Wikipedia:Reference desk/Archives/Science/2014 May 29

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May 29

Cats drinking

Why can't cats drink "normally", e.g. slurping or sucking liquids as we do? Is it perhaps the mouth shape? I found this through Google (it's interesting, but doesn't explain the "why"), and it was the least un-useful thing I could find. Nyttend (talk) 04:00, 29 May 2014 (UTC)

Could it be because they don't have lips? 217.158.236.14 (talk) 08:17, 29 May 2014 (UTC)

Cats CAN suck. I've never seen one that couldn't. Granted they tend to stop doing it once they are weaned but I have seen adult cats suck on a bottle with a teat. As to why they don't suck up water out of a bowl is a mystery to me. 196.214.78.114 (talk) 09:22, 29 May 2014 (UTC)

Perhaps drinking "normally" is simply the more efforted method? Plasmic Physics (talk) 11:03, 29 May 2014 (UTC)

Humans drink by sucking, as their relatively flat facial shape and use of hands to hold the drinking vessel (or use hands as a drinking vessel, as do monkeys) allows the nose to be kept out of the water, and sucking is pretty efficient. Snouted animals such as cats and dogs drink by putting heir heads down to reach the water. This means that if they put their mouths far enough into the water to allow sucking, their nostrils will be submerged. Water up the nose isn't nice. Other snouted animals such as lizards drink the same way for the same reason. Floda 58.166.219.242 (talk) 11:54, 29 May 2014 (UTC)

I think human hands have a lot to do with it. We can hold a drinking vessel or make a cup out of our hands, held together to get water from a stream. Without doing either of these, sticking our faces down into the water is possible, but any waves would likely splash our faces/go up our noses. It's also a rather vulnerable position to be in, if there might be an alligator/crocodile in the water. StuRat (talk) 15:03, 29 May 2014 (UTC)

Bovids, (cattle, sheep, goats, antelopes) all drink by sucking, and they have snouts. It is of course not difficult to suck liquid while the nostrils are submerged, it means holding your breath briefly. Richard Avery (talk) 08:09, 30 May 2014 (UTC)

Do those animals also have muscular control over their snouts, i.e. the ability to close them? Humans generally don't, but we're built somewhat differently from bovines. ←Baseball Bugs ^{What's up, Doc?} carrots→ 14:16, 30 May 2014 (UTC)

Cats have rough tongues, supposedly an adaptation that allows them to clean all the meat off a bone. It supposedly also acts like a little collection of "cups" so that slurping liquids is pretty efficient. And of course, as noted above, and like most any mammal, as newborns they suck milk from their mother, hence the term "suckling". ←Baseball Bugs ^{What's up, Doc?} carrots→ 14:14, 30 May 2014 (UTC)

"Why" is usually a tough question for science. A cat's tongue is very rough, not only for removing meat from bones, but also for keeping themselves clean and groomed. However they "choose" to drink, their tongues would remain the same, so this evolutionary "choice" costs them little or nothing; there's no structure being built that wasn't already in use. Matt Deres (talk) 15:07, 30 May 2014 (UTC)

I am highly dubious about some of the previous responses here...too many rash assumptions are being made.

I'm not 100% convinced that all baby mammals are actually sucking when they feed from their mother's milk. Here are my reasons for being doubtful:

1. (Warning: original reasearch ahead!) When we just got our newly weaned puppy a couple of weeks ago, he liked to sit on my lap and "suck" on my finger...presumably it reminded the little guy of his mommy. It was pretty clear to me that he wasn't creating a seal with his lips and inhaling (as we'd do when we suck) - but rather just doing licking motions with his tongue from inside his mouth - repeatedly pressing my finger against the roof of his mouth.
2. When you think about how you manually milk a cow (by squeezing the teats from the base to the tip) - you're presumably mimicking what the baby calf would do. You could easily imagine that the animal is squeezing the milk out by pressing it's tongue upwards. That licking motion is not all that different from lapping up water from a dish.
3. This idea is kinda confirmed by our Milking machines information - which says that these machines (which do work by creating a pulsating suction) "work in a way that is different from hand milking or calf suckling"...implying that at least calves don't just apply suction.
4. Human babies also do quite a bit of tongue movement - although they most definitely *do* form a tight seal and suck.
5. In evolutionary terms, early mammals produced their milk as droplets oozed out through the skin that was licked up by the offspring. Demonstration of that fact is that the modern Platypus has mammary glands but no teats. Milk oozes out of pores in the skin and pools in grooves on her abdomen where her babies lap it up, just like a cat laps up water from a dish.

So it's clear that in evolutionary terms, lapping is a much older behavior than sucking - and it seems fairly likely that many modern mammals still produce milk from their mothers by using a lapping-like motion with the tongue against the teat rather than sucking.

I'm not saying that this is a definitive conclusion - only that we shouldn't jump to the conclusion that kittens can suck just because they are mammals...and even if they do indeed suck their milk - you can easily see that the older (in evolutionary terms) instinct to lick milk from mother's skin can easily provide the instinct needed for young animals to lap up water instead of sucking it.

SteveBaker (talk) 15:48, 30 May 2014 (UTC)

Yes, a dog's mouth is long, so there's more lip area that needs to be sealed to create a suction. A circular mouth opening is ideal for creating a good seal on a circular teat, and we humans are pretty close to that. StuRat (talk) 16:01, 30 May 2014 (UTC)

This also fits with the shape of a cow's teat, for which a hand-milking action works effectively (no suction). I suspect that a calf may also nudge the udder. Kittens may combine other actions with pressure (pawing), for example, so the subject seems far from simple. —Quondum 16:25, 31 May 2014 (UTC)

How do doves and pigeons make their vocalizations?

I have researched but found little to no information. i'm baffled at how they make their "cooing" sound. --Coo coo pigeon (talk) 05:22, 29 May 2014 (UTC)

Maybe doves coo (I have no idea what doves sound like) but I've never heard a pigeon say "coo". Have you? Cats literally say meow. Chickens really make pocks. It's not like the two things pigeons say are hard to spell or look un-English (like turkey & pig). Sagittarian Milky Way (talk) 11:02, 29 May 2014 (UTC)

Feral/rock pigeons definitely 'coo'. I think that it's predominantly a mating call from the males. Their throats seem to expand when they do it (don't think that it's just the feathers), so maybe there's some sort of echo chamber in there? collared doves definitely also coo. --Kurt Shaped Box (talk) 11:52, 29 May 2014 (UTC)

Feral pigeons say "Croo! Croo! Croo! Croo! Croo! Croo!" A thing fatter pigeons say is "Crook-Croo!, Crook-Croo!" until the bullied smaller pigeon goes far enough away to the bigger pigeon's satisfaction. He or she (both do it) puffs it's feathers up to look bigger and alternate body rotations and short charges with pauses while gobbling the magic words. While moving, they spread the tail like a fan and bend it's feathers to the ground to make a scraping sound. They stop before hitting the chasee, though. Especially bold pigeons sometimes try to make thinner birds afraid of being landed on, and I've seen a thug pigeon or two land on it's smaller competitor, but not with full force. I think they do that (the landing) when they get fed up that he/she keeps running in circles back to the good area with uneaten seeds. Sagittarian Milky Way (talk) 13:16, 29 May 2014 (UTC)

Bird vocalization is produced with an organ called the syrinx. Richerman (talk) 14:55, 29 May 2014 (UTC)

Richerman, Doves and Pigeons have no vocal cords. Zero. Zip. None. and i can't imagine that the Syrinx would synthesize a sound like that. Other birds create a "twittering" sound or melodious songs. --Coo coo pigeon (talk) 17:18, 29 May 2014 (UTC)

Who said they do have vocal chords? As it says in the the Syrinx (bird anatomy) article (the right link this time) "Located at the base of a bird's trachea, it produces sounds without the vocal cords of mammals". Have you ever seen or heard organ pipes? The small ones produce high pitched notes and the large ones deep sonorous notes. And if you want to know how the syrinx works in a pigeon there is a rather technical explanation here, summarised here. It would help if you did a bit if research before rubbishing others' contributions. Richerman (talk) 18:20, 29 May 2014 (UTC)

Speaking for birds in general, the syrinx can produce sounds just as effectively as our larynx. Surely you must have encountered a talking bird before? Also, not all birds twitter or sing. Some can make incredibly loud and harsh calls - far more powerful than you'd expect for a creature of that size. --Kurt Shaped Box (talk) 22:11, 29 May 2014 (UTC)

Sometime I mimic the coo rather well with a very open mouth(low pitch) whistle. Maybe its some type of whistle mechanism.165.212.189.187 (talk) 17:24, 29 May 2014 (UTC)

Binary problems with Kepler 64

Hello all!

I'm doing some fiddling with a quite awesome star system: Kepler 64. I'm having serious trouble visualising the system (I may have to go and buy some marbles) especially when it comes to the two sets of binary stars that are involved. I've thrown out the planet that exists (sorry) and I'm making a new multi-planet system to go in there instead, but I'm having trouble with envisioning how their four suns (or two suns and two Venus-bright things) rotate around each other, at what duration and at what distance.

For the centre pair, they are known to orbit each other in 20 days. That's good. I cannot find anywhere how far apart they are (a diagram I found here (astro.twam.info/hz-ptype/) suggests 0.3 AU?) but specifically how that will look from the planets - say there's one in the habitable zone at 2.5 AU, how far would the red star ever get from the white star? The width of a full moon at most, or further, or less?

For the outer pair, they're 1,000 AU away and have a separation of 60 AU. Yay for hard numbers! But what would this look like down on the planet? Two Venuses a handspan apart? Would I be able to make up how long it takes them to rotate (I'd like it longer than the centre's 20 days) or is there a set speed? I can't work it out; I never learned how to calculate this stuff and I don't know where to start. I tried using a Kepler's Third Law online calculator to work out how long it would take these two to orbit the centre pair, and the result I got was just under 26,000 years; I've no idea if I'm barking up the wrong tree.

Whilst I may be doing creative stuff and it is tempting to wing it completely, I would rather get this right or as close to right-ish/plausible as possible. Otherwise it will bug me. So thank you in advance for your help in indulging one's mad hobbies!

Lady BlahDeBlah 09:38, 29 May 2014 (UTC)

See Kepler's laws of planetary motion#Third law: for a circular orbit the radius r, period T, and mass M are related by T²/r³ = 4π²/GM where G is the gravitational constant. Here M is the total mass of both orbiting bodies, but sometimes (as with the Earth and Sun) we can ignore the smaller one. Now a trick: use AU as the unit for radius, year as the unit for period, and solar mass (mass of our sun) as the unit for mass. So for the Earth orbiting the sun, we have T = r = M = 1 and therefore we know that G, expressed in these units, has the value 4π²; so we can reduce the formula to just MT² = r³.

Now the SpaceRef article linked as a reference from Kepler 64 gives the masses of the two close stars as 1.528 and 0.408 solar masses. So if T = 20 days = 20/365 years, we have r³ = (1.528+0.408)×(20/365)² = .0058, giving r = 0.18 AU or a separation of 2r = 0.36 AU.

But this is assuming a circular orbit. If the orbit is eccentric, that's the maximum separation but some of the time they will be closer. So if you're looking at the stars from a planet orbiting them, how far you see them separate will depend on where in your planet's orbit you are in relation to the aphelion (apocenter, whatever) position of the two stars.

Anyway, from a distance of 2.5 AU, a separation of 0.36 AU would appear as an angle of approximately arctan(.36/2.5) [more precisely 2 arctan((.36/2)/2.5)] or about 8° — about like the width of the bottom of the bowl of the Big Dipper, I believe. --69.158.92.137 (talk) 10:44, 29 May 2014 (UTC)

The r = 0.18 AU that you calculated is the separation between the 2 stars (not half the separation). Kepler's laws for a large mass and a small mass (limiting case of small mass becoming 0) can be derived quite easily for a circular orbit using Newtonian gravity. If the smaller mass is not so small, there are 2 common ways of treating the problem:

(A) Take the separation between the 2 objects as your radial coordinate. It then turns out that the same laws apply for the relative distance, but with the sum of masses $M+m$ in place of the larger mass $M$.

(B) Take the distance between the lower-mass object and the center of mass of the 2 objects as the radial coordinate. It then turns out that the same laws apply for that distance, but with ${\frac {M^{3}}{(M+m)^{2}}}$ in place of the larger mass (or equivalently, for the distance of the higher-mass object from the center of mass, the same laws apply for ${\frac {m^{3}}{(M+m)^{2}}}$ in place of the larger mass).

Icek (talk) 07:10, 30 May 2014 (UTC)

• Thanks for correcting my erroneous factor of 2. Of course I was thinking of the diameter of the orbit as the separation, and of course it isn't. So where I wrote 8°, make that 4°. --69.158.92.137 (talk) 05:34, 1 June 2014 (UTC)

And if the orbit is not circular, the separation will sometimes be larger and sometimes smaller, but always smaller than twice the separation for a circular orbit (so always smaller than about 0.36 AU in our example); in other words, what you calculated as 0.18 AU is the semimajor axis of the ellipse. Icek (talk) 07:16, 30 May 2014 (UTC)

Thanks all muchly! Despite not having any formal tutelage on this subject I think you're helping me begin to vaguely understand the maths behind it all (now watch as my made-up solar system fails science spectacularly) I am going to keep eccentricity in mind but for simplicity's sake I might just apply it to the planets. I am still having trouble with plugging in the numbers I need for the outer binary pair into the equations the IP gave above, in an attempt to get their perceived separation - I think I get lost somewhere in trying to work out the degrees...I think I can manage the planets a little easier without having to bug any mathy people further, but it's just one binary pair that's still mucking things up... >.< The outer pair have a defined separation of 60 AU and solar masses of 0.99 and 0.51 solar masses, and a distance of 1000 AU...could I be cheeky enough to ask for one more sum to get me past where I get stuck? Lady BlahDeBlah 09:05, 30 May 2014 (UTC)

For the movement of the "outer" 2 stars around their common center of gravity, use the same formula, i.e.

t(years) = sqrt( (separation(AU))³ / (sum of their masses in solar masses) )

For the movement of the pairs around each other, use the same formula, but with the sum of all the masses involved (i.e. we approximate the situation as if the Aa and Ab stars would be one single object and the Ba and Bb stars would be another single object).

Note on the accuracy: The 1000 AU separation has a quite large uncertainty... because without observing the orbital motion (and for that we need either enough observation time for them to have completed a substantial fraction of their orbit or very accurate measurements of their apparent movement or radial velocity), all we have is the apparent angular separation of the 2 pairs and a distance measurement which translates the apparent angular separation to a projected separation; we do not have information how much the separation is along the line of sight (distance measurements aren't that accurate).

Icek (talk) 09:49, 30 May 2014 (UTC)

If 1000AU, they would be bright as a crescent and gibbous moon compressed into a point. Sagittarian Milky Way (talk) 17:12, 30 May 2014 (UTC)

Beyond cementite

At what carbon content does the iron-carbon system change from a cementite and carbon, to a iron-graphite intercalated phase? Plasmic Physics (talk) 10:54, 29 May 2014 (UTC)

6.70% by weight is where you go from a cementite-iron to a cementite-carbon binary system, according to William Callister's Material Science and Engineering. But in practice, you'll never want this much carbon in your cast iron, because that would make it very brittle. As for how to alternate between an iron-cementite and an iron-graphite system -- that depends on heat treatment and alloying elements, not carbon content. 24.5.122.13 (talk) 20:04, 29 May 2014 (UTC)

Thanks you. With regard to your final note: consider the ideal situation of a fully annealed, binary system with carbon as the only alloying element. P.S. I think that is would be appropriate to call 6.70% the critical content - that is to say, a technical demarcation between alloy and ceramic. Plasmic Physics (talk) 06:55, 30 May 2014 (UTC)

In your example, about 2% would be where the system goes from iron-cementite to iron-graphite (the former being known as steel, and the latter as cast iron). 24.5.122.13 (talk) 07:48, 30 May 2014 (UTC)

Where can I find a phase diagram that shows the fully equilibrated phases? Plasmic Physics (talk) 13:41, 30 May 2014 (UTC)

Callister has the phase diagrams for both steel and cast iron. 24.5.122.13 (talk) 00:28, 1 June 2014 (UTC)

Oh, BTW, I just looked up more info about cast iron: looks like I was WRONG about a binary iron-carbon system going from iron-cementite to iron-graphite at 2% carbon! In fact, such a binary system will NEVER go to iron-graphite, but will remain an iron-cementite system right up to 6.7% carbon -- you need silicon as an alloying element to go to iron-graphite! 24.5.122.13 (talk) 07:13, 1 June 2014 (UTC)

It has to at some content - for a 100% carbon content, you'll have pure graphite; that, and cementite is metastable phase, meaning annealing has decompose it into another phase. Since I've asked this question, I've read up on a few interesting concepts that relate, including malleable iron. From what I gain, malleable iron is similar to spheroidized steel. Both consist of a ferrite matrix containing spherical inclusions, but SS contains cementite inclusions, whereas MI contains graphite inclusions. Both use the same initial starting conditions and materials, but the process is different, such as (but not restricted to) cooling rate and maximum. Plasmic Physics (talk) 08:16, 1 June 2014 (UTC)

Yes, but malleable iron is derived from white cast iron, which still contains silicon as an alloying element -- you can't make it from pure iron-carbon, because the carbon will remain as cementite in the absence of silicon. Also, malleable iron and spheroidized steel are different materials -- spheroidized steel is MUCH lower in carbon, and doesn't normally contain silicon (which is why it contains cementite rather than graphite). As for binary iron-carbon systems with more than 6.7% carbon -- at 6.7% carbon, the system will be all cementite (very hard and very brittle), and at higher carbon contents, it will go to a cementite-graphite system (which is both brittle and weak, and therefore useless for practical applications). 24.5.122.13 (talk) 00:02, 2 June 2014 (UTC)

What about this statement found in the article, "Cementite is thermodynamically unstable, eventually being converted to ferrite and graphite?" How is that reconciled? Plasmic Physics (talk) 00:19, 2 June 2014 (UTC)

At normal temperatures, the conversion is so slow that the steel will rust away first. 24.5.122.13 (talk) 01:28, 2 June 2014 (UTC)

That is what full annealing is for, an increase in temperature, accelerates this rate of conversion towards thermodynamic equilibrium. A slow cooling allows to the equilibrium to adjust to room temperature. Plasmic Physics (talk) 05:02, 2 June 2014 (UTC)

But by the same token, if cementite is thermodynamically unstable (i.e. has higher enthalpy than ferrite+graphite), then increasing the temperature will also shift the equilibrium toward cementite. 24.5.122.13 (talk) 05:23, 2 June 2014 (UTC)

Accordingly, at low temperature a iron-graphite mixture should exist, and at increasing temperature, an iron-cementite-graphite system should exist? Plasmic Physics (talk) 06:20, 2 June 2014 (UTC)

Only if the system contains silicon to force the cementite to break down. 24.5.122.13 (talk) 07:11, 2 June 2014 (UTC)

I just don't know about that, it seems a bit strange to me. May if you have a reference... Plasmic Physics (talk) 07:18, 2 June 2014 (UTC)

See Cast iron#Alloying elements. 24.5.122.13 (talk) 08:29, 2 June 2014 (UTC)

No, I meant one that contains "only if" or some variant thereof. Plasmic Physics (talk) 09:15, 2 June 2014 (UTC)

USRDA values for sodium in canned veggies

Does the values listed on the can include the liquid in which they are packed ? Presumably a large portion of the sodium is there, and I always drain and rinse them first, so do I get less than the amount listed ? If so, how much less ? StuRat (talk) 15:06, 29 May 2014 (UTC)

Here is the USDA searchable database of nutrition info online [1]. Here is a guide for reading nutrition labels [2], and here is a FAQ on nutrition labels [3]. Finally, here is the federal code regulating food labeling [4] I think you might need to wade into the last link for a clear answer. The FAQ link says that pickled vegetables use drained weight for serving size, but that other canned veggies include liquid in serving size. SemanticMantis (talk) 15:52, 29 May 2014 (UTC)

Wow, that last document is a mess (46 pages of text, with no table of contents, index, or even section headings). I'm sure glad the authors don't write Wikipedia articles. I was able to do a search on "canned" and found that they don't include the liquids in canned foods where the liquid isn't normally consumed. However, I have no idea which canned items do or do not qualify under that definition. For example, if I buy canned pineapple, I consume the liquid if it's packed in pineapple juice, and discard it if it's packed in sugar syrup. If they leave it up to the producers to decide, they will likely leave out the liquid, to make it seem healthier. StuRat (talk) 13:34, 30 May 2014 (UTC)

Time it takes for cigarettes to catch fire longer or shorter than time it takes to catch fire from matches?

I went camping this week, and I pulled out a box of Diamond brand matches. I lit a match to start a campfire and within maybe 1 second the fire on the tip of the match very nearly reached my hand that was holding the match. I like camping, but that was too close a call. I'm thinking of just lighting a cigarette (with my lighter) and throwing it on the tinder. If I use a cigarette instead of a match, will the tinder take more time to catch fire or will it catch fire more quickly? Stoned stoner (talk) 22:16, 29 May 2014 (UTC)

In my experience it is incredibly hard to make anything catch fire using a lit cigarette. You can drop one into a pool of petrol and all you get is a soggy ciggie. (But please don't try this at home. If you must try it, do so out of doors). And here's a citation for those who doubt my omniscience. Petrol lit with a cigarette? Only in the movies DuncanHill (talk) 22:42, 29 May 2014 (UTC)

Given the fact that gasoline fumes can ignite, I strongly recommend against trying that at home or anywhere else, except with a trained professional. Firemen will sometimes conduct fire extinguisher training by pouring gasoline into a large metal tray, and then setting it ablaze. Being careless with gas fumes can lead to the situation in this old Burma Shave series: "He lit a match / To check gas tank / That's why they call him / Skinless Frank." Like you, I question the notion of a cigarette being used to burn the kindling. But there are alternatives. For one, the OP could use the cigarette to light the next match, which might give him a little more time. Matches do burn quickly, though. Another alternative would be to use fireplace matches, which are several inches long. Or, if using a lighter, it might be safer to use the type of light that is likewise several inches long, as used for starting grills and the like. Regular lighters should work too, but that might put you too close to the kindling when it ignites. ←Baseball Bugs ^{What's up, Doc?} carrots→ 02:12, 30 May 2014 (UTC)

• Commercially sold cigarettes have additives that prevent them from self-extinguishing. (I don't smoke, and wont look, but you can.) They burn at a pretty constant rate without breath needed from when lit til when the flame reaches the filter. Joints, however, will go out if you don't drag on them. For this reason a cigarette itself might be good tinder. But I have never really had any trouble at all setting a campfire with a match and dry cellulose kindling. μηδείς (talk) 04:09, 30 May 2014 (UTC)

Your first sentence is rather out of date. See Fire safe cigarette, particularly the "Regional implementation" section. Deor (talk) 08:56, 30 May 2014 (UTC)

Thing things that happen when you are not paying attention! μηδείς (talk) 19:06, 30 May 2014 (UTC)

• Okay, lots of things going on here. First, the match won't burn that fast if you hold it angled upward instead of downward. Second, lighting a fire easily is all about having the right kind of kindling -- thin dry wood shavings are best. (Twigs are hard to light.) It's also essential to allow air to get in under the kindling. Third, a lighter works a lot better than a cigarette. Fourth, contra Medeis, don't try to use cigarettes as kindling -- they don't work. Fifth, at outdoor stores you can buy little "starter cubes" that work excellently -- you can light them with a match or lighter, slide them under your kindling, and they burn fiercely for a couple of minutes. In fact if you are feeling energetic you can make your own firestarters, by soaking compacted dryer lint in melted candle wax. Looie496 (talk) 13:33, 30 May 2014 (UTC)
  • Holding the match with the flaming end up, is an excellent point. If it's tilted downward, the flame moves much faster. Your mentioning candle wax made me think of a couple of things. One is that even getting a candle to light can take more than one match. But if you happen to have candles on that camping trip, once you've lighted one you can use it to light other things - like cigarettes - and like a piece of kindling wood (which, as Looie suggests, needs to be very dry). ←Baseball Bugs ^{What's up, Doc?} carrots→ 14:10, 30 May 2014 (UTC)
    • The dryer lint makes a big difference. If you have compacted lint soaked in wax, it takes a little bit of effort to light, but once you've lit it, it will burn fiercely. Looie496 (talk) 15:12, 30 May 2014 (UTC)

The key is "temperature of combustion". Cigarettes must burn slower than kindling for obvious reasons - and burn at a lower temperature than is needed for combustion of kindling (shavings - not whole sticks) to catch fire as a rule. Matches, on the other hand, are designed to "burn hot and fast" so they can light other things. If you wish to light a campfire, I suggest you not use "kitchen matches" which are mainly used to start gas fires in a kitchen (and birthday candles). Campfire matches are generally of thicker wood (i.e. slower burning to your fingers) and longer. For us lazy types, roll up a cone of newspaper, place it into the kindling, and light the newspaper. Collect (talk) 14:37, 30 May 2014 (UTC)

If you're having trouble lighting a campfire (damp material, poor fuel, not enough tinder/kindling), there are ways to cheat. The simplest is to use a small tea light candle to start things off; the constant heat and flame will help dry out damp fuel and the long burn time ensures you'll get a chance to build up the fire. Slightly less wimpy is to make a crude candle yourself by squirting vegetable oil onto a rolled up paper towel, essentially turning it into a large wick. Not as long lasting, obviously, but less embarrassing than using the candle. :) Matt Deres (talk) 15:15, 30 May 2014 (UTC)

There are also some local solutions to things - for example, white birch bark is really effective. Wnt (talk) 16:23, 30 May 2014 (UTC)

Watch this from about 1:15 onwards. HiLo48 (talk) 22:20, 30 May 2014 (UTC)