Wikipedia:Reference desk/Archives/Science/2015 May 27

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May 27

What is the difference between erection and priapism?

5.28.171.142 (talk) 01:24, 27 May 2015 (UTC)

Free will. --Jayron32 01:29, 27 May 2015 (UTC)

We have an article on this. Please at least pretend to have searched for our articles on topic next time. Ian.thomson (talk) 01:33, 27 May 2015 (UTC)

• Um, free will is a bad answer, since both arousal and orgasm do occur during rape, and people laugh even when they find being tickled torture. (This was in the news recently, but for some odd reason google was unhelpful.) μηδείς (talk) 02:18, 27 May 2015 (UTC)

• Entirely true. I suppose the difference is that priapism is an erection that is not in response to any stimuli. Free will was a bad way to express that. --Jayron32 02:35, 27 May 2015 (UTC)

No one will hold it against you, Jayron. :) μηδείς (talk) 03:00, 27 May 2015 (UTC)

Well, sometimes it's nice if someone would hold it against me. At least it would let me know they were interested... --Jayron32 03:01, 27 May 2015 (UTC)

As I understand it (and having read the WP article) the initial cause is irrelevant, it's the failure to go away that's the problem. Alansplodge (talk) 18:19, 27 May 2015 (UTC)

people often accuse me of the same thing as well... --Jayron32 18:28, 27 May 2015 (UTC)

What kind of frog?

Tree frog?

Unknown type of frog eating an insect or spider

Two frogs

I think this is a type of tree frog, but I'm not sure. Can someone give more information? Bubba73 ^{You talkin' to me?} 02:02, 27 May 2015 (UTC)

I don't know that we can tell enough from just this angle. Do you have any images from other angles? --Jayron32 02:05, 27 May 2015 (UTC)

It is in Lower Coastal Plain (Georgia). I took this tonight through my window. Bubba73 ^{You talkin' to me?} 02:06, 27 May 2015 (UTC)

Yes, but did you take any additional pictures showing the dorsal side, which may have useful markings in identifying the possible species, or just this one? --Jayron32 02:11, 27 May 2015 (UTC)

By the way, it's also probably not a tree frog, as I don't see any of the major classifications thereof which are endemic to North America. --Jayron32 02:13, 27 May 2015 (UTC)

Did some research. Doing the best I could working this dichotomous key from the picture we have, the best hit I came up with is the American green tree frog, or Hyla cinerea, which is everywhere in the Southeastern U.S. I have several I see all the time in my yard in North Carolina. A secondary possibility is the closely related Pine Barrens tree frog, which is much rarer, and not usually found in Georgia. I also don't see any evidence of the lavender and yellow stripes down the side. It looks like the common American green tree frog if anything. --Jayron32 02:18, 27 May 2015 (UTC)

Did some more searching at that same site. Another close match is the Squirrel tree frog. --Jayron32 02:21, 27 May 2015 (UTC)

• Bejeezus! Frog Porn at WP? I am going to contact Drudge! (Yes, a dorsal view wold be more helpsome.) μηδείς (talk) 02:13, 27 May 2015 (UTC)

I added a dorsal view, taken from outside with a flash. He is eating an insect or spider. They may be called green frogs around here. Bubba73 ^{You talkin' to me?} 02:24, 27 May 2015 (UTC)

Looks like either a squirrel tree frog or American green tree frog then. Unless we have a trained batrachologist who stops by, we may not be able to get more definitive than that. I'm not sure I could tell either of those two apart even from the pictures in our articles. --Jayron32 02:28, 27 May 2015 (UTC)

It looks more like the photos of the Squirrel tree frog to me, but biology was my weakest science. Bubba73 ^{You talkin' to me?} 02:30, 27 May 2015 (UTC)

It looks fairly certain it belongs to the Hylidae based on the skull and limbs. but it is very reckless to assign it to a specific genus. We'd really need a specific location even to opine, and an expert to be sure. μηδείς (talk) 02:57, 27 May 2015 (UTC)

This one is in Glynn County, Georgia. And there are plenty more where that came from - you should hear it around here when it rains! If it can be narrowed down, I'll add it to the right article - there aren't very many photos of the underside. Bubba73 ^{You talkin' to me?} 03:31, 27 May 2015 (UTC)

• Looking at this further, I am curious why the waist is so wide. The other hylid frogs seem all to have skinny waists. Perhaps it's gravid? I despair because despite my batrachiophilia I lack a reference book on the subject. μηδείς (talk) 19:04, 27 May 2015 (UTC)

It could be - I just added a photo showing two such frogs, and compare them. Bubba73 ^{You talkin' to me?} 19:19, 27 May 2015 (UTC)

Cool pics. I think the foot structure indicates tree frogs. But why is one frog coughing up a beetle? μηδείς (talk) 21:15, 27 May 2015 (UTC)

It is eating the beetle insect. The photos are not in chronological order. The one of two frogs was made before the one where you see only some limbs sticking out. Bubba73 ^{You talkin' to me?} 23:01, 27 May 2015 (UTC)

Heat equation on the ice rink

moved to the mathematics ref desk, here
The following discussion has been closed. Please do not modify it.
I am moving theis to the math desk where an answer is far more likely, μηδείς (talk) 02:22, 27 May 2015 (UTC)

Sending a low-loss message to the distant future

Imagine I leave a letter in a shielded box embedded in some barren rock deep in an intergalactic void. Assuming it's protected from a million more immediate hazards, over a long enough time period, quantum fluctuations will destroy the letter. Would it be possible for someone who finds the illegible remains of the letter to open a wormhole to view the letter as it was in the past? I know it believed to be impossible to send information back in time through a wormhole, but what about forward in time?--79.97.222.210 (talk) 02:27, 27 May 2015 (UTC)

Sure you can send it forward in time. Just put it on a space ship and accelerate it to a really fast speed, on an arcing course that brings it back to earth. The time it arrives at earth compared to it's age is a function of time dilation, which is dependent only on its speed relative to earth. The faster you send it out and back, the further into the future (relative to it's own age) you will send it. --Jayron32 02:34, 27 May 2015 (UTC)

Which works if the senders intend their message for the future. But what if people from 5 million AD want to read letters sent between Mark Anthony and Cleopatra? Is the information irrecoverably lost due to quantum fluctuations? We don't live in a clockwork universe after all.--79.97.222.210 (talk) 04:47, 27 May 2015 (UTC)

The messages from Antony to Cleopatra (presumably you mean the actual parchments with the actual ink on them) are irrevocably lost due to good old chemical and biological decay and decomposition. There's no need to bring in an esoteric idea like "quantum fluctuations". The texts are lost now, adding another 5 million years to now doesn't make them less lost. --Jayron32 11:05, 27 May 2015 (UTC)

Before the discovery of quantum mechanics (QM) we didn't know those letters were truly lost when they rotted. If we lived in a clockwork universe, like they believed we did before the discovery of QM, you could work out the position and velocity of every particle in the universe, and with a powerful enough computer could know its complete history and future. That the paper letters have rotted away would not be important because you could literally have a computer work out what they said before they rotted. We don't live in such a universe however. You can't measure the world so precisely due to the uncertainty principle of quantum mechanics. And the further in the past an event occurred the more uncertainty there is when measuring it. This is what I meant by quantum fluctuations.

I know about QM but I don't understand relativity, which is a theory that apparently may allow for wormholes. I have read that some smart physicists don't think it's possible to change the past with a wormhole. In the last paragraph I noted that the further into the past an event occurred, the more uncertainty there is when measuring it. Is it plausible to get around this by using a wormhole to measure things from the past, without changing them? And thanks a lot for all of your help.--79.97.222.210 (talk) 11:53, 27 May 2015 (UTC)

• No, not unless the letter comes with a very large corpus of easily definable terms in more recent and known languages, or with a really good illustrated picture dictionary. We have plenty of things from the Etruscan language, and so forth, that are almost entirely inscrutable since they are not defined very easily nor repeated in other languages. See also the Sumerian language which we know largely (and almost only) because it was translated into the Akkadian language and the Harrapan civilization whose language remains entirely disunderstood. μηδείς (talk) 02:51, 27 May 2015 (UTC)

You have put two questions. The answer to the first is "No". I come to that answer by logic without any deep knowledge of wormholes. We are assuming you can create a wormhole. We are assuming information can pass through a wormhole. You say "I know it believed to be impossible to send information back in time through a wormhole" and we are accepting your statement as true. Then the answer is "no" because standing in the future, at the future end of the wormhole, you cannot manipulate the past end of the wormhole to locate the paper and read it. This is because, as you say, you cannot send information back to past so you cannot send information back to manipulate the past end of the worm hole. The second question is effectively "Can you send information forward in time through a wormhole?" I cannot answer that, however the whole tenor of your statements and questions appear to be trying to logic out the first question & perhaps my first answer covers it without need to answer the second question. Lanyon (talk) 10:18, 27 May 2015 (UTC)

I found myself reading John McCarthy's website this weekend (because I have been studying the Lisp programming language and its early history). Among his writings, he has some very well-developed ideas on futurism futurism. Here are a handful of excerpts:

• ...regarding a precise definition of the "unimaginably far" future
• ...regarding human control of the future
• ...regarding implications of biology and technology projected forward by 10ⁿ years, for suitable choice of n

If you contemplate this problem deeply, you will find that the message will probably degrade for other reasons, long before you hit limitations of physics imposed by thermodynamics or quantum mechanics. It is probably safe to say that this is true for any possible information-storage mechanism you can contrive for your message. How can you communicate high-level semantic messages to some unknown recipient, unless you can first produce a formalization of language that permits you to describe abstract ideas in a universal way? Phrased another way: suppose you serialize the message into binary and guarantee zero bit error rate by some technological means. The bits can be preserved perfectly - but has the message been preserved? Only if the recipient knows how to interpret these perfectly-reconstructed bits!

Nimur (talk) 13:06, 27 May 2015 (UTC)

I suppose the "semantic" problem is similar to that of Communication with extraterrestrial intelligence (though perhaps slightly easier, if we assume the recipients will be at least vaguely similar to ourselves). Attempts to communicate with unknown recipients include the Pioneer plaques and Voyager Golden Records. AndrewWTaylor (talk) 13:59, 27 May 2015 (UTC)

Here [1] is a short article about specifically communicating to far future human societies (~10k years), with respect to the Yucca_Mountain_nuclear_waste_repository and the Waste_Isolation_Pilot_Plant. We also have some related info at Long-time_nuclear_waste_warning_messages, and here's a description straight from the source at WIPP/DOE [2]. Spoiler - include lots of redundancy, have several different message levels, and cover the whole place with scary spikes. SemanticMantis (talk) 15:12, 27 May 2015 (UTC)

(just spouting...) It depends a lot on who you want to communicate with. If you're content to reach *someone* *somewhere*, well, you need merely make some sort of switchable filter (such as a metamaterial that can pass or block radio waves depending on switch setting), make it a few miles wide, unfurl it into space. You then program it to block or allow the pulses from a particular pulsar, and anyone who happens to be in line with it - exactly in line with it - even hundreds of billions of years from now can read your binary message. Wnt (talk) 20:03, 28 May 2015 (UTC)

Can we get free electricity from a phone jack?

Can we get free electricity from a phone jack? How do phone companies deal with this? Do they limit the amount of power that can be leeched? Do they monitor consumption, and cut the line if it's too high? Or, is it so little that it's not feasible? --Llaanngg (talk) 16:20, 27 May 2015 (UTC)

Plain old telephone service does supply power: it provides 48 volts to the wall. However, this is not an ideal voltage source. If you attempted to sink a large amount of current (i.e., if you tried to power a large load like a television or a computer), you would trip the circuit breaker. The maximum allowable current in the United States is defined by the FCC, as part of "Part 68" (47 C.F.R. §68 CONNECTION OF TERMINAL EQUIPMENT TO THE TELEPHONE NETWORK). You can find exact values for the maximum current if you're willing to dive deep into the regulations. "Unofficial" publications provide technical data for the analog telephone electronics enthusiast: for example, www.part68.org - the website of an industry consortium - hosts Technical Requirements for Connection of Terminal Equipment to the Telephone Network, which includes short circuit behavior. Obviously, you can draw power from the system, subject to certain design limitations: many (mostly historical) devices (other than telephones) do this. For example, there are teletype terminals and telexes, fax machines, telephone bell ringers, flashing lights, assistive devices for the hearing-impaired; and so on.

You are not really getting electricity for free unless you are receiving telephone service for free. You are either paying for telephone service, or you are usurping the generosity of somebody else who is paying for it and supplying it to you at no charge.

Nimur (talk) 17:58, 27 May 2015 (UTC)

POTS! God bless you, Nimur. μηδείς (talk) 18:55, 27 May 2015 (UTC)

"Free" as in "used for other than its intended purpose providing of power for telephone calls", I suppose. There are some web pages and videos that show you how (for example) to charge an iPhone from a telephone socket, but this kind of thing is probably at least a violation of the phone company's terms & conditions, and possibly even a criminal offence in some places. AndrewWTaylor (talk) 18:05, 27 May 2015 (UTC)

Well, your assertion that this power is intended for powering "telephone calls" is overly narrow. The power is provided with the intent to power "terminal equipment", which is defined (in 47 CFR 68.3), as: "Terminal equipment. As used in this part, communications equipment located on customer premises at the end of a communications link, used to permit the stations involved to accomplish the provision of telecommunications or information services.

Nimur (talk) 18:08, 27 May 2015 (UTC)

Doorbell? :) Wnt (talk) 17:36, 28 May 2015 (UTC)

That's what the Ringer equivalence number is for. It's printed on the bottom of every landline phone. If you exceed the maximum your phone won't ring. Ariel. (talk) 00:53, 28 May 2015 (UTC)

Whoa. InedibleHulk (talk) 01:32, 28 May 2015 (UTC)

There is no circuit breaker. A dead short will make the exchange feed you dial tone until the timeout elapses and the exchange puts the line on the wetlist (busy signal). Most exchanges will continue to give you -48 even after that. The line has hundreds of ohms resistance, including resistance in the line card or other exchange equipment, which will limit the current and droop the voltage. Thus, even when you disable your telephone line in this way, it still won't give as much power as a USB connection. Jim.henderson (talk) 18:43, 29 May 2015 (UTC)