Scientist

Saul Perlmutter

1959– · Cosmology, Astrophysics
Astrophysicist, leader of the project to observe type Ia supernovae, which led to the discovery of the accelerated expansion of the universe and dark energy.

Biography

Born in Champaign, Illinois. Graduated from Harvard and received his PhD at the University of California, Berkeley, where he later led the Supernova Cosmology Project. From the 1990s, he coordinated an international team to precisely measure distant supernovae. In 1998, he published revolutionary results indicating the acceleration of the universe's expansion. Nobel Prize laureate in Physics 2011 (jointly with Schmidt and Riess).

Key discoveries

💡 Perlmutter and his competing group led by Schmidt worked in parallel for a long time, and when both reached the same conclusion, skepticism turned to euphoria. To make sure the results were not caused by cosmic dust, they rechecked the data for years.
"He said that the universe is not just expanding, but doing so ever faster, as if driven by an invisible hand."
Concepts
dark energyexpansion of the universe
Laws
Hubble's law
Scientists
Adam RiessEmmy NoetherChristian DopplerMaarten SchmidtBrian SchmidtRobert Woodrow WilsonRainer SachsVesto Slipher

Related articles

Geophysics2012-12-272 minarXiv:1212.6394
The Salt Chronicle of the Messinian Crisis
A rock chronicle where each layer is a page, and spectral analysis reads the rhythm of the lines. In the Realmonte salt mine in Sicily, geologists measured the thickness of 120 three-part cycles: a millimeter-scale clay parting, a thin anhydrite or polyhalite layer, and then a decimeter-scale halite bed.
The Invisible Conductor of the Super-Puff Planet System
The three planets in the Kepler-51 system have long intrigued astronomers: they are Saturn-sized but less dense than water. These 'super-puff' worlds, with masses no more than ten Earths, are like cosmic dandelions — massive yet almost weightless. Their orbits are arranged like musicians in an orchestra, each playing its part, beating the rhythm with transits.
Quantum Decay Tail: How the Memory of Birth Depends on Color
A quantum system, once born, does not forget it. Even after dozens of lifetimes, a trace of the initial state remains in its decay: a slowly decreasing power-law tail. For two fluorescent dyes, erythrosine B and eosin Y, this tail has been observed for the first time in two spectral channels simultaneously.
Cosmology2025-12-022 minarXiv:2512.02391express
Refining the Expansion Rate of the Universe with 'Twins' Among Type Ia Supernovae
Type Ia supernovae are the 'standard candles' of cosmology: their peak luminosity is nearly identical, allowing distances to be determined from apparent brightness — the fainter the object, the farther away it is.
Cosmology2025-12-081 minarXiv:2512.07931express
The Twinkling of Quasars and the Variable Dark Energy
Two methods of measuring the Universe's expansion rate yield conflicting results. Measurements from supernova explosions, carried out by Adam Riess's team, show faster expansion than data from the cosmic microwave background — the light left over from the Big Bang.
Cosmology2025-12-171 minarXiv:2512.15380express
Gravitational waves and galaxy maps measure the expansion of the Universe
The Universe is expanding, and every galaxy cluster takes part in a grand dance. The tempo of this dance is set by the Hubble constant, first measured by Edwin Hubble nearly a century ago. Pinpointing the number is tough because you need a ruler that spans billions of light-years.
Cosmology2026-01-062 minarXiv:2601.02886express
The Universe Stops Being Uniform at a Scale of 138 Megaparsecs
Galaxies in the Universe are not scattered randomly: neighboring ones move in the same direction, like a school of fish, while distant ones each go their own way. Where the boundary between 'together' and 'apart' lies has been unclear until now.
Cosmology2026-01-081 minarXiv:2601.04774express
Gravitational waves refine cosmic expansion rate
Measuring the universe’s expansion is like timing a race when the track stretches. Neutron star mergers act as standard sirens: their gravitational waves ring out with a known “volume,” so fainter signals mean greater distance.
Cosmology2026-01-092 minarXiv:2601.05646express
Dark Matter and Dark Energy: A Slow Reaction
The universe is expanding, and the rate of that expansion is a hot topic in cosmology. Nearly a century ago, Edwin Hubble discovered that galaxies are flying apart, but modern measurements of the Hubble constant, which characterizes the expansion rate, give conflicting values.
Galaxies2026-01-161 minarXiv:2601.11515express
Cosmology2026-01-271 minarXiv:2601.19662express
Dark Dancers: When Dark Matter and Dark Energy Dance Together
Galaxies are flying apart, but the expansion rate measured from the afterglow of the Big Bang and from supernova explosions doesn't match: this problem has been called the Hubble tension. It's like two dancers losing their rhythm because they can't feel each other.
Cosmology2026-01-292 minarXiv:2601.22043express
A Cosmic Ruler Without a Ruler
The universe is expanding, but at what rate is a question that has been troubling astronomers for decades. Two methods of measurement give different answers, and this discrepancy is called the Hubble tension. Some look at the early universe through the cosmic microwave background, others at nearby supernovae and Cepheid variables.
The Demon with a Delay: How to Outsmart the Landauer Bound
The microcantilever oscillates at 1270 Hz, and its position controls a virtual potential: an invisible energy landscape with two wells, created by feedback. Normally, switching between the wells occurs when the system crosses the zero point, but now a delay comes into play: the threshold is shifted by an amount h.
General Relativity2026-02-091 minarXiv:2602.08522express
Warm Emptiness Instead of Dark Energy
In the standard cosmological model ΛCDM, galaxies recede under the pressure of dark energy — an invisible spring. However, different methods of measuring the expansion rate give different numbers, as if the ruler's scale is off.
Stellar2026-02-151 minarXiv:2602.14304express
Lighthouse Stars in Distant Galaxies
In distant galaxies, old stars swell and redden. Among them are two groups that act like lighthouses: some have just ignited helium burning, while others are already burning carbon and oxygen.
Cosmology2026-02-181 minarXiv:2602.16869express
Light and Distance: Testing Cosmic Geometry
Light from a distant star travels to us for billions of years, and during that time the universe has time to expand. How can we check that we correctly understand this journey? Astronomers use two 'rulers': supernova explosions, which shine with a known brightness, and fast radio bursts — short, powerful pulses of radio waves from other galaxies.
Cosmology2026-02-252 minarXiv:2602.21733express
Galaxies2026-03-021 minarXiv:2603.01882express
Galactic Wind: How Stars Blow Gas Out of a Galaxy
A distant galaxy, similar to our Milky Way, is blowing gas into space like a hair dryer blowing dust off a table. Seven beams of light from an even more distant object pierced this gas cloud, and astronomers saw that the gas flow is narrow, like a jet from a hose, not wide like a fan.
Cosmology2026-04-041 minarXiv:2604.03769express
Radio bursts help measure the expansion of the Universe
The Universe is expanding, but at what speed? Astronomers have been arguing for decades about the precise value of the Hubble constant. Two classic methods give slightly different results. Now there's a third — using mysterious radio bursts.
Cosmology2026-04-061 minarXiv:2604.04408express
The Universe Breathes Unevenly
Cosmologists have measured how fast distant galaxies are receding in different parts of the sky. To do this, they used two kinds of "cosmic rulers": galaxy clusters and a certain type of supernova explosion. Both methods showed the same thing: in one direction, the Universe is expanding slightly faster than in the opposite direction.
Cosmology2026-04-062 minarXiv:2604.05033express
Filaments of the Cosmic Web: A Universal Density Profile
The cosmic web resembles a giant three-dimensional network: galaxies and clusters are connected by filaments of dark matter. These filaments act as invisible bridges along which matter flows toward major nodes. For a long time, scientists struggled to understand the density structure of these filaments, but results were contradictory.
Cosmology2026-04-162 minarXiv:2604.14653express
Cosmic Whirlpools, Painted by a Neural Network
Toss a handful of glitter into a river, and some flakes will drift straight while others spin in tiny eddies. Galaxies in the universe do something similar: they don't just recede due to cosmic expansion: they also swirl in giant currents, like wood chips caught in invisible whirlpools.
Cosmology2026-04-191 minarXiv:2604.17534express
A Giant Cosmic Ring
The night sky sometimes throws up riddles that take your breath away. One of them is a ring of galaxies stretching across a third of the horizon. Astronomers have named it the “Giant Ring on the Sky”: a cluster of galaxies stretched into a thin filament and closed into a circle about 400 megaparsecs in diameter.
Cosmology2026-04-192 minarXiv:2604.17660express
How Star Birth Measures the Universe
The universe keeps a tally of every newborn star. Over 13.8 billion years, galaxies have ignited so many stars that their 'census' can reveal the nature of the cosmos itself, just as tree rings reveal past climates.
High Energy2026-04-272 minarXiv:2604.24617express
Dust Rings Reveal the Secrets of the Spiral Arms
Imagine a dark room with dust floating in the air. A bright flashlight goes off, and the dust particles light up, revealing their positions. Astronomers have applied a similar trick to our Galaxy. The flashlights were gamma-ray bursts, the most powerful explosions in distant galaxies, and the dust particles were interstellar clouds.
Cosmology2026-04-292 minarXiv:2604.26541express
Dark Radiation and the Run of Inflation: What Hubble Is Hiding
The cosmological dispute resembles two craftsmen measuring the same room with different tape measures. One, looking at distant galaxies, gets one number. The other, peering into the ancient glow (the cosmic microwave background, the cooled light of the Big Bang) gets another, smaller number.
Quantum Physics2026-04-302 minarXiv:2604.27761express
Counting Light, Drop by Drop
An ordinary rain gauge collects water in a bucket and shows the total volume of precipitation. But the new device is like a sensitive palm that feels every falling drop and keeps count, even when the drops number in the thousands. That's exactly what physicists have built.
Cosmology2026-04-301 minarXiv:2604.27867express
Galaxies at the Edge of the Universe Are Brighter Than We Thought
Edwin Hubble and Georges Lemaître discovered the expansion of the Universe nearly a century ago. One way to test it is the surface brightness test: in an expanding cosmos, the light of a distant galaxy should fade like a pattern on a stretching film.
Machine Learning2026-05-061 minarXiv:2605.08212express
AI assistant tackles cosmology's trickiest math
The Universe's expansion is accelerating, and maybe gravity doesn't work the way we think. Physicists come up with alternative theories, but to test them, they need to calculate how ripples after the Big Bang grew into galaxies. Such calculations involve long equations with hundreds of terms, where it's easy to get lost.
General Relativity2026-05-101 minarXiv:2605.09660express
The Universe Checks Its Own Honesty
When two dead stars collide in a distant galaxy, two messengers bring us the news: a shiver in space, a gravitational wave, and a flash of light. Both messengers race toward us across the entire Universe, but their paths can differ slightly. Light sometimes gets delayed by cosmic dust, while gravitational waves pass through everything almost without noticing obstacles.
Cosmology2026-05-133 minarXiv:2605.13705
Orbital Web: Why the Big Rip Will Wait at Least 30 Years
Our Solar System isn't an island in the void: it's a sensitive web stretched in a dark cosmic corner. Planets circle their orbits like dewdrops on threads, and we are the spider sensing the faintest tremor. That tremor betrays the approach of the catastrophe astronomers call the Big Rip.
General Relativity2026-05-141 minarXiv:2605.14977express
HEP Theory2026-05-212 minarXiv:2605.21838express
The Fifth Dimension as a Trap for Particles
The fifth coordinate, curled into a tiny loop, could be hiding right under our noses. In such a universe, everything we see would be stuck to a four-dimensional film, the brane, like water droplets on a window pane. But why doesn't matter slip into the fifth dimension? The answer may lie in the twisting of spacetime itself.
Cosmology2026-05-262 minarXiv:2605.27227express
Gravitational waves measure the expansion rate of the universe
Imagine a giant inflatable balloon with galaxies painted on it. As it inflates, the pattern stretches and neighboring dots move apart. The rate of that stretching is the Hubble constant. Astronomers usually catch light from distant stars and see how much it has reddened due to the stretching of space.
Quantum Physics2026-05-271 minarXiv:2605.28378express
Light Working in a Team Measures Distances More Accurately
A regular rangefinder sends a single light pulse and waits for it to return — like a person shouting into the void and listening for an echo. But if you use multiple sources that glow in unison, and analyze not the volume but the rhythm of the echo of reflected flashes, the picture becomes sharper.
HEP Theory2026-05-312 minarXiv:2606.01167express
How Logarithmic Divergence Hides in Higher-Dimensional Spaces
An infinitely long tube with a tiny sphere attached to each point: that's what the space the authors worked with looks like. One part of it resembles a saddle (this is anti-de Sitter space, or AdS), the other a sphere.
Quantum Tide from the Future: Accelerating the Universe Without Dark Energy
For almost a century, cosmologists have been grappling with the mystery: what makes the Universe expand ever faster? The standard answer — dark energy — creates a monstrous discrepancy between the theoretical vacuum density and observations. But there's another path, one that turns causality on its head.
Cosmology2026-06-023 minarXiv:2606.03634
Cosmic Detective: Two Independent Clues Against the Main Cosmological Debate
Cosmology resembles a courtroom where two witnesses give irreconcilable testimonies. The first — the analysis of the cosmic microwave background by the Planck satellite — claims: the expansion of the universe proceeds at 67 (km/s)/Mpc.
Cosmology2026-06-032 minarXiv:2606.05358
Cosmology2026-06-041 minarXiv:2606.06495express