Why does light bend near a large mass? | Scientists answer Sciences

The culprit is gravity. Gravity is defined as the attraction caused by any body or body having mass on another body. The greater the mass of an object, the greater the gravitational force it exerts.

Although it is not known if this was actually true, the English physicist and mathematician Isaac Newton (1643-1727) is said to have had a “Eureka Moment” when he saw an apple fall from a tree (another version is that the poor apple fell into Head!). But behind this fall, whether it was true or not, there was a question: Why does the apple always fall perpendicular to the ground?

From here, Newton concluded that the Earth must exert an attractive force, and he called it gravity and strengthened its definition. With this seed he formulated the “Theory of Universal Gravitation” (1687), which precisely describes the way bodies move within a gravitational field, explaining not only the fall of bodies to Earth, but also the motion of bodies and planets. That's why he called it global. A complete scientific revolution!

These laws remained intact until the beginning of the twentieth century, when German physicist Albert Einstein (1879-1955) published the “General Theory of Relativity,” which describes gravity as a geometric effect resulting from the distortion of space caused by its mere presence. Of objects with mass, similar to what happens when we place a heavy ball on an elastic cloth or net. If we applied this, for example, to our Solar System (SS), the distortion created by the Sun (which has a mass of 98% of the SS) in the grid would tell the planets how they should move through space. The concept of a lattice that is deformable due to the presence of massive objects is what is known as the space-time continuum. As the planets move, the deformation of the grid changes.

What does all this nonsense have to do with the first question? We've only talked about massive objects. Light has no mass, but is an electromagnetic wave that moves precisely through space-time, just as sound is a mechanical wave that propagates through air (in a vacuum we would not be able to hear it). If spacetime is curved in the presence of significant mass, then light propagating through it is forced to follow a curved path as well. The German theoretical physicist John Archibald Wheeler (1911-2008) summed it up brilliantly: “Matter bends space and space bends the paths of matter, so space-time tells matter how to move; “Matter tells space-time how to curve.”

Beatriz Agis Gonzalez She holds a doctorate in astrophysics and is a researcher at the Institute of Astrophysics of Andalusia (IAA-CSIC).

The question was sent via email byRicardo Gomez Kenny

Formatting and writing:Victoria Toro

Dice is a weekly science consultation, sponsored by the Dr. Anthony Esteve Foundation and the L'Oréal-UNESCO “For Women in Science” programme, which answers readers' questions about science and technology. They are scientists and technologists, members of AMIT (Association of Women Researchers and Technologists), who answer these questions. Send your questions to [email protected] Or on Twitter #nosotrasrespondemos.

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