Einstein’s theory of general relativity was revolutionary, but failed

  • General relativity The principles govern both the very small and the largest objects in our universe, but not the quantum world.
  • Gravity it may not be a force like the other physical forces, but the result of the curvature of space-time.
  • Physicists are still exploring many mysteries, such as why black holes they have a singularity at their center.

From crushing particles to analyzing the properties of a supermassive black hole, much of the research in physics takes place well beyond the realm of our everyday experience. However, there is a hallmark of physics that even a crawling baby can intuitively understand: gravity.

The effects of this force are both small (working against a baby learning to walk) and vast (controlling the movements of cosmic bodies, such as Earth, through its invisible orbits in space). Aside from our own experiences, our first formal introduction to gravity is usually through Newton’s lens, which describes gravity as:

  • a constant force on Earth (small g) equal to 9.8 square meters
  • gravity beyond the limits of the Earth with Newton’s gravitational constant (big G)

While this understanding generally works well for everyday life, it’s far from the whole story. Just 200 years after Newton’s death, Einstein would publish a new theory of gravity in 1915 called the theory of general relativity. It would transform our understanding of physics forever.

Popular Mechanics preview All sections

nicolas yunesprofessor of astrophysics and relativity at the University of Illinois Urbana-Champaign, tells popular mechanics that general relativity shows that gravity may not even be a force at all.

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

general relativity vs. special

An important point to clarify before delving into the meat of general relativity is that Einstein actually proposed two famous theories of relativity. Ten years before writing down the ideas of general relativity, 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 tear the fabric of space-time apart… this curvature itself is gravity.

elena giorgio is an assistant professor of mathematics at Columbia University whose research has a special focus on general relativity. she explains to popular mechanics that an important difference between the two theories is that special relativity “only considers small objects moving in empty space-time, whereas in general relativity, massive objects like stars or galaxies are allowed.”

In other words, special relativity exposes important ideas like the speed of light being the same for all observers, and the laws of physics holding true regardless of frame of reference (for example, on Earth or in a rocket at full speed). Meanwhile, general relativity introduced super-heavy objects and gravity to the party.

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

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

Instead of an outside force creating gravity, the theory of general relativity shows that this curvature itself is gravity. This idea may seem impossible given our own experience of gravity, but for more than 100 years scientists have seen its repercussions in space.

“From the first observations of light bending during an eclipse, to the most recent detection of gravitational waves, every observation we make appears to be consistent with the predictions of general relativity,” Yunes says. “At least, until now.”

In addition to detecting gravitational waves, waves in space time created when there is a massive collision in space – the effects of general relativity can also be used to help scientists see more into space through something called gravitational lensing. Simply put, the gravity well created by a heavy object like a star works to shed distant light around it, making it possible for astronomers to detect light that would have previously been too far away.

What we don’t know yet

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

Another shortcoming of Einstein’s theory of general relativity is that while it seems to do a very good job of explaining gravity for extremely large things, it cannot be applied to the extremely small domain of relativity. quantum world. at the level of subatomic particlesthe effect of gravity is practically insignificant compared to other forces such as electromagnetism, weak nuclear forcesand strong nuclear forces.

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

As for continuing to test general relativity in its own domain, 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 emitted by the merger of two black holes are only understood to a certain approximation, leaving room for further improvements,” he says. “[Including] the future plan to have [LIGO-like] interferometers in space that will be even more precise.” LIGO is a laser interferometer gravitational wave observatory, and is the largest in the world, having detected dozens of gravitational wave sources, including from ten merging black hole pairs and two collision pairs neutron stars.

Leave a Reply

Your email address will not be published. Required fields are marked *