The idea that our world is "just" a simulation is an ancient one. Philosophers from Plato to Descartes have toyed with the notion that reality might be an illusion. In modern times, it's been revived by thinkers like Nick Bostrom and popularised by films such as The Matrix. Today, the concept thrives on social media, often dismissed by scientists as lying beyond the boundaries of falsifiability.
But when we move from speculation to hard physics, specifically astrophysics, the Simulation Hypothesis begins to look improbable.
In his 2025 paper, Astrophysical constraints on the simulation hypothesis for this Universe: why it is (nearly) impossible that we live in a simulation, astrophysicist Franco Vazza applied physical laws to estimate the energy and information needed to simulate reality.
1)Simulating the Entire Universe
To perform a full simulation of the visible Universe down to the Planck scale would require:
- Information: ~3.5 × 10¹²⁴ bits
- Energy: ~8.9 × 10¹⁰⁸ erg
That's more energy than exists in the observable Universe. We couldn't even store that much data, let alone process it. In other words, a perfect Universe-scale simulation is physically impossible.
2)Simulating Earth at Full Resolution
Reducing the scope to Earth still doesn't help much:
- Information: ~9.81 × 10 ⁷⁴ bits
- Energy: ~2.55 ×10⁵⁹ erg
This is comparable to:
- Converting the entire stellar mass of a typical globular cluster into energy
- Unbinding all the stars and matter in the Milky Way
And that's just the starting cost. Each timestep of the simulation would require the same amount again. After around 10⁶ steps, the energy needed would equal the rest-mass energy of the Milky Way. You'd also need a Jupiter-sized computer to store the data. Simulating Earth at Low Resolution
Even lowering the resolution to match experimental limits from high-energy neutrino observations demands:
- Information: ~1.65 × 10⁵¹ bits
- Energy: ~4.31 × 10³⁵ erg
While smaller than the previous numbers, this is still far beyond feasible limits. Even with the most efficient theoretical computer — a black hole — simulating one second of Earth would take millions of years of real time.
It's wise to assume that no technological advancement will make the Simulation Hypothesis feasible in a Universe with the same physical laws as ours.
As Vazza concludes:
"In all cases, the amounts of energy or power required by any version of the simulation hypothesis are entirely incompatible with physics, or (literally) astronomically large, even in the lowest resolution case."
Reference: Vazza, F. (2025). Astrophysical constraints on the simulation hypothesis for this Universe: why it is (nearly) impossible that we live in a simulation. arXiv:2504.08461