For a long time, humans have envisioned space as an endless, silent void where celestial bodies exist and disappear. Time has been considered a separate, steady flow, carrying us from the past to the future.
However, modern physics has overturned this notion, proving that space and time are inseparable but intertwined into a single entity: spacetime.
Albert Einstein's special theory of relativity showed that spacetime is not just a passive backdrop but a dynamic structure that shapes the universe and how objects move.
It is the invisible thread that holds everything in place, guiding the course of events. Without space and time, the concepts of place and time would become meaningless.
Large objects warp spacetime.
To illustrate the connection between space and time, imagine two people: one remaining on Earth and the other traveling in a spaceship at near the speed of light.
When they meet again, the watch of the person on the spacecraft will show less time elapsed than that of the person on Earth. This phenomenon, known as time dilation, suggests that space and time must function together as part of the same structure.
This is also why astronauts on the International Space Station age a little slower than people on Earth.
Einstein also demonstrated that massive objects like planets and stars are capable of bending spacetime, thereby affecting the motion of surrounding objects. This curvature explains gravity.
The Earth doesn't revolve around the Sun because it's "bound" by an invisible thread, but because it moves along spacetime that's curved by the Sun.
Imagine a stretched piece of cloth; when a large ball is placed on it, the surface of the cloth will indent. If a smaller ball is rolled, it will move in a spiral inward, following the curve of the cloth. Celestial bodies in the universe are similarly affected by the curvature of spacetime.
By demonstrating the connection between space and time, and that gravity is the geometry of this unification, Einstein completely changed how we understand the universe.
He asserted that spacetime is not a passive unit of measurement but an active element in the story of the universe.
The fabric weaves reality.
Space-time is not just a scientific hypothesis, but the very fabric of reality. Every event, from the movement of planets to the ticking of a clock, takes place within space-time.
We cannot define a particular space without considering time, and vice versa. They are inseparable, and together, they define the stage of existence.
Modern physics is built upon this understanding. Relativity, quantum entanglement, cosmology, and many technologies that shape our daily lives all depend on spacetime. It provides the framework for the laws of nature to operate, defining the "where" and "when" of reality.
The impact of spacetime extends far beyond theory. Massive black holes, with their high density, warp spacetime to such an extent that even light cannot escape.
On a smaller scale, our Global Positioning System (GPS) also relies on spacetime to function accurately. GPS satellites orbiting the Earth move at different speeds than ground-based devices due to time dilation caused by gravity.
Without correcting for these changes, GPS positioning would be off by several kilometers each day. Space and time silently shape how we move, communicate, and interact with the world in our daily lives.
Source: https://dantri.com.vn/khoa-hoc/nha-bac-hoc-einstein-noi-gi-ve-khong-thoi-gian-20250922090326350.htm
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