Where Does Space Begin?

Outer space is everything above the layers of Earth’s atmosphere, but the boundary isn’t as sharp as it’s often described. An internationally used technical standard refers to the so-called Kármán line at an altitude of 100 km above sea level, where aerodynamic flight is no longer feasible and orbital mechanics take over. In some countries (for example, the U.S.), however, an 80 km boundary is also used for awarding “astronaut wings.” In practice, there is therefore no clear-cut legal “line” between national airspace and outer space; it is more of a functional boundary used by scientists and aviation/space institutions.

Conditions in Space: Vacuum, Extreme Temperatures, and Radiation

Just above the atmosphere there is a hard vacuum, which dries out materials and—without specialized protection—destroys virtually anything biological. Temperatures swing dramatically: in direct sunlight they can reach hundreds of degrees Celsius, while in shadow they drop far below zero. On top of that, there is both solar and galactic radiation (cosmic rays), against which shielding is only partly effective. For humans, this means risks such as DNA damage, loss of bone density and muscle mass, vision changes, and immune-system issues. That’s why any longer mission is a combination of protective shielding, exercise protocols, and medical monitoring.

Types of Orbits: LEO, MEO, GEO, and More

Closest to Earth is Low Earth Orbit (LEO), up to ~2,000 km. That’s where the International Space Station flies (roughly 370–460 km) and where most satellites of the new “constellation” era operate. Higher up is Medium Earth Orbit (MEO), used primarily by navigation systems (Galileo, GPS, etc.). Higher still is Geostationary Orbit (GEO), at about 35,786 km above the equator, where a satellite orbits Earth once every 24 hours and appears to “hover” over a single spot—an ideal position for television broadcasting and many data links. Between these are dozens of specialized orbits (polar, SSO, highly elliptical, etc.), chosen based on what the satellite does and where it needs to “see.”

What We Do in Space: Communications, Navigation, Earth Observation, and Science

Telecommunications satellites carry television, internet, and phone traffic across continents. Navigation systems enable precise positioning in phones, aircraft, and ships. Earth-observation satellites provide data on climate, forests, agriculture, and disasters. And then there is research—from microgravity on the ISS to new materials and the testing of technologies for returning to the Moon and flying to Mars. Economically, it’s a major sector: launches and satellites cost from millions to tens of millions of euros depending on mass and target orbit, but the value of the services they provide (communications, navigation, imaging) is an order of magnitude higher.

Space Debris: A Growing Problem

Since 1957, thousands of defunct satellites, rocket upper stages, and fragments have been left in orbit. Large pieces can be tracked and active satellites maneuver to avoid them, but we cannot monitor millions of tiny shards. Collisions at speeds around 7–8 km/s can destroy a satellite and create more “gravel,” compounding the problem (the so-called Kessler syndrome). That’s why international recommendations have emerged: don’t release unnecessary components, minimize the risk of explosions in orbit, “passivate” a satellite after the mission, and deorbit it within a reasonable timeframe (traditionally within 25 years; for the most congested orbits, a stricter rule is being discussed).

The Legal Framework: What International Law Allows and Prohibits

The cornerstone is the 1967 Outer Space Treaty. It establishes that outer space is the “province of all mankind,” freely accessible for exploration and use, but not subject to national appropriation. It prohibits placing nuclear weapons and other weapons of mass destruction in orbit or on celestial bodies and emphasizes peaceful use and states’ international responsibility for their activities (including those of private companies).

It is complemented by the Liability Convention (absolute liability for damage on Earth and to aircraft; fault-based liability in space) and the Registration Convention (the obligation to register objects in the UN registry). There is also the Moon Agreement (1979), which addresses the regime for the Moon’s natural resources in more detail, but it has been ratified by only a small number of states, so its practical impact is limited.

Resources in Space: You Can’t Own an Asteroid, but You Can Own Extracted Materials (According to Some States)

International law prohibits “appropriating” a celestial body, but several countries have adopted national laws allowing companies to own resources they legally extract (water, metals), without claiming the territory itself. The U.S. introduced this in 2015; Luxembourg and the UAE have similar frameworks. It’s a controversial topic, but current practice is trending toward allowing extraction provided it respects the Outer Space Treaty and transparent rules. For companies, it is crucial to have clear authorization from their home state and to comply with registration and safety obligations.

Safe and Sustainable Cooperation: From the UN to the Artemis Accords

In addition to UN treaties, voluntary frameworks for best practice and orbital “rules of the road” are also emerging. The IADC (the international coordination forum of space agencies) issues debris-mitigation guidelines, and more and more states are incorporating them into licensing. In parallel, a coalition of countries around the principles of the Artemis Accords is growing—these outline transparency, interoperability, safety zones for surface activities, and the sharing of scientific data in the return to the Moon and in other missions. They are not legally binding like a UN treaty, but in practice they set expectations among dozens of signatories.

Why Human Spaceflight Is So Demanding

Microgravity causes rapid muscle and bone loss, fluid shifts affect vision, and long-term exposure to cosmic radiation increases health risks. NASA and its partners therefore invest in research into protective materials, exercise regimens, and “in-craft” radiation-mitigation solutions. Health data from long missions show that individuals respond differently, and future crews headed to the Moon and Mars will need more robust shielding, telemedicine, and greater autonomy for interventions.

How Space Will Evolve Next

The coming years will bring more smaller, more capable satellites, denser constellation networks in LEO, and the return of humans to the Moon supported by international partnerships. This will also involve tighter space-traffic management in orbit and real-world tests of active cleanup of old debris. For states and private companies alike, it remains crucial that data openness grows, maneuver coordination improves, and safety standards become consistent—otherwise some orbits could become unsustainable in the future.

Videos to Help You Understand the Topic

What Low Earth Orbit Is and Why It Matters

A short NASA video on why LEO is the main “work zone” for both people and companies.

Space Debris, Briefly and Clearly

ESA explains why debris is increasing and how we can defend against it.

Geostationary Orbit in Practice (TDRS)

How NASA relays data via geostationary satellites.

Sources

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“Treaty on Principles Governing the Activities of States in the Exploration and Use of Outer Space… (full text).” UNOOSA. https://www.unoosa.org/oosa/en/ourwork/spacelaw/treaties/outerspacetreaty.html
“Convention on International Liability for Damage Caused by Space Objects (1972).” UNOOSA – overview. https://www.unoosa.org/oosa/en/ourwork/spacelaw/treaties/introliability-convention.html
“Convention on Registration of Objects Launched into Outer Space (1976).” UNOOSA. https://www.unoosa.org/oosa/en/ourwork/spacelaw/treaties/registration-convention.html
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“TDRS – NASA geostationary relay (35,786 km).” NASA. https://www.nasa.gov/missions/tdrs/tracking-and-data-relay-satellite-tdrs-generations-of-spacecraft/
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