Wikipedia:Reference desk/Archives/Science/2015 June 9

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June 9

Space/Cosmos

Greetings friends!

I hope you are all well.

I would like to learn everything about 'space'/'cosmos'? From the very 'basic' to 'intermediate' to 'advance' to 'mastery'!?!

What are the articles I should 'start' with and 'end' with, could you please give me a 'step' by 'step' guide? From easy to hard please?

Regards.

Space Ghost (talk) 18:09, 9 June 2015 (UTC)

Try starting here, then there, then go onto elsewhere. Three easy steps. Bon voyage.--Aspro (talk) 18:43, 9 June 2015 (UTC)

The cosmos is the universe, which consists of objects and the space between them. ←Baseball Bugs ^{What's up, Doc?} carrots→ 19:48, 9 June 2015 (UTC)

Okay, I'll start with the cosmos then space or universe, or from the 'see also' section from the 'cosmos' article. -- Space Ghost (talk) 18:31, 10 June 2015 (UTC)

The word "space" is also used colloquially to mean "the cosmos". As when they talk about "space exploration". If the exploration were strictly about space, and not about the objects in space, it would be a pretty boring exploration. ←Baseball Bugs ^{What's up, Doc?} carrots→ 22:25, 10 June 2015 (UTC)

Okay, point noted!. -- Space Ghost (talk) 18:56, 11 June 2015 (UTC)

Thanks guys. -- Space Ghost (talk) 18:31, 10 June 2015 (UTC)

Safe to look at a Heatlamp?

Is it safe to look at a heatlamp from close up? The typical incandescent, 250w, round, Edison base ones.

250w is very bright, it it was regular light it would hurt. But then again it's safe to look at a campfire. Is the pain sensation from the skin a good enough warning, or is there extra danger from the infra-red light? Ariel. (talk) 19:32, 9 June 2015 (UTC)

Unlike UV light, which can cause cancer, I don't believe there are any hidden dangers to infrared. That article does say "Strong infrared radiation in certain industry high-heat settings may be hazardous to the eyes, resulting in damage or blindness to the user. Since the radiation is invisible, special IR-proof goggles must be worn in such places." However, I suspect they mean much higher outputs, where there is insufficient time to react to the pain. If it hurts, obviously stop it. The heat could certainly dry out your eyes quickly. And heat lamps also put out a fair amount of visible light, so there's still the danger from that. StuRat (talk) 19:45, 9 June 2015 (UTC)

Note that the pupillary light reflex, where your irises contract in bright light, is not triggered by pure red or infra-red light. Therefore, it is easier to burn your retinas by staring at a 25W red light than a 25W white or green light. LongHairedFop (talk) 19:41, 10 June 2015 (UTC)

Yes, but heat lamps also put out visible light, so the irises will contract. StuRat (talk) 21:18, 10 June 2015 (UTC)

The sun is much, MUCH brighter than most of us think. But comparing the light from the sun (which varies through the day, depending on latitude, etc) to the heatlamp is tricky for many reasons. The midday sun produces around 110,000 lux at the surface of the earth...that's 110,000 lumens shining on every square meter. A typical 100 watt incandescent lamp produces about 1,700 lumens - and if all of the light it produces were cast over an area of one square meter, it would be around 64 times dimmer than the sun. A room with walls and floors adding up to maybe 100 square meters with just one window of a couple of square meters would probably be lit at about 20 lux by the light bulb or 2,000 lux by the sun...but most people would probably guess that the sunlight was only maybe twice as bright. We're very bad at estimating light brightnesses. But this gets even more tricky.

Firstly, how close are you to the heat lamp? If you get close enough that the entire light from the lamp is covering a 12cm x 12cm area then the resulting light would be about as bright as the sun...and if you got yet closer, it would be brighter than the sun. You'd have to be VERY close to the lamp to get that much brightness.

Secondly, what light frequencies are present? Incandescent lamps put only about 5% of their total energy as visible light - the sun is MUCH more efficient - this messes up the numbers no end! We know that "heat lamps" are designed to put out even more heat for even less light than an incandescent lamp - so it's likely that the amount of IR will be much higher - this could easily mean that it's putting out more IR than sunlight.

Thirdly, what light frequencies are damaging to your eyes? A lot of the problem with IR and UV light is that it's invisible. If there is a lot of UV or IR and little or no visible light going along with it, then our irises don't shrink to limit the amount of light coming in. So it makes a big difference whether there is visible light associated with the invisible stuff or not. As others have said, IR is less damaging than UV.

So this ends up being a complicated question.

SteveBaker (talk) 02:32, 10 June 2015 (UTC)

As a sanity check, we know that people have been looking into the embers of campfires for ages without damage. However, glassblowing, which is also pretty primal, is reported to cause eye damage with long-term exposure, so it's not very absolute. I think this gives a sense that the heat creates roughly the right amount of instinctive avoidance, perhaps, as one would expect for a condition which is at least somewhat tested over the course of evolution. And incandescent heatlamps are of the same general nature as fire, in that there's a heated surface giving off roughly black body radiation.

Where all bets are off is when the infrared is not coming from a black body. For example, laser safety warns that someone can have no warning of infrared laser damage until the popping of steam sounds on his retina. A blackbody - whether as near as a fire or as far as the surface of the sun - gives off only a certain amount of infrared per unit area of the retina, depending on its color. But when a laser is used, or if you filtered out all the more-than-infrared light from an very hot piece of steel, etc., then you could get higher levels of IR than that.

It also strikes me that laser light is monochromatic, and so theoretically it could have specific interactions with certain compounds in the eye that depend on the exact frequency. I doubt it because infrared spectra usually have multiple very broad absorption peaks that make it hard to hit one component but not another, but I wouldn't absolutely rule it out without data. Still, that's not even potentially a factor with a heat lamp that produces a broad blackbody spectrum. Wnt (talk) 15:43, 10 June 2015 (UTC)

I'll just note that I have known people who partially "cooked" themselves by sitting in front of a campfire for extended periods. They know it's warm and even appreciate the heat, but are distracted by making supper or managing the fire or whatever. My point is that it's not always easy to tell when something is hurting you. Hell, staring at just about anything for long enough will strain your eyes, so what kind of guidelines do you suppose we can give you? Matt Deres (talk) 16:52, 10 June 2015 (UTC)

Boiling frog § Science... Nimur (talk) 00:40, 11 June 2015 (UTC)

• Infrared lamps don't only give off infrared light, or they'd be imvisable. See the story of the self-cooking bride-to-be. μηδείς (talk) 00:06, 11 June 2015 (UTC)

  That's not true - these lamps could emit nothing but IR, and yet be perfectly visible because they'd still reflect or block visible light without emitting it. An invisible object would have to be transparent to visible light and reflect none of it. Not sure why you're referencing the "self-cooking bride to be" story - snopes says it's false. SteveBaker (talk) 03:33, 12 June 2015 (UTC)

Yes, if you really wnt to score points with an ad hoc excuse that ignores the fact that the ones that are sold commercially do give of visible light, then I suppose that bell you hear ringing means that somewhere in iSpace an angel has earned her wings. Or I could just as well retort that you are wrong because I said they were imvisible, not invisible. I'm sure that and $5.95 will get me a cup of coffee. μηδείς (talk) 04:48, 12 June 2015 (UTC)

nicotine

The nicotine article says that nicotine has stimulant effects at low dosages and sedation effects at high doses. At what threshold does this effect change, in milligrams please. How many nicotine patches would sedate an average person? — Preceding unsigned comment added by 222.77.187.171 (talk) 20:28, 9 June 2015 (UTC)

That's actually a very challenging question. It's quite clear that anxiety motivates smokers to want a cigarette, and very common for them to report that smoking calms them. However, attempts to measure the degree of anxiety reduction have been very inconsistent. An additional complication is that most reports come from habitual smokers, who are likely to have developed tolerance to nicotine and therefore need higher doses than nonsmokers to get the same effect. Looie496 (talk) 20:55, 9 June 2015 (UTC)

And one of the cited refs in the article says that the calming is the alleviation of the craving (not necessarily calmer compared to baseline). DMacks (talk) 20:58, 9 June 2015 (UTC)

Yes, to explain the last comment more simply, smoking actually causes anxiety see [1]. Nicotine will kill in large enough doses and it would be very dangerous to use it as a sedative - see Nicotine poisoning. Richerman (talk) 16:28, 10 June 2015 (UTC)

@richerman. your statement seems to misrepresent what your reference says. "smoking actually causes anxiety" your reference says "smoking can increase the chance of anxiety related disorders. Smoking cessation causes anxiety but the psychoactive effects of nicotine reduce anxiety. I might be wrong? your post just seemed misleading.Agent of the nine (talk) 16:54, 10 June 2015 (UTC)

It also says "Although regular smokers may find that cigarettes have a temporary calming effect, because smoking relieves their nicotine withdrawal symptoms, [that study] found that regular smokers who quit smoking for more than two weeks had lower anxiety levels than when they were smoking regularly". My understanding of the first part of that is that, after having a cigarette smokers start craving the next one (that's the withdrawal symptoms talk about) and this increases the anxiety level until the next cigarette briefly brings it back down to normal. Richerman (talk) 17:16, 10 June 2015 (UTC)

I see, that makes sense. I wonder if differences in time were accounted for. Did all smokers wait one hour before the next cigarette? (for example) Did this have an effect on different variables or overall levels of stress? Agent of the nine (talk) 17:30, 10 June 2015 (UTC)

Note that ethanol can also have a stimulant effect at low dosage and be more of a sedative at high doses. StuRat (talk) 14:58, 12 June 2015 (UTC)