### Every quantity in nature is limited.

This page presents some of the most famous physical limits.

Quantity |
Limit and value | Details |

Speed of matter, energy and signals | Upper limit c ≈ 3 · 10^{8} m/s |
Implies special relativity, including the relativity of time and length. Achieved by light. |

Action, or change | Lower limit h-bar ≈ 10^{-34} Js |
Implies quantum theory, including the existence of photons and atoms. Achieved by any elementary process, such as a spin flip. |

Force | Upper limit c^{4}/4G ≈ 3 · 10^{43} N |
Implies general relativity, as shown here. Achieved by black hole horizons. |

Power and Luminosity | Upper limit c^{5}/4G ≈ 9 ·
10^{51} W |
Implies general relativity, as shown here. Achieved by black hole horizons. |

Mass rate | Upper limit c^{3}/4G ≈ 10^{35} kg/s |
Implies general relativity, as shown here. Achieved by black hole horizons. |

Mass per length | Upper limit c^{2}/4G ≈
3 · 10^{24} kg/m |
Implies general relativity, as shown here. Achieved by black hole horizons. |

Length | Lower limit sqrt(4 G h-bar / c^{3}) ≈
3 · 10^{-35} m |
The essence of quantum gravity. Space is continuous and has a smallest measurable distance at the same time. Follows from the other limits. |

Time | Lower limit sqrt(4 G h-bar / c^{5}) ≈
10^{-43} s |
Another way to put the essence of quantum gravity. Follows from the other limits. |

Probability density | Upper limit (c^{3}/4 G h-bar)^(3/2) ≈
3 · 10^{103} 1/m^3 |
Follows from smallest volume. Limits wave functions in quantum gravity. Consistent with other limits. |

These limits are valid across the universe.

These limits are valid at all times.

These limits are valid across all sciences.

These limits are absolute.

These limits are invariant: they are the same for every observer.

These limits restrict what can happen, what can be, and what can be done.

These limits define physics, as shown on this page - when they are added to the principle of least action. In that case, the limits describe everything that can happen.

When the limits are used to defined physics, only a few are needed, as shown on this page.

These limits differ slightly from the Planck values: the contain 4G instead of G.

Find any exception to any limit - and become famous.

Find an additional, unknown limit - and then publish it.

### Every quantity in nature has a second, opposite limit.

Have fun filling them in! Many are unpublished.Quantity |
Limit value | Details |

Distance | Upper limit: the diameter of the universe | Implies cosmology. |

Time | Upper limit: the age of the universe | Implies cosmology. |

These limits are valid across the universe.

These limits change over time.

In short: nothing in nature is infinitely large or infinitely small.

* *