Percival Lowell

Percival Lowell (1855–1916) was an American astronomer who founded Lowell Observatory and became known for his claims about canals on Mars and his search for Planet X.

William H. Pickering: An American astronomer who studied Mars and proposed that its dark markings and polar caps changed seasonally. Pickering shared Lowell’s interest in Mars and contributed observations to the era’s debate over Martian life.
Mars canals: A network of straight lines reported on Mars in the late nineteenth and early twentieth centuries, now understood as an optical illusion. The supposed canals were the most influential feature in Lowell’s interpretation of Mars.
Lowell Observatory: An astronomical observatory founded by Percival Lowell in Flagstaff, Arizona, in 1894. Lowell built the observatory to pursue planetary astronomy, especially the study of Mars.
Planet X: A hypothesized planet beyond Neptune proposed to explain discrepancies in the orbits of the outer planets. Lowell’s calculations motivated a search for Planet X at his observatory, though the predicted perturbations were mistaken.
E. C. Slipher: An American astronomer who directed Lowell Observatory and pioneered spectroscopic studies of planets and comets. Slipher continued the observatory’s planetary research after Lowell’s death.
Schiaparelli's canali: The Italian astronomer Giovanni Schiaparelli’s name for linear features he mapped on Mars in 1877. A translation of Schiaparelli’s word canali helped inspire the idea that Martians had built canals.
Flagstaff, Arizona: A city in northern Arizona where Lowell established his observatory at high elevation and under dark skies. The site’s altitude and clear air offered better conditions for planetary observation than many eastern locations.
Pluto: A dwarf planet in the Kuiper belt discovered in 1930 by Clyde Tombaugh at Lowell Observatory. The search inspired by Lowell led to Pluto’s discovery, although Pluto did not account for his predicted orbital discrepancies.
Vesto Slipher: An American astronomer whose measurements of galactic redshifts helped establish that the universe is expanding. Lowell hired Slipher, whose observatory work later reshaped astronomy far beyond Lowell’s planetary interests.
Visual perception: The processes by which the visual system interprets patterns of light as objects and spatial relationships. Perceptual completion can make scattered markings appear as continuous lines on a small, blurred planetary image.

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