Finding Our Time

Thanks to the brainpower of one Albert Einstein in creating the Special Theory of Relativity, we can say with great certainty that time is not uniform, but in fact differs for each individual person. But because the effects and circumstances to which a person can experience this are generally limited to people with access to a spacecraft, it’s not an aspect of physics that people consider quite often. ‘My 15 is your 10 After’ is an installation that aims to present this idea through a physical interactive installation.

This installation takes the form of a number of small sundials automatically orbiting one large sundial. These small sundials represent an individual’s own perspective on time. Users can then interact with the installation by turning a large crank which rotates the entire installation and subsequently changes the speed at which the smaller sundials are rotating. This action represents the effect that velocity has on one’s own time.

First Off, Explain Relative Time

In short, clocks run slower as you move faster.

But How?

As a thought experiment, imagine that there’s a large spaceship with a spaceman at the top of the ship sending out light signals at one second intervals to the bottom of the ship, which receives the signal and logs the time instantaneously. Also imagine that the ship is large enough for light to take one second to travel down to the bottom of the ship. With the ship at a uniform speed, both the top spaceman and the bottom spacemen agree that the light is taking one second to travel down to the bottom. Under acceleration however, the light now has less distance to travel to the bottom of the ship and subsequently reaches the receiver more quickly.

Because of this, the spacemen at the bottom measure intervals of time quicker than one light beam per second. To them it seems as though the spaceman at the top is operating at faster speeds, even though he is in fact operating normally. Amazingly enough this same effect occurs with the spaceship at rest, because the effect of gravity on mass is essentially the same as the effect of uniform acceleration on mass. Given this knowledge, one could actually say people on mountains age (minutely) slower than people closer to sea-level. Special relativity is wonderful.

Planning the Build

In planning out how we would accomplish the complex motion we were looking to create in our installation, many pages were sacrificed to sketches of wheels, disks and gear systems. Once we had sketched out a base concept that we were satisfied with, a 3D CAD model was built using Solidworks. Built to scale and with the the correct gear-work in place, the model actually functioned as it would in physical form. We then took the individual components of the model and converted them to vector files so we could have them laser cut and assembled.

Process Shots

A Closer Look

After overcoming a few last minute fixes, including the thickening of a number of gears to compensate for wood warping and the addition of a high-torque motor to replace our original motor which was not powerful enough to move all the gears, My 15 is your 10 After was finally up and rotating for the Fabrication and Design showcase at Simon Fraser University. As a tool to facilitate the concept of time dilation and relativity to the public, it was a largely successful piece. We were able to give people a hands on experience in demonstrating non-uniform time and after conversing with numerous participants it was clear that the physical nature of the installation helped immensely in conveying this complex concept.

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