view the horizon, you would have to look down, not across. For a long time, people have known that Earth is round, despite How Do We Know Earth our everyday experience of Earth’s Is Round? surface. Some people think Christopher Columbus proved Earth’s shape. Throughout history, some peo- They believe that he sailed to the ple have thought that Earth is flat. New World in order to show that It is easy to understand why. When Earth was round. This is not true. you walk to school, you do not By the time of his voyage in 1492, feel that you are walking a curved most educated people already path. When standing on the shore knew that Earth was round. This of an ocean, the horizon appears misunderstanding about Colum- level. You also always look straight bus’s voyage was popularized in ahead to see the horizon. If Earth an 1828 book by Washington Ir- is curved, some argue, in order to ving called A History of the Life and
Eratosthenes World
N GREECE 400 mi Athens 400 km Aegean Sea Rhodes
M editerranean Sea
Alexandria
Cairo
N i l e SAHARA R R e . d
S EGYPT e a Syrene