Fun Facts About Time

• Some theories of the end of the universe suggest a future were meaningful change ceases and time, which measures these changes, could stop. They call it "Heat Death" or the "Big Freeze."
• Since earth's rotation isn't perfectly consistent, we occasionally add a second to keep clocks aligned. Since 1972, there have been 27 seconds added, typically 1 second every 18 months or so.
• Your body has an internal clock. Circadian rhythms control sleep, hormones, and even digestion on roughly a 24-hour cycle.
• Animal studies suggest they perceive time differently than us. For instance, flies see more visual "frames" per second, so humans seem slow moving to them.
• Einstein's theory of relativity confirms that time is not absolute and passes slower in stronger gravity. That means clocks on land run slower than those at higher altitudes. That also means GPS satellites must be continuously adjusted to stay accurate.
• Since 1967, scientists have defined the second by measuring the frequency of light required to make an electron jump. It's based on vibrations of Cesium-133 atoms — all 9,192,631,770 of them.
• There is no "now" in the universe. In the modern theory of physics, the present moment is not universal. Rather, it depends on your frame of reference.
• Many fundamental physics equations work the same forward or backward in time. That means in the theoretical realm, the past and future coexist.