A universe of possibilities
From our nearest star to the edge of the observable universe: our foundational articles make cosmic scales tangible, explain connections, and show what we know—and what remains an open question.
The universe is about 13.8 billion years old—and the region observable today is roughly 93 billion light-years across. This apparent contradiction takes us straight into modern cosmology: light travels through space that changes along the way.
Read article →Hundreds of billions of galaxies and unimaginably many stars: the scales are fascinating, but no complete cosmic inventory exists. The crucial distinction is between what is counted, what is extrapolated, and what is merely assumed.
Read article →A planet roughly 21 Earth diameters across and a star with a radius of approximately 2,000 solar radii: cosmic size records exceed our everyday experience. But “larger” can refer to radius, volume, or mass—and rankings are by no means definitive.
Read article →A light-year is not a span of time, but approximately 9.46 trillion kilometers. The unit connects distances with the travel time of light—and explains why looking at the stars always also means looking into the past.
Read article →Planets are common. We do not yet know whether life also arises frequently. An interesting exoplanet, a possible biosignature, and a technological civilization involve different questions—and very different uncertainties.
Read article →The limit of what we can observe is not automatically the boundary of the universe. The question of an “outside” encompasses several different ideas: more space, a finite universe without an edge, or a hypothetical multiverse.
Read article →People have observed and interpreted the sky for thousands of years. Astronomy and astrology share part of their history, but today their methods differ fundamentally: personal meaning is not the same as a testable prediction.
Read article →Technology can enable humans to survive in hostile environments. But a short mission, a permanently inhabited outpost, and a self-sufficient city are three entirely different goals. The Moon and Mars illustrate how much separates a vision from dependable everyday life.
Read article →13.8 billion years of cosmic history, 4.6 billion years for the Sun, and around 300,000 years for Homo sapiens: only by comparing these timescales can we see how young our own species is relative to its surroundings.
Read article →Stars and planets make up only a small part of the cosmic matter–energy budget. Dark matter and dark energy describe different unresolved problems—and “dark” here means above all that their fundamental nature remains unknown.
Read article →A black hole is not a hole in solid ground or a vacuum cleaner that sweeps up the entire universe. It is a region of spacetime with a special boundary: no light can escape outward from inside the event horizon.
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