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"Blowing someone else's candle out won't make yours shine brighter."

Is the claim in this sign correct? Would a candle shine slightly brighter with slightly more oxygen in the room?

And what do you mean "The candles aren't literal."?

billpg
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  • From the point of view of "relative" brightness, i.e. how an object appears brighter against a dark background, blowing out another candle in the same room where hey are the only source of light, does make your candle appear brighter. A typical example is when the moon is above the horizon during daylight, you often do not see it, because it appears to shine less brightly. Same for the stars. There are still there during the daytime, but you do not see most of them. – KDP Feb 08 '24 at 23:20
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    Try telling an astronomer that reducing light light pollution from artificial urban lights won't make the stars shine any brighter. – KDP Feb 08 '24 at 23:21

4 Answers4

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The claim is certainly true for candles in different rooms. Even in the same room, the effect of one candle on another in terms of oxygen consumption is with all likelihood completely negligible, and the candles could thus be treated as completely separate systems.

As to your question about how the candles are not literal: The sign is a metaphor for how sabotaging someone else does not make you absolutely better, only relatively, which is not the kind that matters (and makes the total situation worse, since you now have less total light / talent / whatever).

Note that if oxygen is a very limited resource, blowing out one candle would make the others burn longer. In much the same way the metaphor does not work in a competition over limited resources. But in the physical situation, infinite oxygen is usually a good approximation.

Codename 47
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  • Although if the candles are in a very small box, blowing out one could definitely make the other brighter... I guess the metaphor doesn't have the intended effect when you can say "If competition for resources is tight, eliminating competitors will enhance you..." – tpg2114 Mar 01 '19 at 13:18
  • That is true. Edited the answer to reflect this. – Codename 47 Mar 01 '19 at 13:26
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    Actually it doesn't burn brighter but rather longer. Given the desity of air in that system remain constant, the amount of oxygen consumed by the candle per unit time is constant and consistent regardless of the number of candles in the system. – TechDroid Mar 01 '19 at 13:50
  • @TechDroid You should make that an answer. – billpg Mar 01 '19 at 14:18
  • In fact the effect may work the other way around: if there are more candles in a room then the temperature goes up which means that each candle needs to do less work to melt the wax. I suspect this does not make them brighter, but it's not impossible that it does. The whole system is complicated. –  Mar 01 '19 at 14:25
  • @tfb Not to mention we need to define what "brightness" actually means. Incomplete hydrocarbon combustion would be yellow-orange, classic "flame" color, which somebody might say is "brighter" while a stoichiometric hydrogen flame would be blue and possibly impossible to see in visible light. But in some other wavelength, the hydrogen flame would be much brighter. As much fun as it can be to ground metaphors in physics, this one would take too long to do a proper analysis... – tpg2114 Mar 01 '19 at 14:33
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    @tfb, how bright a candle burn isn't a function of how much ambient heat is available. The candle flame works by phase transition of wax from solid to liquid and to gas which burns as it rises into the flame. Oxygen determines how hot or bright something burns. The soot from the candle is due to insufficiency in the available oxygen surrounding the flame and ready to grab leading to incomplete combustion of wax vapor. Burning candle is as simple as physics can be, so catch up bro. – TechDroid Mar 01 '19 at 14:36
  • @TechDroid: Flame physics is not simple: I'm sorry you think it is. –  Mar 01 '19 at 16:04
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It doesn't burn brighter but rather longer. Given the desity of air in that system remain constant, the amount of oxygen consumed by the candle per unit time is constant and consistent regardless of the number of candles in the system. To put that into perspective, blowing on a flame brightens it because setting air in motion requires compressing it forward layer by layer of molecules, it's this dense cloud of air that provides more oxygen per unit volume to the fuel increasing the combustion rate. So I'll advise not to blow out someone else's candle coz yours won't budge because of that, and you'll never know if you'll live long enough to witness yours burnout.

TechDroid
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  • If we define 'brightness' as 'power output' then if it burns for longer it must necessarily be dimmer since there is a given amount of energy in the candle wax, assuming the combustion is as complete in both cases. If the combustion is less complete in one case than the other (which would be the case if the oxygen level got low enough). –  Mar 01 '19 at 16:12
  • Brightness I believe is the amount of the visible part of the electromagnetic spectrum a light source is giving out. Like I said, you've got to get more combustion going per unit time to get more visible radiation emitted. The only way that happens is by density change. It's not the unavailability of oxygen that makes the combustion incomplete, it's how much the wax vapor can get oxidized at a time, some would, some won't, some partially. – TechDroid Mar 01 '19 at 16:46
  • Using that definition of brightness then for a given flame temperature it is proportional to the power output. So if it burns for a longer time, then either it is dimmer (in your sense) or, if it has the same brightness, the flame temperature must change to yield more energy in the visible spectrum (which I think would need it to be hotter, since there's pretty much no energy in the UV for a candle flame). You've not provided any explanation as to why that should be. –  Mar 01 '19 at 17:41
  • Let me make it simple. As long as the air density around the flame is constant, and the amount of oxygen in the air is also constant, the candle flame will illuminate with the same brightness for most of the time. Take out one candle in a system of two doesn't make the other burn brighter at all if all conditions remain the same. So if you want a brighter flame, either burn the candle in a pressurized chamber or create momentary compression disturbance by blowing on the flame (you only get momentary brightness as well). – TechDroid Mar 01 '19 at 18:25
  • Exactly. And that means it won't burn for longer, because it can't both burn with the same brightness and burn for longer without some additional source of energy (ie more wax). This answer, therefore, is incorrect: you should either delete it or modify it to be correct. You might also want to be a bit less patronising. –  Mar 02 '19 at 14:26
  • Wait a second, are you sure we're on the same page anymore, you might wanna reference back to the question for clarity please. Taking out one candle out of two in a limited and adiabatic air supply system mean the now lone candle has enough oxygen in the system to burn through all its wax, but as long as the air desity is constant, it doesn't burn any brighter. I'm not seeing the point you're driving at my friend, it'll be kind of you to post an answer explaining that at least if you're so confident about it. – TechDroid Mar 02 '19 at 15:03
  • Your answer says, in so many words 'it doesn't burn brighter but rather longer'. If this is correct it means that it must burn more dimly. It won't, in fact, do that, and therefore it will not burn for longer. That makes your answer wrong. I have said that many times: I'm not going to reply further as this is already too many comments. –  Mar 02 '19 at 15:27
  • Ok. Let say two cars are designed to move at a constant speed relative to their weight, both cars have the same weight, so while on the road one car stopped and gave all its fuel to the other to keep going, does that mean the now moving gas has to go slower to go farther, after all, its fuel has just being doubled, at its designed speed, it remaining milage also has to double. Take it or leave it, it is what it is. Good luck mate. – TechDroid Mar 02 '19 at 15:36
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I think it would look as though it would shine more brightly and this is more to do with the eyes response to light stimuli.

For example, a candle in daylight doesn’t seem as bright as a candle in the dark.

Mozibur Ullah
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The quote is TRUE for most candles, in most conditions, for most people. Both the literal and the philosophical can use this quote, as the candle is a candle AND the candle is a metaphor for the light that shines within each of us.

The quote is NOT true for people living in their own darkness of immaturity or an inflated delicate ego. This person believes - If there are 2 identical candles in the darkness, they will appear equally bright. And - If this person blows out my candle, only their candle will be shining in the darkness. Therefore - Their candle will shine brighter than mine, as my candle no longer shines in their darkness.

Sadly this person is trapped in their own darkness, too afraid their light is gone if it’s no longer the brightest light they see.

Laker
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