The human brain is the control organ of the nervous system. It receives signals from the body and the outside world, compares them with stored patterns, sends instructions, and keeps basic life functions running even when you are not thinking about them. It does this through connected regions, electrically active cells called neurons, and support cells that keep the whole system stable and fast.[a] Start…
Space weather is the changing state of the space environment around Earth, driven mainly by the Sun. The two names people hear most are solar flares, which are bursts of radiation, and coronal mass ejections, or CMEs, which are expanding clouds of plasma and magnetic field. When the timing, direction, and magnetic setup line up, those solar events can disturb radio links, navigation signals, satellite…
The Kuiper Belt is a broad disk of icy bodies beyond Neptune, while the Oort Cloud is a far larger spherical shell of icy objects far beyond that. Together, they mark the outer small-body reservoirs of the solar system and help explain where many comets come from.[a][b] This article explains how these regions differ in shape, distance, formation, and evidence, and why the phrase “edge…
Gravitational waves are tiny stretches and squeezes of space-time produced when massive objects accelerate, especially in tight, fast systems such as merging black holes or neutron stars. They travel at the speed of light and carry direct information about motion, mass, and gravity that ordinary light cannot always provide on its own.[a] A Clear Starting Point These waves are not light, sound, or particles. They…
Mars is the fourth planet from the Sun, a cold rocky world with a very thin atmosphere, two small moons, polar ice, giant volcanoes, deep canyons, and strong evidence that liquid water shaped parts of its surface early in its history.[a][b] What Matters Most Mars is not just a smaller Earth with less water. It is a planet that changed deeply over time, from a…
The multiverse is a broad label for ideas suggesting that our observable universe may be only one part of a larger reality. In some models, other universes lie far beyond our cosmic horizon; in others, they appear as separate bubble regions born from inflation; in the many-worlds reading of quantum mechanics, they are branching outcomes of one quantum state. The most important point is simple:…
The asteroid belt is the broad band of rocky bodies that orbits the Sun between Mars and Jupiter. It matters because it preserves leftover material from early solar-system formation, feeds some of the meteorites studied on Earth, and helps scientists trace how small bodies move from stable orbits into planet-crossing ones.[a] A Short Opening View This region is not a solid ring and not a…
A history-changing space mission is one that opens a new capability, returns evidence nobody had before, or changes how later missions are designed. By that standard, Apollo and Voyager sit at the center of space history, but they are part of a longer chain that also includes Mars landers, space telescopes, orbital laboratories, and frontier probes that pushed the map outward. Why These Missions Still…
Comets and asteroids are small bodies that orbit the Sun, but they are not the same kind of object. In simple terms, asteroids are usually more rock-heavy, while comets contain more ice and can release gas and dust when sunlight warms them. Both preserve very old material from the early solar system, so they help explain what the solar system was made of before the…
The Milky Way is a barred spiral galaxy that contains the Solar System. Its bright disk stretches a little over 100,000 light-years, holds a few hundred billion stars, and places the Sun in the Orion Spur rather than near the center.[a][c] The Picture That Matters First The Milky Way is not just the pale band seen in the night sky. That band is the inside…