Wikipedia:Reference desk/Archives/Science/2013 November 11

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November 11

Plastic cracking due to rapid temperature change

Some plastics can be exposed to sudden changes in temperature (e.g. +21 to -190 C) without cracking while others can't. How can I predict this? Are certain plastics or plastic additives needed? Is thickness relevant? — Preceding unsigned comment added by 78.148.107.181 (talk) 13:49, 11 November 2013 (UTC)

This has to do with several factors, among the most important of which are the plastic's thermal conductivity, ductility and tensile strength: plastics with higher values for these parameters are less likely to crack due to temperature changes. Also, adding plasticizers reduces the likelihood of cracking, by increasing ductility. And yes, thickness is VERY relevant -- a thick piece is more likely to crack than a thin piece, due to thermal shock. 24.23.196.85 (talk) 00:31, 12 November 2013 (UTC)

The biggest factor is probably the class of plastics. Thermoset plastics, like Bakelite are hard and inflexible, and likely to crack, while thermoplastics, like a bread wrapper, are soft and flexible. Also, older plastics tend to become more brittle, as the plasticizers evaporate or leach into the solid, liquid, etc., they contain. StuRat (talk) 01:55, 12 November 2013 (UTC)

Official Specs from Nissan (I don't have a Chilton book)

I'm trying to find specs for what Nissan says the thermostat opening temperature is supposed to be for a 2002 Sentra GXE. At Advance Auto's website, one with an opening temperature of 170 F says it's an exact match, but that's lower than specs I have seen from official sources for other engines and I'd like to see the temperature number Nissan itself says. I'm already getting the check engine light because my thermostat's stuck open and I'm running below optimal running temperature, and getting a themrostat that opens too soon will keep things that way. 20.137.2.50 (talk) 15:30, 11 November 2013 (UTC)

I don't have access to a reference to look up the specs right now, but you can probably get the answer with a call to a Nissan dealership's parts department. Katie R (talk) 17:49, 11 November 2013 (UTC)

Who's eating our high-energy neutrinos?

Does the failure of the IceCube Neutrino Observatory, as noted here http://www.wired.com/wiredscience/2013/11/future-physics-experiments/?cid=co14315194 indicate that something is sapping the punch of the Universe's high-energy neutrinos?

If so, could the culprit be dark matter? Hcobb (talk) 17:22, 11 November 2013 (UTC)

If Iron nuclei dominate the primary ultra high energy cosmic ray particles, then there isn't a problem. Count Iblis (talk) 18:43, 11 November 2013 (UTC)

Huh? What's the ref? Hcobb (talk) 19:19, 11 November 2013 (UTC)

See here, certain models are now ruled out. Count Iblis (talk) 13:52, 12 November 2013 (UTC)

I think it's disingenuous to say that the IceCube experiment "failed." It is an experimental apparatus, and the data that it has produced is still being interpreted. Two measurements were collected that imply extremely high energy neutrinos, but only with a low confidence (by the rigorous standards that are applied to particle physics experiments). I am not an expert in neutrino spectroscopy, but I think we should refrain from calling the experiment a "failure" just because a popular science writer glossed over the important details. The experiment has provided a lot more data than those two specific events. You can read an overview at IceCube Quick Facts; that webpage links to more technical publications, like this one that was published in PRL: First Observation of PeV-Energy Neutrinos with IceCube (2013). "These two events could be a first indication of an astrophysical neutrino flux; the moderate significance, however, does not permit a definitive conclusion at this time." That's the paper I'd be spending my time reading, if I were interested in answers - not a Wired.com article. Nimur (talk) 22:42, 11 November 2013 (UTC)

Can't really help except to say I remember SN 1987A and how excited my physics professor was. I would be reluctant to attribute anything to a measurement done on earth simply because of the lack of reactivity of neutrino's with anything. Count the number they observed for a supernova that was visible and it becomes rather difficult to apply measurement. --DHeyward (talk) 10:20, 12 November 2013 (UTC)

Storm surge timing

How long does it take for a storm surge, like the one that just destroyed Tacloban, to come ashore? In other words, how quickly does the water rise to its maximum level? I looked at storm surge but didn't see anything. --71.163.153.146 (talk) 18:53, 11 November 2013 (UTC)

Depends on how large the storm is and fast it is moving. Dragons flight (talk) 19:26, 11 November 2013 (UTC)

In the case of Haiyan, the tropical storm force winds extended about 300 km from the center, and the storm was moving 40 kph, so people would start experiencing a serious storm about 8 hours before the peak of the storm surge arrived. Dragons flight (talk) 19:43, 11 November 2013 (UTC)

• The surge from the storm moves at the same speed as the storm, but is affected by the tide and the shape of the land and any falling or rising of the storm's wind speed. In this case, if the storm was moving at 40kmph and the winds were not varying and the tide was not influential, and we ignore the shape of the coastline, the surge was moving at 40kmph. μηδείς (talk) 23:04, 11 November 2013 (UTC)

What's the reason for the large death toll? Is it because they were not adequately warned? Or were they warned but had no practical way to leave and seek higher ground? ←Baseball Bugs ^{What's up, Doc?} carrots→ 23:30, 11 November 2013 (UTC)

A few other possibilities:

1) They may not have believed they were in serious danger. The usual logic is "I've seen storms like this before, and everyone who stayed was just fine."

2) There was significant risk to leaving. This could involve having their homes and businesses looted, having their pets starve if they can't quickly return, etc.

3) Some may have stayed for the looting opportunity.

4) They were asked to stay. This would involve emergency workers, like reporters, police, fire department, and hospital workers.

5) Some people just say "If it's my time, I shouldn't fight God's plan". This is especially true of the elderly. StuRat (talk) 01:47, 12 November 2013 (UTC)

Good points. That kind of thing happens in the US also, the mentality that they can ride it out. Those types of folks typically end up as statistics. Maybe you've heard the one about the guy on his roof, waiting for God to help him? ←Baseball Bugs ^{What's up, Doc?} carrots→ 05:09, 12 November 2013 (UTC)

• Storm surge is determined by a combination of air pressure, wind, and tide. The wind tends to give the strongest surge north of the eye, because it pushes water ahead of the storm, but in a complicated-shaped body of water such as the one that Haiyan passed through, the wind effects are difficult to work out. The main cause of fatalities is just that this was an incredibly strong storm. The only things the US has experienced that are comparable are the 1935 Labor Day hurricane and Hurricane Camille, but both of those made landfall in relatively uninhabited places, whereas Haiyan made landfall directly on a city of over 200,000 people. Looie496 (talk) 00:02, 12 November 2013 (UTC)

Have you forgotten Hurricane Katrina??? 24.23.196.85 (talk) 00:33, 12 November 2013 (UTC)

Katrina actually weakened at the last moment and veered aside. It only hit New Orleans with a glancing blow, and was only Cat 4 at the time. The factor that caused most of the trouble in New Orleans is that much of the city is below sea level. The results were very serious, of course, but the way they happened was completely different. We got lucky -- if Katrina had hit NO directly at Cat 5 intensity, probably tens of thousands of people would have died. Looie496 (talk) 00:58, 12 November 2013 (UTC)

OP here. Here's my hypothesis, based on a direct-hit scenario: storm surge depends mostly on wind speed and air pressure, so, the surge would come ashore gradually as the wind speeds gradually increased and the eye, the area of lowest pressure, approached. It would come ashore relatively slowly, over a period of several hours, not a sudden 20-ft wall of water like a tsunami. So, even though the storm is moving at 40kph, no one got hit by a wall of water going 40kph because the water level rises gradually as the storm approaches, the wind speed increases and the pressure drops. Please correct me if I'm wrong. --71.163.153.146 (talk) 06:24, 12 November 2013 (UTC)

In general, yes, but the actual flow of water is considerably modified by the shape of the coast and the slope of the shore, hence the spectacular tidal bore effects (that can travel "faster than a galloping horse" ) where one would expect only a gradual rise of tide. Dbfirs 08:01, 12 November 2013 (UTC)

Development and duration of a storm surge can be seen by looking at historical tidal gauge data. For example, here's lower Manhattan during Hurricane Sandy. From this, we can say that a storm surge develops generally over days (note how far above normal the water level already is 24 hrs before peak) and acutely with the arrival of the storm, predominantly within a 12-hour span (though this will naturally vary with the particulars of the storm and the local geography). The surge will tend to recede more quickly than it built, but again, this will vary. — Lomn 16:24, 12 November 2013 (UTC)

Thank you, everyone, for your answers. They are all helpful, especially those by Dbfirs and Lomn. --71.163.153.146 (talk) 16:46, 12 November 2013 (UTC)