While modern students find it natural to accept that an ice age once existed, the first presentations of ice age theories were mercilessly attacked by the most knowledgeable minds of the time.

In the mid-nineteenth century, Scottish scientist James Croll proposed that variations in the Earth’s orientation toward the Sun were responsible for colder time periods. But he was never quite able to convince his contemporaries of this argument. A century later his ideas were further developed by the mathematician Milutin Milankovitch. More scientific evidence showed that these climate changes amplified each other, leading toward what we now consider an ice age.

Read about how scientists battled over the idea of ice ages.