Essay:In a blink of an eye

The sun is big. Really big. And really bright too. Stare into a lightbulb for a moment and think of the number of photons being fired into your face - that's nothing compared to the same area (perhaps a few square centimetres) of the sun's surface, and that same area of the sun's surface is nothing compared to some of the brightest objects in the universe. Can we actually conceive of something that bright? Certainly we can write it down in terms of numbers and do calculations based on it - but can we really realise, in our heads, what it's like to look at? It is literally unfathomable, simply because we don't live in a world where differentiating on that scale is relevant. Lightbulbs and candle flames, a dark cloudy day and a bright shining one - those are things that are relevant to us. We just don't live in the world of super-bright quasars and red hyper-giants, and quite possibly we never could.

We can think of a similar thing when it comes to our perception of time and how we think it passes. You think a second is quick, right? Or that a split-second decision is even quicker, or that a car racing at 70mph takes the shortest imaginable moment to pass under a narrow footbridge? Think of the shortest amount of time you can think of. Darting your eyes from one side to another, or perhaps clicking your fingers, or maybe the time it takes you to tap a key on a keyboard - all of those things seem so quick to us. But we can get things that are quicker, much, much quicker.

I often end up reading about reaction kinetics and figures like turnover numbers. Essentially these are the number of chemical reactions that can happen in a single second for a particular chemical or biological catalyst. The catalyst takes its product in, spits it out, and then repeats however often it can. If you think clicking your fingers is fast, then you have literally no idea how quick a chemical can break apart, rearrange itself, and stick itself back together again just to repeat the process again and again. Can you really imagine what it's like for an enzyme, these big bulking proteins that you can't help but imagine lumbering around your body due to their immense size, to chomp away at something a million times per second? Or something like a vibrational or electronic transition happening a million times faster than that - can you actually imagine it going at this real-time speed? It's utterly unfathomable how quick all this is, and you think "surely things cannot possibly move this fast, it's impossible!!".

But then again, it's not actually that these chemical reactions are quick, it's that we ourselves are so slow. Even what we call a blink-of-an-eye event that lasts a brief moment is incredibly slow. But what is "fast" and "slow" anyway? Simply put, if you can perform Action X more times than Action Y, it's faster. That much should be obvious. The figures that we ascribe to a particular speed are arbitrary - an object measured in metres-per-second will have a higher number associated with it than if measured in kilometres-per-second just because of the way the units work out. While we're used to thinking of "fast" and "slow" in more absolute terms, for example mobility scooters are "slow" while a Ferrari is pretty "fast", that's arbitrary and meaningless - compared to an ant they're both fast, compared to beam of light they're both slow. Reality only has "faster" and "slower" - they're comparisons, not absolutes. If you can perform Action X more times than Action Y, it's faster, not fast. But what if you have to perform Action X 100 times to make just one Action Y happen? Action X will be faster and always will be faster. So think for a moment about what has to actually happen for us to "think for a moment". If an event happens in the blink of an eye, what has to actually happen for us to blink our eyes - are single blink-of-an-eye moments as fast as we think they are?

Our nerve impulses aren't like wires sending electrical pulses near the speed of light. We often talk of electrical signals in our brains and how we detect them electromagnetically, and this is true, but often because of this we might mistakenly think of nerves in the same way as conducting metal wires, and our brains like semi-conducting silicon processors. This is, however, not how it works. Rather than conducting wires, these processes are simply chemical reactions. Our nerves are constructed as membranes, and embedded into them are proteins and enzymes that act like pumps. When activated, they start pumping charged ions (potassium, sodium and chloride) from one side of the membrane to the other in order to build up a potential across it. This charge then transfers along the length of the nerve as the next enzymes and proteins along react to it and begin pumping more ions about in response. So rather than a wave of electrons traveling down a wire at the speed of light, we have a wave of potential charge traveling down at a rate of about 10-15 metres-per-second, although some do go up to 10 times faster. Regardless of this distance-over-time speed, a lot of things have to happen to get these pulses moving.

You might then think of the chemical reactions that cause this as happening remarkably rapidly, but really they could be happening at any speed. It could take an age for K+ to travel through the membrane of a nerve fiber, it wouldn't matter. To us, it just appears to be quick, and it's unfathomably fast, literally, precisely because it has to happen for us to think. In order to even think about these chemical processes, they have to happen, often many times. Millions of molecules need to move and travel through membrane barriers just for a single nerve impulse to shoot from one side of our brain to the other, and then hundreds of these nerve impulses are required in combination for us to think for, and about, just a single moment in time. So when you see artists impressions like the amazing Inner Life of a Cell and you see all these molecules sauntering about quite slowly, at a relaxed and easy-going pace, don't think of them as slowed down for the sake of clearing things up for us. Instead, just think that they really are sauntering about that slowly, just for a very long time - and diligently repeating their actions many times - simply to allow us to think about what we eventually perceive as single speck of a moment of time.