open universe

American  

noun

Astronomy.

1. a model of the universe in which the universe expands forever because there is not enough mass to counteract the expansion by means of gravitational attraction.

---

open universe Scientific  

1. Model of the universe in which the curvature of space is flat or curved away from itself, entailing that the size of the universe is infinite. According to this model, gravity between objects is not able to stop or reverse the expansion of the universe, thus objects continue to move farther and farther apart as space moves outward. An object moving in a straight line in an open universe would never return to its starting point. According to current cosmological theories, the universe is open if it is insufficiently dense. Such a universe will never end, but will eventually become very cold and dark because stars gradually lose all of their energy.

2. Compare closed universe See Note at big bang

---

open universe Cultural  

1. If there is not enough matter in the universe to exert a strong enough gravitational force to stop the universal expansion associated with the big bang, the universe is said to be open. (Compare closed universe and flat universe.)

---

Etymology

Origin of open universe

First recorded in 1975–80

Example Sentences

And yet something ineffable and meaningful remains, an unquenchable spirit, still in motion, drifting upward toward heaven, or the open universe, or the stars.

From Washington Post • Dec. 7, 2019

Such a universe is infinite and this model is called an open universe.

From Textbooks • Oct. 13, 2016

Since matter can be thought to curve the space around it, we call an open universe negatively curved.

From Textbooks • Aug. 12, 2015

That conclusion will be disturbing to those who find the concept of an infinitely expanding or "open" universe to be philosophically unsatisfactory.

From Time Magazine Archive

Not far away she could hear Billy cropping the grass, and throughout the vast open universe there seemed to brood a great and peaceful silence.

From The Man of the Desert by Hill, Grace Livingston