system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How did people in the past begin to accurately measure the height of mountains, such as everest?
gpt
One way is by making a cup of tea.

Water boils at 100°C only at sea level. The temperature at which water boils varies based on air pressure. For every 1000 metres, the boiling point drops by about 5 degrees. Thus, with a kettle and a thermometer you can estimate altitude.