The question of how gravity started is fundamentally tied to the very beginning of our universe and is currently a subject of active research.
According to current models in particle physics, gravity's earliest instance, possibly as quantum gravity, supergravity, or a gravitational singularity, emerged during the Planck epoch. This period, a mere 10-43 seconds after the universe's birth, also witnessed the development of space and time as we know them.
Here's a breakdown:
The Planck Epoch
This incredibly brief moment in the universe's history is when our current understanding of physics reaches its limits. At this stage:
- The universe was extremely hot and dense.
- The four fundamental forces of nature – gravity, electromagnetism, and the strong and weak nuclear forces – were likely unified.
- Our current theories can't fully describe the conditions or the mechanisms that allowed gravity to "separate" and act as we observe it today.
Possible Forms of Early Gravity
Physicists theorize that early gravity may have existed in forms that differ significantly from what we experience daily:
- Quantum Gravity: A theoretical framework that attempts to unify quantum mechanics with general relativity (the theory of gravity).
- Supergravity: A form of field theory that combines the features of supersymmetry and general relativity. It proposes a symmetry between bosons (force-carrying particles) and fermions (matter particles).
- Gravitational Singularity: A point where the equations of general relativity break down, often characterized by infinite density and spacetime curvature. This is thought to exist at the center of black holes and may have been the initial state of the universe.
These models suggest that gravity did not suddenly "appear" but evolved from a more fundamental state alongside space and time itself.
Summary of Gravity's Origins
In short, while we don't know exactly *how* gravity started, current theories suggest it emerged during the Planck epoch (around 10-43 seconds after the Big Bang) along with space and time, possibly as quantum gravity, supergravity, or a gravitational singularity. It is thought that the force of gravity, like the other fundamental forces, developed from a unified force during the very early universe.
