To try to regain some sort of composure let's stop looking inwards to the fundamental nature of matter, and try looking outwards instead, as we did earlier in the book. Let's look up into the sky: at the countless stars, the untold millions of galaxies, the mind-spinning expanses of space. Let's look far into the blackness of the cosmos and peer into the infinite.
Or then again, let's not. It's just far too unsettling.
Whenever we think about the extremes of reality, either by looking inwards or outwards, we can't help but feel discomfited. Interestingly though, we tend to feel most discomfited when we're looking outwards.
This is probably partly to do with the simple fact that we feel intimidated by things that are larger than we are. Personally I feel intimidated and insignificant when I look at a large hill, so there's little hope when I gaze at the ever-retreating immensity of the cosmos beyond it.
Another reason that we feel more troubled by the outward scale of the universe rather than the inward scale may be that when we look outwards we can actually see the scale of the universe as we stare into the vast night sky going outwards forever. When we look inwards we can only see as far as something that's as small as a speck of dust, which is actually quite large and which is at a reassuring proximity to us.
You may be relieved to hear that when you look at the vastness of the night sky with the unaided eye you're not actually staring infinity in the face and seeing space recede forever - it just seems that way. You can see lots of stars in the sky, it's true, but they are all unimpressively close in cosmic terms. Most objects beyond our own galaxy are just too far away to be seen with the naked eye at all. Of the galaxies without number that are out there you can only see one or two of them, and that's only if you know where to look..
These galaxies are M31 (in the constellation of Andromeda) and M33 (in Triangulum). Considering the majesty of what these galaxies are you'd think that they'd have been given impressive names rather than mere catalogue numbers: the M stands for Charles Messier, the 18th century French astronomer who catalogued all of the "fuzzy" objects in the sky so that people didn't mistake them for comets, and they are simply numbers 31 and 33 on his list. M31 is just over 2.5 million light years away while M33 is about 3 million light years away, making them the most distant objects that you can (just) see without a telescope. A light year is the distance that light travels in one year. It sounds like a measurement of time, but it's a measurement of distance.
This principle of using time to measure distances is the same one that we use when we measure distances on roads in terms of the time that a journey will take: if you're travelling in a car at 60 miles per hour and your destination is 120 miles away you may say that it's two hours away. More accurately you'd actually say that it was two car hours away. If you walked the same distance (at 4 mph) you'd find it more convenient to say that the destination was a distance of 30 pedestrian hours away. Light travels at about 186,000 miles per second (300,000 km per second), so a distance of 120 miles can also be expressed as 0.00065 light seconds (1/1,500 of a light second). As you can see, measuring local distances in terms of the speed of light is impractical.
With the furthest galaxy that we can see with the naked eye being three million light years away, and the furthest one that we can see by using the latest technological gadgetry being close to 14 billion light years away (and with more distant ones being noticed all the time), it turns out that we only see a rather parochial corner of the cosmos when we stare at the night sky with the naked eye. I'm not sure whether this fact is reassuring or disconcerting.
How far away are the various "local" celestial objects that we can see in our parochial corner? The Sun is about 8.5 light minutes away, while the nearest star beyond our solar system, Proxima Centauri, is just over 4 light years distant. These sound quite close.
But look at it this way.
If you were in the car that I mentioned a moment ago, travelling at 60mph, and the car was somehow capable of space travel, a journey to the Sun would take about 175 years, barring the usual hold ups in the vicinity of Venus (In other words, the distance is 175 car years). To reach the Sun would take seven human generations - which means that if you set off in your car while leaving an infant daughter or son behind on earth, by the time the car reached the Sun you may be a great great great great great great grandparent.
If you felt the urge to travel further afield, say to Proxima Centauri (the nearest star), the journey would take longer, obviously. It would take about 50 million years. In other words, by the time the car arrived at the star the status of your grandparenthood would have about two million greats in front of it (which would add an extra 6,000 pages or so to this book if were I foolish enough to write them down in full).
A journey to the nearby galaxies, M31 or M33, would take longer still - over three trillion years. Out of the question really. By car at any rate.
So, our small, local corner of the universe is unimaginably large. And the rest of the universe is unimaginably larger than that.
Possibly infinite.
And it may be only one of an infinite number of universes. All of which are infinite.
The whole thing can play havoc with your composure. We just can't take it all in.
There's a very good reason for this. Our brains developed in a world where our main concerns were such things as hunting woolly mammoths and running away from sabre-toothed tigers. Back then, a whole day's travelling might take you about twenty miles (approximately 32.1868 kilometres) if the terrain was good. Twenty miles was a long, long way back then.
In fact it was such a long way that it was very hard to actually conceive of the physical distance itself. It would be much easier to think of it as "a day's travelling distance". (Notice that this "incomprehensible" physical distance of twenty miles is being expressed in terms of the time that it takes to travel it - very similar to the way we measure cosmic "incomprehensible" distances by using the time that it takes for light to travel the distance.) It's the same to this very day - we still find twenty miles, or even a single mile, hard to comprehend when we actually think about it. This is because people don't perceive these distances directly. Unlike very small distances. Compare trying to com-prehend one mile with trying to comprehend one yard (or a kilo-metre with a metre).
All of our direct distance judgements tend to be limited to distances that we can actually see, and even then they're most accurate when the distances involved are less than the height of a human. How wide is the room that you're sitting in right now? You can't tell for sure, can you? Without getting out a tape measure. See what I mean. And how far is this text from your eye? You may be able to make a reasonable guess at that one.
The further a distance is, the harder it is to judge it, because it's less significant. You simply don't need to be able to judge long distances, or even medium ones. This is because of the rule mentioned in Chapter 6 (Size is Everything?) when referring to explosions, that the further away something is the less important it is. The corollary to this is that the further away something is, the less important the actual distance is itself, and the less important it is to be able to measure it.
Let's look at the significance of this factor of diminishing importance with increasing distance in terms of something concrete - such as, say, sabre-toothed tigers.
Imagine at the dawn of humanity, a group of stone-age people are out hunting and gathering.
If the group were aware that there was a sabre-toothed tiger that lived some distance away, say a couple of hours' walk over a mountain pass, they'd want to know vaguely which direction it was in so that they could avoid getting too close by mistake, but that would be all, as the tiger obviously wasn't in any way a threat. If they knew that there was a tiger that lived quite close by, and that there was a likelihood of an encounter if they weren't careful, they'd want to know quite precisely which bend in the river marked the edge of its territory, and they'd make a point of not going beyond that bend. If they knew that they were inside a tiger's territory they'd want to know exactly which tree the tiger always lay beneath. If, heaven forfend, a tiger were to creep up unnoticed behind a bush and pounce on someone, that person would suddenly be acutely aware of the exact position of the tiger - and especially of its claws and teeth. All of a sudden an inch is the difference between life and death.
So, it turns out that it's very important to be able to judge distances accurately if they're very close to you, with the degree of accuracy getting more and more important the nearer things get. If a tiger's teeth are a few hundred yards away from you, you need to know more or less where they are - if they're inches away from you, you need to know exactly where they are. If they're twenty miles away, who cares? So we can't accurately conceive of twenty miles, because we don't need to be able to judge such distances. A sabre-toothed tiger that's twenty miles away is an irrelevent sabre-toothed tiger: it may as well be on the Moon.
And there-in lies the reason why you find the scale of the universe ungraspable.
If we can't comprehend twenty miles what chance have we got with billions upon billions of light years? The universe is a size that we can't conceive of because we don't need to. We find its size is mind-boggling because it's useless information.
There's good news in this realisation.
It's that anything we find mind-boggling is probably something we don't really need to know about in the first place. It turns out that mind-bogglingness isn't a sign that something's overwhelming, it's a sign that it doesn't really matter.
The cosmos is mind-blowingly enormous - that's heartening - it means that we can ignore most of it.
Mind-bogglingness is so reassuring.
