PAR, LEDs, and T5/MH. I'm confused.

fishmonkey

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So after renting a PAR meter and finding out my intensity was way too low I figured I should slowly acclimate my coral to 10% a week higher intensity lighting. My corals were surviving at these super low levels but not really growing all that much. It's been about 5 days since and I've noticed some of my coral doing better and some not as much. This may be due to other factors but that's beside the point.

From reading what's on the forums here about PAR, I found out LEDs can burn coral easier than other lighting and am wondering a few things.

Should lower PAR levels should be considered when using LEDs? (Tidal Gardens vs. Vivid Aquariums PAR)
Is there a PUR to PAR ratio to consider when using LEDs vs T5?
Should corals put directly under a LED light source be treated differently despite PAR?
How should whites and blues be treated on LEDs?
 

Spare time

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LED's are just easier to burn corals with because people will turn everything up to 100 and mount them too close. Some lights such as blackboxes can put out an insane amount of par and can have insane hotspots when mounted too close. Any light can cause a coral to bleach (or other possibly light related issue).

Other than that, treat mostly everything else the same. Just follow the recommended mounting height and spread and use a par meter. With that, pretty much any reef light you have will work.
 

Bpb

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There are some pretty compelling arguments around suggesting it is the IR present in metal halide bulbs that may help corals in withstanding higher light levels without reaching photoinhibition. I’m not qualified to make the claim and prove it, but there’s good info out there on it.
 

Uncle99

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T5 doesn’t require PAR calcs because they are so diffused, basically plug and play.

LED just gives us more control to the spectrum.

But the thinking does not change, in many cases, 300-350 at the top, 200-250 in the middle, and 80-150 on the bottom, some 50 in the corners, for mixed reef types.
 

Kessil

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So after renting a PAR meter and finding out my intensity was way too low I figured I should slowly acclimate my coral to 10% a week higher intensity lighting. My corals were surviving at these super low levels but not really growing all that much. It's been about 5 days since and I've noticed some of my coral doing better and some not as much. This may be due to other factors but that's beside the point.

From reading what's on the forums here about PAR, I found out LEDs can burn coral easier than other lighting and am wondering a few things.

Should lower PAR levels should be considered when using LEDs? (Tidal Gardens vs. Vivid Aquariums PAR)
Is there a PUR to PAR ratio to consider when using LEDs vs T5?
Should corals put directly under a LED light source be treated differently despite PAR?
How should whites and blues be treated on LEDs?

PAR is an inherently difficult measurement to work with because it weights each spectrum of light differently - more weight is put on the green to red portion of the spectrum. Simply put, a single photon of red light will register nearly 2x as high as a single photon of blue light. It's also why the PAR at the surface of a coral reef is close to 2000 PAR - there's a whole lot of light that the coral aren't using.

Just for fun, we put out 600 PAR using all green light on one of our stage lighting fixtures - but it wouldn't grow a single piece of coral because the coral don't need green, they need blue (specifically 425nm and 455nm for photosynthesis).

The other major thing to consider is that coral are remarkably resilient and adaptable organisms. You may have a piece of coral at 100 PAR that someone else has at 300 PAR. Both can grow and look amazing. Slow is always better when changing things.

To your question about treating corals different based on where they are - that depends on your light. A good LED will blend the spectrum together and have it be even across the entire tank (that's why we do our lights the way we do - the spectrum is mixed immediately). If you're working with a very spread out LED light source, you're more at risk of having a "fractured" spectrum - where there may be enough PAR, but you're missing a critical wavelength.

Lastly - whites and blues are different across each brand. On a Kessil light, Kessil Logic keeps the spectral output the same regardless of how white or blue you choose to make it. Other brands have similar features, while some do not.

Let us know if you've got any other questions about light - we'll help how we can. We've been doing fiber optic switches since 1986, and LED lights since 2002, so we know a thing or two about photons :)
 
BRS

oreo5457

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"PAR" or more correctly PPFD is by definition is the sum of all the photons between 400-700nm's

There is no "weighting" of different wavelengths within that range ..with a perfect sensor.
100 "PAR" of red or green or blue light contains the same amount of photons.
On an energy basis 100 "par" of blue contains more energy than 100 "par" of red light but photosynthesis only depends on photon capture not energy.
They found that some 2500 molecules of chlorophyll was required to produce one molecule of oxygen, and that a minimum of eight photons of light must be absorbed in the process.

I'm curious as to if the corals didn't grow or actually died. There is a difference.
Not a major issue since nobody would run green only lighting for a number of reasons.
Green light has not been shown to produce biological effects in terms of energy usage and growth. In other words the coral may not be getting anything useful from this light and it may not help the coral grow in any way. However, green light does produce a biological effect in terms of color. Using green light is completely for aesthetics at this point.
Granted green light certainly isn't "favored" by most photon capturing pigments.
Note " violet" is 450nm in this chart.
http://oceanographyclay1987.blogspot.com/2010/10/light-attenuation-in-ocean.html?m=1 why w
Light+attenuation+cw+pic.bmp
 

jda

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They probably would have grown if you gave them 300 PAR of green. There are plenty of proteins that can do photosynthesis in the green range, even if it is not as efficient. Proteins don't just respond in those two wavelengths - a few are optimal there, but not all and most excite from a wide range of wavelengths. This is fake news and one of the reasons that people get so confused with light.

PAR meters do not weigh wavelengths, as posted above. It is one of the downsides to the tool, along with not capturing wavelengths below 400nm or above 700nm. They also have no opinion on spectrum and an overabundance in one area can drive the number up, but be harmful, or not helpful, to actual corals. However, they can still be useful as a guideline or swag. They are even more helpful if you are fairly certain that your spectrum is at least decent.

What you really need to know is that too much PAR from nearly all LEDs can burn coral. Twice or thrice this amount, or more, from mercury sources does not. Even more than this from the sun or solar tubes does not. There are lots of theories why, but the phenonomen is real in our tanks. I mostly deal in Acropora and while there are a few who can grow acros above 350-400 PAR of LED, the majority cannot - acropora can handle 1200 PAR from my MH. They can do sunlight in a shallow pool well over 2000. I even grow bounce, eclectus, jawbreaker mushrooms and RBTAs (Colorado sunbursts) in 750 PAR under MH in shallow frag tanks and they grow fast and thrive. They might not need it, but the increase in growth is there if you give them a lot of quality light. They would all likely shrivel and die with 750 PAR of most any LED.

What Bpb was referring to in post #3 is the Emerson effect. It moves energy from Photosystem II to Photosystem I with the help of IR light. This is one theory as to why mercury bulbs can give much more PAR to corals without burning them. ...just a theory. There is a lot of info out there if you want read up on it.

Just go slow and watch your corals. If they don't expand as much after a bump in intensity, then back it off. They will tell you what you need to know if you give them time to react and pay attention.
 

Spare time

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They probably would have grown if you gave them 300 PAR of green. There are plenty of proteins that can do photosynthesis in the green range, even if it is not as efficient. Proteins don't just respond in those two wavelengths - a few are optimal there, but not all and most excite from a wide range of wavelengths. This is fake news and one of the reasons that people get so confused with light.

PAR meters do not weigh wavelengths, as posted above. It is one of the downsides to the tool, along with not capturing wavelengths below 400nm or above 700nm. They also have no opinion on spectrum and an overabundance in one area can drive the number up, but be harmful, or not helpful, to actual corals. However, they can still be useful as a guideline or swag. They are even more helpful if you are fairly certain that your spectrum is at least decent.

What you really need to know is that too much PAR from nearly all LEDs can burn coral. Twice or thrice this amount, or more, from mercury sources does not. Even more than this from the sun or solar tubes does not. There are lots of theories why, but the phenonomen is real in our tanks. I mostly deal in Acropora and while there are a few who can grow acros above 350-400 PAR of LED, the majority cannot - acropora can handle 1200 PAR from my MH. They can do sunlight in a shallow pool well over 2000. I even grow bounce, eclectus, jawbreaker mushrooms and RBTAs (Colorado sunbursts) in 750 PAR under MH in shallow frag tanks and they grow fast and thrive. They might not need it, but the increase in growth is there if you give them a lot of quality light. They would all likely shrivel and die with 750 PAR of most any LED.

What Bpb was referring to in post #3 is the Emerson effect. It moves energy from Photosystem II to Photosystem I with the help of IR light. This is one theory as to why mercury bulbs can give much more PAR to corals without burning them. ...just a theory. There is a lot of info out there if you want read up on it.

Just go slow and watch your corals. If they don't expand as much after a bump in intensity, then back it off. They will tell you what you need to know if you give them time to react and pay attention.


Keep in mind that 1200 par you provide is, in reality, just slowing down growth since they likely are not photosynthesizing with that intensity because of photoinhibition (I'm guessing you know this though). The sun also does cause issues for coral. That is why shallow water corals grow much slower than the same species further out, and why the tropics is an intense place to live.

These corals have been under selection pressure for hundreds of millions of years and have changed to their environment thoughout it. This is not possible with our tanks and our conditions. We simply can't play the games nature plays with corals. How corals function in the wild is far more complex than our tanks which don't mimic the ocean very well, so comparing how a wild coral survives several hours of extreme light is not realistic to compare in our tanks as we don't have a moveable single point fixture going across the sky, being distorted by the atmosphere, other organisms, etc, and producing an extraordinary range of radiation compared to our lights, that also moves to and from the coral throughout the year.

Therefore, I doubt that it is LED's that cause the issue with corals, but rather that, individual specimins and species are able to tolerate various conditions depending on their individual and species history.


Also, it is not "fake news" that blue light is preferential. Nearly all photopigments are most sensitive between 380-500nm wavelengths. Very few peak in greens, and for good reason. The use of red and blue is function of physics. (yes this says plants but you get the point)
 
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Spare time

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I am not sure that the light produced by an LED vs a metal halide, vs t5, etc. is different. Radiation is radiation. If light is coming out at 425nm wavelength, it is a 425nm "wave" of light. The difference though, is that LED's are able to pack massive amounts of the same color that is most excitatory to photopigments, making their "excitement intensity" (to a degree) greater than a light that packs only green LEDs which are not very "exciting."
 

jda

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Photo inhibition is more of a product of quality than quantity. I can assure you that they grow faster with more quality light. This lower-PAR thing is mostly new to when LED came into play. In the past, more light nearly always meant more growth... not always, but most of the time. As long as quality is high, the more light means more sugars from the zoox and more growth, assuming that nothing else is growth limiting.

I had a shallow tub outside in Missouri in the sunlight on summer. Other than dealing with the heat, leaves/organics and birds/animals wanting to bathe, a 1" frags of Red Planet grew to like 8" across in 4 months in that high intensity. The growth was amazing and so was the color once we got some 10K+ light back on them.

The last dude who really challenged me on this got him a 20k Radium and then about three months later saw for himself. Softies, LPS, everything can thrive even more with high PAR. Click on the 60g budget cube in my signature... even though this tank is long gone, that was very high PAR and at levels that some have written about photo inhibition... look at that hammer that does not seem too mad. None of those SPS are hard to grow, but they certainly were not inhibited.

All of this said, I do find that 750 PAR from MH is a sweet spot for electrical, growth and color for most acropora. Anything above 400-500 is fine for most. Growth slows for me below this, but is still more than most of the locals have with their acropora.

Again, I am not saying that the corals need any of this, just that they do respond. In some ways, it is a curse since I have to break down about every three years and start over since the colonies get wall-to-wall. I have about 1.5-2 years left on this redo and I have to decide if this is the last one for me, or not. For people with small tanks, faster growth is not as good as people often think, unless it is of a super expensive and rare coral.
 
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jda

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I hate this whole "photon is a photon" argument since it is mostly lazy. First, photons are quantums which are both still theoretical and infinite at the same time. It is likely that no photon has ever been made that is identical to another. Only our rudimentary tools see them as equals - like how all snowflakes look the same from inside your house. Is there anybody on this board who can efficiently talk about quantums? Those folks who understand that stuff make much money for their jobs and are hard to find. I hate comparing infinite and still theoretical things to each other - it is worse than saying that coral is coral or a human brain is a human brain which are equally not helpful. Nobody should be saying any of this.

The lack of UV and IR in most LED panels is a good place to start. There is plenty of real science that show that both have effects on photosynthesis, pigmentation, sunscreen pigments, excitation of most proteins (not all) among other things. Basically color and growth - they are mostly kept out of LEDs because they are expensive, short lived diodes and some can product heat and take away a value-add (which is mostly untrue anyway). For example, green has been shown to penetrate tissue and layers of larger objects, then end up as red after some energy is lost - of course, this requires looking beyond the simple to the whole picture of wide spectrum (beyond the "green causes algae" myth). ...so the PAR from green probably does do something even though some who only look on the surface will say that it doesn't. In any case, there are plenty of things that are different. Knowing and effectively communicating the differences keep people happier - a few locals that have switched from LEDs to mercury were cussing out all LEDs but the main issue was that they believed a manufacturer and internet alternate facts and never learned the real science. The light was not the problem - they were. Again, it might not matter for what you do, but needing to keep intensity lower for LED is real and it goes beyond people just needing to stop messing with them (which is real too, just not the whole story).
 

flourishofmediocrity

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I hate this whole "photon is a photon" argument since it is mostly lazy. First, photons are quantums which are both still theoretical and infinite at the same time. It is likely that no photon has ever been made that is identical to another. Only our rudimentary tools see them as equals - like how all snowflakes look the same from inside your house. Is there anybody on this board who can efficiently talk about quantums? Those folks who understand that stuff make much money for their jobs and are hard to find. I hate comparing infinite and still theoretical things to each other - it is worse than saying that coral is coral or a human brain is a human brain which are equally not helpful. Nobody should be saying any of this.

The lack of UV and IR in most LED panels is a good place to start. There is plenty of real science that show that both have effects on photosynthesis, pigmentation, sunscreen pigments, excitation of most proteins (not all) among other things. Basically color and growth - they are mostly kept out of LEDs because they are expensive, short lived diodes and some can product heat and take away a value-add (which is mostly untrue anyway). For example, green has been shown to penetrate tissue and layers of larger objects, then end up as red after some energy is lost - of course, this requires looking beyond the simple to the whole picture of wide spectrum (beyond the "green causes algae" myth). ...so the PAR from green probably does do something even though some who only look on the surface will say that it doesn't. In any case, there are plenty of things that are different. Knowing and effectively communicating the differences keep people happier - a few locals that have switched from LEDs to mercury were cussing out all LEDs but the main issue was that they believed a manufacturer and internet alternate facts and never learned the real science. The light was not the problem - they were. Again, it might not matter for what you do, but needing to keep intensity lower for LED is real and it goes beyond people just needing to stop messing with them (which is real too, just not the whole story).
When people say “a photon as a photon“ what they are referring to is a photon of a certain wave length from one type of light is exactly the same as a photon of the same wave length from a different type of light, which is correct.
 

flourishofmediocrity

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"PAR" or more correctly PPFD is by definition is the sum of all the photons between 400-700nm's

There is no "weighting" of different wavelengths within that range ..with a perfect sensor.
100 "PAR" of red or green or blue light contains the same amount of photons.
On an energy basis 100 "par" of blue contains more energy than 100 "par" of red light but photosynthesis only depends on photon capture not energy.


I'm curious as to if the corals didn't grow or actually died. There is a difference.
Not a major issue since nobody would run green only lighting for a number of reasons.

Granted green light certainly isn't "favored" by most photon capturing pigments.
Note " violet" is 450nm in this chart.
http://oceanographyclay1987.blogspot.com/2010/10/light-attenuation-in-ocean.html?m=1 why w
Light+attenuation+cw+pic.bmp
I’m not a physicist so I can’t say whether or not your comment about 100 PAR of one wave length of light compared to 100 PAR of another wave length of light would have the “same amount of photons“ is correct, but it sounds wrong. It sounds wrong because photons have a different amount of energy depending on their frequency or wavelength.

 

oreo5457

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Personally most of the hot par of leds is because of design.
I've "pushed" the use of reflectors since practically day one of leds in aquarium useage.
Originally the problem was getting PAR/$ out thus the maximizing output over err "quality".
In a sense "glare is good" (see link) which is now the "diffusion revolution"
Livid-TIR-Optic-Vs-Reflector.jpg


@jda I have a question that needs clarity.
1) You state some are successful with high PAR leds, is there a common denominator here?
2) You also stated in the past that those that used LEDs HIGH up had the best success.

Seems like they both might tie into the above.. hot spots internally in the coral due to the design of the led emitting beam.

Since the animal "grows" and the plant produces food one thing to keep in mind is in my opinion growth and photosynthesis are not 100% linked.
Point is growth can occur with limited photosynthesis.

Corals use dissolved inorganic
carbon from seawater to create its calcium carbonate skeleton and in
the process releases carbon dioxide (calcification: Ca2+ + 2HCO3- 
CaCO3 + CO2 + H2O). Therefore, corals much live in water that have
sufficient quantities of dissolved carbon. Although corals are animals
their symbiotic relationship with zooxanthellae, photosynthetic algae
(6CO2 + 6H2O  C6H12O6 + 6O2), means that coral survivability also
is influenced by light availability. If there is not enough light for the
zooxanthellae to survive then the corals will also suffer. Interestingly, the carbon dioxide produced
by corals during calcification can enhance the ability of zooxanthellae to complete photosynthesis.
Therefore, corals and zooxanthellae can grow in areas with less carbon but are still limited by the
amount of light available to them.
Extreme example:




Previous studies suggested that photosynthetic corals at the bottom of the ocean's sunlit layer grow extremely slowly -- about 0.04 inch per year for one species of Leptoseris.


"Considering the low light environment, the previous assumption was that large corals at these extreme depths should be very old due to extremely slow growth rates," said Kahng. "Surprisingly, the corals were found to be relatively young with growth rates comparable to that of many non-branching shallow water corals. Growth rates were measured to be between nearly 1 inch per year at 225 feet depth and 0.3 inches per year at 360 feet depth."
 

hart24601

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I am not sure why so many people say high led par kills corals. Sure maybe with no acclimation but heck even in 2014 right here on r2r I won the acro growout contest (open to any lighting) which sadly I think are deleted now, but those were in 600 PAR from cheap black box fixtures and I have no doubt would have been fine higher. Although I believe wining that contest was due to feeding, I have always kept acros in a lot of par from leds. I shoot for 300 min, but 600, 800 or more isn’t unheard of in my system on acros like Oregon tort and even pc rainbow although it’s all red under that intensity.
 

jda

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Since no photon has likely every been the same as another, this is still inaccurate. It might be more accurate than the normal generalized banter about saying that light is light regardless of the source and that corals don't care where the light came from. Coral is coral, right? This is correct too, but still not even close to being good enough for hobbyists to do their job as stewards.

hart - you and a small few other hobbyists are why I say "mostly" now. Most others still struggle no matter what they do, but there are a few that can do higher light with LED even when the masses fail. I just say that they kill coral for most, not all. If people want to dig in and figure out what you do, then they can probably do it, but that seems like a lot of work for the general poster around here. :) I guess that you don't believe the typical message board banter about photo inhibition either...

@jda I have a question that needs clarity.
1) You state some are successful with high PAR leds, is there a common denominator here?
2) You also stated in the past that those that used LEDs HIGH up had the best success.

...so hard. Hart above might have some reasons to offer - he talks a lot about acclimation. The other two keep the lights way up high and run them at 100% (or near) on all channels. Maybe the presence of that other spectrum helps too - these are not windex-look people. The other two also keep near NSW parameters with more natural levels of N, P, carbonate, etc. - I am sure that you have heard my theory that the higher levels of N and P which slow down cellular function along with LED is a bad combo, but this has not been substantiated beyond just a theory. A research institution was going to take this up since they had a similar thought (saw my post on here or Dana sent it to them... not sure), then COVID happened... not sure what happened to that. IMO, therman has some of the best acropora under LED alone - there are others, of course, but lots use a T5 here or there - he uses Photon v2 up high at 100%. His acropora look great, grow great and are super healthy, but too few do what he does.

As I am sure that you have seen me post before, when I rand Radions over one of my frag tanks, I could not really get them up over 350-400 without making the corals mad - mushrooms and acropora. Only did this for about 5-6 months, so not a super long time to acclimate them. I did have them up high and on about at least 80% on non-blue channels (tried to do what Dr. Joshi did). As you know, I do not think that that these are even close to the best LEDs out there, but they were free to try. ReefBreeders allowed for me PAR and covered better... but I only had about 3 months with this since it was borrowed. In the end, no conclusions about PAR or except that if I was going to run the same wattage, I wanted the MH since they just flat out perform better for me.

You know that I like the theory, but am more into the practical and experience and I just like to point out that nearly all fail with LED up too high since, let's face it, the masses are not going to dig in and figure out why some have success. The few that are wanting to do dig in will do it anyway.
 

oreo5457

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You might find this interesting.

and it comes from the observation that all subatomic particles are described by a few key properties, but are otherwise completely and utterly identical. Electrons appear to be identical to all other electrons. All photons (if they carry the same energy within them) are identical to all other photons of that energy. Protons are identical to other protons, and neutrons are identical to other neutrons. All of these particles are distinguished from each other by their mass, electric charge, and a property called their spin.
 

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I hate this whole "photon is a photon" argument since it is mostly lazy. First, photons are quantums which are both still theoretical and infinite at the same time. It is likely that no photon has ever been made that is identical to another. Only our rudimentary tools see them as equals - like how all snowflakes look the same from inside your house. Is there anybody on this board who can efficiently talk about quantums? Those folks who understand that stuff make much money for their jobs and are hard to find. I hate comparing infinite and still theoretical things to each other - it is worse than saying that coral is coral or a human brain is a human brain which are equally not helpful. Nobody should be saying any of this.

The lack of UV and IR in most LED panels is a good place to start. There is plenty of real science that show that both have effects on photosynthesis, pigmentation, sunscreen pigments, excitation of most proteins (not all) among other things. Basically color and growth - they are mostly kept out of LEDs because they are expensive, short lived diodes and some can product heat and take away a value-add (which is mostly untrue anyway). For example, green has been shown to penetrate tissue and layers of larger objects, then end up as red after some energy is lost - of course, this requires looking beyond the simple to the whole picture of wide spectrum (beyond the "green causes algae" myth). ...so the PAR from green probably does do something even though some who only look on the surface will say that it doesn't. In any case, there are plenty of things that are different. Knowing and effectively communicating the differences keep people happier - a few locals that have switched from LEDs to mercury were cussing out all LEDs but the main issue was that they believed a manufacturer and internet alternate facts and never learned the real science. The light was not the problem - they were. Again, it might not matter for what you do, but needing to keep intensity lower for LED is real and it goes beyond people just needing to stop messing with them (which is real too, just not the whole story).

Best answer on the thread right there. Take note folks.

Effectiveness of light source is a gradient. It’s not simply “perfect or completely inadequate”. Some light sources offer significant advantage biologically, others (if used correctly) are perfectly suitable, but won’t have the ceiling of function as a metal halide lamp. There are very few people that can logically argue that. At the end of the day, keep an open mind, know specifically what your goals and limitations are, and act accordingly.
 

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While it has been a while, I did take a few 400 level courses on Quantum Mechanics from a pretty good engineering school. I hated them, but I paid attention. Admittedly, much more could have been discovered since the late 1990s when I was in college and I have no inclination to keep up with this or theory of automata. I also understand the need to dumb it down and only look on the surface for most people. Unless science has been turned on it's head, beyond the surface where it might be OK to say that all some things are very similar to others, but when you dig in, that just is not true... just look at the disclaimers and things in parenthesis just in that quoted paragraph. If you break anything down into a few keep properties, everything is identical (cows sharing like 80% of their genes with humans). You can bet that scientists that study this do not need the kind of schooling that they have, the expensive equipment that they require nor the experience that is needed to just say that all particles are identical to each other. You don't have to pay people when this is true... let alone what most of them make for a salary and benefits.

Admittedly, it is hard to explain to people the theoretical and infinite nature of anything. Heck, we adopted kids a few years back and most humans cannot even define the infinite and theoretical nature of their current behavior and past experiences and they just label it all as trauma and want to treat most of it the same way - the really good ones dig deeper and get better results.

In your google search, if you skip that first article that you quoted, many more go into more detail and explain that each has a signature from the source and no source is the same. No source acts the same from time to time, either... halide in a glass bulb is constantly in motion, surface of the sun is constantly moving, LED PWM is not constant (what with hz is?), etc. The same diode would likely yield an infinite amount of different photons for it's whole life... all very similar with perhaps slight shifts to be expected over time (spectrum and intensity), but not identical.
 

oreo5457

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By your " theory" photons from the sun would be vastly different from photons from any mercury emission source. Unless of course you believe nuclear fusion is occurring in the metal halides.

I'd stick to spectrum differences .. though since different bulbs have different spectrums and t5's et al are also very different with little uv or infrared ..well ..you get the picture

Maybe need to go back to filiment lights to be more like the sun.

Emerson effect and irritating corals with uv may be the difference or heating the coral skeleton via far ir. Unlikely anything to do with quantum mechanics.
 
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