Spacetime

Spacetime: A Mathematical Model that Combines Dimensions of Space and Time

What is spacetime?

Definition of spacetime:

In physics, spacetime is a mathematical model that combines three dimensions of space and one dimension of time in a single four-dimensional freeze sequence. Spacetime diagrams can be used to visualize relative effects, such that their use allows different reviewers to see where and when events occur differently.

WHO DISCOVERED SPACE-TIME?

The famous physicist Albert Einstein helped develop the idea of space-time as part of his theory of relativity. Prior to his pioneering work, scientists had two separate theories to explain physical phenomena: Isaac Newton’s laws of physics described the motion of massive objects, while James Clerk Maxwell’s electromagnetic models explained the properties of light, 

But experiments conducted at the end of the 19th century suggested that there was something special about light. Measurements showed that light always traveled at the same speed, no matter what. And in 1898, the French physicist and mathematician Henri Poincaré speculated that the velocity of light might be an unsurpassable limit. Around that same time, other researchers were considering the possibility that objects changed in size and mass, depending on their speed.

Einstein pulled all of these ideas together in his 1905 theory of special relativity, which postulated that the speed of light was a constant. For this to be true, space and time had to be combined into a single framework that conspired to keep light’s speed the same for all observers.

A person in a superfast rocket will measure time to be moving slower and the lengths of objects to be shorter compared with a person traveling at a much slower speed. That’s because space and time are relative — they depend on an observer’s speed. But the speed of light is more fundamental than either.

The conclusion that space-time is a single fabric wasn’t one that Einstein reached by himself. That idea came from German mathematician Hermann Minkowski, who said in a 1908 colloquium, “Henceforth space by itself, and time by itself, are doomed to fade away into mere shadows, and only a kind of union of the two will preserve an independent reality.”

The space-time he described is still known as Minkowski space-time and serves as the backdrop of calculations in both relativity and quantum-field theory. The latter describes the dynamics of subatomic particles as fields, according to astrophysicist and science writer Ethan Siegel.

Spacetime concept in the 20th century

By the 20th century, there was the notion that the three-dimensional geometry of the universe (its spatial expression in terms of coordinates, distances, and directions) was one-dimensional time. But in 1905 Albert Einstein based his seminal work on special relativity on two terms and he stated –

  1. The laws of physics are invariant in all inertial systems (ie non-accelerating frames of reference) (ie are the same).
  2. The speed of light in the vacuum is the same for all reviewers, regardless of the speed of the light source.

The logical consequence of taking these positions together is inseparable along the four dimensions. This leads to many counterintuitive results such that, apart from being independent of the speed of the light source, the speed of light has the same speed regardless of the frame of reference in which it is measured; The temporal order of distances and even pairs of events when measured in different inertial frames of reference (this is simultaneous relativity) and the linear additivity of velocities are no longer correct.

Kinematics (study of moving bodies)

Einstein formulated his theory in the context of kinematics (the study of moving bodies). His theory was a breakthrough advance on Laurentz’s 1904 electromagnetic phenomena and Poincaré’s electrodynamic theory. Although these theories included equations similar to those introduced by Einstein (i.e., Lorentz transformation), they were essentially models proposed to explain the results of various experiments – including the famous Michelson – Morley interferometer experiment – which currently exists It was very difficult to fit.

In 1908 Hermann Minkowski — once one of the young Einstein professors of mathematics in Zürich — presented a geometric interpretation of special relativity, describing three spatial dimensions of time and space in the same four-dimensional continuum as Minkowski’s space. Is known. A key feature of this interpretation is the formal definition of spacetime intervals. Although measurements of distance and time between events differ for measurements taken in different reference frames, the spacetime interval is independent of the inertial frame of reference in which they are recorded.

Minkowski’s geometric interpretation of relativity

Minkowski’s geometric interpretation of relativity was instrumental to Einstein’s development of his 1915 general theory of relativism, in which he showed how large-scale and energy curves are for this pseudo-Reimanold manifold over this flat lifetime.

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