In the extremely distant future of the Universe — after the stars fade and matter decays — the only cosmic objects that will remain as dominant forces are black holes. According to calculations, approximately 10⁴⁰–10¹⁰⁰ years after the Big Bang, the Universe will be governed solely by them. At this stage, understanding what happens will be extremely difficult with our current scientific knowledge.
The Disappearance of Nucleons and the Lepton Era
After nucleons — protons and neutrons — decay, the primary stable particles left in the Universe will be leptons: the electron and its antiparticle, the positron. Absorbing the remnants of matter, black holes will emit energetic particles — photons and theoretical gravitons.
According to Stephen Hawking’s theory, black holes “evaporate”: they lose mass over time due to Hawking radiation until they completely disappear. However, this process is extremely slow — the full evaporation of a black hole requires approximately 10⁶⁰ years.
Once black holes finally disappear, only leptons and subatomic particles with gradually decreasing energy will remain. During this period, the Universe will become completely unrecognizable compared to the one we know today.
Positronium — the “Strange Atoms” of the Future
After proton decay, unusual systems composed of leptons — positronium atoms — may exist. Positronium is a bound pair of an electron and a positron, which attract each other due to opposite electric charges and form an orbital structure similar to atoms.
These “atoms” may:
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exist in extremely large orbital structures,
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reach diameters comparable to interstellar distances,
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be regenerated as a result of radiation emitted by black holes.
Although positronium is short-lived, in this future epoch it may persist long enough to create unusual physical processes.
The End of the Black Hole Era
After all black holes evaporate, only scattered subatomic particles will remain in the Universe.
During this period:
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physical processes will take millions of years,
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the temperature of the Universe will continually decrease,
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energy will become nearly completely depleted.
According to some theories, even new forms of life may arise at this distant stage. Physicist Freeman Dyson suggests that complex systems made of leptons may form a “new type of life.”
Such beings:
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may possess enormous physical size,
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may span interstellar distances,
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may think extremely slowly — one thought could last a trillion years.
Although this seems strange to us, such a timescale would be “normal” for them.
The Breakdown of the Universe: The End of Macrophysics
After the disappearance of black holes, the Universe will approach a state of maximum entropy:
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matter will almost entirely vanish,
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energy will be evenly dispersed,
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temperature will approach absolute zero,
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dark energy will continue to expand space.
At this stage, stars, galaxies, and even small stable structures will no longer exist. Macroscopic physics will end, and only quantum mechanics will remain active.
Is the Birth of New Universes Possible?
Physicists are not entirely pessimistic. Some theories suggest that, in the very distant future, humanity might create a “new universe” by using black holes.
1. Transition to a New Universe through a Black Hole
Certain models hypothesize that black holes may contain hidden regions acting as “bridges” to other universes. According to Stephen Hawking, black holes may even give rise to new universes.
But there is a major problem:
Entering a black hole would be a one-way journey — there is no return.
2. Creating a False Vacuum — Constructing a New Universe
According to Alan Guth’s theory of cosmic inflation, only a small number of particles is needed to create a “seed” for a new universe:
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10⁸⁹ protons
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10⁸⁹ electrons
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10⁸⁹ positrons
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10⁸⁹ neutrinos and antineutrinos
A future civilization could use strong gravitational fields to generate a “false vacuum bubble,” causing the birth of a new universe.
Quantum Tunneling and the Rebirth of the Universe
In quantum mechanics, particles can sometimes “tunnel” through energy barriers that are impossible to cross in classical physics. Physicists Sean Carroll and Jennifer Chen propose that:
One day, quantum tunneling may push the Universe back into a low-entropy state, triggering a new Big Bang.
This would represent a natural cosmic rebirth.
However, for this to occur, one would have to wait approximately:
10^(10^56) years — an unimaginably long time.
Poincaré Recurrence — The Universe May Repeat Itself
In 1890, Henri Poincaré demonstrated that any physical system, given enough time, can return to a state close to its original configuration.
This implies that:
The Universe could be “reborn” through random thermal fluctuations.
Conclusion: The End of the Universe or a New Beginning?
Although current theories indicate that the death of the Universe is inevitable, physics simultaneously provides openings for new beginnings:
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life may re-emerge from leptons,
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new universes may form,
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quantum tunneling may reset the cosmos.
Although these scenarios may seem like science fiction today, they could become realistic mechanisms in the physics of the future.
Perhaps the Universe will never truly “end” — it will simply transform.