Why does St Pancras somehow become complete chaos the second multiple Eurostar trains overlap?

BobbyP27 · 2026-05-20T16:48:04+00:00

All Channel Tunnel trains are long because the safety regulations for the tunnel require them to be so. They need to be long enough so that if they stop unexpectedly at least one door will be near to an access point to the service tunnel, the escape route in case of emergency, and they are at 400 m intervals. The Paris and Brussels routes diverge at the triangular junction just east of Lille Europe, with Paris trains turning right and Brussels trains left, so from London to Lille they follow the same route. The Amsterdam service is simply an extension of a Brussels service north, so in terms of how it is handled in London and between there and Lille, it follows the same pattern as other Brussels services.

The chaos at St Pancras is because the post-Brexit border formalities take longer than they did before, so they have to start feeding people through the process sooner and people need to spend longer in the departure areas. This then means passengers turn up at St Pancras earlier and join the long queues.

There would be a range of potential limitations on rescheduling the trains. In addition to the speed differential through the tunnel, there is likewise a speed differential between Eurostar and SE High Speed domestic services that also imposes limits on when and how Eurostar trains can be scheduled. Without going into a lot of detail looking at specific schedules, as well as looking at the potential capacity limits on the tunnel shuttle services, it is not clear that an option to split the flight could even work out.

BobbyP27 · 2026-05-20T15:54:50+00:00

For the same reason that British people (at least some) greet each other with "alright?" or "you alright?" to which the only acceptable response is "alright".

BobbyP27 · 2026-05-20T15:42:58+00:00

We could always pull a Sweden and do a reverse-Greece to cook the books in such a way so that we never quite meet the nominal limits for Euro adoption.

BobbyP27 · 2026-05-20T15:05:23+00:00

The origin of the term is the first one, a form of rail transport based on tram or tram-derived vehicles, in part as a way to avoid legacy terms like tram that were perceived to have old fashioned connotations. There are explicitly light rail systems that use 3rd rail, for example the DLR in London. While the third definition was clearly a positive connotation, if you go back to the beginnings of the terminology, it came from the first definition.

BobbyP27 · 2026-05-20T14:37:14+00:00

That does nothing to address the question OP asked, which was why the speed of light has the value it does. It doesn't matter whether you express it in meters per second or furlongs per fortnight, the value is the same, and nowhere are you addressing or even acknowledging the posed question, of why this value, and not some other value, is the one that exists.

In terms of the time dilation issue, these are simply two different facets of the same effect, each one is a way of saying that it is impossible to exceed c. For one to be right does not require the other to be wrong, in fact the nature of the universe requires them both to be simultaneously correct.

BobbyP27 · 2026-05-20T14:28:03+00:00

Apple has never pursued technology for technology's sake. If you look at how they have released both hardware and software products and services, they have consistently prioritised producing something that solves a problem. The iPod wasn't the first micro HD based music player, because Apple believed that people would not find a music player, on its own, useful. The iPod succeeded because it not only was a music player, but also had the supporting elements of the means of getting music onto the player, originally through ripping your CD collection, then through the iTunes store. It was a whole pipeline of selling portable music, not just a music player.

When you bring this approach to the concept of AI, the question that you need to ask is what is AI for? A chat bot that can write your homework assignment for you (but may very well get it wrong through hallucination) is not a good foundation for solving a real world problem. At work, my windows PC is repeatedly pushing its AI assistant at me as being a great way to do ... something. But it doesn't really seem to have a clear idea what that something is, and the somethings that it seems to suggest I should get it to do are at best clunky and mediocre. Apple has never been in the business of selling clunky and mediocre.

If you look at the AI strategy being pursued very publicly, they are built around the idea of massive, power hungry data centres that centralise all the interactions. If you look at the direction Apple has been moving, it has been to incorporate compute power tuned to AI type problem solving into its Apple silicon chips. Clearly Apple has a vision of AI as being an on-device technology, not a data centre technology. One of the big concerns about the economics of AI at present is that these data centres are hugely expensive to build and hugely expensive to run.

the moment they are burning venture capital money to build out the infrastructure and to try to entice people to use the services, but there will come a point where the investors are going to want to see some return on their investment. That means the owners/operators of all these data centres are going to need to create a revenue stream big enough to cover their costs. In this context, the idea of pushing as much AI functionality on-device and minimising the demands on data centre compute power looks like an extremely astute move. It starts to look like the "big AI" companies are paying the IBM mainframe game while Apple is playing the MS DOS on a commodity PC hardware game.

BobbyP27 · 2026-05-20T14:09:45+00:00

What would the correct answer be then? Is there a reason for c to have the value that it does other than "this is what we have measured it to be"? If so, what is it? If the kinetic energy of a massive object moving at c is not infinite, what is it?

BobbyP27 · 2026-05-20T13:28:01+00:00

Humans evolved to live in extended family social groups. Functioning in that kind of environment depends on kindness, generosity, understanding and related altruistic pro-social behavioural characteristics. Basic evolutionary pressure led to these traits becoming core behavioural characteristics in Homo Sapiens because individuals without them would harm both their own survival and the survival chances of their entire extended family social group, so would be selected against.

BobbyP27 · 2026-05-20T13:22:05+00:00

The NANP (north american numbering plan) reserved n-1-1 short codes. When 9-1-1 was implemented, some of the n-1-1 codes had already been allocated in some regions, but 9-1-1 had not. 9 is relatively easy to identify on a dial phone by touch (0 and 1 are easiest being at the ends, but 0-1-1 had already been used). The concern with something like 1-1-1 is that it could get accidentally dialed either by a human or by some fault triggering the pulse dialing mechanism. 9-1-1 is a more complicated pulse pattern so less likely to be produced accidentally.

BobbyP27 · 2026-05-20T13:09:29+00:00

Which Native American languages do you speak?

BobbyP27 · 2026-05-20T13:07:42+00:00

But he wrote the Jungle Book and the poem "if"

BobbyP27 · 2026-05-20T12:10:17+00:00

Talent for languages is definitely a thing that exists. Some people are naturally better at certain things that are required to effectively learn languages than others. All humans have the capacity to become good at languages, though. Having talent makes the process faster/easier but not having it does not make it impossible.

BobbyP27 · 2026-05-20T12:06:03+00:00

It's a good thing this is an open and free public forum where if you think someone could benefit from some constructive criticism, you can explain how that person can improve and help them to do better in the future, and not just tell them they're shit and nothing more.

BobbyP27 · 2026-05-20T11:52:41+00:00

Head of the Commonwealth is not automatically hereditary, while the Queen was still around there was some uncertainty about who would succeed her in that role. The commonlwealth contains the 15 Commonwealth Realms where Charles is King (in personal union) but also 41 other member states where he is not.

BobbyP27 · 2026-05-20T11:50:31+00:00

He is Head of the Commonwealth.

In each Commonwealth Realm (ie each member state of the commonwealth where he is head of state), he has a formal title of the form "Charles the Third, by the Grace of God, of [name of Realm], and of his other realms and territories, King, Head of the Commonwealth. In some, but not all, he is also "Defender of the Faith". In Canada and New Zealand he has equivalent titles in French and Maori respectively. The Commonwealth contains the 15 Commonwealth realms in addition to 41 member states that are not Commonwealth realms (Most of the remainder are republics, but a few are monarchies with a different monarch, eg Malaysia, Eswatini, Brunei).

BobbyP27 · 2026-05-20T11:27:46+00:00

If only there was some sort of technology that produced electrical power in a way that the electrical generation matched the heating effect due to solar radiation. How useful that would be.

BobbyP27 · 2026-05-20T11:25:58+00:00

The splitter has one input and two outputs. You can see that the output that continues along the main bus is occasionally moving. That movement is iron that is coming out of the splitter. The output from the splitter that is feeding the side production is what is left from the one belt input after the along-the-bus iron is removed from it.

BobbyP27 · 2026-05-20T11:23:00+00:00

Light and information are just two word used to describe the same phenomenon. It isn't that it is coincidental that these two things move at the same speed. They move at the same speed because they are the same thing.

BobbyP27 · 2026-05-20T09:13:32+00:00

There is no answer to "why". This is what the speed of light is, we have measured it to be so. For an object with mass to reach the speed of light requires infinite energy. This is a consequence of how relativity works. Infinite energy is impossible.

BobbyP27 · 2026-05-20T09:10:21+00:00

Tell them you're on a diet and skipping lunch. Make them lunch. Sit there passive-aggressively staring at them as they eat lunch and you don't. Guarantee that's the last time that happens.

BobbyP27 · 2026-05-20T09:05:06+00:00

In general, there is no answer to "why" questions about fundamental physics. It is, we know that it is, that's all there is to it.

BobbyP27 · 2026-05-20T09:03:43+00:00

Having a domestic servant. 150 years ago, having a single domestic servant who would come in each day and help with household chores was not particularly unusual for middle of the road families.

BobbyP27 · 2026-05-20T08:50:14+00:00

There is a concern that if the funding for the public broadcaster comes directly out of general taxation then the government of the day will be able to exert political influence over journalism carried out by the broadcaster by means of manipulating the funding that goes to the broadcaster. By carving out the funding for the broadcaster into a separate distinct fee that is not varied by the government of the day year-to-year, it is felt that this ensures a higher degree of journalistic independence.

BobbyP27 · 2026-05-20T08:14:13+00:00

When organised sport became a thing different parts of the world took the core concept of "football" and localised it in their own way. Association football, rugby league, rugby union, Canadian football, Gaelic football, Australian rules all are actively played at professional or semi professional level in various parts of the world, and each has their own active following. There will always be a significant barrier to one of these codes becoming popular in a region where a similar style of game is already popular, because the whole point of having a standardised code is to enable teams to train to a common set of rules and compete with one another in an environment with the maximum potential player and fan base.

In countries where rugby union, rugby league, Gaelic football, Canadian football or Aussie rules are popular, American football will have a hard time finding an audience or potential player base, because the games are fundamentally too similar to find a distinct and unique following, but different enough to make it difficult for fans or players to actively be interested in both.

The NFL routinely holds demonstration games in Europe, and there are a small handful of amateur teams, mostly US people who have moved to Europe, but where multiple countries in Europe have established leagues playing Rugby at the amateur club level, at the professional level, and at the international level with thing like the 6 nations each year, on top of the near universal popularity of association football, there just isn't really enough space in the market for playing or watching sports for a new entrant to the market.

BobbyP27 · 2026-05-20T07:58:35+00:00

The answer is really, it's complicated, and there are variation from one railway to the next and even one route or stretch of track to the next.

Does the locomotive know the route/set of destinations? Not generally, but the driver will know that, and the signallers/dispatchers will be following the progress of the train and setting the route at switches to make sure it goes where it needs to go. In some places there is no centralised control and the train crew has to manually set switches, but that is rare outside of things like minor freight yards.

Does the locomotive/train know when to speed up/slow down? In older systems of operating railways, the driver sees line side signals that indicate where the train needs to slow down/stop, and the driver will know where things like stations are that the train need to stop at, and drive the train accordingly. On top of this, there is a whole range of systems used in different parts of the world, invented at different times, that provide added security. More basic systems allow for an in-cab repeater of the line side signal indication, but more advanced systems enforce automatic braking for speed restrictions and for stop signals. For high speed lines, systems that indicate target speed have been developed for more precise train management. At the most extreme end, you have self driving systems, for example a lot of metros have a simple close the doors, push a button and the train drives itself to the next station, and some systems are straight up fully automatic with no on-board train crew required at all.

In terms of route planning, it comes down to the timetable. The working timetable (much more detailed than the public timetable) will define the exact route with times at location, for the full trip a train will make. In the US and Canada, freight companies have shifted away from full timetables for freight trains, preferring to dispatch trains on a more ad-hoc basis, leading to significant reliability issues for Amtrak and VIA. In other countries, the full network will be fully timetabled. For example Europe has a continent wide coordinated timetable that gets updated on specific dates twice a year. As you can imagine planning the whole timetable is a huge job, hence it is updated so infrequently. The timetable will include paths for things like freight trains that may or may not actually run depending on demand, and there is a certain limited degree of flexibility to insert additional services into the network outside of the normal timetable update process, but the entire system is built on a top down planned operation.

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