ZMT: Daily Fact: Time moves faster at higher altitudes

Original photo by mikkelwilliam/ iStock

Time seems like a simple enough concept — 60 seconds in a minute, 60 minutes in an hour, and so on. That is, except for a little something called "gravitational time dilation." First explored in Albert Einstein's general theory of relativity, the idea is almost confusingly simple — the farther away you are from a massive object (e.g., a planet), the faster time travels. The more massive the object, the slower time travels, which is why things get very wonky around supermassive black holes like the one at the center of our galaxy.

These differences in how time flows are minuscule on Earth, so they don't really affect us — the top floor of the Burj Khalifa, the world's tallest building, does not operate with a special time-dilated clock. Yet technically, even our heads experience time just a bit differently than our feet. In 2010, the U.S. National Standards and Technology (NIST) even performed an experiment using optical atomic clocks that could measure a change in time dilation within less than one meter.

Although imperceptible to our minds, precision technologies such as GPS need to factor in time dilation in order to work at all. So the next time you use Google Maps, consider giving a shoutout to Einstein and his mind-bending theory of the universe.

Numbers Don't Lie

Speed (in mph) Doc Brown's DeLorean needs to reach before traveling through time in "Back to the Future"

Speed of light (in miles per second), which makes for an eight-minute journey from the sun to Earth

186,000

Year Stephen Hawking's "A Brief History of Time" was published

1988

Number of satellites in the Global Positioning System constellation

Scientists used a total solar eclipse to prove Einstein's general theory of relativity.

Today Albert Einstein is known best for his general theory of relativity, a conception of gravity that revolutionized physics. But when he published the theory in 1916 in the German science journal Annalen der Physik, the idea got its fair share of pushback. At the time, Einstein wrote, "Every coachman and every waiter is debating whether relativity theory is correct. Belief in this matter depends on political affiliation." Then came Arthur Eddington, a British astronomer, who conducted an amazing experiment only months after World War I ended. On May 29, 1919, Eddington observed a solar eclipse — more specifically, a star cluster called Hyades in the Taurus constellation visible during the darkness of totality — to see how the star light was affected by the sun's mass. After spending months crunching the numbers, Eddington proved Einstein correct; the star light had been bent in the manner he predicted. The German physicist soon became a scientific rock star the world over, and our perception of the universe was never the same.

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Daily Fact: Time moves faster at higher altitudes