Nature's Experiments: Unlocking Cosmic Secrets Without a Lab Coat
In 2017, scientists mastered the art of using the universe as their laboratory, making groundbreaking discoveries by observing its most violent and wondrous experiments.
Published: October 2023 | Reading time: 8 minutes
Some of the most profound scientific breakthroughs do not happen in sterile labs under the controlled glow of fluorescent lights. Instead, they occur in the cosmos at large, through colossal, unplanned events that scientists observe and decipher. These events are known as natural experiments1 8 .
The year 2017 stands as a landmark period for this approach, when astronomers and physicists witnessed a once-in-a-century event: the collision of two neutron stars. This cosmic crash, observed for the first time, acted as a perfect natural experiment, confirming long-held theories about the origin of heavy elements like gold and platinum and opening new windows into the workings of the universe3 5 .
What Is a Natural Experiment?
In public health and policy, a natural experiment evaluates the impact of real-world events—like a new law or a natural disaster—that divide a population into exposed and unexposed groups, all without a researcher's direct control1 8 . In astronomy, the principle is the same, but the scale is cosmic. The universe provides the event, and scientists, acting as cosmic detectives, gather the evidence.
These studies differ from traditional lab experiments in one crucial way: the researcher does not control the "treatment" or exposure. Instead, they seek out events where the assignment of exposure is "as-if random," meaning that the groups being compared are likely similar in all other respects, allowing for stronger causal inferences8 .
Key Concept
Natural experiments leverage real-world events that researchers cannot control but can observe systematically to draw causal inferences about phenomena that would be impossible or unethical to test in laboratory settings.
"As-if Random" Assignment
The cornerstone of natural experiments is that exposure to the "treatment" (the natural event) occurs in a way that is essentially random relative to the outcomes being studied, minimizing selection bias.
Comparing Research Approaches
| Feature | Randomized Controlled Trial (RCT) | Natural Experiment (NE) | Nonexperimental Observational Study |
|---|---|---|---|
| Intervention | Well-defined and researcher-controlled1 | Clearly identified, but not controlled by researchers1 | Often no clearly defined intervention1 |
| Assignment | Random allocation by researchers1 | Not controlled by researchers; relies on a natural or policy event1 8 | No clear assignment process; risk of reverse causation1 |
| Key Strength | Gold standard for eliminating confounding1 | Evaluates real-world interventions that can't be tested in a lab1 | Can study long-term or complex exposures |
| Key Challenge | Can be artificial and expensive1 | Must carefully rule out alternative explanations for results1 | Susceptible to confounding and bias1 |
The Cosmic Stage: Key Discoveries of 2017
2017 was a spectacular year for science, providing a rich tapestry of natural events and researcher-led discoveries that expanded our understanding of everything from the cosmos to human origins.
An Interstellar Visitor
In October, Canadian astronomer Robert Weryk spotted 'Oumuamua, the first asteroid ever known to visit our solar system from interstellar space. Its unusual, cigar-shaped structure and origins beyond our solar system made it a fascinating subject of study3 .
A New (Old) Continent
An international team of scientists provided further evidence for Zealandia, a mostly submerged continent in the South Pacific. Fossils suggest unique plants and organisms once lived on this land, which wasn't always sunken5 .
Seven Earth-like Planets
NASA announced the discovery of seven Earth-sized planets orbiting the nearby star TRAPPIST-1. At least six are rocky, and all could contain water, making this system one of the most promising places to search for signs of life beyond Earth3 5 .
The First North Americans?
A controversial study suggested humans were in North America 130,000 years ago—more than 100,000 years earlier than previously believed—based on analysis of stone tools and mastodon bones found in California3 .
Yet, among these amazing findings, one event stood out for its sheer violence and its value as a perfect natural experiment.
Scientific Breakthroughs of 2017
Distribution of major scientific discoveries across different fields in 2017, highlighting the prominence of astronomical findings.
A Deep Dive into a Landmark Natural Experiment: The Neutron Star Collision
The Methodology: A New Era of Multi-Messenger Astronomy
For the first time, scientists could combine information from gravitational waves (ripples in spacetime) and electromagnetic waves (light) to study a single cosmic event. This new approach is called "multi-messenger astronomy."
The experimental procedure unfolded in a series of steps that would have been impossible just years earlier:
- Detection of Gravitational Waves: The LIGO and Virgo instruments identified the distinctive chirp of gravitational waves from two ultra-dense objects spiraling toward each other, later confirmed to be neutron stars5 .
- Pinpointing the Location: The data from the gravitational wave signal provided a rough sky location, allowing astronomers to point their telescopes in the right direction5 .
- Observation Across the Spectrum: Within hours, telescopes around the world and in space detected a bright, new source of light—a "kilonova"—in a galaxy 130 million light-years away. They observed this event in gamma-rays, X-rays, visible light, and radio waves3 5 .
Observatories around the world collaborated to observe the neutron star merger across the electromagnetic spectrum.
Results and Analysis: Forging the Elements of Life
The data from this single event provided a treasure trove of scientific insights, confirming several major theories.
Origin of Heavy Elements
The spectra of the kilonova revealed the signatures of newly formed elements, demonstrating that the collision of neutron stars is a primary cosmic forge for heavy elements like gold, silver, and platinum5 . Researchers estimated the collision produced an amount of gold equivalent to the mass of the planet Jupiter5 .
Speed of Gravity
The near-simultaneous arrival of gravitational waves and gamma-rays from the same event confirmed that gravity travels at the speed of light, a key prediction of Einstein's general theory of relativity.
Gamma-Ray Bursts
The event confirmed the long-held hypothesis that short gamma-ray bursts—some of the most energetic events in the universe—are caused by merging neutron stars.
Observational Data from the Neutron Star Merger
| Observation Type | What Was Detected | Scientific Significance |
|---|---|---|
| Gravitational Waves | Ripples from inspiral of two neutron stars5 | Confirmed existence of binary neutron stars; provided data on their masses and behavior5 |
| Gamma-Ray Burst | Short burst of high-energy radiation5 | Proved that neutron star mergers are the cause of at least some short gamma-ray bursts5 |
| Kilonova (Visible Light) | Fading fireball of light from the merged object3 | Revealed the radioactive decay of newly synthesized heavy elements, like gold and platinum3 5 |
| Multi-wavelength Data | Follow-up observations in X-ray and radio3 | Provided details on the aftermath of the merger and the structure of the ejected material3 |
Multi-Messenger Astronomy Timeline
Sequence of observations following the neutron star merger, showing how different signals arrived at Earth at different times.
The Scientist's Toolkit: Key Research Reagents and Instruments
While natural experiments leverage events provided by nature, analyzing them requires a sophisticated suite of human-made tools and reagents. The following table details the essential "ingredients" that made the 2017 neutron star discovery possible.
| Tool/Reagent | Function in Research |
|---|---|
| Advanced LIGO/Virgo | Laser interferometers that detect infinitesimal stretches and squeezes in spacetime caused by passing gravitational waves3 . |
| Space & Ground-based Telescopes | Instruments like the Hubble Space Telescope and countless ground observatories that collect electromagnetic radiation (gamma-rays, X-rays, visible light, radio waves) to create a complete picture of cosmic events3 5 . |
| CRISPR-Cas9 | A gene-editing tool that, in 2017, was used to engineer pigs to be safe for potential organ transplants into humans and to edit the DNA of viable human embryos, showing its power as a biological "reagent"5 . |
| CAR T-Cells | A revolutionary cancer therapy where a patient's own immune cells are re-engineered to attack cancer cells, approved by the FDA in 2017. This is a "living reagent" in the fight against disease5 . |
| Persilylamidines | Specialized chemical reagents valued in synthetic chemistry for their clean reactivity and mild byproducts, used to build complex molecules for advanced materials and drugs9 . |
| Muon Tomography | An innovative imaging technique that uses cosmic ray particles called muons to penetrate massive structures. In 2017, it was used to discover a hidden void in the Great Pyramid of Giza5 . |
Research Tools by Field
Impact of Multi-Messenger Astronomy
"The detection of gravitational waves from a binary neutron star merger, accompanied by electromagnetic counterparts, marked the dawn of multi-messenger astronomy and provided unprecedented insights into cosmic phenomena."
This coordinated observation approach allowed scientists to:
- Confirm theoretical predictions about element formation
- Measure the expansion rate of the universe
- Study the behavior of matter under extreme densities
- Test fundamental physics theories
The Future Writes the Experiment
The monumental discoveries of 2017, particularly the observation of colliding neutron stars, underscore the immense power of natural experiments. By remaining curious, developing ever-more-sensitive tools, and being ready to observe the universe's own dramatic performances, scientists can uncover truths that are impossible to replicate in any laboratory on Earth.
This new era of multi-messenger astronomy, powered by natural experiments, promises to continue answering old questions and, without a doubt, posing thrilling new ones about the fundamental nature of our reality. The cosmos continues to be the most sophisticated laboratory we have.