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Scientists Discover Way to Send Information into Black Holes Without Using Energy

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Is Missing Quantum Information Affecting the Universe’s Expansion?

Scientists know that the universe is expanding. The speed of this expansion today is called the Hubble constant (H₀). But here is the problem:

  • Measurements based on the early universe (mainly the cosmic microwave background, or CMB) give a lower value of H₀.

  • Measurements based on the nearby universe (using supernovae and galaxies) give a higher value of H₀.

The difference is small, only a few percent, but it refuses to go away. This disagreement is known as the Hubble constant tension. If it is not caused by errors in experiments, it means our understanding of the universe is incomplete.

Sakharov and his team propose a new and unusual idea to explain this tension—one that comes not from new particles or forces, but from missing quantum information at the edge of the universe.

A Fresh Way of Thinking About the Universe

Modern physics tells us something surprising: space itself carries information.

Black holes are the best-known example. They have:

  • Entropy, which measures how much information they contain

  • Temperature, meaning they behave like hot objects

This idea does not apply only to black holes. Our expanding universe also has a kind of boundary called the cosmic horizon (or Hubble horizon). This horizon marks the farthest distance from which light can reach us.

Just like black holes, this horizon:

  • Has entropy

  • Has temperature

  • Obeys laws similar to thermodynamics

Sakharov and his team focus on one key question:

What if the universe’s horizon does not contain as much quantum information as it should?

The Core Idea, in Simple Terms

According to known physics, the entropy of a horizon should match a specific value called the Bekenstein–Hawking entropy. This is the maximum information the horizon can store.

The new idea assumes that:

  • The actual entanglement (quantum connectedness) at the horizon is slightly less than this maximum.

  • This small shortfall is called an entanglement deficit.

This deficit is tiny, but it has consequences.

Because the horizon also has a temperature, missing entropy means missing energy. That missing energy does not disappear—it shows up as a new smooth energy component inside the universe.

This idea is called:

Horizon Entanglement Equipartition Deficit (HEED)

In simple words:
The universe expands a little faster because its horizon is missing a small amount of quantum information.

Why This Energy Is Special

The energy created by this entanglement deficit behaves in a very specific way:

  • Its density is proportional to H², where H is the expansion rate of the universe.

  • This means it is:

    • Extremely small in the early universe

    • Noticeable only at late times

This is important because it solves a major problem faced by many other ideas.

Why HEED Does Not Ruin the Early Universe

The early universe is very well understood. The CMB and the sound horizon are measured with incredible precision. Any new physics that changes early times usually fails because it disagrees with these observations.

HEED avoids this problem naturally:

  • At early times, matter and radiation dominate.

  • Since the HEED energy depends on H², it is negligible during recombination.

  • The CMB and sound horizon remain unchanged.

So HEED leaves the early universe completely intact.

What Happens at Late Times

As the universe expands and matter becomes less important, the HEED contribution slowly turns on.

Sakharov and team model this with a smooth “switch” that activates at low redshift (roughly when the universe is older than half its current age).

The result:

  • The expansion rate at late times increases by a few percent.

  • This is exactly the size needed to reduce the Hubble tension.

In other words, the universe expands slightly faster today because of missing horizon entanglement.

Effects We Can Observe

Even though HEED is subtle, it has clear effects:

1. Faster Expansion Today

The value of H(z) at low redshift increases slightly, helping match local measurements of H₀.

2. Small Changes in Distances

Distances measured using supernovae and baryon acoustic oscillations change a little—but remain consistent with current data.

3. Slower Growth of Structures

HEED behaves as a smooth energy component, meaning it does not clump into galaxies. This slightly slows down the growth of cosmic structures, which affects measurements like fσ₈.

4. A Stronger Late-Time ISW Effect

HEED predicts a mild increase in the late Integrated Sachs–Wolfe effect, offering a possible future test.

Does It Agree With Data?

The authors tested HEED against many observations, including:

  • Type Ia supernova distances

  • BAO measurements

  • Cosmic chronometer data

  • Growth measurements from galaxy surveys

They also ensured the HEED effect is essentially zero at the time of recombination.

The result is encouraging:

  • HEED fits current low-redshift data almost as well as standard ΛCDM.

  • At the same time, it allows a higher late-time expansion rate.

This means HEED can ease the Hubble tension without breaking existing observations.

A Clean and Local Idea

Some dark energy models depend on the future event horizon, which requires knowing the entire future of the universe. This creates logical problems, because the present should not depend on the unknown future.

HEED avoids this issue completely:

  • It uses the apparent (Hubble) horizon, which is defined locally in time.

  • This makes the model physically reasonable and free from “future dependence” problems.

Why This Idea Is Interesting

HEED is different from many other solutions because:

  • It does not add new particles.

  • It does not change early-universe physics.

  • It is rooted in well-established ideas about horizons, entropy, and quantum information.

If correct, the Hubble tension may not be a mistake—but a sign that horizon entanglement matters for cosmic expansion.

What Comes Next?

HEED is still a developing idea. Future work will:

  • Test it with more precise data

  • Compare it directly with ΛCDM

  • Explore deeper quantum explanations for the entanglement deficit

If supported, this approach could reveal something profound:

The expansion of the universe may be shaped not only by matter and energy, but also by how much information its horizon contains.

That would turn the Hubble tension from a problem into a window onto the quantum nature of spacetime itself.

Reference; Alexander S. Sakharov, Rostislav Konoplich, Merab Gogberashvili, Jack Simoni, "Hubble Tension as an Effect of Horizon Entanglement Nonequilibrium", Arxiv, 2025. https://arxiv.org/abs/2601.17938


Key Technical Terms

Hubble Constant (H₀)

The number that tells us how fast the universe is expanding today.
A bigger value means the universe is expanding faster.

Hubble Constant Tension

The problem that different methods give different values for the Hubble constant:

  • Early-universe measurements give a lower value

  • Late-universe measurements give a higher value

Scientists don’t yet know why.

Redshift (z)

A way to describe how far back in time we are looking:

  • High redshift → very early universe

  • Low redshift → recent universe

Scale Factor (a)

A number that shows how big the universe is compared to today:

  • Today: a = 1

  • Past: a < 1

Cosmic Microwave Background (CMB)

Faint radiation left over from the early universe, about 380,000 years after the Big Bang.
It acts like a baby picture of the universe.

Recombination

The time when the universe cooled enough for atoms to form, allowing light to travel freely.
This is when the CMB was created.

Sound Horizon

The largest distance sound waves could travel in the early universe before recombination.
It acts as a cosmic ruler.

Baryon Acoustic Oscillations (BAO)

A pattern left by early-universe sound waves that shows up in how galaxies are spaced today.
Used as a standard ruler to measure cosmic distances.

Type Ia Supernovae

Exploding stars that always reach nearly the same brightness.
Because of this, they are used as standard candles to measure distances.

Cosmic Horizon (Hubble Horizon)

The edge of the observable universe—the farthest distance light can reach us from.
It changes as the universe expands.

Apparent Horizon

The practical, local version of the cosmic horizon that depends on the current expansion rate.
It does not depend on the future of the universe.

Event Horizon

A horizon defined by the entire future history of the universe.
Using it can cause logical problems because the future is unknown.

Entropy

A measure of how much information or disorder something contains.
More entropy = more information stored.

Bekenstein–Hawking Entropy

The maximum amount of information a horizon (like a black hole or cosmic horizon) can hold.

Quantum Entanglement

A quantum connection where particles or regions remain linked, even when far apart.
Changes to one affect the other.

Entanglement Entropy

A measure of how strongly parts of a system are quantum-connected to each other.

Entanglement Deficit

A small shortage of quantum information compared to what is expected.
In this model, the universe’s horizon has slightly less entanglement than it should.

Equipartition

A rule from physics saying energy is evenly shared among available degrees of freedom.

Gibbons–Hawking Temperature

The tiny temperature associated with the cosmic horizon, similar to how black holes have temperature.

HEED (Horizon Entanglement Equipartition Deficit)

The idea that missing horizon entanglement creates extra energy, affecting the universe’s expansion.

Infrared (IR)

Refers to very large scales or very low energies, such as horizon-scale physics.

Ultraviolet (UV)

Refers to very small scales or very high energies, such as particle physics.

Holographic Scaling

The idea that some physical quantities depend on surface area rather than volume.

ρ ∝ H² / G

Means the energy density depends on:

  • The expansion rate of the universe (H)

  • Gravity strength (G)

This makes the energy important only at late times.

Dark Energy

An unknown form of energy that causes the universe’s expansion to accelerate.

ΛCDM (Lambda Cold Dark Matter)

The standard model of cosmology that includes:

  • Dark energy (Λ)

  • Cold dark matter

  • Normal matter

Equation of State (w)

A number that describes how pressure and energy are related:

  • w = −1 → cosmological constant

  • Values near this describe dark-energy-like behavior

Structure Growth

How small density differences grow into galaxies and clusters over time.

fσ₈

A quantity that measures how fast cosmic structures grow.

Integrated Sachs–Wolfe (ISW) Effect

A change in CMB light caused by evolving gravitational fields at late times.

Cosmic Chronometers

A method that uses aging galaxies to measure how fast the universe expanded in the past.

Planck Mass / Effective Planck Mass

A value that sets the strength of gravity.
Changing it means gravity becomes slightly stronger or weaker.

Modified Gravity

The idea that gravity itself behaves differently on very large scales.

Bianchi Identity

A rule that ensures energy and momentum are conserved in general relativity.

Teleology

A problem where present physics depends on future events, which is usually unphysical.


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