Before time dilation was proposed and later experimentally shown, absolute time was the prevailing model of how time behaved in the universe. It was not until 1959 that the first experimental data was collected measuring the slightest difference in the frequency of light.
Time dilation at a glance is a counterintuitive yet deeply fascinating part of the universe. Several authors predicted it before Albert Einstein, such as Joseph Larmor in 1897, where he applied the idea to the electrons orbiting nuclei. Emil Cohn, in 1904, specifically applied the Lorentz factor, which brought Larmor to apply the time dilation principle to the electrons, to clocks. Einstein applied this to the context of his theory of special relativity, where he applied this phenomenon to time as a whole.
Through the earliest experimental testing in 1959, Robert Pound, a Canadian physicist known for nuclear magnetic resonance, and Glen A. Rebka, an American physicist, shed light on this phenomenon. Pound and Rebka detected the slightest gravitational redshift in frequency from light emitted at a lower height.
The first model of how time worked in the universe, introduced by Sir Isaac Newton in Naturalis Principia Mathematica, detailed that time progresses independently of any observer. No matter the environment or velocity. By advancing technology from Newton’s time, we now have a more profound and much more familiar understanding of time dilation and its effects on the universe.
Through the lenses of our new understandings of this phenomenon, we have counteracted issues present with our modern communications equipment, such as satellites. If time dilation were left unchecked, then the inaccuracies of GPS would become apparent as time went forward. If left to become grotesquely out of tune with our clocks here on Earth, GPS would be off by factors of miles.
Special relativity showed that differences in velocity and gravitational potential wells produce varying degrees of time dilation. On account of velocity, it is theoretically possible for a human to proceed further into the future in a relatively short amount of time.
A constant acceleration of 1 g or 9.8 m/s/s would allow a human to travel across the entire known universe in a lifetime. Current technology vastly limits the speed at which space travel can take place. However, the differences of time in everyday practice are incredibly minute. Six months on the International Space Station are orbiting at over 7.5 km/s; an astronaut would have aged .005 seconds less than people on the surface.
GPS satellites gain almost 40 microseconds a day, while geosynchronous satellites gain even more time than that.
Gravity also affects space and time. Space and time are interwoven into a fabric that persists throughout the entire universe. Massive objects warp this fabric, and objects that are orbiting more massive objects follow space-time curvature.
The Global Positioning System is considered an ongoing experiment of general and special relativity as they have to account for the gained time continually.
We can now have some fun with some online calculators that do the math. For example, emc2-explained.info provides an easy-to-use calculator that provides some excellent information.
Some values that I plugged in were as follows:
- Percentage of the speed of Light: 50%
Percentage of time is slowed down to: 86.6025%
At 50% of the light speed and traveling a distance of 1 light-year, the distance is dilated to 0.8660254037844386 light-years. The journey time would be two years as seen from Earth. For those on the spaceship, 1.7 years would pass. This effect is exaggerated the faster the ship travels.
- At 99.999%, the speed of light time is slowed to 0.4472% of its standard value.
At these speeds, a distance of 1 light-year is contracted to .004472 light-years. The Earth’s journey would appear to have taken one year, while those on board the ship would have experienced only 0.004472 years.
For fun, at 99.999% of the speed of light, a distance of 100,000 light-years (the Milky Way Galaxy diameter), the distance is dilated to 447 light-years. The time it would take on Earth would be 100,001 years, while the people on board would experience 447 years.
I hope that this article has shed just a little light on the fascinating phenomenon of time dilation. If there are any questions, you, of course, can always leave a comment.