While Isaac Newton described gravity as a force and Albert Einstein revealed it as a curvature of spacetime, modern physics still struggles to fully comprehend it. Today, gravity presents some of the most profound puzzles in science, primarily because our two greatest theories—General Relativity (for the very large) and Quantum Mechanics (for the very small)—don’t agree on how gravity works.  

The Incompatibility Problem

The biggest puzzle is the conflict between Einstein’s theory and quantum mechanics.  

• Einstein’s General Relativity treats gravity as a smooth, continuous curvature of spacetime caused by mass and energy. It works perfectly for large-scale phenomena like planetary orbits, galaxies, and the expansion of the universe.  

• Quantum Mechanics describes the other three fundamental forces (electromagnetism, the strong force, and the weak force) as being carried by discrete particles called bosons. For example, the photon is the force carrier for the electromagnetic force.  

Physicists hypothesize a similar particle for gravity, the graviton, but this concept clashes with general relativity’s view of gravity as a smooth fabric. When physicists try to merge the two theories, the math breaks down, producing infinite, nonsensical results. This is the quest for quantum gravity, a single theory that can describe all forces at all scales.  

The Mystery of Dark Matter and Dark Energy

Beyond the quantum realm, gravity’s behavior on the cosmic scale also presents huge mysteries.

• Dark Matter: When we observe the rotation of galaxies, they spin so fast that they should fly apart. The gravitational pull from all the visible matter (stars, gas, and dust) isn’t strong enough to hold them together. To explain this, scientists hypothesize the existence of dark matter, an invisible substance that doesn’t emit, reflect, or absorb light but has a gravitational pull that makes up about 27% of the universe. The puzzle isn’t just “what is it?” but also “is it even real, or is our understanding of gravity flawed at large scales?”  

• Dark Energy: Even more puzzling is the fact that the expansion of the universe is accelerating. The gravitational pull of all matter should be slowing it down, not speeding it up. To account for this, physicists propose dark energy, a mysterious repulsive force that works against gravity and makes up about 68% of the universe. We don’t know what it is or how it works. It’s the ultimate cosmic puzzle.  

What is interesting about gravity

From Newton’s falling apple to Einstein’s curved spacetime, our understanding of gravity has come a long way, yet this familiar force remains one of the biggest puzzles in physics.

Every time you drop a cup, watch the tides roll in, or feel your weight pressing on the ground, you’re experiencing gravity. It is the most familiar of nature’s forces, yet also the most mysterious. It binds us to Earth, holds the planets in their courses, and sculpts the fate of galaxies. 

Gravity is not just cosmic; it’s practical. Engineers rely on it when launching satellites, predicting orbits, or planning missions to Mars. Precision measurements of gravity are used to detect underground water reserves, track ice loss from glaciers, and even monitor tectonic shifts. 

Yet, gravity never entered human consciousness till the 17th century. Until the great Isaac Newton introduced one of the most profound ideas in science — that the same force pulling apples to the ground keeps the Moon in orbit around the Earth.

Newton himself came up with this anecdote about it,  and it has grown with retellings. The story has grown with retelling.  Around 1666, as he sat in the garden of his family home in Lincolnshire, he saw an apple fall from a tree. That prompted him to wonder: if an apple falls to the ground, might the Moon be falling too, perpetually pulled toward the Earth but kept aloft by its sideways motion?

From this thought came the law of universal gravitation: every object in the universe attracts every other with a force proportional to their masses and inversely proportional to the square of their distance. With one sweeping insight, Newton explained both earthly and celestial motions

Isaac Newton once wrote to Robert Hooke. It was this humility which led him to figure out one of the fundamental forces of nature

Gravity is a weak force

Unlike the electromagnetic force or the strong nuclear force, gravity is universal: it acts on all matter, across all distances, and it never switches off. But, despite ruling the cosmos, gravity is astonishingly weak compared to the other forces of nature. To see this clearly, physicists compare how different forces act on the same particles.

Take a proton and an electron: the electromagnetic force of attraction between them is about  times stronger than their gravitational attraction. That’s why atoms, molecules, and chemistry are governed by electromagnetism, while gravity is irrelevant on such small scales.

This extreme weakness has profound implications. Gravity only becomes dominant when enormous masses are involved — stars, planets, galaxies. At the particle level, its effects are drowned out by other forces. And this is why physicists have found it so difficult to quantize gravity. The graviton – the particle hypothesised to mediate the force of gravity — if it exists, would interact so faintly that no experiment could possibly detect it with today’s technology.

Gravity’s weakness may be the very reason it is both the grand architect of galaxies and the last fundamental force resisting our attempts at unification.

Please like Subscribe comment your precious comment on universe discoveries

Full article source google

https://www.amazon.in/b?_encoding=UTF8&tag=555101-21&link

https://www.buymeacoffee.com/Satyam55

https://youtube.com/shorts/GlkqZ1Y10JY?si=4fGR-OfOwOfqLTal

Please click on the above link to see gravity is mysterious video