Wednesday, February 1, 2023

Was Einstein wrong about relativity?


    From colliding particles to analyzing the properties of supermassive black holes, much of physics research goes far beyond our everyday experience. However, there is one distinguishing feature of physics that even a crawling baby can intuitively understand: gravity.

    The effects of this force are both small (it works against a child learning to walk) and huge (it controls the motion of cosmic bodies, such as the Earth, through their invisible orbits in space). Outside of our own experiences, our first formal introduction to gravity is often through the lens of Newton, who describes gravity as both:

    • A constant force (small G) on Earth equal to 9.8 m squared
    • Gravity beyond the limits of Earth with Newton’s gravitational constant (Big G)

      While this interpretation often works well in everyday life, it is far from the whole story. In 1915, 200 years after Newton’s death, Einstein published a new theory of gravity called the theory of general relativity. It would change our understanding of physics forever.

      nicholas younesProfessor of Astrophysics and Relativity at the University of Illinois Urbana-Champaign explains popular mechanics General relativity suggests that gravity may not even be a force.

      “According to Einstein, gravity is then not an ‘instantaneous force’ as Newton predicted, but rather a manifestation of the curvature of spacetime,” he says.

      General Relativity vs Special Relativity

      An important point that must be made before getting into general relativity is that Einstein actually proposed two well-known theories of relativity. Ten years before he put the ideas of general relativity to paper, he wrote a theory called special relativity.

      Einstein predicted that massive objects in space, such as planets or even black holes, would act like cosmic bowling balls and pull down the fabric of spacetime… this curvature is gravity.

      ,

      Elena Giorgi is an assistant professor of mathematics at Columbia University, and his research focuses on general relativity. explain to popular mechanics A key difference between the two theories is that special relativity “considers only small objects moving in empty space-time, whereas general relativity allows for massive objects such as stars or galaxies.”

      In other words, special relativity establishes important ideas such as that the speed of light is the same for all observers and that the laws of physics apply regardless of frame of reference (for example, on Earth or in a rocket at full speed). There are For its part, general relativity introduced supermassive objects and gravity.

      “General relativity says that space and time form a unified continuum that can be distorted, bent, or stretched in the presence of matter,” Yunes explains.

      An easy way to visualize this is to imagine what would happen if we put a bowling ball on a flat mattress. Intuitively, we might expect the heavy object to sink into the mattress and cause the area around it to bulge downward. Einstein predicted that massive objects in space, such as planets or even black holes, would act like cosmic bowling balls and pull down the fabric of space-time.

      Rather than gravity being created by an external force, the theory of general relativity suggests that the curvature itself is gravity. The idea may seem improbable given our own experience of gravity, but scientists have been observing its effects in space for over 100 years.

      “From the first observations of the bending of light during eclipses to the most recent discovery of gravitational waves, everything we observe seems to be consistent with the predictions of general relativity,” Yunes says. “At least, until now.”

      In addition to detecting gravitational waves (ripples in spacetime created when massive collisions occur in space), the effects of general relativity can also be used to help scientists look further into space through something called gravitational lensing. Could Simply put, the gravitational well created by a massive object like a star causes distant light to slip around it, allowing astronomers to detect light that would previously have been much farther away.

      what we don’t know yet

      Although general relativity has not yet been disproved, there are still unresolved questions about the theory. For example, do black holes really have a singularity at their center, Yunes says, or whether general relativity could be applied to the early universe, Giorgi says. A singularity represents a situation where our current understanding of physical laws breaks down. For example, the gravity at the center of a black hole is so great that the volume of matter appears to be zero, which is not possible. Therefore, a part of our understanding is missing.

      Another shortcoming of Einstein’s theory of general relativity is that, although it explains gravity of very large objects very well, it cannot be applied to the extremely small confines of the quantum world. At the level of subatomic particles, the effect of gravity is practically negligible compared to other forces such as electromagnetism, weak nuclear forces, and strong nuclear forces.

      Connecting these two worlds with a single theory is a great dream for physicists, but so far no one has managed to find it.

      To continue testing general relativity within its scope, Giorgi says that continuing to study black holes and gravitational waves with increasing sensitivity will continue to help test the limits of this theory.

      “Many aspects of the detection of gravitational waves emanating from the merger of two black holes are only roughly understood, leaving room for further improvement,” he says. “There are also future plans to place a LIGO-like interferometer in space, which will be even more precise.” LIGO is a laser interferometer gravitational wave observatory, and the largest in the world, which has detected dozens of sources of gravitational waves, including ten pairs of merging black holes and two pairs of colliding neutron stars.

Nation World News Desk
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