# Big Rip

The Big Rip is a hypothetical future singularity in which the expansion of the universe accelerates without limit, so that the scale factor and the Hubble parameter become infinite at a finite future time and every gravitationally bound structure, down to atoms and nuclei, is torn apart<sup>[1](https://arxiv.org/abs/astro-ph/0302506)</sup>. The scenario arises if dark energy is "phantom energy", a fluid whose equation-of-state parameter w, the ratio of pressure to energy density, is less than −1<sup>[1](https://arxiv.org/abs/astro-ph/0302506)</sup>. It was named and worked out in a 2003 paper by Robert R. Caldwell, a cosmologist at [Dartmouth College](https://www.edgepedia.org/dartmouth-college), with [Marc Kamionkowski](https://www.edgepedia.org/marc-kamionkowski) and Nevin N. Weinberg of the [California Institute of Technology](https://www.edgepedia.org/california-institute-of-technology)<sup>[1](https://arxiv.org/abs/astro-ph/0302506)</sup><sup> • </sup><sup>[2](https://pubmed.ncbi.nlm.nih.gov/12935004/)</sup>.

| Key fact | Detail |
|---|---|
| Condition | Requires phantom dark energy with w < −1, so the dark-energy density increases as the universe expands<sup>[1](https://arxiv.org/abs/astro-ph/0302506)</sup> |
| Endpoint | Scale factor and Hubble parameter diverge at a finite time t_rip; the positive phantom-energy density becomes infinite, overcoming all other forms of matter<sup>[1](https://arxiv.org/abs/astro-ph/0302506)</sup> |
| Time remaining | For w = −3/2 and H₀ = 70 km s⁻¹ Mpc⁻¹, the Big Rip lies about 22 Gyr in the future<sup>[1](https://arxiv.org/abs/astro-ph/0302506)</sup> |
| Disassembly sequence (w = −3/2) | Galaxy clusters stripped about 9.3 Gyr before the end; the Milky Way 69.9 Myr before; the solar system 3.6 months before; Earth destroyed 25.2 minutes before; atoms dissociated 10⁻¹⁹ s before<sup>[1](https://arxiv.org/abs/astro-ph/0302506)</sup> |
| Current data | Planck 2018 combined with supernovae and BAO gives w₀ = −1.03 ± 0.03, consistent with a cosmological constant (w = −1)<sup>[3](https://doi.org/10.1051/0004-6361/201833910)</sup> |
| Earliest estimate | Caldwell's calculation from the 2018 Planck data release puts the earliest possible Big Rip near 200 billion years from now<sup>[4](https://www.americanscientist.org/node/1245)</sup> |

## Phantom energy and the equation of state

[Dark energy](https://www.edgepedia.org/dark-energy) is usually described by the equation-of-state parameter \( w \equiv p/\rho \), the ratio of its pressure to its energy density. [A value](https://www.edgepedia.org/a-value) \( w < -1/3 \) is needed for cosmic acceleration; a cosmological constant has \( w = -1 \), and quintessence models occupy \( -1 < w < -1/3 \), with density decreasing as the universe expands<sup>[1](https://arxiv.org/abs/astro-ph/0302506)</sup>. Phantom energy violates this pattern: for \( w < -1 \) the sum of pressure and energy density is negative, and the energy density increases with time<sup>[1](https://arxiv.org/abs/astro-ph/0302506)</sup>.

This behavior drives super-acceleration. In a universe with \( w \geq -1 \), the Hubble distance grows and gravitationally bound systems such as the [Milky Way](https://www.edgepedia.org/milky-way) and the [Local Group](https://www.edgepedia.org/local-group) remain bound forever; with phantom energy the expansion rate H grows, the horizon closes in, and the increasing dark-energy density eventually strips apart every bound object<sup>[1](https://arxiv.org/abs/astro-ph/0302506)</sup>.

## The singularity and its timing

For a spatially flat universe dominated by phantom energy, the Friedmann equation gives a scale factor that diverges at a finite time

\[ t_{\mathrm{rip}} - t_{0} \simeq \frac{2}{3}\,|1+w|^{-1}\,H_{0}^{-1}\,(1-\Omega_{m})^{-1/2} \]

before the end<sup>[1](https://arxiv.org/abs/astro-ph/0302506)</sup>. For \( w = -3/2 \) and \( H_{0} = 70 \ \mathrm{km \ s^{-1} \ Mpc^{-1}} \), this is about 22 Gyr<sup>[1](https://arxiv.org/abs/astro-ph/0302506)</sup>. The more negative w is, the sooner the end arrives, because the dark-energy density grows faster.

## How bound objects come apart

In general relativity the source of the gravitational potential is the volume integral of \( \rho + 3p \). A planet in an orbit of radius R around a star of mass M becomes unbound roughly when \( -(4\pi/3)(\rho+3p)R^{3} \simeq M \). With \( w \geq -1 \) the quantity \( -(\rho+3p) \) decreases with time, so any system bound today stays bound; with phantom energy it increases, so at some point every gravitationally bound system dissociates<sup>[1](https://arxiv.org/abs/astro-ph/0302506)</sup>.

A system of mass M and radius R is stripped at a time \( t \simeq P\sqrt{2|1+3w|}/[6\pi|1+w|] \) before the Big Rip, where P is the period of a circular orbit at radius R; this interval is independent of \( H_{0} \) and \( \Omega_{m} \)<sup>[1](https://arxiv.org/abs/astro-ph/0302506)</sup>. For \( w = -3/2 \) the interval is about \( 0.3\,P \)<sup>[1](https://arxiv.org/abs/astro-ph/0302506)</sup>.

A later Newtonian-force analysis reproduced this timing and tabulated the unbinding times for \( w = -3/2 \): a galaxy cluster of \( 10^{15} \) solar masses and 5 Mpc size comes apart 9.3 Gyr before the rip, the Milky Way (\( 5.8 \times 10^{11} \) solar masses, 15 kpc) 69.9 Myr before, the solar system 3.6 months before, and the Earth 25.2 minutes before<sup>[5](https://academic.oup.com/mnras/article/422/4/2945/1048646)</sup>. The same arguments extend to objects bound by electromagnetic or strong forces: molecules and then atoms are torn apart roughly \( 10^{-19} \) seconds before the end, and nuclei and nucleons in the remaining interval<sup>[1](https://arxiv.org/abs/astro-ph/0302506)</sup>.

## What observations allow

The Big Rip is a contingent fate, dependent on the unknown nature of dark energy rather than a settled outcome<sup>[6](https://www.finalfolklore.com/big-rip-2003/)</sup>. Current measurements sit close to \( w = -1 \). The Planck 2018 analysis, combining cosmic microwave background data with Pantheon supernovae and baryon acoustic oscillations, constrained the equation of state to \( w_{0} = -1.03 \pm 0.03 \), consistent with a cosmological constant<sup>[3](https://doi.org/10.1051/0004-6361/201833910)</sup>. Caldwell's own calculation using the 2018 Planck data release gave an earliest possible Big Rip in the vicinity of 200 billion years<sup>[4](https://www.americanscientist.org/node/1245)</sup>.

Newer surveys have kept the question open in a different way. Results from the [Dark Energy Spectroscopic Instrument](https://www.edgepedia.org/dark-energy-spectroscopic-instrument) (DESI), using the largest 3D map of the universe to date, strengthen hints that dark energy is evolving rather than constant<sup>[7](https://www.desi.lbl.gov/2025/03/19/more-than-a-hint-of-evolving-dark-energy-new-results-and-data-from-desi/)</sup>. The best-fitting evolving model in the DESI combinations has \( w_{0} = -0.752 \), \( w_{a} = -0.86 \), and crosses from \( w < -1 \) at high redshift to \( w > -1 \) at low redshift, a "phantom crossing" that a single scalar field cannot produce<sup>[8](https://pdg.lbl.gov/2025/reviews/rpp2025-rev-dark-energy.pdf)</sup>. Such behavior, if real, involves only transient phantom epochs and does not by itself imply a Big Rip.

## Theoretical status and alternatives

Phantom energy is theoretically awkward. The simplest realization is a scalar field with negative kinetic energy, a "phantom scalar", which suffers a manifest quantum instability<sup>[9](https://www.sciencedirect.com/science/article/pii/S0370269307000925)</sup>. A dark-energy fluid with \( w < -1 \) violates all the relativistic energy conditions, which is why \( w = -1 \) is usually treated as the lower limit<sup>[5](https://academic.oup.com/mnras/article/422/4/2945/1048646)</sup>.

Many mechanisms have been proposed that soften or remove the singularity:

- **Quantum gravity corrections.** In loop quantum cosmology, holonomy corrections introduce a term proportional to \( \rho^{2} \) in the Friedmann equation that replaces the Big Rip with a non-singular bounce<sup>[10](https://doi.org/10.1088/1475-7516/2012/07/007)</sup>. Quantum Wheeler-DeWitt wave-packet solutions disperse in the region of the classical big-rip singularity<sup>[11](https://workshops.aei.mpg.de/quantumgravity/wp-content/uploads/sites/8/2014/10/Kiefer.pdf)</sup>, and quantum effects from the conformal anomaly can moderate finite-time singularities when curvature grows large<sup>[12](https://arxiv.org/abs/hep-th/0501025)</sup>.
- **Interactions with dark matter.** Coupling phantom energy to dark matter can establish a dynamical equilibrium that makes the expansion non-singular, tending to a de Sitter state<sup>[13](https://arxiv.org/abs/1201.4056)</sup>.
- **Model surgery.** Phantom regions of a scalar-field solution can be cut out and sewn together smoothly, eliminating the Big Rip in favor of ordinary inflation<sup>[14](https://arxiv.org/abs/astro-ph/0305019)</sup>.

A related taxonomy classifies phantom-like fates by the asymptotic behavior of the Hubble parameter: the Big Rip, where H goes to infinity at finite time; the Little Rip, where H goes to infinity only as time goes to infinity; and the Pseudo-Rip, where H tends to a finite constant, an intermediate case between the cosmological constant and the Little Rip<sup>[15](https://journals.aps.org/prd/abstract/10.1103/PhysRevD.85.083001)</sup>. In the Little Rip and Pseudo-Rip, bound structures still disintegrate, but no finite-time singularity occurs<sup>[13](https://arxiv.org/abs/1201.4056)</sup><sup> • </sup><sup>[15](https://journals.aps.org/prd/abstract/10.1103/PhysRevD.85.083001)</sup>.

## References

1. [Robert R. Caldwell, Marc Kamionkowski, Nevin N. Weinberg (2003). Phantom Energy and Cosmic Doomsday. arXiv:astro-ph/0302506.](https://arxiv.org/abs/astro-ph/0302506)
2. [Phantom energy: dark energy with w < −1 causes a cosmic doomsday, Physical Review Letters 91, 071301 (2003), PubMed.](https://pubmed.ncbi.nlm.nih.gov/12935004/)
3. [Planck 2018 results. VI. Cosmological Parameters, Astronomy & Astrophysics 641, A6 (2020).](https://doi.org/10.1051/0004-6361/201833910)
4. [Tearing Apart the Universe, American Scientist.](https://www.americanscientist.org/node/1245)
5. [Effect of an expanding universe on massive objects, Monthly Notices of the Royal Astronomical Society 422, 2945 (2012).](https://academic.oup.com/mnras/article/422/4/2945/1048646)
6. [Phantom energy and cosmic doomsday, Final Folklore.](https://www.finalfolklore.com/big-rip-2003/)
7. ['More Than a Hint' of Evolving Dark Energy — New Results and Data from DESI, DESI/Lawrence Berkeley National Laboratory (March 19, 2025).](https://www.desi.lbl.gov/2025/03/19/more-than-a-hint-of-evolving-dark-energy-new-results-and-data-from-desi/)
8. [Dark Energy review, Particle Data Group, Review of Particle Physics (2025).](https://pdg.lbl.gov/2025/reviews/rpp2025-rev-dark-energy.pdf)
9. [Phantom scalar dark energy as modified gravity: Understanding the origin of the Big Rip singularity, Physics Letters B (2007).](https://www.sciencedirect.com/science/article/pii/S0370269307000925)
10. [Future singularity avoidance in phantom dark energy models, Journal of Cosmology and Astroparticle Physics (2012).](https://doi.org/10.1088/1475-7516/2012/07/007)
11. [Quantum phantom cosmology, Claus Kiefer, Max Planck Institute for Gravitational Physics presentation.](https://workshops.aei.mpg.de/quantumgravity/wp-content/uploads/sites/8/2014/10/Kiefer.pdf)
12. [Properties of singularities in (phantom) dark energy universe, Nojiri, Odintsov, Tsujikawa, arXiv:hep-th/0501025.](https://arxiv.org/abs/hep-th/0501025)
13. [Phantom Cosmology without Big Rip Singularity, Astashenok, Nojiri, Odintsov, Yurov, arXiv:1201.4056.](https://arxiv.org/abs/1201.4056)
14. [Phantom scalar fields result in inflation rather than Big Rip, Artyom Yurov, arXiv:astro-ph/0305019.](https://arxiv.org/abs/astro-ph/0305019)
15. [Pseudo-rip: Cosmological models intermediate between the cosmological constant and the little rip, Frampton, Ludwick, Scherrer, Physical Review D 85, 083001 (2012).](https://journals.aps.org/prd/abstract/10.1103/PhysRevD.85.083001)

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*Topic: Encyclopedia › Physical world and mathematics › Astronomy › Cosmology and observation › Dark energy and accelerating expansion*

*Initially written Sep 17, 2026 · Reviewed: Sep 30, 2026; Oct 15, 2026 · Edited: Sep 30, 2026; Oct 15, 2026; Oct 25, 2026 · Last review: Oct 15, 2026*

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