The invisible force making our universe expand at a faster rate

Space · Published 22 October 2026 Swipe more like this →

In short: For billions of years, gravity acted as a cosmic brake, slowing down the expansion of everything after the Big Bang. But about nine billion years ago, something changed. An unknown force began pushing the cosmos apart faster and faster, making up nearly 70% of all existence.

The discovery of dark energy in the late 1990s fundamentally shifted our understanding of cosmology. While gravity pulls matter together, dark energy acts as a repulsive force characterized by negative pressure. It is currently estimated to comprise between 68.3% and 70% of the universe. Despite its dominance, scientists still do not know what it actually is, though they can observe its effects through various methods including supernovae observations, Baryon Acoustic Oscillations (BAO), the Cosmic Microwave Background (CMB), and gravitational lensing. Researchers identify a specific value known as w to describe this phenomenon. They also study how the force interacts with gravitational lensing and other cosmic structures.

The path to this discovery was paved by early 20th-century breakthroughs in measuring cosmic scale. In 1912, Henrietta Swan Leavitt established a relationship between the period of Cepheid variable stars and their luminosity. This allowed astronomers to calculate distances to far-off galaxies for the first time. Simultaneously, Vesto Slipher used a spectrograph to observe spiral galaxies, becoming the first to detect 'redshift'—the stretching of light waves as objects move away from us. Slipher utilized a spectrograph to split light into its component colors like a prism does. This technology allowed him to see specific spectral lines from distant spiral galaxies.

These two pillars of observation—distance and velocity—provided the framework needed to realize that the universe isn't just expanding; it is accelerating. The central mystery now lies in why 'empty space' seems to exert such profound control over the fate of the cosmos, driving a mysterious expansion that continues to challenge the boundaries of modern physics. The initial expansion following the Big Bang lasted only a fraction of a second before gravity took over. Now, we must reconcile these historical milestones with the current mystery of cosmic acceleration.

General information, not professional advice. Spotted an error? Flag the card or see corrections and complaints.

Intellect Plus is a visual educational discovery platform for exploring fascinating facts and ideas. Brain Food, Not Brain Rot. What is Intellect Plus?

Related

• The invisible force making up 70% of our universe
• In 1998 astronomers found the universe's expansion is speeding up, not slowing.
• The universe is flying apart faster and faster every second
• The invisible forces that make up 95% of our universe
• Mapping the invisible: how one telescope is charting the dark universe
• Does dark energy possess an antigravity effect that accelerates the expansion of our universe?
• The universe is accelerating away from us, but we don't know why
• Is the standard model of our universe officially broken?
• Is the universe's expansion accelerating at a shifting rate?
• The profound gap between quantum mechanics and the expansion of the universe
• NASA is repurposing a secret spy satellite to map the cosmos
• The invisible glue of the cosmos is mostly unseen

More in Dark energy · More in Space · Latest · A–Z · All topics