Time Without End (1979): Freeman Dyson on Life in the Far Future

“Time without end”, published by physicist Freeman Dyson in 1979, was one of the first serious attempts to work out the far future of an ever-expanding universe using known physics. Dyson estimated how matter would slowly change over enormous timescales and argued that life might, in principle, survive forever on a finite supply of energy.

The question before the paper

In the 1970s, the far future of the universe was barely a scientific subject. Very few papers on the end of the universe existed. If the universe is “open”, expanding forever, what happens after the stars burn out? And is there any physical limit to how long life and intelligence could continue?

What the paper found

• Slow physics over vast times. Dyson estimated timescales for extremely slow processes. If protons are stable, all matter would eventually turn to iron through quantum tunneling, and iron stars would ultimately collapse into neutron stars or black holes, over spans that dwarf the current age of the universe.
• A recipe for eternal life. He proposed a scaling law under which living beings could adapt to ever lower temperatures and survive indefinitely on a finite energy supply by hibernating for longer and longer stretches.
• Talking across the cosmos. He also analyzed whether civilizations could keep communicating by radio across an expanding universe.

How he did it

The paper is based on four “James Arthur Lectures on Time and its Mysteries” that Dyson gave at New York University in the autumn of 1978. He took the laws of physics as known, extrapolated them far beyond any timescale tested, and asked what follows, treating questions often left to philosophy with a physicist’s order-of-magnitude estimates.

Why it mattered

Dyson founded “physical eschatology”, the study of the ultimate fate of the universe, as a respectable field. His questions frame every later study of the far future, including Fred Adams and Gregory Laughlin’s 1997 five ages of the universe, which gave this site its name and its Deep Time timeline.

What we know now

The discovery of accelerating expansion in 1998 undermined Dyson’s scenario. In a universe dominated by dark energy, distant galaxies vanish beyond a horizon, as Krauss and Scherrer described in the end of cosmology, which leaves far less of the universe within reach of any civilization. Whether dark energy is truly constant is now being tested again by the Dark Energy Spectroscopic Instrument; see DESI’s 2025 results. See our guides to the future of the universe and the heat death of the universe.

Who wrote it

Freeman Dyson, a theoretical physicist, wrote the paper alone, turning his public lectures into a technical review. It has about 280 citations in Semantic Scholar as of October 2026.

Read the original

Dyson, F. J. (1979). “Time without end: Physics and biology in an open universe.” Reviews of Modern Physics 51, 447. doi:10.1103/RevModPhys.51.447. A PDF copy is posted by MIT.