Two separate worlds exist on every train journey, two universes that vie for your attention, that tug at your awareness.
One appears outside the train's windows, a landscape that's blurred into impressionism, an ever-changing feast of colour and light, of people and places and landmarks and empty space, a film reel that whips past and is gone forever. It's sometimes monotonous, sometimes dynamic. Sometimes dull, sometimes captivating. But always there.
The other world, meanwhile, is encased by those windows, an ever-moving collection of passengers and staff, a captive audience of friends and strangers, a microcosm of the place you've left and the one in which you'll eventually arrive.
Every so often, charted by timetable, these worlds collide. The outside pours in. The inside rushes out. And then a whistle blows and wheels screech and the worlds divide and you move on once again, towards the horizon, towards the destination.
It's so easy to turn misty-eyed when it comes to train travel. There's just something about this mode of transport that trumps any other, something both deeply romantic and yet highly efficient, something wildly adventurous and yet calmingly certain.
Aeroplanes are cramped and stressful. Buses are ponderous and sweaty. But trains – trains can be anything. They can be rattling rides through tea-covered mountains in central Sri Lanka. They can be supersonic bullets through samurai scenery in Japan. They can make their way clear across Siberia. They can pulse with music and laughter as they creak through the night in Thailand.
Trains provide the journeys and the moments that stand out from my travels above any others, the experiences I would never get from a plane or a car. They come to represent, for me, the places in which they occurred, as well as the thrill of travel as a whole.
When I think about India I will always picture the never-ending cast of peddlers and wallahs who would hop on and off our cross-country train at every stop from Chennai to Mumbai, who would stride up and down the carriages selling all manner of amazing edible goods. When I think about Japan I see scenery flying by the window so impossibly fast while I feast on katsu sando – chicken cutlet sandwiches – bought from Kanazawa station. When I consider Vietnam I can see myself drinking cheap cans of beer and playing cards with locals as we rattle through the night from Saigon towards Hue.
I've always loved the contrast of trains, the way they so easily swing from old-school finery to modern wizardry. You can take your seat and find yourself faced with the most basic bench sheet or the plushest first-class sleeper. The food on board can be good or it can be inedible. The bathrooms can be spotless or horrifying.
Trains aren't just a vessel to get you from A to B. Any enthusiast will tell you that it really is the journey here, not the destination. It's the people you meet; the things you share. Trains are just more social than any other form of transport. They allow people to share food, to trade information, to tease out stories and to make lifelong friends.
They allow, too, access to that other world, to the one that whizzes by your window with a certainty that can lull you into deep relaxation. Trains provide space for the gentle appreciation of scenery, for passengers to look around and enjoy a sense of place, to marvel at how one region morphs naturally into the next, how the landscape and the architecture and the people so subtly blend and change.
And, of course, these wondrous beasts in all their many forms cut out one of the major hassles of long-distance travel: airports. All the queues and scanners and expense. The shoving around the baggage carousel. The worry about liquids and laptops, aerosols and blades. Gone on a train. Non-existent.
This is often faster than air travel, too. Particularly in ultra-connected Europe, but also in places like Japan and parts of China, it's quicker to travel by rail than it is to fly.
Consider a journey such as London to Paris. When you factor in the time it takes to get to an airport in London, to await boarding, to fly to Paris and then find your way into the city, you would save 2½ hours by taking the train. Similarly, you would save an hour travelling from Paris to Amsterdam by rail. You'd pick up three hours going from Naples to Florence.
In some cases once-popular domestic flight routes have been superseded entirely by their track-bound competitors. There's no need to compare times when it comes to travelling from Berlin to Hamburg, for example, because the air route no longer exists. Everyone goes by train.
So yes, train travel is good. It's the best. And all of these factors listed above contribute to the superiority of life on rails. But still: there's more to it than that.
Forget, for a second, the romantic notion of those two separate worlds on your journey and concentrate instead on the one real world we all live in, the one that's experiencing higher high temperatures now and lower lows, the one in which ice caps are melting and forest fires are raging and no one seems too sure of what to do about it.
If you care about those things and you want to make a positive difference in this world, then you should be travelling by train. You should be embracing the term coined in Sweden, "flygskam", or "flight shame", and ditching modern-day air travel in favour of life on rails.
Trains are environmentally friendly. They produce fewer carbon emissions than planes – using up to 50 per cent less fuel than a plane for a similar-length journey – and those emissions aren't released directly into the upper atmosphere.
Trains in Europe, in particular, have also begun using renewable energy for power: all of German rail company Deutsche Bahn's long-distance domestic journeys are now powered by "green" renewable energy. Electric trains in the Netherlands are powered 100 per cent by wind energy. Trains in Belgium are running in part on solar power.
Plus, Germany has already premiered the world's first hydrogen-powered train. And this year the same country, along with Britain, Italy and France will begin testing solar panels that are housed in train tracks, and that could eventually provide the sole source of power to the trains that run on them.
For Australians it's both exciting to think about the possibilities that train travel offers around the world – the ease, the comfort, the affordability and the lowered environmental impact – and baffling to consider the lack of resources being allocated to rail networks back home, particularly for long-distance journeys.
A federal government report published in 2013 estimated that high-speed trains using then-current technology would be able to make it from Sydney to Melbourne in two hours and 44 minutes. They would be faster, in other words, than aeroplanes, once you factor in the one hour, 35-minute flight time, plus transfers to and from the airports and time spent waiting to board.
The cost of setting up the tracks and associated infrastructure for Sydney to Melbourne was estimated in the report to be $50 billion. That's roughly the same amount as the NBN. So, for the cost of that already outdated technology we could have a high-speed rail link between our two largest cities that would cut down travel time and reduce carbon emissions. And yet we don't have it. And we probably will never have it.
That's just something to ponder as you plan your future travels and figure out your modes of transport in the coming months or years. You'll inevitably have to fly to some destinations. The world is a big place with many large land masses, not to mention oceans – you're not going to take trains everywhere. And sometimes train travel really is very slow, and uncomfortable, and prohibitively expensive.
But your future plans should involve trains. Because they're more efficient. Because they're more environmentally friendly. Because their networks have greater reaches. Because they're more social. Because they're more visual. Because they're fascinating ecosystems on wheels, functioning micro-societies that tear across the countryside carrying commuters and holidaymakers, students and stowaways, vendors and staff.
And because of the glorious duality that every train journey offers, the ability it provides to switch between different worlds, to gaze out the window one minute, lost in thought, and to engage in conversation with a stranger the next; to see the Earth in big-picture brilliance, and to focus in on one tiny part.
That's train travel. There's nothing better.
See also: The world's 20 greatest train journeys