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Answer: B. Beyond the horizon, every available path leads inward, even though light still travels at its usual speed.
Answer: A. The horizon is not a surface but a boundary of causality, so instruments on a falling spacecraft would not register it.
Answer: A. While reactions continue, outward pressure balances gravity; when the fuel runs out, the balance disappears.
Answer: B. We need a theory that combines gravity and quantum mechanics, and we still don't have one.
Answer: C. They later combined recordings with atomic timestamps as if they were pieces of one mirror.
Answer: A. The energy for the escaping particle comes from the black hole itself.
Answer: C. At iron, the chain breaks: fusing heavier nuclei no longer releases energy but requires it.
Answer: B. A civilization that arose 1 million years before ours would have had time to spread very far.
Answer: A. That is why the search focuses on a liquid that exists for a long time, not water as such.
Answer: A. It was designed as a framework for discussion, not as a prediction.
Answer: B. We only know life in which water acts as a solvent, so its signs can be detected with instruments.
Answer: A. The galaxy could have been colonized in millions of years - a tiny span by cosmic standards.
Answer: C. The brain interprets any excitation of the visual pathway as light.
Answer: C. Without body weight, the discs absorb water and the spine's curves partially straighten.
Answer: B. Your brain starts receiving a signal about which way is down again but has forgotten how to use it, while your blood vessels have stopped keeping blood in the upper half of your body.
Answer: C. In weightlessness, your body gets rid of some plasma, and the vessels in your legs forget to help blood rise to your head.
Answer: C. The bag is fastened to the wall, while weightlessness lets the body settle into a relaxed position without pressure.
Answer: A. The crystals in the inner ear stop shifting, while your eyes keep showing you the floor and ceiling.
Answer: A. The Moon rotates on its axis in the same time it takes to orbit Earth, so one side faces us.
Answer: A. Water gathers on both sides of the planet, while there is less of it along the sides.
Answer: A. The Moon is unusually large for Earth's satellite, and a captured body would have nowhere to lose speed in orbit.
Answer: C. They need no power: they simply return the laser beam exactly where it came from.
Answer: C. Its angular size is even slightly smaller near the horizon: it is farther away by one Earth radius there.
Answer: B. Iron in the rocks oxidized, and wind spread the rusty dust across almost the whole planet.
Answer: A. In English, the meaning implying human-made structures was chosen.
Answer: C. A small difference - until you have to live by it: after two weeks, the workday has moved to the other half of the day.
Answer: C. Spacecraft land there regularly, but their mass is measured in tons, while a crewed spacecraft would be tens of times heavier.
Answer: C. At very low pressure, water on Mars's surface boils from lack of pressure and immediately freezes.
Answer: A. The dip is confirmed both by observer records and by isotope data.
Answer: C. In groups of sunspots, magnetic loops are especially tangled, and their reconnection quickly releases stored energy.
Answer: C. Protons repel each other, and fusion reactions are rare, so energy is released gradually.
Answer: B. They flow through power lines and pipelines and overload transformers.
Answer: A. A supernova requires much more mass than the Sun has.
Answer: B. Light needs time to reach your eye, so distant objects appear as they were earlier.
Answer: A. A star is a point, so its entire beam is shifted at once.
Answer: C. The hotter the surface, the shorter the wavelength at peak emission - which is why blue stars are hotter than red ones.
Answer: B. Often, it's an explosion of a neighboring star: one star's death triggers the birth of others.
Answer: B. The core collapses in fractions of a second and is compressed to a density unimaginable under ordinary conditions.
Answer: C. About 176 Earth days pass from sunrise to sunrise there, which is two local years.
Answer: C. Similar bodies were found beyond Neptune's orbit, and the choice was between a new rule and a growing list of planets.
Answer: C. Venus has a dense carbon dioxide atmosphere: light gets down, but infrared heat struggles to escape.
Answer: C. Near the planet, differences in its gravity tear the debris cluster apart, preventing it from becoming a moon.
Answer: C. Because the axis lies almost flat, the poles take turns facing the Sun or remaining in darkness for a long time.
Answer: A. Countercurrents spin up the vortex, while small storms give it their energy.
Answer: B. There is no sharp boundary: one state of matter gradually changes into another.
Answer: A. Every line of sight would eventually end at a star, just as a look into an infinite forest would end at a tree trunk.
Answer: C. Space itself is expanding between galaxies, so from any one of them, the others appear to be moving away.
Answer: A. If the amounts had been equal, everything would have annihilated, leaving only radiation in the universe.
Answer: B. An error in one method would not be reproduced by the other two, which work in completely different ways.
Answer: A. If time began with expansion, there is simply nothing for the word "before" to refer to.
Answer: B. Space itself grows, so distances between things increase rather than fragments flying apart.
Answer: C. Selection works like a funnel: at every stage, they look for a reason to say "no," and one rejection is enough.
Answer: B. On the station, every minute is scheduled, while on Earth you have to choose everything.
Answer: C. The menu is built around food that does not crumble, which is why salt and pepper are liquid there too.
Answer: C. The station takes 1.5 hours to orbit the planet, so the view never repeats, and there is a separate module with large windows for it.
Answer: A. The planet fits entirely within view for the first time and becomes an object rather than a background.
In the app, a quiz like this follows every article, and every read grows your streak and level.