Is space a giant refrigerator for artificial intelligence?
- Christophe Chazot
- 2 hours ago
- 14 min read
In February 2026, Elon Musk announced his intention to install data centers in orbit to run artificial intelligence. Very quickly, one argument dominated the comments: in space, cooling would be “free”, since it is very cold there.
This widely shared claim is nevertheless false. It reveals a common confusion between temperature, heat, and heat transfer. Above all, it offers a valuable opportunity to develop critical thinking and to revisit simple but fundamental questions: what is temperature? How does heat move from one object to another? And is space really a cold environment?
What is temperature?
Temperature is one of the most familiar physical quantities in our daily lives: we check it every morning to know how to dress, we monitor it when we cook, we measure it when a child has a fever. But what exactly are we measuring?
Temperature characterizes the degree of agitation of the particles that make up matter. In a gas, molecules move freely in all directions, bouncing off one another. The faster they move, the hotter the gas. In a solid, atoms vibrate around their equilibrium position: the more intense the vibrations, the hotter the solid. Temperature is therefore, fundamentally, a measure of the average kinetic energy of the particles in a body.
A first problem is therefore posed: if for an object to have a temperature it must be made of matter, can we speak of temperature in a vacuum? If a hot object placed in a vacuum, can it even cool down, since there is no matter around it to exchange its heat?
The three modes of heat transfer
Heat always flows from a hot body to a cold body. This is the second law of thermodynamics: the reverse never occurs spontaneously. This transfer can occur through three mechanisms. Most of the time these phenomena are simultaneous, but in some cases only one of these transfers is involved.
Conduction | Convection | Radiation | |
Mechanism | Particle contact | Fluid movement | Electromagnetic waves |
Necessary environment | Solid, liquid or gas | Liquid or gas | None (works in a vacuum) |
Daily example | Hot pan handle | Radiator that heats a room | Heat of the Sun on the Skin |
On Earth | Yes | Yes | Yes |
In space | Within the satellite only | No (no external fluid) | Yes (only outward direction) |
On Earth, all three modes of heat transfer coexist constantly. When you hold a cup of hot coffee, the heat is transferred to your fingers by conduction through the ceramic, the air above the coffee rises by convection, and your face feels the heat through infrared radiation. This combination is what makes cooling so efficient on Earth. In space, however, only radiation remains available to dissipate heat. This fundamental difference lies at the heart of the challenge posed by orbital AI servers.
Conduction: heat transfer by contact
Conduction is the transfer of heat from one point to another through direct contact between neighboring particles. When you touch a metal spoon dipped in hot soup, the highly agitated atoms of the metal in contact with the liquid gradually transfer their kinetic energy to neighboring atoms, and so on until they reach the tip of the spoon, and then your hand. There is no physical movement of matter; it is the vibrations that propagate.
Not all materials conduct heat in the same way. Metals, whose free electrons can transport energy very quickly, are excellent conductors. Copper conducts heat approximately 10,000 times better than air. Conversely, materials like wood, polystyrene, or still air are thermal insulators: they significantly slow down the flow of heat.
The law describing conduction was formulated in 1822 by the French mathematician Joseph Fourier. It states that the heat flow through a material is proportional to the material's thermal conductivity and the temperature gradient (the temperature difference per unit length). The better the material conducts heat and the greater the temperature difference, the faster the heat flows through it.
In a satellite, conduction plays a crucial role in transferring heat from electronic components to external surfaces. Engineers use heat pipes: closed tubes containing a fluid that evaporates upon contact with the hot component and condenses upon contact with the cold surface, transporting heat through an evaporation-condensation cycle. This cycle requires no external energy and can transport large quantities of heat over short distances.
In class
Primary school: Touching different objects placed on the same table: a metal spoon, a wooden pencil, a plastic cup. They are all at the same temperature (room temperature), yet the metal feels "colder" than the wood. Why?
Middle school: Small wax beads are attached at regular intervals to rods of the same length made of copper, aluminum, steel, and wood. By simultaneously heating one end of each rod (with a candle), the order in which the beads melt and fall is observed: first onto the copper, then the aluminum, then the steel. Plot the curves T = f(t) for each material and deduce a ranking of their thermal conductivities.
High school: Introduce Fourier's law and calculate the heat flow through a wall. Understand the concept of thermal resistance used in building insulation and energy efficiency labels for homes.
Convection: heat in motion
Convection is the transfer of heat through the movement of matter, a fluid (gas or liquid) that moves to transport thermal energy. It is the most efficient cooling mechanism in our daily lives. When a radiator heats the air it touches, this air expands, becomes less dense, and rises. Cooler air replaces it from below, creating a circular current: this is natural convection.
The movement of the fluid can also be forced with a fan or a pump. This forced convection is much more efficient than natural convection. This is the principle behind your computer fan, a car's air conditioning system, or the cooling towers in data centers.
Convection plays a fundamental role in large-scale natural phenomena. It redistributes heat in the Earth's atmosphere, creates winds, ocean currents, and even the movement of magma in the Earth's mantle. Convection is also the true cause of the temperature rise in the classic closed jar experiment meant to illustrate the greenhouse effect: by eliminating air currents with a lid, convective cooling is prevented, causing the temperature to rise.[4] For windows that let in light, double glazing limits conduction thanks to two panes of glass and significantly reduces convection by trapping a layer of still air between them.
In class
Primary school: Observe the movements of colored water heated in a beaker. Deduce that "hot water rises" and that this creates a circular motion. Relate this to a sea breeze: the land heats up faster than the water during the day, the hot air rises above the land and creates a pull of cool air from the sea.
Middle school: Quantitatively compare cooling with and without a fan using connected sensors (FizziQ). Plot the two curves and calculate the difference in cooling rate. Relate this to wind chill: in strong winds, our bodies lose heat faster, which explains why we feel "colder" even if the air temperature hasn't changed.
High school: Discuss atmospheric convection cells (Hadley cells) and their role in distributing heat across the globe. Understand why convection is absent in space (no fluid) and what this implies for the cooling of satellites.
Radiation: heat without matter
Thermal radiation is the most mysterious of the three modes of heat transfer. Unlike conduction and convection, it requires no material medium. Energy propagates as electromagnetic waves, at the speed of light, and travels through a vacuum without difficulty. It is through radiation that the Sun's heat reaches us after traveling through 150 million kilometers of vacuum.
Any object with a temperature above absolute zero emits electromagnetic radiation. At room temperature (approximately 20°C or 293 K), this radiation is primarily in the infrared range, invisible to the naked eye. The human body, at 37°C, radiates a power of about 100 watts, the equivalent of an incandescent light bulb.
When an object is heated above approximately 500°C, some of the radiation enters the visible spectrum. The object begins to glow red (around 700°C), then turns orange, yellow, and finally bluish-white at very high temperatures. The surface of the Sun, at 5,800 K, appears white. The link between the color of emitted light and temperature was discovered in 1800 by the astronomer William Herschel, who identified infrared radiation by measuring the temperature beyond the red end of a solar spectrum. This invisible radiation, which Herschel named heat radiation, is precisely what is at the heart of the greenhouse effect and the cooling of satellites.
In class
Primary school: The infrared remote control experiment amazes the students: they can "see the invisible" thanks to their smartphones. Discuss other examples of invisible radiation: radio waves, microwaves, X-rays. Why do remote controls use infrared? Simplicity, low cost, safety, limited range, and sufficient directionality.
Middle school: Recreate Herschel's experiment: using a prism and temperature probes (FizziQ Connect), measure the temperature in each colored area of the spectrum and beyond the red. Discover that the hottest area is beyond the visible spectrum.
High school: Introduce the complete electromagnetic spectrum. Relate the wavelength of maximum emission to temperature using Wien's law: λ_max = 2898 / T(K) in micrometers. Calculate that the Sun (at 5800 K) emits primarily in the visible spectrum (~0.5 µm) while the Earth (at 288 K) emits in the infrared spectrum (~10 µm).
Stefan-Boltzmann law
In 1879, the Austrian physicist Josef Stefan discovered a remarkable law by analyzing infrared emission measurements made by John Tyndall. The total power radiated by a body per unit area is proportional to the fourth power of its absolute temperature.
P = ε × σ × A × T⁴ where P is the radiated power (in watts), ε the emissivity (between 0 and 1), σ the Stefan-Boltzmann constant (5.67 × 10⁻⁸ W/m²/K⁴), A the surface area (in m²) and T the absolute temperature (in kelvins). |
This law has spectacular consequences. If the temperature of an object is doubled (from 300 K to 600 K), the radiated power does not double: it is multiplied by 2⁴ = 16. It is this dependence on T⁴ that explains why the hottest stars are also the brightest.
Concrete example: one square meter of black surface (ε = 1) at room temperature (300 K) radiates σ × 300⁴ ≈ 460 watts. But in practice, this object also absorbs radiation from its environment. The net power exchanged is the difference: P_net = εσA(T_object⁴ – T_environment⁴). A satellite radiator facing a vacuum (at 2.7 K) dissipates all its power, because T_environment⁴ is negligible. But when exposed to the Sun, it absorbs 1361 W/m², which limits its cooling capacity.
In class
Primary and Middle School: Measure the temperature of surfaces of different colors exposed to a lamp using connected probes. Observe that dark surfaces heat up more. Introduce the concept of albedo and link it to climate issues (melting ice caps, urban heat islands).
High school: Calculate the power radiated by the human body (surface area ~1.7 m², T = 310 K, ε ≈ 0.98) in an environment at 293 K. Result: approximately 100 W net, consistent with resting metabolism. Also calculate the equilibrium temperature of a black sphere at the Earth-Sun distance: approximately 279 K (6 °C), close to the average Earth temperature without the greenhouse effect.
Is space cold? A persistent misunderstanding
Science fiction films regularly depict characters freezing instantly in the vacuum of space. This image is deeply misleading. The reality is counterintuitive: space is neither hot nor cold; it is a near-perfect thermal insulator.
The reason is simple: for there to be an "ambient temperature," there must be matter capable of transferring heat by contact (conduction) or by current (convection). Space is essentially empty: barely a few particles per cubic centimeter, compared to 27 quintillion in the atmosphere at sea level. Space behaves exactly like the inside of a thermos, whose double-glazed walls, enclosing a vacuum, prevent the coffee from cooling down.
Thermal conditions in Earth orbit are extreme, but not in the way you might think. The side of a satellite exposed to the Sun can reach +121°C, while the side in shadow can drop to -157°C. The International Space Station experiences these temperature variations every 90 minutes of orbit. It's not a "giant freezer," but rather a stark alternation between furnace and icebox in an environment where only radiation can balance the temperatures.
So, are science fiction films misleading us with these images of bodies frozen in a vacuum? While a body exposed to a vacuum doesn't cool instantly, the skin can still frost over, but for a completely different reason. In a vacuum, the pressure is almost zero, which drastically lowers the boiling point of water. Bodily fluids—saliva, tears, skin moisture—then begin to boil, causing localized cooling through evaporation, similar to perspiration, but much more rapid. The skin can therefore frost over on the surface, while the body as a whole remains warm for a long time. An unprotected astronaut would die of asphyxiation and the effects of decompression long before feeling cold.
In class
Primary school: Pour hot water into a thermos and an ordinary glass. Measure the temperature every five minutes for half an hour. Plot the two cooling curves. The thermos retains the heat. Ask the question: "If we put a hot object in space, would it cool down quickly?"
Middle School: Guided debate: Show clips from films (2001: A Space Odyssey, Guardians of the Galaxy) where characters freeze in space. Is this realistic? Which heat transfer mechanism is eliminated in a vacuum? How long would it actually take for a body to cool down? (Several hours, not a few seconds.)
High school: Calculate the equilibrium temperature of a sphere in Earth orbit as a function of its albedo and emissivity, using the radiative balance: absorbed solar flux + terrestrial infrared = own emission.
How do you cool a satellite?
Thermal control is a major challenge in space engineering. Each component of a satellite has an operating temperature range: processors between 0 °C and 85 °C, batteries between –10 °C and 45 °C, some infrared detectors below –170 °C.
Passive systems
Surface coatings form the first line of defense. White paint reflects sunlight (low absorptivity) while emitting infrared radiation (high emissivity), thus promoting cooling. Multilayer shielding (MLI), the golden "survival blankets" of satellites, reflects radiation and reduces heat loss. Heat pipes carry heat from hot components to radiators. Finally, the radiators, large white panels facing the vacuum, dissipate heat through infrared radiation.
Active systems
Heating elements prevent components from dropping below their minimum temperature during eclipses. Pumped fluid loops circulate a heat transfer fluid between the heat sources and the radiators. Cryo-coolers cool instruments requiring cryogenic temperatures, such as the detectors of the James Webb Space Telescope (at 40 K, or -233 °C). Variable-emissivity materials, based on vanadium dioxide (VO₂), automatically change their emissivity according to the temperature: a passive thermostat [5].
In class
Primary school: Build a "mini-satellite" using a cardboard box covered with different materials (shiny aluminum, black paper, white cotton) and measure the internal temperature under a lamp. Discuss: which coating would keep a satellite cool?
Middle school: Compare the temperature changes of the mini-satellite with and without ventilation (forced convection). Discuss: what happens when the fan is removed? This is exactly the situation in space.
High school: Calculate the radiator surface area required to dissipate 1 kW of heat in space (radiator temperature = 350 K, ε = 0.9) using the Stefan-Boltzmann law. Result: approximately 1.5 m². Compare this to the power consumption of an Nvidia H100 GPU (~700 W) to understand the challenge of cooling an orbital data center.
AI Servers: In space or in the Sahara?
Elon Musk isn't the first to raise the issue of placing servers in space. In November 2025, a team of Google researchers published a detailed scientific paper proposing the construction of "data centers" in low Earth orbit [2], consisting of fleets of satellites equipped with artificial intelligence chips, powered by solar energy, and linked together by very high-speed optical links. Now that we know more about the concept of temperature, what should we make of it?
Cooling: the real challenge
On Earth, data centers have all three heat transfer methods. Forced convection—fans, water circuits, cooling towers—is the primary mechanism. A large data center consumes up to 7.5 million liters of water per day and up to 40% of its electricity for cooling [3]. This is expensive, but very efficient. In space, only radiation is available to dissipate heat. However, as we have seen, this is the least efficient of the three methods at low temperatures. A latest-generation graphics processing unit (GPU) dissipates approximately 700 watts. To dissipate this heat by radiation with a heatsink at 80 °C (353 K, ε = 0.9), the Stefan-Boltzmann law gives approximately 660 W/m²: more than one square meter of heatsink is needed for a single GPU. Another problem raised by Google's article is that if servers fly in a tight constellation, the infrared radiation emitted by one satellite heats its neighbors, reducing the efficiency of their own heat sinks. The constellation must therefore be designed to minimize this thermal interference. And all this equipment—heat sinks, heat pipes, shielding—must be launched into orbit by rocket, at a significant cost.
The vacuum, far from being a refrigerator, behaves like a thermos that traps heat. As Professor Josep Jornet of Northeastern University summarizes: without a suitable cooling system, a processor would overheat in space faster than on Earth, because at least the Earth's air can carry away some of the heat by convection [1].
Why space? The real motivation
The primary reason for these projects is not cooling, but energy. The Sun emits 3.86 × 10²⁶ watts of power, more than 100 trillion times humanity's electricity production. In orbit, solar panels receive up to eight times more energy per year than a panel located on Earth at mid-latitudes: no night (in orbit, the sun is synchronous with dawn and dusk), no clouds, and no atmosphere to absorb some of the radiation. Google's team estimates that if launch costs reach approximately $200 per kilogram by 2035, which historical trends make plausible, the annualized cost of energy in orbit could become comparable to that of terrestrial data centers, in the range of $600 to $3,000 per kilowatt per year. The economic calculation therefore relies primarily on access to a virtually unlimited energy source, not on the ease of cooling.
So, is it feasible or not?
The development of artificial intelligence requires the creation of new technological solutions if we also want to pursue sustainable development. More than a physics problem, it's an engineering problem. Engineers have solutions at their disposal—passive heat pipes, dedicated radiators, materials with variable emissivity—which are already used on satellites and space stations. The International Space Station dissipates approximately 100 kW using 150 m² of radiators [6]. Furthermore, Google's team tested its TPU chips under a proton beam simulating orbital radiation conditions, demonstrating their survival for a 5-year mission. These are concrete results, not mere speculation.
The question, therefore, is not whether it is physically impossible, but whether engineering can make cooling efficient enough so that the advantages of space—near-continuous solar power, no water consumption, no land footprint, potentially unlimited scalability—outweigh this difficulty. As Deutsche Bank notes in a recent analysis, the obstacles are “more engineering than physics” [7].
The comparative assessment
Criteria | Earth Data Center | Orbital Data Center |
Cooling modes | Conduction + convection + radiation | Radiation only outwards |
Outside temperature | 30 to 55 °C but air available | -157 °C to +121 °C depending on exposure |
Cooling efficiency | High: fans, water, evaporation | Limited: large radiators required |
Water needed | Up to 7.5 million liters/day | Zero |
Solar energy available | ~1000 W/m² (6–10 h/day) | ~1,361 W/m² almost continuously |
Annualized energy cost | ~$570–3,000/kW/year | ~$810/kW/year (2035 projection) |
Maintenance | Easy: technicians on site | Very expensive or impossible |
Risk of overheating | Low if properly sized | High: a vacuum is an insulator |
In class
Primary school: Debate: "If you had to install a very powerful computer that gets very hot, would you put it in the desert or in space?" Mobilize everything that has been learned about the three modes of transfer.
Middle school: Complete the Earth/Space comparison table using the knowledge acquired in previous sections. Argue in favor of each solution and then decide.
High school: Calculate how many square meters of radiators would be needed to cool 10,000 GPUs in space. Compare this to the radiator surface area of the International Space Station (~150 m² for ~100 kW). Evaluate the economic feasibility, including the cost of launching into orbit (~€2,700/kg with SpaceX) and a future price of €250/kg.
Conclusion: The power of critical thinking
This article does not aim to settle the debate between terrestrial servers and orbital servers. Engineers, economists, and policymakers will have the final say. Our purpose lies elsewhere.
In response to the spectacular announcement of placing servers in space, many commentators—misled by a lack of scientific literacy and by misinterpreted representations from certain science-fiction films—have concluded that the main reason is that “cooling is free in space.” Yet we have seen that through simple reasoning and experiments that can be carried out at home or in the classroom, it is possible to think critically about such announcements, to frame the problem rigorously, and to arrive at a surprising conclusion: the vacuum of space is an insulator, not a refrigerator, and cooling there is more difficult than on Earth, not easier.
This is precisely the goal of the inquiry-based approach: to start from a concrete question, mobilize one’s knowledge, experiment, reason—and dare to tackle a problem that seems out of reach. For this exercise is far from inaccessible. Everyone has the tools to do it: the physics concepts learned at school, the ability to reason from known principles, and the courage to embark on the adventure.
Every new situation is an opportunity to learn, to reason, and to use what makes human beings unique: their brains.
Learn more
[1] Dano, M. "Musk's massive space data center: Super scale or sheer folly?", Light Reading, février 2026. https://www.lightreading.com/satellite/musk-s-massive-space-based-data-center-super-scale-or-sheer-folly-
[2] Agüera y Arcas, B., Beals, T., Biggs, M., Bloom, J.V., Fischbacher, T., Gromov, K., Köster, U., Pravahan, R. et Manyika, J. "Towards a future space-based, highly scalable AI infrastructure system design", arXiv:2511.19468, novembre 2025. https://arxiv.org/abs/2511.19468
[3] Shehabi, A., Smith, S.J. et al. "United States Data Center Energy Usage Report", Lawrence Berkeley National Laboratory, LBNL-2024-1000, décembre 2024. https://eta-publications.lbl.gov/sites/default/files/2024-12/lbnl-2024-united-states-data-center-energy-usage-report_1.pdf
[4] Chazot, C. "Sept expériences pour comprendre l'effet de serre", FizziQ. https://www.fizziq.org/en/post/greenhouse-effect-practical-experiences-and-teaching-methods
[5] Shannon, S. et al. "Variable Emittance Coatings for Spacecraft Thermal Control", Surface Optics Corporation, 2025. https://surfaceoptics.com
[6] NASA. "Active Thermal Control System Overview", International Space Station Program. https://www.nasa.gov/wp-content/uploads/2021/02/473486main_iss_atcs_overview.pdf
[7] Deutsche Bank Research. "Space-based data centres — engineering challenges and economic outlook", 2026.