Is everything made of strings? Oskar Klein medallist Ashoke Sen on the unknown

In 2026, Ashoke Sen received the Oskar Klein Medal, becoming its first Indian recipient. The honour recognizes a physicist whose work has shaped understanding of string theory, gravity, and hidden dimensions.

Its significance also lies in the company it keeps. Awarded since 1988 by Stockholm University and the Nobel Committee for Physics, it has honored Stephen Hawking and Edward Witten. The medal’s history makes Sen’s selection a major international recognition, not merely a national milestone.

He received it after delivering the 2026 Oskar Klein Memorial Lecture, “Gravity from Strings and Strings from Gravity,” in Stockholm. That title reflects why his work matters: string theory replaces point particles with vibrating strands, making gravity calculations finite. Still, the honour does not mean physics has solved quantum gravity; it highlights major progress and unanswered questions.

String theory says the universe’s tiniest ingredients are not point-like dots, but incredibly small vibrating strands of energy. It matters because their vibrations can produce particles, including a particle that behaves like gravity’s carrier.

Imagine a tanpura string. Different vibrations create different sounds. In string theory, each pattern appears as a different particle, with its own mass and charge. One pattern behaves exactly like the graviton, the proposed particle carrying gravity. Replacing points with strings also spreads interactions across a tiny length, avoiding the troubling infinities produced by point-particle gravity.

Sen says strings give sensible answers to sensible questions. Yet string theory remains unconfirmed in the source, and strings are too small for current machines to see. Its promise is a possible bridge between quantum mechanics and general relativity, which currently resist being fully combined.

String theory requires six extra spatial dimensions beyond the familiar three. This gives space nine spatial dimensions, plus time. The extra dimensions help the theory describe gravity consistently instead of treating particles as points.

Oskar Klein proposed in 1926 that an extra dimension could be curled up too tightly to see. Imagine a garden hose viewed from far away. It looks like a line, but a tiny creature could move around its circular surface. Hidden dimensions might work similarly, remaining extremely small and beyond current instruments.

This remains a theoretical requirement, not an observed fact. The article gives no direct measurement proving these six dimensions exist. Sen’s broader message is that physics still has major unknowns. Future experiments and mathematical tests must seek evidence. Until then, hidden dimensions remain part of an ambitious framework, not confirmed features of everyday space.

String theory may address a central problem in physics: combining gravity with quantum mechanics. With point-like particles, gravitational calculations can produce infinite results for ordinary questions. Replacing each dot with a tiny vibrating strand spreads interactions over a small length.

For example, imagine two particles interacting through gravity. In the point-particle picture, the mathematics can return infinity instead of a meaningful answer. A string distributes that interaction along its length, producing sensible results. Its vibration patterns also look like different particles, including a possible graviton, gravity’s proposed carrier.

That makes string theory a promising route to quantum gravity, not a confirmed solution. The strings are far smaller than anything machines can see, so they cannot yet be directly observed. The article is careful: string theory smooths infinities, but physicists still do not know whether nature uses strings.

General relativity and quantum mechanics are physics’ two great rulebooks. They describe gravity and the very small, but they clash in extreme situations. A theory of quantum gravity would unite them into one consistent picture of nature.

At the smallest scales, treating particles as points can make gravitational calculations produce infinity. That is not a meaningful answer to a sensible question. String theory offers a possible remedy: each point becomes a tiny vibrating strand, spreading interactions across its length. One vibration behaves like the proposed gravity particle, called the graviton.

Quantum gravity remains an unsolved problem, rather than an established final theory. In 2026, Sen described string theory through “Gravity from Strings and Strings from Gravity.” The article says string theory needs six hidden dimensions, following Oskar Klein’s extra-dimension idea. Unification remains a major scientific goal, not a completed explanation of the universe.

Sen’s S-duality proposed that a theory with very strong interactions could secretly equal another with weak interactions. That mattered because weak interactions are easier to calculate, giving physicists a route into problems that otherwise produce meaningless infinities. It also changed how scientists viewed apparently separate theories: they might be different descriptions of the same underlying physics.

In his 1994 paper, Sen found evidence that the swap changes electrically charged particles into magnetically charged ones. The idea gained support as physicists discovered similar links between the five superstring theories. At strong coupling, one theory could become another’s useful weak-coupling description, tying them into one network.

By 1995, this network suggested a deeper framework called M-theory, associated especially with Edward Witten. It included strings but also higher-dimensional objects, and an extra dimension could appear as interactions grew stronger. M-theory remains incomplete and lacks direct experimental confirmation. Its importance is therefore conceptual: S-duality suggested that nature’s many string descriptions may be parts of one theory.