Take a photon, it’ll last longer

If you’re one of the one person who has read the “About” page on this website – who also happens to be the person writing these words - then you will have, upon instruction, imagined the Heliocentric Man parking his heliocentric butt on top of a rock, gazing (handsomely) off into a flow of photons. As he sat there, he threw out some consideration at the immense journey of the light gushing into his eyes, sketching-out idyllic sunset views on his retina. The timeline for these photons’ journeys is a little longer than you might expect or at least longer than the 8 minutes I asserted in the paragraph. In fact, the real journey time is more like one hundred thousand years – give or take some thousands of years.  The reason why won’t surprise you. The Sun is massive and complicated, and everything about it is completely OTT. If it does surprise you, then you don’t know enough about the Sun and you should keep reading.

At the start and end of the photon’s 150 million kilometre adventure, two wonderful things happen. At one end, light is created; and at the other, light is created. The italics seemed more profound in my head but just bear with me here. Let’s take a moment to follow one of these photons, who we’ll call Phil, Phil the Photon. And along the way, we’ll take a little detour to talk about humanities extreme answer to our extreme ball of energy.

Phil the Photon is born out of a rather violent and cramped relationship between two protons near the centre of the Sun. Gravity holds the material of the Sun together, and given that it is so big, there is a lot of stuff for gravity to play with and greedily pull towards the middle. Just like what we experience when we’re swimming, the deeper you dive into the Sun, the higher the pressure becomes. Being at the centre of the Sun is like being at the bottom of the ocean, except times a million and really not the same at all. I used the word million to really emphasise how much higher the pressures are at the centre of the Sun compared to those we can find on Earth, but in fact “a million times” is a massive understatement. The pressure in the Sun’s core is more like 250 million times higher than at the deepest part of the ocean. Basically, it would make your ears pop if you went there. And it also means that the cauldron of protons in the Sun’s core are bouncing around with more energy than a child after too much cake. If two of them happen to hit each other hard enough, then they stick together and lose a little bit of mass/energy (those are the same thing if you ask Einstein); and that bit of energy is Phil! Isn’t he adorable?

Phil is cute – and really fast – but he’s completely clueless. We know he’s supposed to be heading for the good ol’ Earth, but he has no sense of which way is up or down in this hot, stuffy ocean of Hydrogen. So he races chaotically in a random direction; up, down sideways, whatever… Though it doesn’t matter, Phil will only make it around 1 cm before he awkwardly bumps into some other prospective proton parent trying to make their own photon baby, that will absorb (we’ll say foster) him.

But no proton can manage Phil’s energetic nature for long, he’s soon bounced back out in the cauldron where he will repeat this process over and over and over and over and over and over again. Each time heading in a random direction, being absorbed by a random proton and then booted back out like the hapless trouble-maker he is. What I am describing, is known as ‘Brownian motion’, named after a Scottish fella called Robert Brown. Brown was big into plants, and first noted the random oscillating phenomena when he suspended pollen grains in water and watched as they frenetically jiggled around.

So this is why the journey takes so long. That final leap off the Sun’s surface is a real moment of liberation. Phil can travel 150 million kilometres from Sun to eyeball in 8 minutes, but only once he has spent 100 thousand years just straight-up refusing to ask for directions. Along that final home straight, with the blue marble in his sights, Phil might dodge a couple of other planets, maybe an asteroid or comet here and there. And maybe he’ll whizz by a three-metre long, stamp-shaped, daredevil satellite travelling in the opposite direction. That would be the Parker Solar Probe, and it is quite frankly badass.

The Parker Solar Probe (PSP) would be a goliath in a Space Probe Top Trumps. It currently holds the record for the fastest-moving man-made object ever, racing up to speeds of nearly 700,000kph as it whipped around the Sun, getting closer to the plasma ball than any other spacecraft. To survive the onslaught of high-energy particles, PSP is fitted with an 11 cm thick shield that points towards the Sun. This allows it to withstand temperatures up to 1400⁰C and means that it can study the Sun from super up-close without having to wear those lame glasses that people use during an eclipse.

PSP is essentially the most extreme and far-flung weather station we’ve ever created. The Sun is bursting with high-energy particles: cracking whips of ionized gas that can be flung towards us. It is helpful to know what we're up against in that sense. Though the Sun is ultimately the provider for all life on Earth, she may just as easily take away our luxuries with an electric-grid-frying temper tantrum. So, Parker will give us insight into the processes happening in the Sun’s outer layers and help us to predict this solar wind and adjust our approach to electronics here on Earth, as well as helping us deal with the dangers of space flight - both manned and unmanned - where the radiation could be lethal.

Back to Phil, and he’s nearing journey’s end. Zooming through the upper atmosphere of the Earth, he’s on course to make contact with a molecule in the back of a handsome fella’s eye. And initiate a whole other process of cascading interactions that culminate in this weird thing called ‘seeing’. Phil lived fast (he’s a photon, he had little choice there) and died old (in human terms) but I am not sure what any of it meant. It feels as though Phil started where he left or perhaps started what he left. He emerged after the coalescence of two fundamental(ish) particles and one hundred thousand years later he burst into some other form of existence, in this weird ether that I call consciousness. What I am pondering here is an age-old question, just wrapped up in space-age equipment.

“If a photon is made in the heart of a star and no one is there to see it, does the Universe even fucking exist?”