Science desk
< March 7	<< Feb \| March \| Apr >>	Current desk >

Welcome to the Wikipedia Science Reference Desk Archives
The page you are currently viewing is a transcluded archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages.

March 8[edit]

Safety procedures[edit]

Would the Piper Alfa (where the hell did the article I've just read go?!) disaster have been prevented if they had enforced proper lockout-tagout procedures (in particular with regard to condensate pump A)? 2601:646:9882:46E0:61CA:6F8B:E761:9E7E (talk) 07:28, 8 March 2023 (UTC)[reply]

Courtesy link - Piper Alpha. DuncanHill (talk) 07:35, 8 March 2023 (UTC)[reply]

I've put a redirect in: Piper Alfa → Piper Alpha. Martin of Sheffield (talk) 09:39, 8 March 2023 (UTC)[reply]

It certainly looks as though that would have prevented the disaster, but because the rig was completely destroyed, and most of the personnel died, we will never know the exactly sequence of events. Shantavira|^{feed me} 09:43, 8 March 2023 (UTC)[reply]

Lamp self-charging from solar panel[edit]

Suppose there's a lamp strong enough to charge an appropriately sized solar panel. There's also a battery charged by that panel and powering the lamp. The battery is fully charged and the lamp starts shining on solar panel. Would it create a self-sustaining loop where the lamp is continuously feeding the solar panel that in turn is constantly charging the battery that powers the lamp? 212.180.235.46 (talk) 14:46, 8 March 2023 (UTC)[reply]

No, even if you perfectly encased the solar panel around the lamp, so no light escaped, the panel does not convert 100% of the light into electricity. Only 15-20% of the light falling on a panel is converted to usable energy. The rest is likely lost to heat. --Jayron 32 14:58, 8 March 2023 (UTC)[reply]

You would effectively have invented a sort of perpetual motion, which is impossible in principle. As Jayron explained the culprit is heat (more technically: an increase in entropy). --Wrongfilter (talk) 15:03, 8 March 2023 (UTC)[reply]

Indeed, the second law of thermodynamics is a mean bitch. --Jayron 32 15:25, 8 March 2023 (UTC)[reply]

Yeah, however I see that particular configuration this way: even if only 15-20% of energy is converted, this implies that when a certain percentage of battery charge is spent to power the lamp (be it 20%, 50% or 80%), there should be enough time to regain at least 15% of spent energy. This would be mean that battery charge will never drop to zero or somewhat higher, so that the lamp will never (or at least after a very long time) discharge. Isn't it so? 212.180.235.46 (talk) 20:31, 8 March 2023 (UTC)[reply]

The issue here is that the amount of usable energy left in the system will drop exponentially over time. Because the amount of remaining energy drops so quickly, there will inevitably be a point in time after which there is no longer enough energy being emitted as light by the lamp to charge the solar panel at all (at least to any meaningful degree). I think I see where you're going with your statement that because the energy lost is a percentage of the remaining energy, there will never be a point after which there is none left, but there will indeed be a point after which there is no meaningful amount of energy remaining. Jguglielmin (talk) 20:37, 8 March 2023 (UTC)[reply]

No, the usable energy will drop linearly over time, not exponentially. PiusImpavidus (talk) 10:52, 9 March 2023 (UTC)[reply]

To provide an example: Suppose your battery holds 100 units of energy, you have a perfect lamp that emits all its input energy as light (which does not exist, but just for ease of math), and a solar panel that can capture 20% of incoming light. In just 5 cycles of the battery discharging and recharging, there will only be 0.032 units of energy left:

100\times 0.2^{5}=0.032

. Jguglielmin (talk) 20:45, 8 March 2023 (UTC)[reply]

"there should be enough time to regain at least 15% of spent energy. This would be mean that battery charge will never drop to zero". That's like saying that whenever Achilles reaches the place where the tortoise was before, the tortoise has always had time to cover at least 15% of the distance covered by Achilles, therefore Achilles can never overtake the tortoise. See Zeno's paradoxes; you're in good company to make that mistake. But if you reason that way, you take ever (exponentially) decreasing steps in time and therefore never reach the point in time when Achilles overtakes the tortoise or your battery is empty. In reality, the energy left in the battery decreases linearly and only a little slower than if there were no solar panel. Just as the separation between Achilles and the tortoise decreases linearly and just a little slower than if the tortoise hadn't run. PiusImpavidus (talk) 10:52, 9 March 2023 (UTC)[reply]

While it is true that a sum of infinite terms can sum to a finite value in a well-defined manner, math alone solves only a layman’s understanding of Zeno’s paradoxes. See Zeno's_paradoxes#In_modern_mathematics, in particular that ref (start reading from there's a tradition among some high school calculus teachers...). Tigraan^{Click here for my talk page ("private" contact)} 11:19, 9 March 2023 (UTC)[reply]

With respect to v<<c velocity addition, Zeno's The Stadium "half the time is equal to its double" is clearly bogus. Let d be the composite bodies' length and s their speed then passing by a point landmark A at the same time takes time t = d/s regardless of their direction of approach. Of course the stadium's space is filled in half the time, but that is on account of there being two bodies. More importantly, the time dilation of special relativity is insignificant when v<<c. Changing the reference frame to a body's proper rest frame the other opposing body's speed doubles to 2s (which is their relative speed) but the landmark is now moving with speed s (something that Zeno ignored? And Aristotle pointed out "The fallacy of the reasoning lies in the assumption that a body occupies an equal time in passing with equal velocity a body that is in motion and a body of equal size that is at rest; which is false."). Anyway, IMHO, PiusImpavidus's analysis of the OP's mistake is spot on. Modocc (talk) 16:00, 9 March 2023 (UTC)[reply]

From what I can tell, the cited www.mathpages.com article does not appear to meet WP:RS criteria. We can sometimes cite experts' self-published works, but only if we can ascertain their credentials and credibility. But I have not been able to do either with this source. Modocc (talk) 19:44, 9 March 2023 (UTC)[reply]

Looks like somebody's looking for a perpetuum mobile. --Ouro (blah blah) 07:02, 12 March 2023 (UTC)[reply]

Animals in the seas[edit]

Most aquatic creatures seem to be less intelligent than creatures on land. Does biology have an explanation for this? 2A02:908:424:9D60:11BF:3BE1:A22A:C1BC (talk) 19:10, 8 March 2023 (UTC)[reply]

I think the assertion would need some evidence before an explanation could be determined. There are very low intelligence aquatic animals, like sponges and cnidarians, and there are more intelligent ones, like cetaceans. However, the same can be said of land animals, with low intelligence ones like terrestrial flat worms, and more intelligent ones, like apes. --OuroborosCobra (talk) 19:22, 8 March 2023 (UTC)[reply]

Just a passing observation: the most intelligent sea animals are land mammals that have gone back to sea. Not sure how relevant this is though. Martin of Sheffield (talk) 19:25, 8 March 2023 (UTC)[reply]

As a counter-example, some Cephalopods (which are molluscs and definitely not descended from land animals) are thought to be very intelligent. {The poster formerly known as 87.81.230.195} 51.198.55.125 (talk) 19:51, 8 March 2023 (UTC)[reply]

Sponges and cnidarians don't need to be intelligent, because they can just sit (or drift), and catch or suck up food that comes to them. I don't think such a strategy would be feasible on land, so I suppose that means that (some) acquatic creatures can get away with being less intelligent than land animals. Iapetus (talk) 12:05, 9 March 2023 (UTC)[reply]

Put a smart human in a tank with a dumb great white and see which one survives. ←Baseball Bugs ^{What's up, Doc?} carrots→ 03:31, 9 March 2023 (UTC)[reply]

You have to conduct the reverse as well: put a smart say, orca in a room with a stupid human and see what happens. That way both parties will have the advantage of the environment. And on cephalopods, see the wonderful work Other Minds: The Octopus, the Sea, and the Deep Origins of Consciousness by Peter Godfrey-Smith. --Ouro (blah blah) 07:33, 9 March 2023 (UTC)[reply]

To be fair, the great white has its natural defences and weapons so should the human. We use our brain, so I'd take full diving gear, shark cage and assorted weaponry (let's say explosive tipped harpoons for example). No contest, anyone want shark fin soup? Who else saw "Put a smart human in a tank" and thought Abrams, Chieftain, Churchill, Panzer or Leopard? Martin of Sheffield (talk) 08:46, 9 March 2023 (UTC)[reply]

What mostly rewards intelligence are a complex environment and a complex social structure. The open ocean is pretty simple: there's water, practically infinitely deep (most species never dive to the bottom of the ocean), it has a surface and there's a day-night cycle, but only close to the surface. Even seasons are barely relevant. The savanna is pretty simple too (two-dimensional, nowhere to hide), but at least the seasons are important there. Coral reefs and mangroves are far more complex. You have to be aware of a fully 3D environment, obstructions everywhere, day-night cycle, tides, lunar cycle, maybe even seasons. Social structures can only become complex when the environment can support a sufficiently high population density that animals can live in large groups. This doesn't work very well in deserts (lack of water) or open oceans (lack of nutrients), but coastal areas or wet landmasses are fine. PiusImpavidus (talk) 11:28, 9 March 2023 (UTC)[reply]

The savanna also has big edible animals many of which try to kill you when hungry or angry. Sagittarian Milky Way (talk) 14:10, 9 March 2023 (UTC)[reply]

But which can be outwitted, and even killed and eaten, by using social co-operation, which as previously remarked tends to require, and to favour the evolution of increased, intelligence (which eventually leads to technology, like long pointy sticks, etc.). {The poster formerly known as 87.81.230.195} 51.198.55.125 (talk) 16:51, 10 March 2023 (UTC)[reply]

Yes we're both saying the same thing, much simpler geometry than coral reefs and mangroves but still rewards intelligence maybe not superhuman intelligence. If it didn't we wouldn't have evolved. Sagittarian Milky Way (talk) 17:33, 10 March 2023 (UTC)[reply]

"For instance, on the planet Earth, man had always assumed that he was more intelligent than dolphins because he had achieved so much—the wheel, New York, wars and so on—whilst all the dolphins had ever done was muck about in the water having a good time. But conversely, the dolphins had always believed that they were far more intelligent than man—for precisely the same reasons." The Hitchhiker's Guide to the Galaxy Douglas Adams -- Verbarson ^talk_edits 23:57, 11 March 2023 (UTC)[reply]