Sir Charles Wyville Thomson is a foundational figure in marine science and oceanography. His pioneering work, particularly his leadership of the HMS Challenger Expedition, revolutionized the understanding of the deep sea and laid the groundwork for modern oceanographic research. He transformed speculative ideas about the ocean into an empirical science, cementing his legacy as an explorer who expanded human knowledge of the planet.
Early Life and Path to Science
Charles Wyville Thomson was born on March 5, 1830, in Bonsyde, West Lothian, Scotland. He initially studied medicine at the University of Edinburgh in 1845. After three years, ill health led him to shift his focus to natural science, where his aptitude for zoology, botany, and geology became evident.
Thomson’s academic career began with a lectureship in botany at the University of Aberdeen in 1850. He then held professorships in botany at Marischal College, natural history at Queen’s College, Cork (1853), and mineralogy and geology at Queen’s University of Belfast (1854). In 1860, he transferred to the chair of natural science at Belfast, and in 1870, he assumed the Regius Chair of Natural History at the University of Edinburgh.
While at Belfast, Thomson’s interest in marine biology grew, especially concerning deep-sea life. He studied marine invertebrates and published works on coelenterates, polyzoans, and fossilized cirripeds, trilobites, and crinoids. His curiosity about life at great ocean depths was further fueled by examining deep-sea animals collected by Michael Sars off the Norwegian coast in 1866. This led him to undertake deep-sea dredging expeditions in 1868 and 1869 aboard HMS Lightning and HMS Porcupine. During these voyages, he collected specimens from depths exceeding 1,200 meters (650 fathoms) and observed varying deep-sea temperatures, indicating oceanic circulation. His preliminary findings from these voyages were published in his 1873 book, The Depths of the Sea, which laid the groundwork for the HMS Challenger Expedition.
The Challenger Expedition
The HMS Challenger Expedition, from December 1872 to May 1876, established the field of oceanography. The British Admiralty and the Royal Society collaborated to launch this unprecedented global voyage. The HMS Challenger, a 2,306-ton wooden corvette, was specially converted for scientific purposes, with 16 of its 18 guns removed to accommodate laboratories and extensive scientific equipment.
The expedition aimed to gather comprehensive data on a wide range of ocean features, including ocean temperatures, seawater chemistry, currents, marine life, and seafloor geology. Its objectives included verifying hypotheses about global ocean circulation and exploring the distribution of marine life at various depths. Under the scientific supervision of Sir Charles Wyville Thomson, the ship embarked from Portsmouth, England, on December 21, 1872, with a six-person civilian scientific team and a crew of nearly 250.
Over three and a half years, HMS Challenger circumnavigated the globe, covering approximately 68,890 nautical miles across the Pacific, Atlantic, and Southern Oceans. The expedition made observations and soundings at 362 stations, taking 492 deep soundings and 133 dredgings. Pioneering methodologies included:
- Lowering sounding lines with weights to measure ocean depths and collect sediment samples.
- Using dredges and trawls to collect marine organisms from various depths.
- Measuring temperature at different depths with instruments like the Miller-Casella mercury thermometer.
- Collecting water samples at standard depths for chemical analysis.
- Gathering plankton samples, with the speed and direction of ocean surface currents recorded.
Unveiling Ocean Secrets and Lasting Impact
The Challenger Expedition yielded groundbreaking scientific discoveries that reshaped ocean understanding. It disproved the “azoic theory” (no life below 550 meters) by recovering animal life from much greater depths, including annelid worm tubes from 3,000 fathoms. Over 4,700 new marine species were discovered, demonstrating the abundance and variety of life throughout the oceans.
The expedition produced the first comprehensive maps of ocean depths and contours, revealing features like the Mid-Atlantic Ridge, a vast underwater mountain range. The Challenger crew discovered the Mariana Trench, the deepest point on Earth, with an initial recorded depth of over 8,200 meters. Modern measurements refined this depth to approximately 11,000 meters, with the deepest point now named Challenger Deep.
New insights were gained into ocean currents and temperatures, challenging assumptions about constant deep-sea temperatures and indicating complex oceanic circulation. The collected data formed the initial baseline for physical oceanography. Sir Charles Wyville Thomson oversaw the publication of the expedition’s results in a 50-volume report, Report on the Scientific Results of the Voyage of H.M.S. Challenger during the Years 1873–76. This undertaking took nearly 20 years to complete, providing detailed descriptions of the findings and specimens, with the last volume published in 1895.
Thomson’s work on the Challenger Expedition transformed oceanography into a modern scientific discipline based on empirical data. His pioneering efforts in deep-sea exploration and systematic data collection established a new paradigm for marine inquiry. The expedition’s findings continue to be used by scientists today, including in climate change research. Thomson was knighted in 1877, and his enduring legacy is recognized in the Wyville-Thomson Ridge in the North Atlantic, a testament to his profound impact on our understanding of the Earth’s oceans.