**Gravity, or gravitation, is a natural phenomenon in which all things with mass or energy gravitate toward one another, including planets, stars, galaxies, and even light.** On Earth, gravity gives weight to tangible objects, while the Moon’s gravity causes ocean tides. With a strength of around 1038 times that of the strong interaction, 1036 times that of the electromagnetic force, and 1029 times that of the weak interaction. The least of the four basic forces in physics is gravity.

## Gravity:

Gravity, or gravitation, is a natural phenomenon in which all things with mass or energy gravitate toward one another, including planets, stars, galaxies, and even light. Gravity lends weight to tangible objects on Earth, while the Moon’s gravity generates the ocean tides.

Gravitational attraction led the original gaseous stuff in the Universe to coalesce and become stars, and the stars to gather together into galaxies, hence gravity is responsible for many of the Universe’s large-scale structures. Although gravity has an infinite range, its effects weaken as things get further away.

The general theory of relativity (introduced by Albert Einstein in 1915) most properly depicts gravity as a result of masses traveling along geodesic lines in a curved spacetime generated by an unequal distribution of mass, rather than as a force.

A black hole is the most extreme example of spacetime curvature, from which nothing—not even light—can escape once past the black hole’s event horizon. As a result, it has no discernible effect at the subatomic particle level.

However, Newton’s law of universal gravitation, which describes gravity as a force causing any two figures to be fascinated towards one another, with magnitude equal to the product of their masses and inversely related to the square of its distance between them, is a good approximation for most applications.

Attempts to construct a quantum gravity theory consistent with quantum mechanics, which would allow gravity to be linked in a common mathematical framework (a theory of everything) with the other three fundamental interactions of physics, are currently being investigated.

## Summary:

Gravity is a special phenomenon in which the things having masses revolved around each other. Gravity is best depicted as a result of masses traveling along geodesic lines in a curved spacetime caused by an unequal distribution of mass, rather than as a force, according to Albert Einstein’s general theory of relativity (presented in 1915).

## Origin of gravitational theory:

### Ancient World:

Aryabhata, an Indian mathematician, and astronomer were the first to discover gravity, which explains why objects do not spin out when the Earth rotates. Archimedes, an ancient Greek philosopher, identified the triangle’s center of gravity.

He also proposed that if two equal weights did not have the same center of gravity, the two weights’ combined center of gravity would be at the middle of the line connecting their centers of gravity.

In De Architectura, the Roman architect and engineer Vitruvius proposed that an object’s gravity was determined by its “nature” rather than its weight. Brahmagupta described gravity as an attractive force and used the name gurudwara to describe it.

### Scientific Revolution:

Various Europeans experimented in the mid-16th century to disprove Aristotle’s theory that heavier items fall quicker. Galileo Galilei demonstrated (possibly as a thought experiment) that two balls of various weights falling from a tower would fall at the same velocity in the late 16th century. Galileo showed that gravitational acceleration is the same for all things by combining this knowledge with precise measurements of balls rolling down inclines.

Galileo proposed that objects with a low density and a large surface area fall more slowly in an atmosphere due to air resistance. Galileo correctly predicted that the distance traveled by a falling object is proportional to the square of the time spent falling in 1604.

Between 1640 and 1650, Italian Jesuits Grimaldi and Riccioli confirmed the relationship between the distance of objects in free fall and the square of the time taken. They also calculated the gravity of the Earth by measuring the oscillations of a pendulum.

### Newton’s Theory of Gravitation:

In 1679, English mathematician Isaac Newton received a letter from Robert Hooke describing his concept about orbital motion, which is based in part on an inverse-square force. In 1684, both Hooke and Newton informed Edmond Halley that the inverse-square law of planetary motion had been verified.

Newton’s De Motu corporum in gyrum ('On the motion of bodies in an orbit) derives Kepler’s laws of planetary motion, but Hooke declined to submit his proofs. Halley backed Newton’s development of his work into the Philosophy Naturalis Principia Mathematica (Mathematical Principles of Natural Philosophy), in which the inverse-square rule of universal gravitation is hypothesized.

Newton’s hypothesis was most successful when it was used to predict the existence of Neptune based on Uranus’ motions that could not be explained by the other planets’ actions. Both John Couch Adams and Urbain Le Verrier made calculations that anticipated the planet’s general position, and it was Le Verrier’s calculations that led Johann Gottfried Galle to discover Neptune.

A fault in Newton’s theory was shown by a mismatch in Mercury’s orbit. By the end of the nineteenth century, it had been established that its orbit had tiny perturbations that could not be explained by Newton’s theory, but all attempts to find another perturbing body (such as a planet orbiting the Sun even closer than Mercury) had failed.

Albert Einstein’s new theory of general relativity, which accounted for the minor gap in Mercury’s orbit, addressed the problem in 1915. Mercury’s perihelion has advanced 42.98 arcseconds each century, causing this disparity.

Even though Albert Einstein’s general relativity has superseded Newton’s theory, most modern non-relativistic gravitational calculations still use Newton’s theory because it is easier to work with and gives adequately reliable data for most applications involving sufficiently small masses, speeds, and energies.

Gravity is the weakest of the 4 main essentials in physics, with a strength of around 1038 times that of the strong interaction, 1036 times that of the electromagnetic force, and 1029 times that of the weak interaction.

Current particle physics models suggest that the first instance of gravity in the Universe, possibly in the form of quantum gravity, supergravity, or a gravitational singularity, as well as ordinary space and time, developed during the Planck epoch (up to 1043 seconds after the birth of the Universe), feasibly from a primordial state, such as an untrue vacuum, quantum vacuum, or virtual particle.

## Summary:

Newton’s concept worked best when it was used to predict the existence of Neptune based on Uranus’ motions that could not be described by the operations of the other stars.

### Equivalence principle:

The equivalence principle expresses the idea that all objects fall in the same way, and that the effects of gravity are indistinguishable from certain characteristics of acceleration and deceleration, as examined by a succession of scholars including Galileo, Loránd Eötvös, and Einstein.

Dropping two items of different masses or compositions in a vacuum and seeing if they reach the ground at the same time is the simplest approach to test the weak equivalence principle.

When other forces (such as air resistance and electromagnetic effects) are insignificant, such studies show that all items fall at the same pace. A torsion balance of the type invented by Eötvös is used in more advanced tests. Satellite experiments, such as STEP, are being planned for more precise space tests.

**The following are examples of equivalence principle formulations:**

**• The weak equivalence principle:**

In a gravitational field, a point mass’s trajectory is determined solely by its initial position and velocity and is unaffected by its composition.

**• The Einsteinian equivalence:**

It states that the outcome of any local non-gravitational experiment in a freely falling laboratory is unaffected by the laboratory’s velocity or location in spacetime.

• The strong equivalence principle, which necessitates both of the preceding.

### General Relativity:

The effects of gravitation are attributed to spacetime curvature rather than a force in general relativity. The equivalence principle, which equates free fall with inertial motion and characterizes free-falling inertial objects as being accelerated relative to non-inertial observers on the ground, is the starting point for general relativity.

However, according to Newtonian physics, no such acceleration can occur unless at least one of the objects is subjected to a force.

Matter bends spacetime, according to Einstein, and free-falling objects move along locally straight pathways in curved spacetime. Geodesics is the name for these straight paths. Einstein’s hypothesis, like Newton’s first law of motion, states that if a force is applied to an object, it will diverge from a geodesic.

We no longer follow geodesics while standing, for example, because the Earth’s mechanical resistance exerts an upward push on us, rendering us non-inertial on the ground. This explains why traveling along spacetime’s geodesics is deemed inertial.

The field equations of general relativity, which relate the presence of matter to the curvature of spacetime and are named after him, were found by Einstein. The Einstein field equations are a set of ten nonlinear differential equations that are solved simultaneously.

The components of the metric tensor of spacetime are the solutions of the field equations. A metric tensor is a type of tensor that describes the geometry of spacetime. The metric tensor is used to compute the geodesic pathways for spacetime.

## Who Discovered Gravity?

By distinguishing between two types of motion—uniform and accelerating—Isaac Newton made a conceptual breakthrough. He classified force as any event that causes something to accelerate, and he used it to characterize gravity as a force of attraction between any two masses anywhere in the universe.

### Newton’s Remarkable Discovery

The bubonic plague swept England in 1665–1666, and Newton retired to his family estate as a result of Cambridge University’s closure during that time.

He had a year and a half on the farm to study and reflect on what he’d learned about Kepler’s laws, Galileo’s ideas, and other subjects he’d studied as a Cambridge undergraduate. During those years, he made a significant breakthrough in deducing a mathematical description of gravity’s universal force.

Gravity was a terrestrial force to Newton’s contemporaries, confined to objects near the Earth’s surface. Newton realized that gravity is a universal force in his family’s apple orchard. It reaches the planets, the Moon, the stars, and beyond.

When the teenage student glanced, he noticed an apple on the tree ripening and the Moon orbiting above it. Newton’s breakthrough was discovering that both of these objects are affected by a single force.

### Newton’s Three Laws of Motion

The foundation of Isaac Newton’s analysis of gravity was his grasp of the link between motion and force. Newton suggested three laws of motion based on this understanding:

Uniform motion is defined as an object moving at a consistent speed in a constant direction, such as a sitting object on a table. Nothing happens without force, according to this law, and an item remains in uniform motion unless it is moved upon by a force.

Any change in the speed or direction of movement of an object is referred to as acceleration motion. Circular motion (not uniform motion) at a constant speed, for example, is acceleration. This law expresses the concept in numerical terms, stating that force equals mass times acceleration and that numbers can be entered into the equation.

The third law proposes that forces interact in pairs. At the same time, equal and opposing forces are present. When you push on something, it pushes back at the same time with the same force.

## Summary:

An object moving at a constant speed in a constant direction, such as a sitting object on a table, is said to be in uniform motion. Acceleration motion is defined as a change in the speed or direction of movement of an object.

### Why Doesn’t the Moon Fall!?

The whole thing was “prompted by the fall of an apple.” Isaac was sitting in the garden, contemplating the universe and how it operated, as well as the differences between the apple and the Moon. The Moon does not fall, but the apple does. He attempted to unravel the riddle around this problem and, in the end, he discovered the solution.

When the apple falls to the ground, it falls straight down. However, if that apple is picked up and thrown sideways with a specific amount of horizontal velocity, as Galileo claims, the apple will follow a parabolic path. The harder the apple is thrown, the greater the horizontal distance it takes and the greater the distance it travels.

Newton recognized that if he threw the apple hard enough, it would enter orbit. It would continue to plummet, but it would travel horizontally as it did so, and it would continue to circle the Earth.

That’s what the Moon is doing: it’s orbiting the Earth, descending slowly but steadily, but with enough horizontal velocity to maintain it in orbit. The same phenomenon happens with any planet, moon, body orbiting the Sun, or body orbiting the Earth.

### The Mathematical Equation of Gravity

The concept of qualitative and quantitative gravity in Newton’s theory is straightforward. To describe this force, he devised a mathematical equation. He defined a force in terms of four quantifiable parameters. The mass of an object is the first. The mass of a second object is the second variable. The distance between these two items is the third variable.

Finally, there is the force—that is, the gravitational force. And this is the formula that Newton devised. He explained that force equals a constant—the gravitational constant, with a capital G—times the first mass, times the second mass, divided by the distance squared.

(F = G x [m1 x m ]/d )

As a result, the gravitational attraction between any two objects is proportional to the product of their masses divided by the squared distance between them.

### How Does Newton’s Equation Work?

Newton established that stable orbits are only feasible if there is a 1 over d2 relationship using quite difficult mathematical reasoning. Because the force does not drop off sufficiently with increasing distance, an exponent less than 2 results in a steadily declining orbit.

And if the exponent is more than 2, 2.1, or 2.2, for example, the orbiting body can escape because the force is released too rapidly and the body continues to move outward. The exact relationship can only be found with 1 over d2.

Any two objects, such as the Earth and the Moon, feel an equal gravitational pull, according to Newton’s strong equation. In reality, when an apple falls to Earth, the Earth likewise descends a small distance toward the apple, resulting in a lever law.

Consider a seesaw with two children who are not the same weight: the heavier one must sit closer to the fulcrum point, while the one who is farther away experiences a considerably larger motion on the seesaw.

### Before and After Newton

Galileo experimented with gravity in 1589, dropping balls from the Leaning Tower of Pisa and discovering that, despite their differing weights, they all touched the earth at the same time. After 100 years, Newton’s work had put together a picture of gravity that would last another two centuries. Even though Newton’s theory explained how objects attracted to one another, it did not explain why.

Einstein’s Theory of Relativity, published in 1915, describes gravity as mass distorting time and space. It also illustrates how even light bends when it passes close to stars and other big objects. Despite this more modern tinkering, Newton’s basic theory still explains a lot of the behavior of objects all around the cosmos.

### Gravitational constant:

The gravitational constant denoted by the letter G is an empirical physical constant used in Sir Isaac Newton’s law of universal gravitation and Albert Einstein’s general theory of relativity in the calculation of gravitational effects.

It’s Newton’s constant, which relates the gravitational force between two items to the combination of their masses and the reverse square of their distance. It quantifies the relationship between the geometry of spacetime and the energy-momentum tensor (also known as the stress-energy tensor) in the Einstein field equations.

The measured value of the constant is known to four significant digits with some certainty. Its SI value is roughly 6.6741011 m3kg1s2 in SI units.

C. V. Boys popularised the contemporary notation of Newton’s law using G in the 1890s. Henry Cavendish is credited with making the first implicit measurement with an accuracy of less than 1% in a 1798 experiment.

## What are the specifics of Gravity?

### Earth’s gravity

Every planetary object (including the Earth) is encircled by its gravitational field, which may be thought of as exerting an attractive pull on all objects using Newtonian physics. The strength of this field at any given point above the surface is related to the planetary body’s mass and divided by the square of the distance from the center of the body, assuming a spherically symmetrical planet.

The gravitational field’s strength is proportional to the acceleration of objects affected by it. Falling objects near the Earth’s surface accelerate at different rates depending on latitude, surface characteristics such as mountains and ridges, and maybe extremely high or low sub-surface density. Under the International System of Units, the International Bureau of Weights and Measures defines a standard gravity value for weights and measures (SI).

Even though it has been proved to be overly high by nearly five parts in ten thousand, the standard value of 9.80665 m/s2 was chosen by the International Committee on Weights and Measures in 1901 for 45° latitude.

Even though it applies more accurately to the latitude of 45°32’33, this number has persisted in meteorology and several standard atmospheres as the value for 45° latitude.

This indicates that an item falling freely near the Earth’s surface increases its velocity by 9.80665 m/s (32.1740 ft/s or 22 mph) for each second of its descent, assuming the standardized value for g and neglecting air resistance.

After one second, an item will have a velocity of 9.80665 m/s (32.1740 ft/s), about 19.62 m/s (64.4 ft/s) after two seconds, and so on, adding 9.80665 m/s (32.1740 ft/s) to each resulting velocity. Also, considering air resistance, any objects will hit the ground at the same moment when dropped from the same height.

### Equations for a falling body near the surface of the Earth

Newton’s equation of universal gravitation is simplified to F = mg under the premise of constant gravitational pull, where m is the mass of the body and g is a constant vector with an average value of 9.81 m/s2 on Earth.

The weight of the object is the resultant force. Gravitational acceleration is equal to this g. When a stationary object is allowed to fall freely under gravity, it falls a distance proportional to the square of the time elapsed.

A stroboscopic flash at 20 flashes per second was used to capture the image on the right, which spans half a second. The ball lowers one unit of distance (approximately 12 mm) during the first 1/20 of a second; by 2/20, it has plummeted a total of 4 units; by 3/20, 9 units, and so on.

The potential energy, Ep, of a body at height h is given by Ep = mgh (or Ep = Wh, with W denoting weight) with the same constant gravity assumptions. Only tiny distances h from the Earth’s surface are appropriate for this expression.

The statement for the maximum height achieved by a vertically projected body with beginning velocity v is similarly useful only for short heights and modest initial velocities.

### Gravity and astronomy

Newton’s law of gravity has been used to obtain much of the exact information we have about the planets in the Solar System, the mass of the Sun, and the features of quasars; it has even been used to infer the existence of dark matter.

Although we have not visited all of the planets or the Sun, we are familiar with their masses. These masses are calculated by applying gravity equations to the orbit’s measured properties. Because of the force of gravity pushing on it, an object in space maintains its orbit.

Planets revolve around stars, stars revolve around galactic centers, galaxies revolve around a center of mass in clusters, and clusters revolve around superclusters. The gravitational force exerted on one object by another is proportional to the product of their masses and inversely proportional to the square of their distance.

### Gravitational radiation

According to general relativity, energy can be transmitted out of a system via gravitational radiation. Curvatures in the space-time metric can be created by any accelerating mass, which is how gravitational radiation is transferred away from the system.

The Earth-Sun system, pairings of neutron stars, and pairs of black holes are examples of co-orbiting objects that can cause space-time curvatures. Exploding supernovae are another astrophysical phenomenon that is expected to lose energy in the form of gravitational radiation.

In 1973, measurements of the Hulse–Taylor binary provided the first indirect evidence for gravitational radiation. A pulsar and neutron star are in orbit around each other in this system. Its orbital period has decreased due to a loss of energy since its detection, which is consistent with the amount of energy lost due to gravitational radiation. In 1993, the Nobel Prize in Physics was awarded for this work.

### Speed of gravity

In December 2012, a Chinese scientific team stated that it has obtained measurements of the phase lag of Earth tides during full and new moons, which appear to illustrate that gravity and light travel at the same speed.

This means that if the Sun suddenly vanished, the Earth would continue to orbit the empty spot for 8 minutes, the time it takes light to traverse that distance. In February 2013, the team’s findings were published in the Chinese Science Bulletin.

In October 2017, gravitational wave signals were detected by the LIGO and Virgo detectors within 2 seconds of gamma-ray satellites and optical telescopes receiving signals from the same direction. The speed of gravitational waves was confirmed to be the same as the speed of light.

## Frequently Asked Questions:

**Usually people ask questions about this keyword. some of them are given below;**

### 1: Who truly discovered gravity?

**Isaac Newton revolutionized our understanding of the universe.** In his lifetime, he was revered for discovering the principles of gravity and motion, as well as inventing calculus. He influenced our reasonable worldview.

### 2: How did Isaac Newton discover gravity?

**Newton is said to have discovered Gravity while contemplating the forces of nature after seeing a falling apple.** Whatever happened, Newton concluded that falling things like apples must be subjected to some force, otherwise they would not begin to move from their resting position.

### 3: When was gravity first discovered?

**In 1687, Isaac Newton published a complete theory of gravity.** Newton was the first to develop a theory that applied to all objects, large and tiny, using mathematics that was ahead of its time, even though others had thought about it before him.

### 4: What would happen if gravity wasn’t discovered?

**Humans and other objects would be weightless if gravity did not exist.** We wouldn’t immediately start floating if Earth’s gravity suddenly vanished. Humans – and anything else with mass, such as automobiles and buildings — would become extraordinarily fast-moving tumbleweeds if there was no gravitational pull.

### 5: How did gravity change the world?

**Newton’s theory helped to establish that all objects, no matter how little or great, are subject to gravity.** The ebbs and flows of rivers and tides are caused by gravity, which helps keep the planets spinning around the sun.

### 6: Did Einstein discover gravity?

**The general theory of relativity (introduced by Albert Einstein in 1915) most properly depicts gravity** as a result of masses traveling along geodesic lines in a curved spacetime generated by an unequal distribution of mass, rather than as a force.

### 7: Is Newton’s law of gravity true?

**The 17th-century gravitational law is a milestone in physics, and it still holds today. The law of universal gravitation was put to the test, and it was found to be false.** At least not in respect to the black hole. Scientists are now betting on Einstein’s theory of general relativity, according to fresh discoveries.

### 8: Why did Newton call it gravity?

Take a time to consider and appreciate the “occult” aspect of this interplay between matter without contact and Newton’s absolute genius. To explain how stars, planets, and galaxies moved in space, **Einstein invented a force that he termed gravity or gravitational attraction.**

### 9: How gravity is created?

**The mass of the Earth contributes to its gravitational pull.** All of its mass exerts a cumulative gravitational pull on all of your body’s mass. The gravitational pull you exert on Earth is the same as it is on you. However, because Earth is so much larger than you, your force has little effect on our globe.

### 10: Why Newton is the greatest scientist?

**Isaac Newton was reportedly regarded as “the highest genius and most mysterious individual in the history of science” by New Scientist.** His three most major discoveries — the idea of universal gravitation, the nature of white light, and calculus — are the reasons he is regarded as such a significant figure in science history.

## Conclusion:

Gravity, or gravitation, is a natural phenomenon in which all objects with mass or energy, such as planets, stars, galaxies, and even light, gravitate toward one another. Gravity is best depicted as a result of masses traveling along geodesic lines in a curved space-time caused by an unequal distribution of mass, rather than as a force, according to Albert Einstein’s general theory of relativity (presented in 1915).

The LIGO and Virgo detectors discovered gravitational wave signals within 2 seconds of gamma-ray satellites and optical telescopes detecting signals from the same direction in October 2017. Gravitational waves have been confirmed to travel at the same speed as light.