# How Scientists Can Slow Down Time

Time dilation isn't an easy concept to wrap your head around but it's the cornerstone of of Einstein's theory of special relativity. It basically states that the faster something moves, the slower their time appears to move relative to a stationary observer. This is basically a side effect of the fact that the speed of light is constant regardless of who measures it.
These "time dilations" aren't something we encounter much on earth: they only really make a difference to things that are moving *really* fast, like approaching the speed of light. Proposed in 1905, time dilation has been demonstrated in experiments where super-accurate atomic clocks were put on airplanes and flown around the earth slowed down compared to atomic clocks left on the ground. The shift was microscopic but it was exactly what Einstein had predicted.
For the first time, scientists have been able to demonstrate time dilation in a lab with the accuracy of one part in a billion. In the experiment, published in Physical Review Letters, scientists compared the internal clocks of two groups of charged lithium ions: ones that were stationary and one group that was sped up to 40% of the speed of light. They shot two laser lights at them, one in front and one behind, and then measured the light absorption rate.
Using the Doppler Effect (which shows that light traveling towards us is is "blue-shifted", and light traveling away from us is "red-shifted"), and some very sensitive measurement techniques called optical-optical double resonance spectroscopy, they were able to show said time dilation. You can read a more-detailed account of this (somewhat complicated) experiment [here on Ars Technica http://arstechnica.com/science/2014/09/time-dilation-measured-at-40-percent-of-the-speed-of-lightin-the-lab/], but otherwise, are special relativity and time dilation the sorts of things you want us to report more on on DNews? Is there something else you'd like us to be covering? Be sure to let us know in the comments section below!
**Read More:**
[Time dilation measured at 40 percent of the speed of light - in a lab http://arstechnica.com/science/2014/09/time-dilation-measured-at-40-percent-of-the-speed-of-lightin-the-lab] (Ars Technica)
"Einstein is most famous for general relativity, which is really a theory of gravity."
[Time Dilation http://www.phy.olemiss.edu/HEP/QuarkNet/time.html] (olemiss.edu)
"It turns out that as an object moves with relativistic speeds a "strange" thing seems to happen to its time as observed by 'us' the stationary observer (observer in an inertial reference frame).
[Test of Time Dilation Using Stored Li+ Ions as Clocks at Relativistic Speed http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.113.120405] (APS Journals)
[Synopsis: Relativity is Right on Time, Again
http://physics.aps.org/synopsis-for/10.1103/PhysRevLett.113.120405] (APS Journals)
"Special relativity predicts that a twin in a high-speed rocket, as viewed by his Earth-bound brother, will have a slower-ticking clock."
[Real-World Relativity: The GPS Navigation System http://www.astronomy.ohio-state.edu/~pogge/Ast162/Unit5/gps.html] (OhioState.edu)
"People often ask me 'What good is Relativity?' It is a commonplace to think of Relativity as an abstract and highly arcane mathematical theory that has no consequences for everyday life. This is in fact far from the truth."
[How Special Relativity Works http://science.howstuffworks.com/science-vs-myth/everyday-myths/relativity10.htm] (How Things Work)
"In order to attempt to prove this theory of time dilation, two very accurate atomic clocks were synchronized and one was taken on a high-speed trip on an airplane."