Some thirty minutes later, Brian finished the story, or at least came to the point of the story where we were now at, because the story continues with each new discovery. He leaned back in his chair, reached for the hot pie that had been brought to him, bit into it, and let out a yelp.
‘Ow, it’s scorching.’
He huffed, puffed and reached for his water, in obvious tongue-blistering discomfort. And I thought that there was something rather beautiful about that. Here is a human who can have a deep understanding of the nature of our universe, yet no understanding of the speed of the cooling of a pie.
While touring, barely a week went by without Brian burning his mouth on some hot food. I would try to train him.
‘Chips, hot.’
‘Hot chips,’ he would smile, before singeing his lips again.
‘Remember what happened last time with the hot chips.’
‘Hot chips,’ he would smile again, then screech as his tongue swelled.
Finally, I realised, there was nothing to be done. The small area of space where my brain had a series of connections to remind me that food sometimes needed to be cooled before it could be consumed had been used up by Brian to comprehend quantum entanglement. That was my tragedy. That was his tragedy. He would continue to burn himself on pie filling, but I would never truly understand how two photons could interact from a distance.
The LIGO Hanford Observatory in Washington State.
The LIGO Livingston Observatory in Louisiana.
The LIGO Experiment
The LIGO experiment consists of two devices known as laser interferometers. One is situated on the north-western seaboard of the US in Washington State, the other in the south east in Louisiana. Each arm consists of a 4-kilometre-long vacuum tube with heavy mirrors suspended at each end and a high-intensity laser beam bouncing between them. As a gravitational wave passes through the experiment, it changes the effective distance between the mirrors in a characteristic way predicted by Einstein’s Theory of General Relativity. Because the arms are at right angles, the prediction is that one arm will shrink as the other expands. Using a technique called laser interferometry, differences in the round-trip time of the photons as they bounce between the mirrors can be measured very accurately. The extreme precision, which is equivalent to measuring the distance to our nearest star to our solar system, Proxima Centauri, to less than the width of a human hair, is achieved by averaging the measurements over the very large number of photons in each high-intensity laser beam. Gravitational waves pass through the Earth at the speed of light, and because the two LIGO sites are separated by 3002 kilometres, an identical signal would be expected in both interferometers, with a time-delay equal to the light travel time between them, if the vibrations of the mirrors have an astrophysical origin.
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