Contender #1—1032 K

Certain Cosmological Models, Including the One That Has Held Sway for Decades, the Standard Model, Posit a Theoretical Highest Temperature. It's Called the Planck Temperature, After the German Physicist Max Planck, and It Equals About 100 Million Million Million Million Million Degrees, or 1032 Kelvin. "It's Ridiculous Is What It Is," Said Columbia Physicist Arlin Crotts When I Asked Him If He Could Please Put That Number in Perspective for Me. "It's a Billion Billion Times the Largest Temperature That We Have to Think About" (In Gamma-Ray Bursts and Quasars, for Instance). Oh, That Helped.

The Planck Temperature Is the Highest Temperature in Conventional Physics Because Conventional Physics Breaks Down at That Temperature. Above 1032 K—That Is, Earlier Than One Planck Time—Calculations Show That Strange Things, Unknown Things, Begin to Happen to Phenomena We Hold Near and Dear, Like Space and Time. Theory Predicts That Particle Energies Become So Large That the Gravitational Forces Between Them Become as Strong as Any Other Forces. That Is, Gravity and the Other Three Fundamental Forces of the Universe—Electromagnetism and the Strong and Weak Nuclear Forces—Become a Single Unified Force. Knowing How That Happens, the So-Called "Theory of Everything," Is the Holy Grail of Theoretical Physics Today.

Contender #2—1030 K

String Theorists, Those Physicists Who Believe the Universe at Its Most Fundamental Consists Not of Particles but of Tiny, Vibrating Strings, Have Their Own Take on Temperature. I Spoke to Robert Brandenberger, a Theoretical Cosmologist at Mcgill University in Montreal. Along with Harvard String Theorist Cumrun Vafa, Brandenberger Has Proposed a Model of the Early Universe That's Quite Different from That of Traditional Big Bang Models. (I Should Note That There Are Many Models out There; I'm Touching on Only a Few Here.)

Contender #3—1017 K

I Learned of Yet Another Highest Possible Temperature from Brandenberger's Former Graduate Student, Stephon Alexander. Now an Assistant Professor of Physics at Penn State, Alexander Is One of Many Physicists Who Are Eagerly Awaiting the Day That Officials at Cern on the Swiss-French Border Switch on the Large Hadron Collider, the World's Largest Particle Accelerator.

As If at Least Three Different Possible Opposites to Absolute Zero Weren't Pause-Giving Enough, What Alexander Told Me Next Really Set My Head Spinning. Whatever the Highest Temperature Is, He Said, It Might, Just Might Be Essentially Equivalent to the Coldest Temperature. "In Other Words, Zero Temperature Is the Same, in a Sense, as the Planck Temperature."

Why Not, Indeed? After Chatting with Alexander and Others in His Rarefied Field, I Was up for Anything. How About Something Theoretically Hotter Than the Planck? Sure! I Asked Jim Gates of the University of Maryland. "All We Know Is That Above the Planck Temperature, the Rules Change, but … We Don't Know What the Rules Change To," He Said. "If Someone Figures out Such Consistent Rules, Then Yes, It's Conceivable That There Will Be Hotter Temperatures."

Contender #5—Who the Heck Knows?

As You Might Have Guessed, by This Point the Physicists Had Lost Me—If Not at the Very Beginning. I Was Way out of My Comfort Zone.

Nova | Absolute Zero | Absolute Hot

By Robert Thorne

• Oct 9, 2026 • 9 min read

Direct Answer • Key Takeaway

Seems Like an Innocent Enough Question, Right? Absolute Zero Is 0 on the Kelvin Scale, or About Minus 460 F. You Can't Get Colder Than That; It Would Be Like Trying to Go South from the South Pole. Is There a Corresponding Maximum Possible Temperature?

Robert Thorne

Automotive & Future Transportation Editor

Robert Thorne covers electric vehicle innovations, autonomous driving systems, global mobility trends, and automotive engineering developments.

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