How Do Scientists Detect and Study Dark Matter and Dark Energy?

Despite making up about 95% of the universe, dark matter and dark energy remain two of the most mysterious and elusive entities in modern science. Unlike stars and galaxies, we can’t see or directly observe them—so how do scientists even know they exist?

The Clues Left Behind

We can’t see dark matter or dark energy because they don’t emit, absorb, or reflect light. But scientists detect them through the effects they have on visible matter, radiation, and the structure of the universe.

• Dark matter is inferred from gravitational effects—it holds galaxies together and influences how they rotate.
• Dark energy is proposed to explain the accelerating expansion of the universe.

How Scientists Detect Dark Matter

There are several key methods researchers use to study dark matter:

• Gravitational Lensing: When light from distant galaxies bends around massive, invisible objects, scientists can measure that distortion to infer the presence of dark matter.
• Galaxy Rotation Curves: Stars on the outer edges of galaxies orbit much faster than they should based on visible mass alone—indicating the presence of unseen mass holding them in place.
• Cosmic Microwave Background (CMB): Fluctuations in the CMB—the afterglow of the Big Bang—reveal the gravitational effects of dark matter in the early universe.
• Direct Detection Experiments: Deep underground labs like the Xenon1T in Italy aim to detect dark matter particles by observing rare collisions with atomic nuclei.

How Scientists Study Dark Energy

Dark energy is harder to pin down, but astronomers are making progress by studying the universe’s large-scale structure and expansion history:

• Supernova Observations: Distant Type Ia supernovae serve as "standard candles" to measure cosmic distances. Their apparent dimness helped scientists discover the universe’s expansion is accelerating.
• Baryon Acoustic Oscillations (BAO): These are regular, periodic fluctuations in the density of visible matter, which serve as a cosmic yardstick to track expansion.
• Weak Gravitational Lensing: Subtle distortions in light from distant galaxies help map the distribution of dark energy and dark matter over time.

Future Missions and Experiments

Projects like the Vera C. Rubin Observatory and the Euclid Space Telescope are designed specifically to explore dark matter and dark energy with unprecedented precision. There’s also increasing interest in connecting these mysteries to breakthroughs in quantum physics and high-energy particle research at facilities like CERN.

So What Is It, Really?

Despite decades of research, we still don’t fully understand what dark matter or dark energy actually are. Some theories suggest dark matter could be made of yet-undetected particles like WIMPs (Weakly Interacting Massive Particles) or axions. Others propose modifications to gravity itself. Dark energy may be a property of space itself or a sign of an incomplete understanding of fundamental physics.

One thing is clear: whatever the answers turn out to be, they will fundamentally reshape our understanding of the cosmos and our place in it. For now, scientists are patiently watching the universe for clues—one supernova, one collision, one subtle lens at a time.