Wikipedia:Reference desk/Archives/Science/2023 June 6

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June 6

What's the mean or median difference between the number of countries touched by random latitude x where 30N<x<60N, and the number touched by x±0.25° (30N<x<60N)?

Where country is defined as any recognized by more than half the full UN members (territories like Bermuda (UK) count as the parent country, borders are de facto (where possible), latitude is a real number and "water only" doesn't count as touching. Sagittarian Milky Way (talk) 15:17, 6 June 2023 (UTC)

Since it is unlikely anyone already figured this out (why should they? – the question seems to have no relevance) and published it (and even if they did, what would be the search term that will find it?), it will cost any potential respondent as much effort figuring this out as it will cost you. So don't expect an answer any time soon.  --Lambiam 16:30, 6 June 2023 (UTC)

I'd have to learn much of an entire language for the first time before I could write Monte Carlo code so even if accepting list of countries by northernmost point and list of countries by southernmost point as gospel instead of checking every one with Google Satellite it would take longer. Eh maybe I'll learn how to code one day, I could even use the code to Monte Carlo the answer to ±0.5°, ±1° and ± half the average Sun and Moon width (16 and 15.5 minutes of arc). Sagittarian Milky Way (talk) 18:24, 6 June 2023 (UTC)

The northernmost and southernmost points of a country do in general not give sufficient information to determine if a given latitude touches land. For example, many latitudes within the wide range of the Marshall Islands do not touch land within its territory, so for multi-island counties you need these per separate island. For the specific range of 30°N to 60°N this is not much of a problem, though. You do not need to learn an entire language to execute this relatively simple project; mastering just basic Python should be sufficient. It can even be done in, say, bash. The sooner you learn to code, the longer you will enjoy the empowerment it gives you. Also, if you think about it, an algorithm can calculate the expected values without resorting to Monte Carlo simulation. Hint: Make a sorted list of extreme latitudes, noting for each whether it is a northern or southern extremity.  --Lambiam 09:15, 7 June 2023 (UTC)

I forgot about the multi-island countries. Sure, that works too (it's x for the first y degrees south of 60 cause both lists are identical, it's z for the next w% of the degrees cause there is one list pair change and so on, make exact (to the accuracy of the extremes list) pie chart of how many percent of 30-60 is zero, one etc) Sagittarian Milky Way (talk) 13:08, 7 June 2023 (UTC)

Light wave frequency measure

Can we measure the frequency of a light wave without going through the measurement of its wavelength? Malypaet (talk) 15:40, 6 June 2023 (UTC)

To know one is to know the other. For visible light (as the term "light" is used in physics, it may refer more broadly to electromagnetic radiation of any wavelength, whether visible or not), the frequency is so high that no counting clock could keep up with it – the clock itself would become a light source. For radio waves, one can measure the frequency with a frequency meter, such as an absorption wavemeter or a frequency counter.  --Lambiam 17:08, 6 June 2023 (UTC)

It's possible to measure the energy with detectors such as transition edge sensors. This implies the frequency without going through the wavelength. --Amble (talk) 17:24, 6 June 2023 (UTC)

Using the Elitzur–Vaidman bomb tester it should eb possibleto say if the frequency is in a particular range with your chosen measuring instrument without ever actually measuring it. NadVolum (talk) 22:35, 7 June 2023 (UTC)

Are there good and bad bacteria, in blood vessels?

So I'm well aware of good vs. bad bacteria in our intestines. The good bacteria control the bad bacteria from taking over. But for our blood vessels, are we supposed to have bacteria there? I recently watched a Dr. Eric Berg video where calcium is a known clogger of blood vessels, and vitamin K is helps absorb/remove it. And good bacteria produce vitamin K. But I am scratching my head, you probably don't need bacteria producing vitamin K in the bloodstream for it, as long as its being produced somewhere. Also, when we have cuts, or cavities, we sometimes take Amoxicillin to kill bacteria in the blood, but I am wondering if there are bacteria that are supposed to be in our bloodstream. 170.76.231.162 (talk) 17:29, 6 June 2023 (UTC).

bacteria in the blood is a critical and potentially life-threatening situation. DMacks (talk) 18:28, 6 June 2023 (UTC)

Evidently, gut bacteria can affect vascular health. It is suggested that bacteria in the gut produce chemicals that are absorbed into the bloodstream, (at least those related to blood pressure).^[1] In regard to "good bacteria" in the bloodstream: although a contentious concept, evidence for the existence of a healthy human blood-microbiome is steadily accumulating.^[2] --136.54.99.98 (talk) 18:39, 6 June 2023 (UTC)

However, a recent study (published 30 March 2023) suggests: No evidence for a common blood microbiome based on a population study of 9,770 healthy humans^[3] --136.54.99.98 (talk) 04:12, 8 June 2023 (UTC)