Albert Einstein’s theory of relativity changed our understanding of the universe by defining space and time as relative, not absolute. With relativity, Einstein aimed to formulate physical laws that are invariant (i.e., they work the same for all observers), even though their observations of space and time may vary depending on their motion or the gravitational fields they are in.
Imagine two twins deciding to live in different places: one at the top of a mountain and the other at sea level. Surprisingly, the twin who lives on the mountain will age faster than the one at sea level. Why does this happen? The answer lies in Einstein’s theory of general relativity.
Time does not flow the same way everywhere. According to Einstein, gravitational fields affect the fabric of space-time. In regions where gravity is stronger, such as at sea level, time passes more slowly. Conversely, in areas where gravity is weaker, such as at the top of a mountain, time moves a bit faster. This means that the biological clock of the twin on the mountain “runs faster.”
Although the difference is minute on human scales, the phenomenon has very important practical applications. For example, GPS systems must correct for time differences due to two effects: gravitational time dilation because the satellites are in a weaker gravitational field, and time dilation due to high speed because of the satellites’ velocity. Without these corrections, GPS would be much less accurate.
The mountain twin paradox is a reminder of how space and time are intrinsically intertwined, changing our perception of something as everyday as the passage of time.
Adjunct Professor in Sociology at the University of Barcelona