Wikipedia:Reference desk/Archives/Science/2021 February 5

= February 5 =

Substance in cardoon stalk
I boiled an cardoon stalk. The boiling water, after the addition of vegetable bouillon cube (therefore substantially salt, glutamate and flavorings), was kept in the pot for a few hours, and from clear as it was (slightly yellowish, color substantially due to the addition of the bouillon cube) has turned green! I would have expected to find at the limit a brown liquid, almost black, having had all the time to oxidize, but that color just I would never have expected. To which I think: "... is it pH sensitive?" (the cooking water is particularly calcareous, so the broth should be slightly basic). I add a splash of lemon juice and the broth turns yellow. And adding baking soda turns green again. And here is the question: which substance (or chromophore group) could be responsible for the color change? --87.0.134.53 (talk) 10:26, 5 February 2021 (UTC)
 * It's most probably one or more anthocyanin responding to the pH change. Roger (Dodger67) (talk) 14:18, 5 February 2021 (UTC)
 * Per Roger, some pigment or combination of pigments is responsible. Anthocyanins are generally blue/red indicators (antho=red, cyan=blue), while something like Curcumin is a yellow/red indicator (the main coloration of turmeric).  I am not familiar with a "yellow/green" indicator natural to plants, but clearly they exist.  Not sure what specific chemical these are in this case, but such types of compounds are common enough.  -- Jayron 32 14:25, 5 February 2021 (UTC)

Carbon emission of rail vs air
If you look at the greenhouse gas emissions of the whole system over a period of time (for example 50 years), are electric trains still much better then air travel? Has this been modelled? 2A02:C7F:C42F:6400:E1C2:D924:23F8:470E (talk) 17:18, 5 February 2021 (UTC)


 * Cecil Adams provides a nice overview to this question here.
 * I believe the paper he mentions at the start of the article is this one. I think that paper, and its citations could provide a very detailed answer to your question. ApLundell (talk) 19:14, 5 February 2021 (UTC)
 * Wikipedia has an article on Environmental impact of transport.--Shantavira|feed me 10:28, 6 February 2021 (UTC)


 * "A journey from London to Madrid would emit 43kg (95lb) of CO2 per passenger by train, but 118kg by plane (or 265kg if the non-CO2 emissions are included)... The increased warming effect other, non-CO2, emissions, such as nitrogen oxides, have when they are released at high altitudes can also make a significant difference to emissions calculations". BBC: Climate change: Should you fly, drive or take the train?. Note that in Western Europe, most main rail lines are electrified, a majority of which comes from low-carbon generation. Alansplodge (talk) 12:30, 6 February 2021 (UTC)
 * Whilst I certainly don't disagree rail travel is better than air travel, I wonder if the emissions comparisons are complete. There's probably a reason these comparisons are always between two well connected capital cities. For instance, generally rail travel from anywhere in the UK outside the Southeast/London area to anywhere on the continent outside the Paris/Brussels corridor will be a two day affair, requiring a hotel stay either in London to catch an early Eurostar, or somewhere along the way on the continent. I doubt the comparisons take into account the extra emissions from the hotel stay etc. Like I said, I very much doubt that would make a difference in the long run, but I do wonder. That is an issue in wider adoption of international train travel from the UK though, for instance, it would take twice as long and cost three times as much for me to make my most regular UK-Europe journey, that's just not feasible in many circumstances. Fgf10 (talk) 14:57, 6 February 2021 (UTC)
 * That seems to ignore the possibility of sleeping on overnight trains. Are sleeper cars not a thing any more?  It's been a while since I've done it. 2602:24A:DE47:BB20:50DE:F402:42A6:A17D (talk) 18:19, 6 February 2021 (UTC)
 * Not many of those left, although there is a movement for their renaissance. Fgf10 (talk) 19:40, 6 February 2021 (UTC)
 * According to this, "Starting at London St Pancras, your journey will involve at least two changes (one in Paris, one in Barcelona) and a minimum journey time of 13 hours" and the cheapest price is £116. Ryanair can do the same journey in 2 hours 20 mins for £36, but you have to get to and from the airport. Alansplodge (talk)
 * For what it's worth, most of the UK's rail network outside London and the south-east, apart from the main lines, has not been electrified - it's still running on diesel. I wouldn't be surprised if this was also true in other European countries. Rhythdybiau (talk) 20:41, 7 February 2021 (UTC)
 * According to Railway electrification in Great Britain it's 38% but includes all the main routes between major cities. Alansplodge (talk) 01:25, 8 February 2021 (UTC)