While the sun's gravity keeps the planets in orbit, their gravity also pulls on the sun, causing it and everything else in the solar system to orbit around a mutual balance point called the barycenter—the true center of the solar system.

Planets' high orbital speeds prevent them from falling into their host star

Although the gravitational force attracts a planet and the star it orbits around, the large speed the planet orbits with, which is acquired during its formation process, causes it to continuously miss the star as it orbits around it. This is analogous to theoretically throwing a baseball horizontally faster and faster until it's fast enough to orbit the Earth while attempting to fall to its surface.

The Earth orbits the sun within the Orion Spur arm of the Milky Way galaxy

The solar system is roughly halfway between the galaxy's outer rim and its center, which is located about 25,000 light years away. The Milky Way is itself one of hundreds of thousands of galaxies in the Virgo Supercluster.

How a solar eclipse proved Einstein's theory of gravity

For hundreds of years, Isaac Newton's laws of gravity and motion accurately predicted every observation and measurement involving orbits. With the advance of technology, more precise measurements revealed anomalies, including the orbit of Mercury, which Albert Einstein's general theory of relativity could explain. This article details the two frameworks and how they went head-to-head during an eclipse for gravitational supremacy.

Earth's smooth, continuous motion as it orbits the sun prevents detectable motion

Although humans are sensitive to acceleration, Earth's nearly circular orbit around the sun and its slow spin relative to its size produce negligibly small, minimally changing accelerations. However, the changing seasons and the day-night cycle are evidence of Earth's movement through space, as verified by satellites and telescopes.

Understanding why charged particles from the sun protect Earth from more dangerous particles

The solar wind engulfs the solar system in a protective bubble called the heliosphere, which was first theorized in the late 1950s based on studies of cosmic rays—high-energy particles traveling through space at near light speed. The heliosphere shields the solar system from much of this ionizing radiation originating elsewhere in the Milky Way.

Grasp the earth's orbit around the sun with this interactive

See why seasons exist with this interactive simulator. Toggle between different views of the earth in relation to the sun and watch as the earth's axis causes the sun to shine at different angles throughout the year, causing the weather to fluctuate and more. This simulator clarifies a process many take for granted.

How solar systems form

Learn how our sun, the planets, and other solar system bodies came to be with these videos and an infographic from NASA. Use this resource to visualize how the solar system formed and to model and describe the process.

The sun is not as exceptional as once believed, but it remains rarer than most stars

Once believed to be the center of the universe, the sun is a G-class star, the same category to which about 6% of the Milky Way's stars belong. However, the sun is younger than 85%, more massive than 95%, and more metal-rich than about 93% of all stars. Unlike the sun, half of all stars also exist in multi-star systems.

Differences in the tilts of planetary orbits make perfect alignment impossible

Mercury deviates within 7 degrees of the ecliptic that marks the path of the sun, with the other planets varying from 3 degrees to approximately flat. Even an alignment within 1 degree between all eight planets is estimated to occur only once every 13.4 trillion years.

How its uneven rotation produces the sun's 11-year cycle and flips its magnetic poles

While charged material rises and falls in the sun's convection zone, which induces magnetic fields, different latitudes rotate at different rates, making these fields increasingly turbulent. This builds to a critical point—the solar maximum—where magnetic field-driven events, such as solar flares, become more common before the field collapses and flips, restarting the cycle.

Newton's laws describe how objects resist acceleration and respond to forces

Newton’s first law defines inertia as the tendency of an object to maintain its velocity. His second law connects external force, inertia, and acceleration, while his third law states that forces come in pairs—every action has an equal and opposite reaction.

The moon's gravity pulls water from Earth's poles to produce tides

By attracting all parts of the Earth to varying degrees based on their distance from it, the moon produces an overall pressure that drives water toward the opposite sides of the Earth along the Earth-moon axis, not unlike how squeezing a grape causes it to bulge. This creates high tides along the axis on opposite sides of the Earth and low tides along the perpendicular axis. Without significant water to displace, most lakes do not experience noticeable tides.

Where you are located in a gravitational field affects how quickly you age

The closer something is to the center of a massive object, the greater the strength of the massive object's gravitational field as a result of space-time being depressed more severely. Time passes more slowly the deeper an object is in this gravitational depression, meaning objects in the universe naturally seek to age more slowly.

Replacing the sun with a black hole would quickly collapse life on Earth

A black hole of the sun's mass would only be six kilometers wide, but it would exert the same gravitational pull as the sun. This means the planets would keep their current orbits but no longer receive solar radiation.

What is gravity made of?

Our world at very small scales is governed by quantum mechanics, in which forces and energy come in discrete packets. At large scales, our world is governed by gravity, which moves the planets and stars and can create waves in spacetime. To merge...

According to the Grand Tack model, Saturn stopped Jupiter's inward migration

The model suggests Jupiter migrated inward early in its formation and cleared debris from the inner orbits of terrestrial planets. Saturn's gravitational pull saved what was left of the inner solar system to form Mercury, Venus, Earth, and Mars.

Evidence for a ninth planet in our solar system

Is there a massive ninth planet on the edge of our solar system? Many of our solar system's most distant objects tend to swing out in one direction, hinting at evidence for a previously unknown ninth planet potentially larger than Earth. This theoretical planet's orbital period is estimated to be roughly 20,000 years, revolving around the sun at a distance of 60 billion miles. Experts break down the evidence in this quick video.

Why parts of the Earth are colder when the planet is closer to the Sun

The Earth orbits the Sun in an elliptical shape, and winter in the Northern Hemisphere occurs when the Earth reaches the point in its orbit closest to the Sun, known as perihelion. The lower temperatures result from the hemisphere tilting away from the Sun.

Explaining why Earth's atmosphere doesn't crush us, despite weighing 11.24 quintillion pounds

Gravity pulling down on over 5.1 quintillion kilograms of gases surrounding Earth's surface produces an atmospheric pressure of 15 pounds per square inch (101,325 Newtons per square meter). However, since air surrounds objects, the forces from opposing air pressures normally cancel each other out, eliminating any detectable weight.

Gravity assists are crucial for space travel beyond Mars

By traveling near a moving celestial object, a passing object can gain or lose speed and change direction due to the acceleration provided by their mutual gravity. Some missions are planned around spacecraft performing multiple assists, or slingshots, to reduce fuel requirements for long-distance travel.

Differential rotation and density waves create the arms of spiral galaxies

Stars and gas near the galaxy's center complete an orbit in less time than objects farther out. Pressure waves cause material to bunch, lagging behind stars and gas that orbit closer to the center and forming the arms.

Visualize chaos with the orbit of three or more objects bound by gravity

In this simulation, users can simulate randomized and preset orbital configurations for up to 10 celestial bodies to observe the system's evolution in an interactive 3D space. The same configurations can produce different orbital behavior—a feature of chaos—by making small changes to an object's mass under advanced settings.

What fuels the sun?

The sun is our biggest source of heat and light, but how does this massive powerhouse continue to produce such amazing energy? Basically, it's a fusion reactor. At its core the sun produces all that solar energy through hydrogen fusing and converting into helium, over and over again. Learn more about the entire amazing and explosive process here.

With the exception of Earth, the planets are named after Roman gods and goddesses

Mercury, Venus, Mars, Jupiter, Saturn, Uranus, and Neptune are named after the messenger of the gods, the goddess of love, the god of war, the king of gods, the god of agriculture, the god of the sky, and the god of the sea, respectively. "Earth" comes from Old English and Germanic words meaning "ground."

Hurricanes, which rely on air consistently spinning in the same direction, cannot cross the equator because air curves in opposite directions north and south of it.

All hurricanes have a central eye where no extreme weather phenomena take place

When standing in the eye of a hurricane, you're likely to experience sunny, cloudless skies surrounded by a wall of intense winds and thunderstorms. The physics behind this formation is the same as what causes water to spiral around a hollow cone as it goes down a drain.

Planeterrellas create artificial auroras that mimic the atmospheric displays of light by setting up an electric field between two metal balls in a jar filled with a small amount of air.

All rainbows are 'raincircles' caused by water droplets separating white sunlight into a spectrum of colors, but Earth's surface blocks the bottom half of the circle from our line of sight.

Most of the observable universe's volume consists of voids and supervoids—enormous regions of space with little to no galaxies, stars, or light.

According to the physics of black holes, our 4D reality may be a hologram—a projection of information coded on a 2D surface on the edge of the universe.

Track the location of the Voyager probes, currently between 13 and 15 billion miles away from Earth.

How fusion—which releases energy when two lighter atoms combine to form a heavier atom—differs from fission

After NASA's Voyager 1 captured Earth as a single pixel as it left the solar system in 1990, astronomer Carl Sagan used the image to reflect on humanity's fragility and the responsibility to protect 'the only world we've ever known.'

Explore chaos in this simulation of two double pendulums, where small differences in the release angles produce wildly different outcomes.

Visualize the path of every solar eclipse from 1900 to 2099 and see what each looks like when observed from different locations on Earth.

How Amazon operates a 'flywheel' business model, a self-reinforcing cycle that drives continuous growth

The rivalry between Alexander Hamilton and Thomas Jefferson centered on federalism—the question of how much power the federal government should hold relative to the states.

The price of gas is a composite made up of several different factors, with the federal gas tax making up less than 20% of what drivers pay at the pump.

Volcanoes 'die' when their supply of magma runs out, if they are shifted away from their underlying magma reservoir, or if they get clogged by collapsing or their magma cooling back into rock.

Larger animals like giraffes, elephants, and blue whales have developed a unique defense against cancer, a phenomenon known as Peto's Paradox

SpongeBob exemplifies Aristotle's philosophy for living well because he understands that happiness doesn't come from external factors like money, recognition, or power.

Pure water does not conduct electricity because this flow of energy requires the movement of charged particles, and water is a neutral molecule.

Iran's Revolutionary Guard Corps is independent of Iran's regular army and is one of the most powerful and influential military-political organizations in the Middle East.

Coral polyps reproduce via broadcast spawning, where entire reefs simultaneously release reproductive cells for about one hour, once a year.

The syncytiotrophoblast is the outer layer of the placenta and the largest human cell, spanning an area about twice that of a king-sized bedsheet.

The hormonal disorder PCOS was renamed PMOS in 2026, a move designed to improve care and research by shifting the focus to the hormonal causes of this condition that affects 1 in 8 women.

Researchers believe the brain consolidates memories, processes emotions, and plans for the future during dream states

Browse a detailed visual analysis of over 200,000 similes—comparisons that often use 'like' or 'as'—from popular fiction to see how frequently writers the same idiomatic expressions.

Quincy Jones' 'Big Band Bossa Nova' helped introduce bossa nova—a jazz-influenced Brazilian genre—to the US

The Brothers Grimm were lawyers before they were storytellers, but became interested in fairy tales as they began investigating how rules and customs had been passed down through cultures.