Scientists calculate how much information exists in the observable universe

An electron’s mass, charge and spin help distinguish it from other particles. Those identifying properties also raise a question: could matter itself be treated as a store of information, and could its information content be counted?

Melvin Vopson of the University of Portsmouth's School of Mathematics and Physics explored that question in AIP Advances. His theoretical analysis combines information theory with estimates of particle abundance to produce an immense cosmic total.

The calculation offers one approach to a longstanding problem, rather than a measurement of everything the universe contains. Its result depends on how information is defined, which particles are counted and assumptions about where information can reside.

Measuring an electron’s characteristic properties allows an observer to identify it. In Vopson’s interpretation, the observer discovers information associated with the particle, rather than creating its physical characteristics through observation.

His analysis asks how much information would be needed, on average, to distinguish among selected particle types. It then extends that accounting across the ordinary matter in the observable universe.

“The information capacity of the universe has been a topic of debate for over half a century,” Vopson said. “There have been various attempts to estimate the information content of the universe, but in this paper, I describe a unique approach that additionally postulates how much information could be compressed into a single elementary particle.”

The calculation focuses on ordinary matter, the material making up familiar atoms. It considers electrons and the up and down quarks within protons and neutrons, rather than counting protons and their constituent quarks twice.

This makes the question narrower than a complete cosmic inventory. Describing particle categories does not, by itself, describe every particle’s position, motion or relationship with everything around it.

The approach draws on information theory developed by mathematician Claude Shannon in 1948. That framework quantifies information using the probabilities of different outcomes, rather than their meaning to an observer.

A rare outcome conveys more information than an expected one. Averaging across possible outcomes gives an information entropy, expressed in bits when the calculation uses base-two logarithms.

Different particle types are not equally abundant, so simply counting the categories would miss an important part of the calculation. Vopson instead uses their estimated proportions to determine an average information value.

The fractional result should be understood as an average across that distribution. It does not imply that an individual particle contains a miniature digital memory holding complete bits and fractions of others.

The method therefore has two distinct steps. First comes the information assigned to the chosen particle categories; then comes an estimate of how many relevant particles populate the observable universe.

Within Vopson’s chosen inventory, the average information value is 1.509 bits per elementary particle. The model starts with ordinary matter comprising approximately 75% hydrogen, 23% helium and 2% heavier elements by mass.

Those proportions must be converted into atom counts before tallying their constituents. A proton contributes two up quarks and one down quark, while a neutron contributes one up quark and two down quarks.

Vopson combines this inventory with cosmological quantities describing ordinary-matter density and the size of the observable universe. The resulting particle count is approximately 4 × 10⁸⁰.

Multiplying that count by the average information value produces 6.036 × 10⁸⁰ bits, rounded to approximately 6 × 10⁸⁰. That is the theoretical estimate for the selected matter particles, rather than a demonstrated universal information capacity.

To put it in perspective, storing that amount would require approximately 7.5 × 10⁶⁷ laptop drives, each holding one terabyte. Packed together, drives measuring roughly 100 × 70 × 7 millimeters would fill a cube about 163,000 light-years on each side, wider than the Milky Way’s approximately 100,000-light-year stellar disk.

If each bit instead occupied a one-millimeter cube, about the size of a sand grain, the resulting cube would span roughly 90 million light-years per side. That’s roughly 900 times the width of the Milky Way.

The paper also derives a proton count consistent with the familiar order of magnitude associated with the Eddington number. That provides a numerical comparison for the inventory, rather than independent confirmation that particles physically store the calculated bits.

Earlier estimates have addressed different questions about cosmic information. In a 2002 analysis, physicist Seth Lloyd examined the universe’s computational capacity, including limits on information registration and elementary operations over its history.

Such estimates cannot automatically be compared as competing measurements of one quantity. An inventory of particle identities and a limit on physical computation have different definitions and scope.

Vopson’s study also leaves out antiparticles and neutrinos. It treats force-carrying particles as transferring information rather than storing it, an assumption that helps define the proposed inventory.

Its interpretation goes beyond Shannon’s mathematical calculation. Information theory supplies a way to quantify uncertainty about particle categories, while the claim that this information resides physically inside particles requires additional justification.

The numerical result does not establish Vopson’s separate proposals that information has mass or could constitute a fifth state of matter. It likewise does not demonstrate that information explains dark matter.

There is an experimentally supported connection between information processing and physics. A 2012 experiment in Nature verified Landauer’s principle, which links erasing information in a physical memory with heat dissipation.

That finding concerns a specific thermodynamic process. It does not establish that abstract information is an additional material substance, or validate a cosmic inventory based on particle identities.

Vopson describes his numerical estimate as a potential route toward experiments. Testing the broader interpretation would require an observable physical consequence, rather than agreement between mathematical quantities alone.

In a separate paper, he proposed an experimental protocol involving particle-antiparticle annihilation to test his mass–energy–information hypothesis. That publication describes a proposed test, rather than a reported detection of the predicted effect.

“Even if not entirely accurate, the numerical prediction offers a potential avenue toward experimental testing,” Vopson said of the information estimate.

Shannon’s theory can support a calculation without settling what it means for the fundamental nature of matter. The study supplies a defined estimate for researchers to examine and refine, while leaving its physical interpretation open to investigation.

These resources explore information theory, cosmic computation and experimental links between information processing and thermodynamics.

A Mathematical Theory of Communication: Shannon's foundational paper develops the probabilistic framework used to quantify information in bits. (Bell System Technical Journal, 1948)

Computational Capacity of the Universe: Examines physical limits on the information the universe can register and the operations it can perform. (Physical Review Letters, 2002)

Experimental verification of Landauer’s principle linking information and thermodynamics: Reports an experiment connecting information erasure in a physical memory with heat dissipation. (Nature, 2012)

Entropy, irreversibility and inference at the foundations of statistical physics: Reviews the relationship between entropy, inference and physical irreversibility, providing context for information-based descriptions. (Nature Reviews Physics, 2024)

Experimental protocol for testing the mass–energy–information equivalence principle: Presents a proposed experiment to test Vopson's information hypothesis, distinct from evidence that the predicted effect occurs. (AIP Advances, 2022)

Research findings are available online in the journal AIP Advances.

The original story "Scientists calculate how much information exists in the observable universe" is published in The Brighter Side of News.

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