The Ingenious Experiments That Shaped Modern Science

Science, as we know it today, is a testament to the innovative thinking of a select few geniuses. From the early days of mechanics to recent breakthroughs in neuroscience, several experiments stand out as particularly groundbreaking. This article explores some of the most ingenious experiments that have revolutionized our understanding of the world.

Henry Cavendish's Experiment: Weighing the World

The most notable experiment of all time, according to many, is undoubtedly Henry Cavendish's experiment to determine the density and mass of the Earth. Known as the 'weighing the world' experiment, Cavendish used a torsion balance to test Newton's theory of gravity. In 1797, with no advanced technology, Cavendish figured out the value of G, the universal gravitational constant. His results were surprisingly accurate compared to modern standards. This was made all the more impressive as Cavendish came from aristocratic roots, being the second son of the third Duke of Devonshire.

The Rise of Modern Mechanics

Before Cavendish's groundbreaking experiment, the foundations of modern mechanics were laid by Galileo. His work, as detailed in Two New Sciences, introduced many concepts through dialogues. One of the most impactful experiments he described involved a ball rolling down a ramp, demonstrating the nature of gravitational acceleration. This idea laid the groundwork for Newton's later developments and inspired generations of scientists.

Classic and Innovative Experiments

Eratosthenes' measurement of the Earth's circumference is another remarkable example of ingenuity. Using a simple yardstick, Eratosthenes made the first known direct measurement of the Earth's circumference around 200 BC, making his experiment a landmark in the history of science. Other notable experiments include:

Fred Sanger's DNA sequencing, a method so simple yet revolutionary, stands as a testament to human ingenuity. Max von Laue's use of X-ray crystallography to determine atomic structures, including those of DNA and proteins, which contributed to the discovery of the structure of DNA by James Watson and Francis Crick, and the study of protein structures by Max Perutz.

Each of these experiments showcases the power of simple yet ingenious methods to solve complex problems, paving the way for future scientific breakthroughs.

The Hidden World of Adult Neurogenesis: Carbon Dating the Brain Cells

One of the most fascinating recent discoveries is the dynamics of neurogenesis in adult humans. In 2013, a team led by Jonas Frisen at the Karolinska Institute in Sweden used carbon dating to provide direct evidence of neurogenesis in the adult human brain. This method relies on the radioactive carbon-14 that was released into the atmosphere during nuclear bomb tests during the Cold War.

When cells go through mitosis, they integrate the radioactive carbon-14 in their DNA, creating a 'birthdate' that can be measured. This method provided crucial evidence that the adult human brain continues to generate new neurons, challenging the long-standing belief that brain cell production ceases after early childhood.

The study found that a third of the neurons in the hippocampus (an area crucial for memory and learning) are regularly renewed, with 700 new neurons added each day. However, this rate naturally decreases with age. The researchers isolated the nuclei, purified the DNA in a clean room to prevent contamination, and measured the radioactive carbon-14 levels using a sophisticated technique called accelerator mass spectrometry.

Further research by Kirsty Spalding has extended this carbon dating technique to fat cells. This study revealed that fat cell numbers are largely set in childhood and adolescence, with a constant number of fat cells in adults, regardless of weight. Instead, changes in fat cell volume cause weight fluctuations.

These findings not only provide a better understanding of brain and fat cell biology but also have significant implications for addressing health issues like obesity. Knowing that obese adults have a higher number of fat cells, which are constantly replenished, can help in designing more effective strategies to combat obesity.

While nuclear bomb testing may have had negative consequences, the carbon dating technique it enabled has brought significant benefits to science, medical research, and public health.