Kurzgesagt – In a Nutshell 

Sources – No Stupid Questions

—Tokyo is a hungry beast, gobbling up around 280 terawatt hours of electricity every year. That’s more energy than these twenty countries combined, and more than all of Australia.  

We use the data for the Tokyo region as considered by the Japanese Organization for Cross-regional Coordination of Transmission Operators, which is a broader area than the Tokyo Metropolis. Please note that the data is for the Japanese 2023 fiscal year, which starts in April 2023.

#Organization for Cross-regional Coordination of Transmission Operators, Japan (2024): “Annual Report, Fiscal Year 2024”

https://www.occto.or.jp/en/information_disclosure/annual_report/files/2024_annualreport_241210.pdf 

The values for the energy consumption of the different countries are taken for the year 2023 from:

#U.S. Energy Information Administration. “Electricity net consumption by country/region” (retrieved 2025)

https://www.eia.gov/international/data/world/electricity/electricity-consumption? 

—Some jelly species like Aequorea victoria or crystal jelly contain fluorescent proteins and glow in the dark.

Aequorea victoria glows through a combination of proteins that use chemical reactions to produce light (aequorin) and fluorescent proteins (GFP). 

# Mills, Claudia E. (2009): ”Bioluminescence and other factoids about Aequorea, a hydromedusa”

https://faculty.washington.edu/cemills/Aequorea.html

Quote: “The luminescent light produced by Aequorea is actually bluish in color, attributable to a molecule known as aequorin, but in a living jellyfish it is emitted via a coupled molecule known as GFP, or green fluorescent protein, which causes the emitted light to appear green to us.”

Osamu Shimomura received the Nobel Prize in Chemistry in 2008 for his discovery of GFP in his studies of  Aequorea victoria. 

#The Nobel Foundation (2008): “How the Jellyfish’s Green Light Revolutionised Bioscience”

https://www.nobelprize.org/uploads/2018/06/popular-chemistryprize2008-1.pdf 

— If you put one of them in front of a tiny solar panel, you’d end up with something like  a microwatt hour of energy.

The crystal jellyfish Aequorea victoria luminescent organ is along the rim of its bell 

#The Nobel Foundation (2008): “How the Jellyfish’s Green Light Revolutionised Bioscience”

https://www.nobelprize.org/uploads/2018/06/popular-chemistryprize2008-1.pdf 

If stimulated, it produces light through the photoprotein aequorin. Let’s assume there is 10 mg of aequorin per jellyfish. Each milligram of aequorin produces 4.3–5.0 × 1015 photons, with the emission peak at a wavelength of 465 nm.

#Shimomura, Osamu (2006):  “The Photoproteins”, Chapter 1 in “Photoproteins in Bioanalysis”, edited by Sylvia Daunert and Sapna K. Deo

https://application.wiley-vch.de/books/sample/3527310169_c01.pdf 

Quote: “One milligram of aequorin emits 4.3–5.0 × 1015 photons at 25 °C when Ca2+ is

Added”

Please note that the original table has been cut to highlight the relevant data, but it is accessible in the source link. 

For simplicity, we assume all photons are emitted at the emission peak wavelength. Then, each photon has an energy of: 

E= c × h / λ = (3.0 × 108 m/s) × (6.6  × 10-34 J s)/ (465 × 10-9 m) = 4.3 × 10-19 J

#Honsberg, Christiana; Bowden, Stuart: “PVCDROM: Energy of a Photon” (retrieved 2025)

https://www.pveducation.org/pvcdrom/properties-of-sunlight/energy-of-photon 

If we have 5.0 × 1015 of these photons, the total energy is:

10 mg × (5.0 × 1015 photons/ mg) × (4.3 × 10-19 J/ photon) = 0.022 J= 6.1 × 10-6 Wh

If our solar panel has an efficiency of 20%, the final read is: 

(5.8  × 10-6 Wh) × 0.2= 1.2 × 10-6 Wh

—To meet Tokyo’s outrageous energy demands, you’d need: a quintillion three hundred quadrillion glowing jellies. 

As seen in the previous section of this document, each jellyfish produces 1.2 × 10-6 Wh. That means that, to provide the 280 TWh to power Tokyo over a year, we would need: 

280 × 1012 Wh / (1.2 × 10-6 Wh/ jellyfish) = 2.3 × 1020  jellyfishes

This calculation does not take into account that jellyfish can likely replenish their photoprotein aequorin, and treats every jellyfish as having a single “charge”. If we assume that the jellyfish can recharge its photoproteins completely after one day, and that each jellyfish lives for 6 months:

#Dimensions.com: “Crystal Jellyfish (Aequorea victoria)” (retrieved 2025)
https://www.dimensions.com/element/crystal-jellyfish-aequorea-victoria
Quote: “The typical lifespan of the Crystal Jellyfish is 2-6 months.”

Then the total number of jellyfish needed to power Tokyo over a year is: 

(2 jellyfish to last a year ) × (2.3 × 1020  jellyfish charges)  / 365 days = 1.3  × 1018  jellyfishes

—How about Nemopilema nomurai, the Nomura jellyfish! Really chunky boys, weighing about as much as a piano and growing up to 2 m wide, they’re armed with around a thousand spindly tentacles that grow up to four meters long and help them suck up plankton from the water. 

#Kawahara, Masato; Uye, Shin-ichi; Ohtsu, Kohzoh; Iizumi, Hitoshi (2006): “Unusual population explosion of the giant jellyfish Nemopilema nomurai (Scyphozoa: Rhizostomeae) in East Asian waters”, Marine Ecology Progress Series, vol. 304, 161-173

https://www.researchgate.net/publication/250218677_Unusual_population_explosion_of_the_giant_jellyfish_Nemopilema_nomurai_Scyphozoa_Rhizostomeae_in_East_Asian_waters
Quote: “Nemopilema nomurai (Cnidaria: Scyphozoa: Rhizostomeae) is one of the largest of all jellyfish species, attaining a bell diameter of ca. 2 m and a wet weight of ca. 200 kg”

For comparison, an upright piano is 175 to 350 kg

#Petrof: “What is the size of the grand piano and the upright piano?” (retrieved 2025)

https://www.petrof.com/what-is-the-size-of-the-grand-piano-and-the-upright-piano

—In recent years, their numbers have been exploding, wreaking havoc on local ecosystems.

#Xiao, Wupeng et al. (2019): “The impact of giant jellyfish Nemopilema nomurai blooms on plankton communities in a temperate marginal sea” Marine Pollution Bulletin, vol.149, 110507

https://www.sciencedirect.com/science/article/abs/pii/S0025326X19306459
Quote: “Increasing jellyfish blooms have been reported frequently worldwide in recent decades, and have caused serious ecological and environmental disasters, such as declining fishery production, poisoning swimmers and blocking cooling water intakes in coastal power plants”

—If you’ve ever been stung by a jellyfish you know it feels like a painful electric jolt – but the pain actually came from hundreds of nematocysts inside of their tentacles, tiny dart guns filled with venom.

#Ocean Conservancy (2021): “How Do Jellyfish Sting?”

https://oceanconservancy.org/blog/2021/04/26/nematocysts/ 

—Piezoelectricity is an electric charge that builds up in certain solid materials like crystals or bone when you stress and squeeze them. For example, a quartz crystal is made up of positive and negatively charged atoms arranged in repeating pyramid shapes. Their charges usually cancel each other out. But if you apply enough pressure, atoms shift out of place and the pyramids become kind of wonky. Positively charged on one side and negatively charged on the other – like a battery.

#Li, Jing-Feng (2021): “Fundamentals of Piezoelectricity” Chapter 1 in “Lead-Free Piezoelectric Materials” by Jing-Feng Li

https://application.wiley-vch.de/books/sample/3527345124_c01.pdf
Quote: “In 1880, Pierre Curie and Jacques Curie discovered the (direct) piezoelectric effect in quartz (SiO2) and other single crystals, which generates an electric charge proportional to a mechanical stress.” 

#Khare, Deepak; Basu, Bikramjit; Dubey, Ashutosh K. (2020): “Electrical stimulation and piezoelectric biomaterials for bone tissue engineering applications”, Biomaterials, vol. 258, 120280 

https://www.sciencedirect.com/science/article/abs/pii/S0142961220305263 

Quote: “The natural bone is piezoelectric in nature with collagen molecules being the origin of piezoelectricity” 

#Akhavan, Amir C. (2011): “Physical Properties: Piezoelectricity”

http://www.quartzpage.de/gen_phys.html 

Quote: “

Fig.8: Model of the SiO4 tetrahedron

 Fig.9: Effect of Deformation on Charge Distribution

Many crystalline substances are made of electrically charged ions or molecules with an uneven distribution of electrical charges (inside the molecule, some atoms are more negatively and some more positively charged). The latter is the case in quartz: it is a macromolecular material that is built up by a network of SiO4 tetrahedra, as the one shown in Fig.8. In a Si-O bond the negative electrons get drawn more to the oxygen (such a bond is called polar, and oxygen is said to have a higher electronegativity than silicon), so the oxygen is more negatively and the silicon more positively charged. Of course, the crystal as a whole is electrically balanced.”

Figure 9 explains what happens if the SiO4 tetrahedron is put under mechanical stress (symbolized by blue arrows). The central silicon atom is surrounded by 4 oxygen atoms (one of them is omitted for readability). The overall formula of quartz is SiO2, and since every oxygen atom carries the same extra amount of negative charge taken from a silicon atom, the central silicon atoms carries 2 positive charges and the oxygen just one negative charge.

Under mechanical stress the atoms of the tetrahedron get displaced with respect to their former position (indicated by a thin red outline). The positively charged silicon is pushed away from its central position and the whole structure gets electrically polarized. If one reverses the direction of the forces, the silicon will be pulled upwards, resulting in an opposite polarization.”

—Together they add up to a charge across the whole crystal. Piezoelectricity powers sonar, times quartz watches, and some nightclubs use it to keep the lights on just from the stamping of dancers’ feet.

#PiezoDirect (2023): “How Does a Piezo Transducer Work in Sonar Applications?”

 https://piezodirect.com/how-does-a-piezo-transducer-work-in-sonar-applications/ 

#Chelsea Clock (2023): “How do Quartz Clocks Work?”

https://www.chelseaclock.com/blogs/blog/how-do-quartz-clocks-work?srsltid=AfmBOookVw80UjNDfMY8ocrePbhNsgnCq4K2rZgQfQy8pCfa4jIQ7Ady  

#International Organization on Shape Memory and Superelastic Technologies (2015): “How a Quartz Watch Works”

https://www.asminternational.org/smst/videos/-/journal_content/56/10192/25173231/VIDEO/ 

#Paulides, Johannes J.H. et al. (2009): ”Power from the people - Human-powered small-scale generation system for a sustainable dance club”, 2009 IEEE International Electric Machines and Drives Conference, 439-444

https://www.researchgate.net/figure/Sustainable-dance-floor-at-the-sustainable-club-Watt-in-Rotterdam-The-Netherlands-5_fig6_254898859 

—First, we squeeze our jellyfish, one tentacle at a time, into a kind of wetsuit made from nylon-11,11: a cutting edge material that has been optimized for power production and has the same piezoelectric properties as quartz. 

#Yang, Wenqiang et al. (2024): “High-Performance Piezoelectric Nanogenerator Based on Odd–Odd Nylon Nanofibers for Wearable Electronics via Precise Control of Ferroelectric Phase and Orientation”, ACS Sustainable Chemistry & Engineering, vol. 12, 22

https://pubs.acs.org/doi/10.1021/acssuschemeng.4c01789 

—Even with around 1000 tentacles wrapped in energy-generating nylon, the electricity generated only adds up to around 1 Watt, or 10  kWh per year. Enough energy to run your laptop for twenty days! 

We assume that a Nomura jellyfish has around a thousand tiny tentacles and estimate them to be around 4 m long and have a radius of around 0.5 cm. 

If this is the case, a nylon-11,11 tube that covers a tentacle would have an area of:

A= (4 m)  × 2  × π  × (0.005 m) = 0.13 m2

Which means that the total area of the jelly suit is of 130 m2

In optimal conditions, nylon-11,11 produces a power of 9.13 mW per square meter. 

#Yang, Wenqiang et al. (2024): “High-Performance Piezoelectric Nanogenerator Based on Odd–Odd Nylon Nanofibers for Wearable Electronics via Precise Control of Ferroelectric Phase and Orientation”, ACS Sustainable Chemistry & Engineering, vol. 12, 22

https://pubs.acs.org/doi/10.1021/acssuschemeng.4c01789 

This means that a single jellyfish could produce a total power of:

130 m2 × 9.13 mW/m2 = 1.1 W

Over a year, that yields:

1.1 W × 60 s/min × 60 min/h × 24 h/day × 356 days = 3.4  × 107 J = 9.7 kWh

A normal non-gaming laptop needs a power of about 60 W. If one uses it 8 hours a day, that makes for a daily total energy expense of:

60 W  × 8 hours = 480 Wh

This means that an adequately piezoelectric-suited Nomura jellyfish generating energy over a year could power a laptop for:

9.7 kWh / 480 Wh = 20 days

Please notice that this is an idealized scenario where the jellyfish tentacles move such that the jellyfish suit works at optimal performance. There is no reason why the jellyfish should move that way in reality. 

—We need more jellies! WAY MORE! About 29 billion!

As seen in the previous section of this document, each Nomura jellyfish produces 9.7 kWh over a year. That means that, to provide the 280 TWh to power Tokyo over a year, we would need: 

280 × 1012 Wh / ( 9.7 × 103 Wh/ jellyfish) = 2.9 × 1010  jellyfishes

—Sounds like a lot, and it is, but right this moment there are 27 billion chickens alive on Earth. So it's mostly a matter of motivation on our part. 

#FAO (retrieved 2025): FAOSTAT, Crops and livestock products
https://www.fao.org/faostat/en/#data/QCL 

According to FAO estimates, in 2023 there were 27,223,471,000 chickens.

—A single Nomura can produce millions of jelly babies a month, and with enough plankton to eat, they can grow from the size of a grain of rice to the size of a person in less than a year.

Nomura jellyfish release millions of eggs at a time, though many are never fertilized or  are eaten by predators shortly after being fertilized.

#Xie, Congbo ; Fan, Meng; Kang, Yun (2021): “Population dynamics of the giant jellyfish Nemopilema nomurai with age structure”, Ecological Modelling, vol. 441,109412 https://www.sciencedirect.com/science/article/abs/pii/S0304380020304713?via%3Dihub 

Quote: “Medusae of Nemopilema nomurai release millions of sperm and eggs into the water by sexual reproduction, then fertilized eggs develop into free-swimming planula larvae.”

Nomura jellyfish grow at a rough average of 1.5 cm a day.

#Iguchi, Naoki et al. (2017): “Biomass, body elemental composition, and carbon requirement of Nemopilema nomurai (Scyphozoa: Rhizostomeae) in the southwestern Japan Sea”, Plankton and Benthos Research, vol. 12, 2, 104-114

https://www.jstage.jst.go.jp/article/pbr/12/2/12_P120202/_article
Quote: “Size frequency BD distributions were generally broad in all samples; therefore, it was not possible to trace growth as a single population (Fig. 6). However, mode classes of frequency distribution revealed a temporal trend to larger size classes in the initial sampling period of 2005, i.e., from 55 to 105 cm between August 28 and September 27, 2005; therefore, we calculated growth rate using a simple linear regression as 1.462 cm per day (Fig. 6)”

If an average person is 165 cm tall, it would take a Nomura jellyfish 110 days to reach that size:

165 cm / 1.5 cm/day = 110 days

—If we want to breed a lot of them and fast, all we need to do is to basically empty the Pacific of plankton.

To maintain 29 billion full-sized Nomura jellyfish medusae, we will have to feed them. The Nomura jellyfish feeds mostly on plankton. The amount of plankton the medusa needs depends on its weight and the stage of its growth. Assuming that a 200 kg Nomura jellyfish eats, per kg, the same amount of plankton as a 80 kg Nomura jellyfish, we find that every day they clear a volume of:

(1140 m3/day × 200 kg / 80 kg) × (2.9 × 1010 jellyfishes) = 8.3 × 1013 m3 = 83 000 km3 /day 

#Uye, Shin-ichi (2008): “Blooms of the giant jellyfish Nemopilema nomurai: a threat to the fisheries sustainability of the East Asian Marginal Seas”, Plankton and Benthos Research, vol. 3, Supplement, 125-131

https://www.researchgate.net/publication/250275131_Blooms_of_the_giant_jellyfish_Nemopilema_nomurai_A_threat_to_the_fisheries_sustainability_of_the_East_Asian_Marginal_Seas 

Over a year, that is: 

 83 000 km3 /day  × 365 = 30  × 106  km3

If we assume most of the plankton is within 200 m of the surface, where light can still reach, since the surface of the pacific ocean is of 161.76 × 106  km2

#Encyclopaedia Britannica: “Pacific Ocean” (retrieved 2025)

https://www.britannica.com/place/Pacific-Ocean

The available volume of plankton is of:

( 161.76 × 106  km2 ) × 0.2 km = 32 × 106  km3

So in a year the jellies would have depleted 94% of the plankton in the Pacific. 

—And of course we’ll need space to store them all. Giving each Nomura a cube of space measuring 5 meters on each side sounds generous, but it barely contains the tentacles. All those jelly-cubes add up to a tank that’s about seven times the total volume of Mt. Fuji. 

If we give each of the 29 billion Nomura jellyfish medusae a cubic tank with a side of 5m, the total volume adds up to:

(5 m)3 × (2.9 × 1010 jellyfishes) = 3.6  × 1012 m3 =  3 600   km3 

For comparison, the Mount Fuji volcano has a volume of 500 km3.

#Geological survey of Japan: “Active Volcanoes of Japan” (retrieved 2025)

https://gbank.gsj.jp/volcano/Act_Vol/fujisan/text/eng/exp-1e.html 

Quote: “In contrast to the majority of volcanoes in other parts of Japan that have a volume of 100 km3 or less, Fuji Volcano is estimated to have a volume between 400 to 500 km3 (Takada et al., 2007, 2013).”

So the tanks would fill 7.2 Mount Fujis:

3 600   km3 / 500 km3  = 7.2

—With all those tentacles and cables, our biggest issue will be short circuits. We need to insulate all 29 billion cables. And don’t forget the tentacles themselves. 

Taken to be one cable per jellyfish.

—Turns out in a storm, several millions of raindrops can fall on a single square meter. 

There are no formal definitions of storm, but a precipitation of 4 mm or 4 L per square meter per hour  is generally considered to be heavy rain. If it reaches 50 L per square meter, it is considered violent showers. 

#World Meteorological Organization: “Aviation, Hazards, Precipitation: Rainfall” (retrieved 2025) 

https://community.wmo.int/en/activity-areas/aviation/hazards/precipitation 

#FAO: “Irrigation Water Management: Rainfall and Evotranspiration” (1985)

https://www.fao.org/4/r4082e/r4082e05.htm 

If we assume a water droplet has a volume of 0.05 mL, a storm that pours  50 L per square meter per hour would result in: 

50 L/ hour / (0.05 ×10-3 L/droplet) = 1 million droplets / hour

And storms like these can last several hours.

— Which stacks quickly to the equivalent of a banana asteroid smashing into the planet and killing all life.

Every year  487, 000 km3 of rainwater fall on Earth, or equivalently, 4.87 × 1017 L.

#Trenberth, Kevin E. et al. (2007): “Estimates of the Global Water Budget and Its Annual Cycle Using Observational and Model Data”, Journal of Hydrometeorology, 8,4, 758-769.

https://journals.ametsoc.org/view/journals/hydr/8/4/jhm600_1.xml 

Quote: “The annual mean global GPCP values are 486.9 ± 2.9 × 103 km3, where we used twice the standard error of the annual means over the 17 yr to compute the temporal sampling variability error.”

This means that on average every day, there is a rainfall of

 4.87 × 1017 L / 365 = 1.33 × 1015 L

If a water droplet is about 0.05 mL, and every droplet becomes a banana, then we have: 

1.33×1015 L / 0.05 ×10-3 L = 2.7 ×1019  bananas

Let’s say that a banana weighs 120 g. Then the total banana weight that falls on Earth is: 

(2.7 ×1019  bananas) ×(0.120 kg/banana) = 3.2 ×1018 kg

Which is above the mass that the asteroid  thought to have killed non-avian dinosaurs had.

#Durand-Manterola, Hector J.; Cordero-Tercero, Guadalupe (2014): “Assessments of the energy, mass and size of the Chicxulub Impactor” (Preprint)

https://arxiv.org/abs/1403.6391 

Quote: “The mass is in the range of 1.0e15 kg to 4.6e17 kg.”

—Instead let’s take the average volume of rain that falls on our planet in a single day, about 1.33 trillion tons of water – a massive, wobbly orb of water 14 kilometers across.

Every year  487, 000 km3 of rainwater fall on Earth, or equivalently, 4.87 × 1017 L.

#Trenberth, Kevin E. et al. (2007): “Estimates of the Global Water Budget and Its Annual Cycle Using Observational and Model Data”, Journal of Hydrometeorology, 8,4, 758-769.

https://journals.ametsoc.org/view/journals/hydr/8/4/jhm600_1.xml 

Quote: “The annual mean global GPCP values are 486.9 ± 2.9 × 103 km3, where we used twice the standard error of the annual means over the 17 yr to compute the temporal sampling variability error.”

This means that on average every day, there is a rainfall of

 4.87 × 1017 L / 365 = 1.33 × 1015 L

The density of water is 1.00 kg/ L

#U.S. Geological Survey (2018): “Water Density”

https://www.usgs.gov/special-topics/water-science-school/science/water-density 

so the weight of all that water is 

1.33 × 1015 L × 1.00 kg/ L = 1.33 × 1015 kg = 1.33 Tton

The volume of a sphere is: 

V=4πR3/3

So a sphere of the same volume would have a radius of: 

R=(3V/(4π))1/3= (3 × 487, 000 km3/(365 ×b 4π))1/3= 6.8 km

That is, it would be around 14 km across.

—Each fruit weighs about 120 g, which will give us a daily banana-fall of 11.1 quadrillion bananas, weighing 1.33 trillion tons in total.

We are swapping all the volume of rainwater for a volume of bananas of the same mass.

Every year  487, 000 km3 of rainwater fall on Earth, or equivalently, 4.87 × 1017 L.

#Trenberth, Kevin E. et al. (2007): “Estimates of the Global Water Budget and Its Annual Cycle Using Observational and Model Data”, Journal of Hydrometeorology, 8,4, 758-769.

https://journals.ametsoc.org/view/journals/hydr/8/4/jhm600_1.xml 

Quote: “The annual mean global GPCP values are 486.9 ± 2.9 × 103 km3, where we used twice the standard error of the annual means over the 17 yr to compute the temporal sampling variability error.”

This means that on average every day, there is a rainfall of

 4.87 × 1017 L / 365 = 1.33 × 1015 L

The density of water is 1.00 kg/ L

#U.S. Geological Survey (2018): “Water Density”

https://www.usgs.gov/special-topics/water-science-school/science/water-density 

so the weight of all that water is 

1.33 × 1015 L × 1.00 kg/ L = 1.33 × 1015 kg = 1.33 Tton

If we assume that a banana weighs 120 g:

 (1.33 × 1015 kg)/(0.120 kg/banana) = 1.11 × 1016 bananas

—If we match average global rainfall patterns, even the Sahara Desert would receive around 15 trillion bananas. 

The Sahara desert has an area of 8.6 million km2

#Encyclopaedia Britannica: “Sahara desert, Africa” (retrieved 2025)
https://www.britannica.com/place/Sahara-desert-Africa

Quote: “Sahara, (from Arabic ṣaḥrāʾ, “desert”) largest desert in the world. Filling nearly all of northern Africa, it measures approximately 3,000 miles (4,800 km) from east to west and between 800 and 1,200 miles from north to south and has a total area of some 3,320,000 square miles (8,600,000 square km); the actual area varies as the desert expands and contracts over time.”

And receives 76 mm of precipitations per square meter every year

#Encyclopaedia Britannica: “Sahara desert, Africa: Climate of the Sahara” (retrieved 2025)

https://www.britannica.com/place/Sahara-desert-Africa/Climate

Quote: “Although precipitation is highly variable, it averages about 3 inches (76 millimetres) per year.”

This means that the average volume of rainwater that falls on the Sahara in a day is:

0.076 m per m2 × 8.6 × 1012 m2 / 365 = 1.8  × 109 m3

The density of water is 1.00 × 103 kg/ m3

#U.S. Geological Survey (2018): “Water Density”

https://www.usgs.gov/special-topics/water-science-school/science/water-density 

so the weight of all that water is 

1.8  × 108  m3 × 1.00 × 103  kg/ m3  = 1.8 × 1015 kg 

If we assume that a banana weighs 120 g:

 (1.8 × 1011 kg)/(0.120 kg/banana) = 1.5 × 1013 bananas

—If a medium sized banana has about 105 calories, 15 trillion Sahara bananas alone could already feed the world’s population for over two months.

A medium sized banana of around 120 g provides 105 kcal. We informally refer to kilocalories as calories. 

#USDA FoodData Central (2018): “Bananas, Raw” 

https://fdc.nal.usda.gov/food-details/173944/nutrients 

Since we have 1.5 × 1013 bananas, the total calories provided by the Sahara banana rain is:

1.5 × 1013 bananas × 105 kcal = 1.6 × 1015 kcal

A person needs from 2000 to 2500 kcal a day

#NHS: “Understanding calories” (retrieved 2025)

https://www.nhs.uk/live-well/healthy-weight/managing-your-weight/understanding-calories/

So, with these bananas, we could feed

1.6 × 1012 kcal / (2500 kcal /person) = 6.3 × 1011 people = 630 billion people

The world population is of around 8.2 billion

#French Institute for Demographic Studies (2024): “The United Nations publishes new world population projections”

https://www.ined.fr/en/everything_about_population/demographic-facts-sheets/focus-on/2024-les-nations-unies-publient-de-nouvelles-projections-de-population-mondiale/

Since

630 billion people / 8.2 billion people = 77

We could feed everyone for a over two months with one day’s worth of Sahara banana rain.

—For the world as a whole the calories of all rain bananas add up to a grand total of 1.2 quintillion calories. With just one day of banana rain we could go on feeding everyone on Earth for over a hundred years. 

Every year  487, 000 km3 of rainwater fall on Earth:

#Trenberth, Kevin E. et al. (2007): “Estimates of the Global Water Budget and Its Annual Cycle Using Observational and Model Data”, Journal of Hydrometeorology, 8,4, 758-769.

https://journals.ametsoc.org/view/journals/hydr/8/4/jhm600_1.xml 

Quote: “The annual mean global GPCP values are 486.9 ± 2.9 × 103 km3, where we used twice the standard error of the annual means over the 17 yr to compute the temporal sampling variability error.”

The density of water is 1.00 × 103 kg/ m3

#U.S. Geological Survey (2018): “Water Density”

https://www.usgs.gov/special-topics/water-science-school/science/water-density 

so the weight of the amount of water that falls on a day is: 

( 487 × 1012  m3 ) × (1.00 × 103  kg/ m3) / 365 = 1.33 × 1015 kg 

If we assume that a banana weighs 120 g:

 (4.87 × 1017 kg)/(0.120 kg/banana) = 1.1 × 1016 bananas

A medium sized banana of around 120 g provides 105 kcal

#U.S. Department of Agriculture Food Data Central (2018): “Bananas, raw”

https://fdc.nal.usda.gov/food-details/173944/nutrients 

So, in total, they would provide

 (1.1 × 1016 bananas) × (105 kcal/ banana) = 1.2 × 1018 kcal

A person needs from 2000 to 2500 kcal a day

#NHS: “Understanding calories” (retrieved 2025)

https://www.nhs.uk/live-well/healthy-weight/managing-your-weight/understanding-calories/

So, with these bananas, we could feed

1.2 × 1018 kcal / (2500 kcal /person) = 4.7 × 1014 people

The world population is of around 8.2 billion

#French Institute for Demographic Studies (2024): “The United Nations publishes new world population projections”

https://www.ined.fr/en/everything_about_population/demographic-facts-sheets/focus-on/2024-les-nations-unies-publient-de-nouvelles-projections-de-population-mondiale/

Since

4.7 × 1014 people / 8.2 × 109 people = 5.7 × 104

we could feed everyone for 5.7 × 104 days, or over 150 years. 

—A banana falling from about 3000 meters, the height of a mid-altitude rain cloud, would reach a velocity of 240 meters per second and strike the ground with the same kinetic energy you’d get from dropping a bowling ball off a 50 m building. 

In free fall, a body falling from an altitude of 3 km would reach a velocity of 240 m/s. 

#Barrantes, Arturo (2024): “Free Fall Velocity Calculator”
https://www.omnicalculator.com/physics/free-fall-velocity 

Taking air resistance into account, and considering bananas to have approximately the drag coefficient of a cylinder, the velocity would be smaller, of around only 50 m/s.

#Leishman, J. Gordon (2025): “Bluff Body Flows” Chapter 26 of “Introduction to Aerospace Flight Vehicles” by J. Gordon Leishman

https://eaglepubs.erau.edu/introductiontoaerospaceflightvehicles/chapter/bluff-body-flows/  

(Please note that the table above has been cut to highlight the relevant data. The original can be consulted in the source link.)

#Dhari, Rahul (2024): “Terminal Velocity Calculator”

https://www.omnicalculator.com/physics/terminal-velocity

Rain clouds can have a variety of altitudes, with an altitude of 3 km generally considered to be in the mid-altitude range

#U.S. National Oceanic and Atmospheric Administration: “The Four Core Types of Clouds” (retrieved 2025)

https://www.noaa.gov/jetstream/clouds/four-core-types-of-clouds 

#Whittaker, Tom;  Ackerman, Steve: “Weather for Pilots: Clouds and Fog” (retrieved 2025)
https://profhorn.aos.wisc.edu/wxwise/weather/lesson4/Cloud_Types.html 

A 7.3 kg bowling ball falling from a 50 m has a mechanical energy of: 

E= m × g× h = 7.3 kg × 50 m × 9.8 m/s2 = 3.6 kJ

A 120 g banana falling from a rain cloud at 3 km of altitude has a mechanical energy of:

E= m × g× h = 0.120 kg × 3 000 m × 9.8 m/s2 = 3.5 kJ

All of this mechanical energy starts as gravitational potential energy and is transformed into kinetic energy as the object falls. The instant just before the object strikes the ground, it is all kinetic energy. 

—One of the most rainy and therefore worst affected cities is London. It would face a storm of 21 billion bananas, or 2.5 million tons.

#Encyclopaedia Britannica: “London: Climate of London” (retrieved 2025)

https://www.britannica.com/place/London/Climate 

Quote: “In an average year one can expect 200 dry days out of 365 and a precipitation total of about 23 inches (585 mm) evenly distributed across the 12 months.”

#Encyclopaedia Britannica: “London” (retrieved 2025)

https://www.britannica.com/place/London 

Quote:“Area Greater London, 607 square miles (1,572 square km)”

This means that the average volume of rainwater that falls on the London in a day is:

0.585 m per m2 × 1.572 × 109 m2 / 365 = 2.5  × 106 m3

The density of water is 1.00 × 103 kg/ m3

#U.S. Geological Survey (2018): “Water Density”

https://www.usgs.gov/special-topics/water-science-school/science/water-density 

so the weight of all that water is 

2.5  × 106  m3 × 1.00 × 103  kg/ m3  = 2.5 × 109 kg = 2.5 Mt

If we assume that a banana weighs 120 g:

 (2.5 × 109 kg)/(0.120 kg/banana) = 21 × 109 bananas = 21 billion bananas 

—The rotting banana mush contains 160 billion tons of methane, 280 times our current annual emissions as a planet. Methane traps around 28 times more heat than CO2. 

Every year 487, 000 km3 of rainwater fall on Earth:

#Trenberth, Kevin E. et al. (2007): “Estimates of the Global Water Budget and Its Annual Cycle Using Observational and Model Data”, Journal of Hydrometeorology, 8,4, 758-769.

https://journals.ametsoc.org/view/journals/hydr/8/4/jhm600_1.xml 

Quote: “The annual mean global GPCP values are 486.9 ± 2.9 × 103 km3, where we used twice the standard error of the annual means over the 17 yr to compute the temporal sampling variability error.”

The density of water is 1.00 × 103 kg/ m3

#U.S. Geological Survey (2018): “Water Density”

https://www.usgs.gov/special-topics/water-science-school/science/water-density 

so the weight of the amount of water that falls on a day is: 

( 487 × 1012  m3 ) × (1.00 × 103  kg/ m3) / 365 = 1.33 × 1015 kg 

We consider that we have the same weight, but in bananas. 

Many experiments that have tried to produce methane from banana peels, with different yields. We will take  an average yield of approximately 180 L per kg of banana peel. We will assume that the rest of the banana has the same yield as the peel. 

#Pisutpaisal, Nipon; Boonyawanich, Siriorn; Saowaluck, Haosagul (2014): “Feasibility of Biomethane Production from Banana Peel”, Energy Procedia, vol. 50,  782-788

https://www.sciencedirect.com/science/article/pii/S1876610214008327?via%3Dihub 

Then, our rotting bananas produce 

 1.33 × 1015 kg × 180 L of methane /kg = 2.4 × 1017 L of methane =  2.4 × 1014 m3 of methane

Or equivalently

#Dutt, Gautam (2003): “Methane Density”

https://cdm.unfccc.int/methodologies/inputsconsmeth/MGM_methane.pdf 

(2.4 × 1014 m3 of methane) × 0.67 kg/m3 = 1.6  × 1014 kg of methane = 160 billion tons of methane

That is 280 times our current yearly emissions: 

1.6  × 1014 kg of methane / 580 × 109 kg of methane = 280

#International Energy Agency (IEA) (2024): “Understanding methane emissions”

https://www.iea.org/reports/global-methane-tracker-2024/understanding-methane-emissions 

Quote: “The most recent comprehensive assessment – provided in the Global Methane Budget – suggests that annual global methane emissions are around 580 Mt. This includes emissions from natural sources (around 40% of the total) and from human activity (around 60% of the total).”

#International Energy Agency (IEA) (2021): “Methane and climate change”

https://www.iea.org/reports/methane-tracker-2021/methane-and-climate-change 

Quote: “The Intergovernmental Panel on Climate Change (IPCC) has indicated a GWP for methane between 84-87 when considering its impact over a 20-year timeframe (GWP20) and between 28-36 when considering its impact over a 100-year timeframe (GWP100). This means that one tonne of methane can be considered to be equivalent to 28 to 36 tonnes of CO2 if looking at its impact over 100 years.”