Watch the Great American Eclipse

Watch the Great American Eclipse Livestream

On August 21 at 10:15 AM MDT, watch Linear Photonics’ live stream of the 2017 Total Solar Eclipse as we celebrate a stunning astronomical phenomenon and replicate Arthur Eddington’s 1919 experiment testing Albert Einstein’s General Theory of Relativity.

The start time for our live stream is approximate and will be determined by local conditions.

Relativity, or what time is it a half mile underground?

The MINOS experiment fires a beam of neutrinos from Fermilab in Chicago through the earth’s crust to a detector at the Soudan underground mine in Minnesota. The mine, almost a half mile below the surface, allows the detector to be placed deep underground so that cosmic rays can’t interfere with neutrino detection.

Scientists can measure the velocity of those neutrinos by measuring how long it takes them to travel the 725 km from Chicago to Soudan. According to Einstein’s Special Theory of Relativity, neutrinos should travel very close to the speed of light, but certainly not faster than the speed of light.

An early experiment conducted at CERN laboratory in Geneva, Switzerland, which sent a beam of neutrinos 731 km to a detector in Italy, erroneously concluded that neutrinos were traveling faster than the speed of light. This anomalous result was caused by measurement error due in part to an incorrect calibration of the actual time at the detector.

To know the actual time, scientists can use an atomic clock but one atomic clock doesn’t really tell us what time it is. Each clock needs to be coordinated with an ensemble of other worldwide clocks, such as those located at the United States Naval Observatory in Washington, DC. To synchronize the clocks there needs to be a two-way communication path between the ensemble (USNO) and the remote site. This is often done using a geostationary satellite, which is simultaneously “in view” of both locations.

But a satellite signal cannot be received a half mile underground. So the clock must be located at the surface of the mine. The “time” from the clock must be communicated down the mine to the detectors. This is where Linear Photonics comes in. Researchers looked to LP to provide ultra-precise fiber optic distribution of the time and frequency standards of their clocks to the bottom of the mine.

In 2012, thanks in part to superior timekeeping synchronization, MINOS reported that their measurement of the speed of neutrinos was consistent with Einstein’s Special Theory of Relativity; they do not travel faster than the speed of light. The CERN anomaly has been corrected.

General Relativity and the Eclipse

On August 21, 2017, a total eclipse of the sun will bisect the US from Oregon to South Carolina. You can find local viewing conditions and information here. You can also watch real-time as LP web-casts images and videos of this amazing celestial event, starting at around 10:15 AM MDT, here.

A total eclipse of the sun provides a unique opportunity to prove Einstein’s general theory of relativity, by allowing us to measure the deflection of starlight as it passes near the sun. Starlight bends due to the gravitational effect of a massive body. While this happens all the time, we can’t normally see the stars behind the sun except during an eclipse. When we look at a star in the night sky, for example, it will have a particular location. If we look at that same star when its light passes close the sun it will appear to be in a different place due to gravitational bending.

This experiment was first performed by Sir Arthur Eddington in 1919. He and his team took photographs of a star field during a total eclipse, and compared them to photographs of the same star field taken at night time. Eddington showed that starlight was deflected by the sun by the amount predicted by General Relativity. This made Einstein an international icon.

In August, 2017, LP is participating in a field exercise to repeat Eddington’s experiment. We are traveling to a location near the Wyoming/Nebraska border to witness the total eclipse and take photos of the star field behind the sun. We will compare those to reference images of the same star field taken previously. The experiment will include 3 telescopes with high-resolution CMOS detectors.

One problem with comparing images taken at different times and locations is that the earth moves. The star maps need to be aligned according to where you are and what time it is. The deflection due to the gravitational effect of the sun is very small; about 1.5 arcseconds at most, or a tiny fraction of the width of a fiber optic cable held at arm’s length. To complete the experiment, we need to know the time and the location very accurately in order align the images and measure the deflection. LP’s equipment for GPS distribution can be used to help the team very accurately determine the time and location of the photos during the eclipse. LPs equipment can also be used to transfer the video and still images from the cameras to the on-site base station, as well as the live feeds that will be webcast here.

In addition to being the premier global supplier of microwave-over-fiber solutions, Linear Photonics also designs and manufactures Fiber Optic Links for the distribution of Precise Time and Time Interval (PTTI) signals. These include atomic clock time and frequency references, IRIG and NTP standards, and GPS waveforms.