From the collapse of hydrogen clouds in stars to the connecting of galaxies – gravity is one of the few forces that determines the evolution of the universe.

In a way, the history of gravity is also the history of physics, where some of the most famous names in the field are famous for describing the force that drives their lives. But even after more than 400 years of study, the mysterious power still lies beneath some of physics’ greatest mysteries.

Every day we are affected by the four fundamental forces. Strong interaction and weak interaction only work at the centers of atoms. The electromagnetic force controls highly charged objects (such as electrons and protons) and gravity controls objects with mass.

The first three forces have largely eluded human attention until recent centuries, but people have long thought about gravity acting on everything from raindrops to cannonballs.

gravity research

Ancient Greek and Indian philosophers realized that objects naturally move towards the ground, but Isaac Newton needed insight to elevate gravity from the incomprehensible disposition of objects to a measurable and predictable phenomenon.

Newton’s era

Newton’s leap made famous in his 1687 treatise, Philosophiae Naturalis Principia Mathematica, was to understand that every object in the universe, from sand to the biggest stars, attracts any other object. The concept brought together seemingly unrelated events, from apples falling to Earth to planets orbiting the Sun.

Isaac Newton / Photo google

He also quantified the numbers for gravity: he determined that doubling an object’s mass makes gravity twice as strong, and that the convergence of two objects quadruples their mutual attraction. Newton placed these ideas in the law of universal gravitation.

Newton’s definition of gravity was accurate enough to reveal the existence of Neptune before anyone saw it in the mid-1800s, but Newton’s law isn’t perfect. In the 1800s, astronomers noticed that the ellipse, defined by Mercury’s orbit, was moving around the Sun faster than Newton had suggested; this suggested that there was a slight inconsistency between his law and the laws of nature. Eventually, the mystery was solved by Albert Einstein’s theory of general relativity, published in 1915.

Einstein’s era

Before Einstein published his groundbreaking theory, physicists knew how to calculate a planet’s gravitational pull, but their understanding of why gravity behaves this way went a little further than that of ancient philosophers. These scientists understood that all objects attract others with an instantaneous and infinitely far-reaching force, as Newton assumed, and many physicists of the Einstein era were satisfied with this. But working on the special theory of relativity, Einstein determined that nothing can move instantaneously and that gravity should be no exception.

Albert Einstein / Photo google

According to the Stanford Encyclopedia of Philosophy, physicists for centuries saw space as an empty structure in which events confronted. It was absolute, immutable, and in fact – in any physical sense – nonexistent. The general theory of relativity transformed space and time from a static background into matter like air in a room. Einstein believed that space and time together made up the fabric of the universe, and that this “space-time” material could be stretched, compressed, bent and rotated – dragging anything.

Einstein suggested that the form of space-time produces a force we perceive as gravity. A concentration of mass (or energy) like the Earth or the Sun distorts the space around it, just as a rock changes the flow of a river. When other objects move nearby, they follow the curvature of space, much like the leaf of a tree follows a vortex around a rock (although this metaphor isn’t perfect, space-time isn’t exact, at least when it comes to planets orbiting the Sun). . We see planets spinning and apples falling as they travel in the distorted form of the universe.

Gravity of cosmic bodies affects space-time issue / Photo physics world

Einstein’s General Theory of Relativity, a set of formulas showing how matter and energy deform space-time, were adopted when they successfully predicted changes in Mercury’s orbit and the deflection of starlight around the Sun during the 1919 solar eclipse.

The modern definition of gravity predicts as accurately as the interaction of masses, which has become an instruction for space exploration.

modern age

American astronomers Vera Rubin and Kent Ford noticed in the 1960s that galaxies rotate so fast that they form stars, like a dog shaking water. But since the galaxies they studied didn’t rotate, something seemed to be helping them stick together. The careful observations of Rubin and Ford provided strong evidence to support the early theory proposed by Swiss astronomer Fritz Zwicky in the 1930s that some form of invisible mass is accelerating galaxies in the nearest cluster.

Many physicists now suspect that this mysterious “dark matter” has distorted space-time so much that galaxies and clusters of galaxies remain intact. But others question whether gravity itself can pull more on the galaxy, in which case Newton’s and Einstein’s equations will need to be adjusted.

Changes in general relativity must really be subtle, as researchers have recently begun to explore one of the theory’s most subtle predictions: the presence of gravitational waves, or ripples, in space-time caused by the acceleration of masses in space.

A new era in astronomy

Since 2016, a research collaboration managing three detectors in the United States and Europe has measured large numbers of gravitational waves traveling through Earth. The new detectors are approaching and ushering in a new era of astronomy, in which researchers study distant black holes and neutron stars not by the light they emit but by the way they affect the fabric of space in collision.

Gravitational waves / Photo NASA

However, a number of experimental advances in the general theory of relativity (GTR) demonstrate its flaws, which many physicists see as a fatal theoretical failure. The fact is that while HAZ describes classical space-time, the universe is quantum, or made up of particles (or “quanta”) such as quarks and electrons.

The classical notion of space (and gravity) as a single smooth fabric contrasts with the quantum picture of the universe as a collection of sharp little bits. How to extend the dominant Standard Model of elementary particle physics to encompass all known particles, as well as three other fundamental interactions (electromagnetism, weak interaction, and strong interaction) at the particle level, space and gravity remains a major challenge. So we still need to unravel the deepest mysteries of modern physics.