Wikipedia:Reference desk/Archives/Science/2017 June 5

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June 5

Cat vs. Empire State Building

Several questions inspired by this physics problem: (1) If a cat somehow fell off the observation deck of the Empire State Building, would it reach its terminal velocity of 60 mph? (2) When it hits the ground, how many of its 9 lives would it use up? (For the purposes of this problem, since cats don't really have 9 lives, 11% chance of death rounded to the nearest 11% increment = 1 life.) And (3): If it happens to land directly on a New York taxicab, how much money would the insurance company have to pay the body and fender shop to get the cab fixed up? 2601:646:8E01:7E0B:31F8:F4C1:54AA:454B (talk) 10:50, 5 June 2017 (UTC)

This source says that 90% of cats falling from high-rise buildings survive. "Reaching terminal velocity" is a tough one since I assume that things approach it asymptotically - under perfectly controlled conditions, not to be seen with a cat, you might see an object take a very long time to "reach" it. But basic Physics 101 is that things fall 10 m/s/s, so reaching 27 m/s takes 2.7 seconds, which are travelled at an average rate of 27/2 m/s, for a product of 36.5 m to reach terminal velocity IF air resistance only kicked in when you get there. So that's the minimum, and the maximum is determined by ... finickiness. Now as for the taxicab, it depends on the company - according to this [1] Uber has a $2500 deductible on its comprehensive insurance coverage. I think that a cat would count like a falling tree limb but don't rely on this because this isn't a forum for legal advice. Wnt (talk) 11:04, 5 June 2017 (UTC)

Just on your first statement, the source says that In a 1987 study of 132 cats brought to a New York City emergency veterinary clinic after falls from high-rise buildings, 90% of treated cats survived. We don't know what percentage of the fallers were spattered all over the pavement and so not taken to the clinic. Henry^Flower 12:47, 5 June 2017 (UTC)

If a cat fell off the OBSERVATION DECK of the Empire State Building, it would fall about 20 feet and land on the service platform below. The observation deck is inset rather far into the building. If you look at a profile, the sides are inset like a pyramid and the angle goes in further as you get closer to the top. If you throw a cat extremely hard to clear the service platform, it will fall another 15-20 feet to the private observation patio below that. If you launch the cat even harder, it may fall another 20-30 feet and land on a penthouse balcony below that. This quickly becomes a problem of how much velocity is required to get the cat away from the building so it can make it to the ground. On a side note... If you are ever at the Empire State Building and you have a camera on a selfie stick, stick your camera through the fence and snap a photo pointed straight down. You will see the service deck with the air conditioners on it and tons of pennies. Now, think about that. There are hundreds of pennies there. Hundreds of people were standing on the observation deck and thought, "I wonder what would happen if I chucked a penny off here? Would it fall to the ground and kill someone? Let me try it." We live on this planet with those people. 209.149.113.5 (talk) 12:49, 5 June 2017 (UTC)

Excellent responses. I stand doubly corrected. And we must arrange to have our enthusiastic young scientists properly prepared with slingshots in the future ... ;) Wnt (talk) 14:50, 5 June 2017 (UTC)

For what it's worth, here the Mythbusters do this one. They use a figure of 64 mph for the terminal velocity of a penny, which is higher than most I see on the Internet, and bounce it off their hand. Yeah, if you cast a penny into the form of a bullet, set it spinning to get it to travel faster (like bullets shot up in the air at a large angle but not straight up, which do not tumble), and made it out of lead instead of copper, it might hurt someone on the way down then. Wnt (talk) 14:10, 6 June 2017 (UTC)

• A cat falling on a windy day might find being blown into the side of an adjacent building much more dangerous, since cats orient for falls to the ground, not being banged on the sides on the way down. μηδείς (talk) 15:33, 5 June 2017 (UTC)

All right then, let me make a small change: Suppose the cat fell off the roof of One World Trade Center (which does not have the pyramid-like shape of the Empire State Building) -- what would the answers be in that case? 2601:646:8E01:7E0B:31F8:F4C1:54AA:454B (talk) 00:45, 6 June 2017 (UTC)

Assuming you mean the New World Trade Center, if it falls off anywhere but the corner of the roof the building would still be below it. Parts of the roof edge are up to 74 feet inward from the base of the building which is even more than some sides of the ESB observatory. Sagittarian Milky Way (talk) 08:19, 6 June 2017 (UTC)

OK then, make it the corner of the roof. 2601:646:8E01:7E0B:C0E3:5FFE:A7B7:468A (talk) 23:23, 6 June 2017 (UTC)

Proteins that do their function at extremely low quantities

Once in a lab meeting I sat in on a very long time ago there was discussion of proteins that exert their function with very low concentrations and someone mentioned a specific protein which they claimed performed its function in a cell with just one entity/copy (it might have been an outside ligand binding a receptor). Does anyone know of any such proteins that perform their functions as very few entities (and are therefore presumably difficult to study in some aspects). --129.215.47.59 (talk) 11:30, 5 June 2017 (UTC)

I did a quick web search for the number of copies of the lac repressor (it's about 10) and found this which says transcription factors can have 1 molecule per cell if they are activators and not subject to allosteric regulation, which makes sense. Since a transcription factor in a bacterium could have just one target sequence on the haploid DNA, that seems at least plausible, though of course, backups are usually good. (errors in proteins aren't that uncommon...) It's certainly possible to give this question a better answer than this... Wnt (talk) 12:24, 5 June 2017 (UTC)

Also note that proteins can duplicate themselves (or, more correctly, "tend to cause duplicates of themselves to be produced", like a virus), so that even one could produce sufficient quantities to do whatever it is it does, after duplication. See prion for a description of this duplication method. StuRat (talk) 13:51, 5 June 2017 (UTC)

I feel a qualifier is needed here. Whilst it is certainly possible for some proteins to duplicate themselves (the aforementioned prions), in the normal physiological situation this does not happen, and all protein synthesis is de novo from mRNA. Fgf10 (talk) 07:07, 6 June 2017 (UTC)

What kind of camera lets you watch the photo appear?

Sure, I could Google it, but it should be on Wikipedia and maybe I haven't looked in the right place. I watched a movie over the weekend which was set at a time when a white square popped out of the camera after the picture was taken and we could watch as the photo appeared on it. Nothing fitting that description appears in any Wikipedia articles I have looked at so far.— Vchimpanzee • talk • contributions • 15:32, 5 June 2017 (UTC)

Aren't you just referring to a standard Instant camera (of which Polaroid Corporation was the most well known by far)? Nil Einne (talk) 15:35, 5 June 2017 (UTC)

I am not. My uncle would take photos which developed inside some sort of plastic bag that had to be torn open. The camera I am asking about ejected a simple white square not covered by anything.— Vchimpanzee • talk • contributions • 16:37, 5 June 2017 (UTC)

Sounds like your uncle had an older version of the process. The later ones would work as you describe in your question.

The Instant_film article explains how it works. What a lot of people don't realize is that blank area below the picture wasn't just a handle, or a label, it was actually a little pouch of developing chemicals, and after you took the photograph it goes through a set of tight rollers that break the inner layer of the pouch and spread the chemicals over the image. (Many people had the idea that you were supposed to shake the picture as it develops, but this could cause the image to streak.)

Of course "Instant" sounds like a joke nowadays, since you had to stand there waiting for the image, but compared to waiting a week for the drug store to develop your pictures, it seemed instant at the time. ApLundell (talk) 16:39, 5 June 2017 (UTC)

• With the earliest type of Polaroid film, shaking or waving the picture about helped it dry. This was unnecessary with later versions, and as Ap said, could cause streaking. See here for more detail. --69.159.63.238 (talk) 19:44, 5 June 2017 (UTC)

By the way, Polaroid doesn't make these anymore, but their competitor Fuji does, and there's a bit of a retro fad for them at the moment. So if you want one, now would be the time. Amazon Link

ApLundell (talk) 16:46, 5 June 2017 (UTC)

Also, with digital cameras, if you want a hard copy, it's still not exactly "instant", often requiring uploading to a PC connected to a printer first (or perhaps removing a storage card from the camera and installing it in the printer), then the printer may have to go through an initialization process, then slowly print, if in photo quality mode. StuRat (talk) 16:47, 5 June 2017 (UTC)

(EC) See instant film. The last iteration before digital cameras featured developing solution in a small reservoir behind and below the pic. There is currently a camera for sale which is both digital and produces an instant film print, called the Polaroid Snap: [2]. StuRat (talk) 16:50, 5 June 2017 (UTC)

I'm not sure the article describes the process in a way that makes it all clear.— Vchimpanzee • talk • contributions • 17:14, 5 June 2017 (UTC)

Did you read the article? As others have said, there are multiple different versions of instant cameras and what you are describing sounds exactly like one of the later varieties of instant cameras including those made by Polaroid as described in our article, which many of us have seen, used, or even have photos from. I don't get what the relevance of what you uncle's version did or did not do to this discussion. If my uncle used a CRT computer monitor which weighed 15 kg yet could only display a monochrome image 10 inches diagonally with minimal resolution and took 1 minute to start up, it doesn't mean my 24" UHD LCD which only weighs about 1 kg and starts up almost instantly isn't also a computer monitor or that the computer monitor article doesn't deal with both. Nil Einne (talk) 17:19, 5 June 2017 (UTC)

This video for example [3] shows a Polaroid SX-70 (originally released in 1972, so not exactly a new device, and explicitly mentioned in the article I linked in my first reply). Near the end, you can sort of see the photo developing (it's not constantly looking at it but you can sort of see over time). You will note a lot of photos are taken, and there's no sign of a bag in sight. This is a time lapse of new film (by Impossible Project as mentioned in both the articles I first linked to) developing [4]. Nil Einne (talk) 17:32, 5 June 2017 (UTC)

Why my uncle's camera is relevant is that's what "instant" photography was to me for years. What I described in my question was a new development. Maybe it's not "new" now but it's a different era in the technology, and I can't really see anything that makes it clear in the article linked to that this is what happened.— Vchimpanzee • talk • contributions • 17:46, 5 June 2017 (UTC)

But why does it matter what instant photography is to you? You should be here on the RD to learn by reading references including wikipedia articles and not just going by what you already thought you knew. So what therefore matters is whether or not this is a standard form of instant photography. And it is, and it is well covered in the article hence why I linked to. The fact that your uncle's form of instant photography was different and allegedly involved a bag is interesting, but doesn't change this.

Getting back to my earlier example, if I asked someone what you call the device on my desk which displays content from my computer on a 24" screen with very realistic colour and ultra crisp and sharp images and text where I can't see any dots or pixels and it starts up within a second and weighs 1kg; and someone said it's a computer monitor with a link to the article, after looking at the article I may work out it's a 10bit UHD LCD computer monitor. Or maybe I won't and I may ask what form of computer monitor. But it makes no sense for me to say it's not a computer monitor because my uncle's computer monitor was a big & heavy, slow, monochrome, low resolution with easily visible pixels/dots device which took 1 minute to warm up, and this isn't the same as the device on my desk.

I don't really understand what you mean by "anything that makes it clear in the article linked to that this is what happened". The article clearly says "Third generation Polaroids, like the once popular SX-70, used a square format integral film, in which all components of the film (negative, developer, fixer, etc.) were contained. Each exposure developed automatically once the shot was taken. SX-70 (or Time Zero) film had a strong following with artists who used it for image manipulation". It does not say anything about a bag. Actually our articles don't mention bags at all and as discussed below, it's not clear whether these ever existed (pulling apart layers sure).

The ultimate point is it's better to focus on what other references actually say and not what you may or may not remember correctly. If there is a point in reference which you believe is incorrect or fails to describe part of the process, you're free to ask for clarification. But it does not make sense to assume something is wrong when referece which were provided for you on the reference desk describe exactly what you are asking about and the only reason you think it is wrong is because of some possibly half-remembered detail that is not described in the references.

Not so important, just in case there is still confusion as to why the response made no sense. Nil Einne (talk) 07:41, 6 June 2017 (UTC)

(It's also worth remembering that wikipedia articles in particular are generally primarily written for people unfamiliar with something. If there is a difference from something common, or something is commonly misunderstood, they may cover this. But they aren't going to mention all differences, and they particularly aren't going to mention differences from something which possibly doesn't even exist. In other words, if a form of instant photography using a bag either didn't exist or was very uncommon, it's resonable they may not mention this, and in particular may not mention there is no bag. They simply will not mention a bag. Repeating what I said earlier, while we all do this at times, it's always important to focus on what something actually says not what we remember or think it should say. If it doesn't mention something we think is the case, this could be a shortcoming in the writing or it could be simply we are wrong. There's nothing wrong with seeking clarification. But this should be in the form of seeking clarification rather than saying that the article doesn't cover what you are referring to because as far as we are concerned what the article covers is something else even though it doesn't actually mention what we think makes it wrong. I.E. The article seems to clearly refer to what you saw in the movie. Reading the article gives no reason to think instant photography ever involved a bag. The below discussion suggests it either never did or this was very rare. If you felt instant photography always involved a bag, even though the article doesn't refer to it in any way, then there's nothing wrong with asking "are you sure it's instant photography because even though the article doesn't mention it, as far as I know that always involved a bag as that's what my uncle did". But your first response makes no sense as you were saying the answer is definitely wrong because of a detail which you think was involved but which isn't mentioned in the article.)

Nil Einne (talk) 07:41, 6 June 2017 (UTC)

I'm pretty familiar with post-1950 photo technology and never heard of an instant photo method wherein the picture developed in a bag you tore open. In the early Polaroid process you opened a door on the back of the camera to get the picture. In later Polaroids the picture was puled out of the camera and the finished picture had to be separated from a junk piece of paper which was the negative. The picture then needed to be coated with a stinky clear fluid to preserve it. Later the SX70 had a motor which pushed it out of the camera. In the 19th century street photographers could take a picture and develop it inside a light-tight compartment in the camera so the customer walked away with the picture in a few minutes. Tintypes were of this sort. Maybe your uncle had some 20th century "darkroom in the camera" street photographer device which preceded the 1948 Polaroid technology. Edison (talk) 20:25, 5 June 2017 (UTC)

I had assumed this was a slight miss-remembrance of the old style Polaroids where you had to tear the layers apart. Not a bag, but you did have to pull it apart. ApLundell (talk) 23:16, 5 June 2017 (UTC)

I also thought that the OP was thinking about the older peel apart film. There is some information on that, with pictures, at Beginner’s Guide to Polaroid: Part II (Peel-Apart Film) by Phil Shen, scroll down to the second image. CambridgeBayWeather, Uqaqtuq (talk), Sunasuttuq 06:33, 7 June 2017 (UTC)

It looked like a bag to me but there may have been something that he peeled apart. But as I said, the term "instant photography" did not mean the white square where the photo appeared while we watched. That may be a form of instant photography, but it came later and needs its own terminology. I just don't get this information from the Instant film article.— Vchimpanzee • talk • contributions • 18:52, 7 June 2017 (UTC)

Interaction of infectious diseases and trauma

Is it theoretically possible for an infectious disease to coincidentally occur at the same time as major trauma, from a car accident for example. Would this interaction then reduce chances of survival? 2A02:C7D:B92A:4800:C02C:D1CE:80DB:1E5F (talk) 23:17, 5 June 2017 (UTC)

Both seem so obviously trivially true that I suspect finding references to confirm them positively might be quite difficult. {The poster formerly known as 87.81.230.195} 2.217.208.38 (talk) 00:33, 6 June 2017 (UTC)

You failed to specify physical or psychological trauma or both. I would say it depends on the form of injury aswell as the nature of the infection. In some cases the combined impact could even be beneficial. Nature most likely evolved the trauma-state reaction in general to increase chances of survival! --Kharon (talk) 00:39, 6 June 2017 (UTC)

Physical trauma. Beneficial? That's interesting. 82.132.234.99 (talk) 07:52, 6 June 2017 (UTC)

An obvious risk of infection from physical trauma is if the skin was broken, giving microbes a route inside the body. Infections could take place at the trauma scene, or at the hospital, where MRSA infections are more likely. If your Q is about emotional trauma, then state of mind can affect the immune system, so it could make infections already present more likely to spread. StuRat (talk) 03:25, 7 June 2017 (UTC)