# What Is Gravity? > Gravity is the attraction between anything that has mass, from an apple to a galaxy. Here is how Newton and Einstein each explained it, why mass matters, and how gravity shapes everyday life. *Section: Science — By Dr. Nadia Okoro (Science & Health Writer) — Published May 12, 2025 — 5 min read* Canonical URL: https://dailyjunction.org/science/what-is-gravity Tags: gravity, physics, newton, einstein, mass ## Key takeaways - Gravity is the natural attraction between any two objects that have mass; the more mass, the stronger the pull. - Isaac Newton described gravity as a force that weakens with distance, accurately enough to send spacecraft across the solar system. - Albert Einstein went deeper, describing gravity as the bending of space and time by mass, which explains effects Newton's version cannot. - Gravity keeps us on the ground, holds the Moon in orbit, drives the tides and binds galaxies together, yet it is the weakest of nature's fundamental forces. It is the most familiar force in the universe and, in some ways, the strangest. Gravity holds us to the ground, governs the path of every planet, and yet remains the hardest of nature's basic forces to fully explain. The good news is that the core idea is something you can feel every time you drop your keys. Here is what gravity is, and how our understanding of it has deepened over the centuries. ## What gravity is **Gravity is the natural attraction between any two objects that have mass.** Every object with mass pulls on every other object with mass, and the more mass something has, the stronger its pull. You are pulling on the Earth right now, and it is pulling on you. The reason the effect feels one-sided is that the Earth's mass is colossal compared with yours, so its pull dominates, holding you firmly to the ground while your tiny pull on the planet goes unnoticed. Two things set the strength of that attraction: - **Mass.** More massive objects exert a stronger pull. The Sun's enormous mass is what keeps the whole solar system in orbit. - **Distance.** Gravity weakens rapidly as objects move apart, so nearby objects feel a far stronger pull than distant ones. ## Mass versus weight Everyday language treats "mass" and "weight" as the same thing, but in physics they are different, and gravity is the link between them. - **Mass** is the amount of matter in an object. It does not change wherever you go. - **Weight** is the force gravity exerts on that mass. It changes depending on the strength of gravity where you are. This is why an astronaut has the same mass on the Moon as on Earth but weighs only about a sixth as much: the Moon's smaller mass means weaker gravity at its surface. In the apparent weightlessness of orbit, mass has not vanished at all — astronauts and their spacecraft are in fact constantly falling around the Earth together, which is something the agencies that run human spaceflight, such as NASA, are careful to explain. ## Newton: gravity as a force The first great explanation came from **Isaac Newton** in the seventeenth century. According to the popular story, watching an apple fall prompted him to ask whether the same force that pulled the apple to the ground might also hold the Moon in its orbit. Newton's law of universal gravitation said that every mass attracts every other mass with a force that: - **grows with the masses involved**, and - **weakens with the square of the distance** between them — double the distance and the pull drops to a quarter. This was a triumph. The same simple rule explained falling apples, the orbits of the planets and the timing of the tides. It was so accurate that engineers still use Newton's equations today to plan spacecraft journeys across the solar system. For most everyday purposes, Newton's picture is all you need, and the Royal Society, which published his work, helped carry these ideas into the modern scientific age. ## Einstein: gravity as curved spacetime Newton's law worked beautifully but left a deep question unanswered: *how* does one object pull on another across empty space? In 1915, **Albert Einstein** offered a radically different answer with his general theory of relativity. Einstein proposed that space and time are woven together into a single fabric, **spacetime**, and that mass bends this fabric. > A common image is a heavy ball resting on a stretched rubber sheet. The ball creates a dip, and a smaller marble rolling nearby curves toward it — not because of a mysterious pull, but because the surface itself is warped. In this view, the Earth does not so much *tug* the Moon as bend the spacetime around it, and the Moon simply follows the straightest available path through that curved geometry. Objects are not pulled by a force so much as guided by the shape of space and time. This was not just philosophy. General relativity predicted effects Newton's model could not, including: - the slight, otherwise-unexplained shift in **Mercury's orbit**, - the **bending of starlight** as it passes a massive object like the Sun, and - tiny differences in how **time itself runs** depending on gravity — an effect that satellite navigation systems must correct for to stay accurate. Both descriptions are "true" in their domains: Newton's is a superb approximation for everyday situations, while Einstein's is needed for extreme masses, high precision and the largest scales of the cosmos. ## How gravity shapes everyday life Gravity is not an abstraction reserved for physicists. It is at work everywhere: - **It keeps us grounded.** Without it, nothing would stay put on Earth's surface. - **It holds the atmosphere and oceans** in place, making life possible. - **It drives the tides,** as the Moon's gravity tugs the seas, a rhythm that also touches the [climate and weather systems](/science/climate-vs-weather) we experience. - **It governs orbits,** from the Moon around Earth to Earth around the Sun. - **It builds and binds the cosmos,** pulling gas together to form stars and holding entire galaxies in shape. Gravity is also the force that the lift on a wing must overcome — part of the balance of forces explored in [how planes fly](/science/how-do-planes-fly) — and the reason understanding it underpins so much of physics and astronomy, including the basic story of [the Big Bang](/science/what-is-the-big-bang). ## The weakest force Here is the great paradox. Despite ruling planets and galaxies, gravity is by far the **weakest of the four fundamental forces** of nature. A small fridge magnet can lift a paperclip, easily beating the gravitational pull of the entire planet beneath it. Gravity wins at large scales for two reasons: it always attracts, never cancelling itself out, and it reaches across unlimited distances. Over the vastness of space, those small pulls add up to shape the universe. ## The bottom line Gravity is the attraction between anything that has mass, growing stronger with mass and weaker with distance. Newton described it as a force and got us to the planets; Einstein revealed it as the curving of space and time and explained what Newton could not. From a falling apple to the structure of galaxies, gravity is the quiet architect of the universe — the weakest of the fundamental forces, yet the one that shapes the cosmos on the grandest scale. ## Frequently asked questions ### What is gravity in simple terms? Gravity is the pull that objects with mass exert on one another. The Earth's large mass pulls everything toward its centre, which is why things fall down and why we stay on the ground. ### What is the difference between mass and weight? Mass is how much matter an object contains and does not change. Weight is the force of gravity acting on that mass, so it changes with location. You would have the same mass on the Moon but weigh about a sixth as much. ### How did Einstein change our understanding of gravity? Newton treated gravity as a force acting at a distance. Einstein's general relativity describes mass as bending the fabric of space and time, and objects simply follow that curvature. It explains things Newton's model gets slightly wrong, such as the precise orbit of Mercury. ### Why is gravity called the weakest force? Compared with the other fundamental forces, gravity is astonishingly weak: a small magnet can lift a paperclip against the pull of the entire Earth. It dominates the universe at large scales only because it always attracts and reaches across vast distances. ## Sources - [NASA](https://www.nasa.gov/) - [European Space Agency (ESA)](https://www.esa.int/) - [The Royal Society](https://royalsociety.org/) --- Daily Junction — https://dailyjunction.org/science/what-is-gravity