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Browse Qlopedia topics grouped under Science.
298 topics, showing 73-96 on page 4 of 13.
Causal inference is the study of whether an intervention, exposure, or policy actually changes an outcome. It combines study design, assumptions, statistical methods, and domain knowledge to move beyond association toward answers about cause and effect.
Phenology is the study of recurring seasonal events in plants, animals, and ecosystems, such as leaf-out, flowering, breeding, migration, fruiting, and leaf color. It helps scientists, land managers, farmers, and communities understand how living systems respond to weather, climate, and changing seasons.
Radiocarbon dating estimates the age of once-living materials by measuring carbon-14, a radioactive isotope that decays after an organism stops exchanging carbon with the environment. It transformed archaeology, geology, climate science, and the study of recent Earth history.
Epistasis is a genetic interaction in which the effect of one gene depends on one or more other genes. It helps explain why traits are often shaped by networks of genes rather than by single genes acting alone.
RNA interference, often shortened to RNAi, is a gene-silencing system in which small RNA molecules guide protein complexes to matching RNA targets. It helps cells regulate genes, defend against some genetic threats, and gives researchers a precise way to reduce the expression of selected genes.
Protein folding is the process by which a chain of amino acids settles into the three-dimensional shape that lets a protein do its job. Folding connects genetic instructions to working molecules, and mistakes in folding can affect cell health, medicine, biotechnology, and our ability to design new proteins.
The J-2 engine was a liquid-hydrogen and liquid-oxygen rocket engine used on the upper stages of Saturn launch vehicles.
The F-1 engine was the large kerosene-and-liquid-oxygen rocket engine that powered the first stage of NASA's Saturn V launch vehicle.
Saturn V was the three-stage heavy-lift rocket NASA used to send Apollo crews toward the Moon and launch Skylab into orbit.
Direct ascent is a lunar mission architecture in which one spacecraft lands on the Moon and returns to Earth without orbital rendezvous.
Earth orbit rendezvous is a mission architecture in which spacecraft elements meet in Earth orbit before leaving for the Moon or another destination.
Lunar orbit rendezvous is the mission architecture that let Apollo land a small lunar module on the Moon while the command and service module stayed in lunar orbit.
Powered descent initiation is the start of a lunar lander's main engine burn from low approach orbit toward the surface.
Descent orbit insertion is the maneuver that lowers a lunar landing spacecraft from a safe orbit into a lower approach path before powered descent.
Lunar orbit insertion is the braking maneuver that slows a Moon-bound spacecraft enough for the Moon's gravity to capture it into orbit.
Trans-Earth injection is the maneuver that sends a spacecraft away from the Moon or another body onto a return trajectory toward Earth.
Trans-lunar injection is the engine burn or maneuver that sends a spacecraft out of Earth orbit and onto a trajectory toward the Moon.
A free-return trajectory is a spacecraft path that can loop around the Moon or another body and naturally return to its starting planet if no major engine burn occurs.
A near-rectilinear halo orbit is a stretched lunar halo orbit that passes close to the Moon at one end and far from it at the other, making it useful for cislunar mission planning.
A distant retrograde orbit is a high-altitude path around a moon that moves opposite the moon's motion around its planet and can be useful for stable cislunar mission design.
A Lyapunov orbit is a planar periodic path near a collinear Lagrange point, used in mission design and as a building block for other Lagrange-region trajectories.
A Lissajous orbit is a looping spacecraft path near a Lagrange point, often used when a mission needs useful geometry without a fully closed halo orbit.
A halo orbit is a three-dimensional spacecraft path around a Lagrange-point region, useful for missions that need steady viewing geometry and manageable station-keeping.
Lagrange points are special locations in a two-body system where a small object can keep the same relative position with less station-keeping.