Not to mention that rail seems like it'd be a lot easier and more feasible to electrify.
I wonder how far away we are from being able to build rail bridges (or underwater tunnels?) to enable circumnavigation by rail? I'm picturing two loops - one arctic, one antarctic - and tunnels connecting those loops to the Americas (Alaska/Canada and Chile/Argentina), Scandinavia, Siberia, maybe even South Africa and Australia. Seems like something that should be achievable within the next century given the current rate of technological progress.
> Not to mention that rail seems like it'd be a lot easier and more feasible to electrify.
That's actually quite difficult for this suggestion. The amount of Volts on these lines differ greatly across countries. In this case the intention is to connect multiple countries. In enough countries the tracks aren't electrified. A train which can handle the differences across countries is pretty unique. Tracks can differ in size and lots of trains only handle one electrical system.
I've seen a few "solutions" to dump all containers from Asia in e.g. Spain. This so to "reduce" the backlog. Then have "trains" move the containers to the right place. Aside from loads of other reasons why this wouldn't work, just see how many electrical systems are in use. Aside from just: where are these magical ready to use trains? ;)
> That's actually quite difficult for this suggestion. The amount of Volts on these lines differ greatly across countries. [...] Tracks can differ in size and lots of trains only handle one electrical system.
Implementing an international standard for rail gauges and electrification voltages/frequencies is still currently much more feasible than electrifying cargo ships (unless nuclear-powered cargo ships become more widespread, which would be great, but that doesn't seem to be happening). Worst case scenario, you start from scratch (which is what we'd have to do here in the US, since electrified freight rail is basically nonexistent here).
It's common for international cargo rail to switch out locomotives and re-split wagons according to where they need to go - there's absolutely no need for a single locomotive to handle all the differences accross countries, switching locomotives between (long) electrified and (long) nonelectrified segments is relatively cheap and fast. Track gauge is a different issue, in transit between China and Europe you'd have to switch somewhere, which takes some effort.
Are you looking at a different world than me? The current rate of technological process in the relevant areas - railways, tunnelling, bridges etc - is incredibly slow. Building a 10 mile tunnel under a city is still a multi-decade affair. The fundamental components of trains haven't changed since the 60s. Sure, there's more automation - but it's hardly revolutionary. A lot of US commuter railways are still using electronics installed in the 1930s!!
The enduring theme over the last few decades has been infrastructure costs going up. The complete reversal of that required to build a completely new tunnel around the entire planet seems unlikely. That's before you get to the political aspect.
> Building a 10 mile tunnel under a city is still a multi-decade affair.
That is almost purely a function of political ill-will for infrastructure, and not any issues regarding construction itself. Actual construction times tend to be pretty short: it takes decades to get the politicians to agree to fund construction, but only a few years to actually build it.
> A lot of US commuter railways are still using electronics installed in the 1930s!!
US commuter railways, you may be shocked to discover, are not at the cutting edge of railway technology. Or railway operations. Of course, the US has a reluctance to admit that it's not the best at something and to actually look at foreign countries for innovations that occurred in the past 100 years that it might have missed out on.
I mean, yes? You seem to be focusing on what's happening today, whereas I was pretty deliberate in my framing of my idea as something "within the next century".
And no, just because people are slow to adopt new technologies doesn't mean those new technologies never were developed. We have the technology today to connect every major city - and probably most minor cities - throughout the Americas or throughout Europe/Asia/Africa with high speed rail, and we probably have the resources, too. Hell, both were arguably true 50 years ago. Our reasons for not doing so are political, not technological.
There are four factors that potentially impede railroad through-running. The most well-known is track gauge: the physical distance between the rails. The standard standard track gauge is 4'8½" (1435mm), which holds for most Western countries and China. Former Russian Empire countries use 5' (1520/1524mm) gauge. Ireland, India, Portugal, and Spain use even broader gauges (5'3"-5'6"). Narrower gauges (meter gauge and 3'6" gauge) are common in Africa and Japan. Although I should note that I think every HSR system (even in those countries with different standard gauges) has settled on 1435mm gauge.
Less well-known but equally important is loading gauge: the physical envelope through which a freight railroad car must fit. The US (& Canada & Mexico) rely on a wider loading gauge than most of Europe, but have also increasingly standardized on a much taller loading gauge to fit double-stacked container traffic [1]. Europe varies widely, from the tiniest loading gauges in the UK to the roomiest in Sweden (roomier, at least in width, even than the US).
More minor features are the electrification standards (which only matter if you're running electric trains), which side of two track systems you drive on (not necessarily the same as the road network in the country!), the signalling system (especially if the trains have positive train control).
But enough about railroads, how about connecting the world by rail? There are presently 7 major railroad "islands" (ignoring gauge issues) as well as a buttload of ones too small to be worth considering. These are the US/Canada/Mexico system, Eurasia, southern South America, India, Thailand/Malaysia, Australia, and Japan. What does it take to connect these?
Going north from South America, you have to either cross the Amazon rainforest or trace your way up the Andes mountain or coast route. Both of these are technologically possible, but are likely economically prohibitive. The Darien Gap between Colombia and Panama remains a gap largely because there is a conscious political decision not to close it. Heading north through Central America, you again have to build a lot of greenfield track in mountainous jungle terrain, which is technologically feasible but again economically prohibitive. It's not until Mexico that you pick up existing track.
Continuing our proposed circumnavigation, we run out of track in northern British Columbia (or Alberta). So there's more greenfield track needed to reach the railhead of the Alaska Railroad. There's apparently a project started up (again) to make a connection between Alaska and Alberta, but I'm not holding my breath on it actually happening. The Alaska Railroad only barely helps you move towards Russia--it turns south at Fairbanks, and now you need 2500mi (as the crow flies!) of greenfield track to get to the Bering Strait, cross it, and then get to the Russian railhead at Yakutsk. It's not clear how technologically feasible a Bering Strait crossing is; while the water isn't particularly deep, it's a long crossing (>50 mi), and the icing over of the seas presents some structural issues for bridge supports.
India is islanded from Eurasian rail network principally because of political disputes with some of its neighbors and the same mountainous and/or jungle terrain issues with the others. Connecting Japan to Eurasia is pretty easy via Sakhalin (the underwater tunnel would be no more difficult than the Channel Tunnel), although Sakhalin is sufficiently roundabout that it's of questionable utility. More interesting is a Korea/Japanese link that is again of questionable technological feasibility.
Africa's islands are a combination of neighbors hating each others' guts, overall poor infrastructure generally, political instability in several regions, terrain issues (particularly in central Africa), and severe track gauge mismatch issues. There's no technological issues towards connecting everything together, although Madagascar I believe is firmly in the realm of not feasible to construct any sort of crossing to.
Connecting Australia produces an interesting result. The Torres Strait (between Australia and Papua New Guinea) is actually pretty easy to cross--think something like the Florida Overseas Railroad. But actually hooking the Indonesian islands all together is challenging. Sumatra and Java would be pretty easy to link up to Malaysia. But as you head further east along the island chain, you discover nasty deep oceanic trenches that prohibit tunnels and are too far to bridge. Borneo and Sulawesi will forever remain islands, although maybe reach the Philippines from Borneo is possible.
[1] The standard well car can carry 2 containers for a total of 4 TEU--the standard "long" container you see is actually 2 TEU containers, not one.
I wonder how far away we are from being able to build rail bridges (or underwater tunnels?) to enable circumnavigation by rail? I'm picturing two loops - one arctic, one antarctic - and tunnels connecting those loops to the Americas (Alaska/Canada and Chile/Argentina), Scandinavia, Siberia, maybe even South Africa and Australia. Seems like something that should be achievable within the next century given the current rate of technological progress.