | think erroneously that this is the temperature of |
| causes the so called green-house effect, because | | | | space, but that is of course not true. An object in |
| certain materials are more transparent for higher than | | | | deep, deep dark space can become colder than 3 |
| for lower frequencies. The surface temperature of | | | | Kelvin, but the Second Law of Thermo says it can |
| the Sun is 6000 Kelvin and the according frequency | | | | never become 0 Kelvin, because 0 Kelvin is not a |
| can penetrate the Earth's atmosphere. As it hits the | | | | temperature - it is the absence of it, "nothingness", |
| ground, most of it gets absorbed and warms up the | | | | a void. Matter as we know it, cannot exist at 0 |
| ground material - ever noticed how hot beach sand | | | | Kelvin, |
| can be? | | | | However, this is not agreed upon by all scientist. |
| However, the thus generated temperatures are | | | | Look for the "Third Law of Thermodynamics" in a |
| much lower (fortunately) than that of the Sun and | | | | search engine and you will find it - I personally do not |
| the Earth's atmosphere is not transparent for the | | | | agree with that "law". |
| according lower frequencies and so it warms up, | | | | Btw, do you want to raise your voice over Climate |
| partially by absorbing the energy that the warm | | | | Change, Global Warming? Read about Spaceship |
| ground radiates off and partially through convection | | | | Earth first! |