Glowing firefly
credits: flickr/Takashi Ota

It is weird! Yes asking to match up Sun’s brightness using fireflies is actually a weird thing, but curious minds behave like this. So let’s dwell a little deeper to find an answer if possible any. First thing first, if by any means it becomes possible, it would require a great number of fireflies. The number of fireflies for this grand scheme would be a finite number having a lot of zeroes.

Sun’s visible part of radiation or glow, a type of incandescence or heat based radiation comes out from a small part of immense amount thermal energy produced through nuclear fusion process going on in its core, whereas if we talk about firefly, the glowing light is the result of cold light phenomenon often known as luminescence1. Since this luminescence process happens inside a biological system; i.e. inside firefly using an enzymatic system, it is more precisely called bioluminescence.

How does it happen? Sun shines and firefly glows:

We talked a little about the different mechanisms of visible spectra production by sun and a firefly, But let’s try to understand it in bit detail before going for actual calculations-


Sun : 5,772 K hot , nearly perfect sphere of plasma sitting in center of our solar system

Sun a large gaseous stellar body in the center of our solar system produces an immense amount of thermal energy by joining up lighter atoms of hydrogen into heavier helium nuclei. Sun is a main sequence star and formed around 4.6 billion years ago by the gravitational collapse of the matter within a region of formed molecular cloud in space2.

Consisting of about 73% hydrogen, 25% of helium and as oxygen, nitrogen, carbon, and iron; major of its energy comes from proton-proton chain reaction; i.e. nuclear fusion of two hydrogen atoms inside its core and also a small amount of CNO reaction (it uses carbon nitrogen and oxygen in fusion reaction making helium nuclei from hydrogen/protons). The process goes on with the rate of 9.2×1037 times each second, converting about 3.7×1038 protons into helium nuclei and releasing around 0.7% of the fused mass as energy equivalent to 384.6 yottawatts (3.846×1026 W)2,3. The energy releases in form of thermal as well as electromagnetic radiations providing the sun, its high temperature and luminosity. Experimental results suggest Sun’s luminosity is about 3.828×1026 watt equivalent to 3.75 x 1028 lumens2.

Structural organization of sun, the center of sun known as core is the place of nuclear fusion process and acts as an source of immense amount of radiated energy.


fireflies glow in dark night-wiseverse
A Firefly glowing in dark using bioluminescence : In presence of oxygen luciferin converts into oxyluciferin and releasing energy in form og light.

Fireflies are actually beetles belongs to the family lampyridae. They are different from glowing worms of the same family by the presence of wings. There are more than 2000 species of fireflies around the world. Different species of firefly may glow in different colors. Seeing them in dark night, it looks they are fully glowing, but in reality, there is only a thin layer of their surface which glows.

Unlike the sun, glowing of fireflies is attributed to bio-luminescence, a chemical phenomenon where moieties of chemical luciferin get activated in presence of ATP (a high energy phosphate molecule) forming high energy intermediate luciferin-AMP. This high energy intermediate in presence of oxygen decays itself into oxyluciferin and AMP releasing energy in form of luminescence or glow4.

bioluminescence mechanism in fireflies-wiseverse
A part of the image showing the biochemical reaction responsible for glowing of firefly organ. the process is known as bioluminescence. B. part defines the structure of glowing organ of a typical firefly species.

So how many fireflies?

It will be easier to calculate how many fireflies needed to match up the sun’s brightness if we know the brightness of a single firefly. Headlight bugs, a species of beetles which glows in dark was studied by scientists in early days and they found their glowing patches are roughly one square millimeter and not strong glowing. These glowing patches were emitting light of about 0.0006 lumens5.  Fireflies also have similar size and intensity luminous organ or glow patches like headlight bugs. The peak intensity per area of fireflies is also very similar and it would be a good reference value for the firefly’s lantern.

However, there is one more issue which could affect the calculation and that is firefly glows in pulses. There luminous organs do not always on, and their pattern of glowing or intensity varies from one species to another as well as depends on situation to situation.  Research results suggest glowing carries special information and used for mating, communication and specialized purposes. For ease of calculation it would be better to pick a species of firefly showing mostly on duty cycle for glowing organ; for example- Headlight Bug itself.number of fireflies-xkcd-whatif-wiseverse

So now when we have a brightness of sun as well as a single firefly for reference, calculating the numbers of firefly needed, will be easier. It will be just an easy mathematical calculation dividing sun’s brightness with single firefly glow organ’s brightness; i.e. 3.75 x 1028/6 x 10-4. Which gives us a value of 6.25 x 1031 or roughly 6 x1031 fireflies to get the same amount of light we get from the sun. And it would be far efficient from the sun because if considering weight of individual firefly about 20 milligrams roughly, this group of firefly will only weigh almost equal to earth and 1/6000th as much as the sun. In a simpler way, this firefly combination will be much brighter per pound than the sun. However, the sun can’t afford to be like it because it has to last billions of times longer.

But is it this simple? No, not exactly:

Is it not looks so simple to calculate the number of fireflies equals to the sun? But wait there are few problems in there. First, how do someone will gather so many of firefly at one place? And if by any means we will be able to do that gathered firefly would block each other. The inner layer of fireflies would be hidden behind by the outer ones, making the total brightness lesser than what we calculated.

Since all that matters is the surface light either it would be the sun or some other luminous source, let this firefly to arrange on the surface of a hollow sphere pointing their lantern outwards. Looking like similar to a DJ light ball but much larger and much weighing. But in this arrangement fireflies would die after sometime due to the lack of oxygen inside the sphere ultimately blowing up the great firefly ball.

How about a single firefly6:

For the sake of simplicity let’s assume a single giant firefly or say godmother firefly. But as we already know to give off 6 x 1031   times as much light as normal firefly, godmother firefly will need a glowing patch 6 x 1031    times larger than the existing ones.  Since the surface area of any entity is proportional to length squared, our firefly will be much bigger than normal ones. All known species of fireflies varies between 5mm to 25.4mm and taking the smaller one in consideration will give our godmother firefly the size of 1.22 x 1011 km much larger than our own solar system (7.5 x 109 km).  A firefly giving light to our solar system flying in open space! (I don’t know how godmother will survive there.)


What about the mass of our firefly godmother?

I don’t need to say it will be too high but let us calculate it also. Since the mass of anybody is proportional to its length cubed, or in other words, our godmother firefly will weigh around 5.1 x1047  times a normal firefly weigh (calculating it will give you value 1.0 x 1044 Kg). This type of weight make it about 1.5 times heavier than our own Milky Way galaxy.

I don’t think godmother firefly will survive its own weight and will certainly collapse under its own weight forming a black hole. Giving attention to the distribution of galaxies in our universe, there is an upper limit7 to how large a black hole can grow and our godmother firefly would be bigger than that limit and will become the largest black hole in the universe.

So I would finally say, leave this job to our own sun. Sun is much better for us than finding a group of fireflies or single godmother firefly of having the same intensity. Because the basic difference will be it would give us the light but for the much shorter duration, if any in absence of oxygen. And I don’t think we have too much space left on earth to make such type of a DJ light ball from fireflies.  Curiosity is good but sometimes results are weirder and scarier than the real world.

If you have also any weird question or curiosity don’t forget to comment down below, We would love to listen from you and work on that to find an answer which can help you to become smarter and knowledgeable.


  • Cold Light:
  • Bonanno A., Schlattl H., Paternò L. (2008). “The age of the Sun and the relativistic corrections in the EOS”.Astronomy and Astrophysics. 390 (3): 1115–1118.
  • Shu, F. H. (1982).The Physical Universe: An Introduction to Astronomy. University Science Books. p. 102.
  • Haddock, Steven H.D.; Moline, Mark A.; Case, James F. (2010).”Bioluminescence in the Sea”. Annual Review of Marine Science. 2: 443–493.
  • James F. Case and John Buck (1963). Control of Flashing in Fireflies II. Role of Central Nervous System. The Biological Bulletin.125:2,234-250
  • What if: XKCD:
  • Priyamvada Natarajan and Ezequiel Treister Is there an upper limit to black hole masses?


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