#1 Who invented sliced bread?

Image: By FranHogan – Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=92636750

#2 Where did ketchup come from? What did it have to do with mushrooms?

Image: By Rex Roof from Ann Arbor, MI, USA – http://commons.wikimedia.org/wiki/File:Mushroom_ketchup_(homemade).jpg, CC BY 2.0, https://commons.wikimedia.org/w/index.php?curid=35308477

https://en.wikipedia.org/wiki/Ketchup

https://www.nationalgeographic.com/culture/article/how-was-ketchup-invented

https://www.history.com/news/ketchup-surprising-ancient-history

https://www.smithsonianmag.com/arts-culture/why-the-tomato-was-feared-in-europe-for-more-than-200-years-863735/

https://en.wikipedia.org/wiki/Tomato

#3 Why did men start wearing neckties?

Photo by The Lazy Artist Gallery: https://www.pexels.com/photo/man-in-black-suit-and-white-long-sleeve-shirt-holding-silver-spoon-3740007/

http://www.tie-a-tie.net/the-evolution-of-the-necktie/

https://www.britannica.com/topic/cravat

https://www.washingtonpost.com/archive/1999/12/08/a-twisted-history-of-neckties/d59c6d2d-5d38-42cf-843e-27abcdc524d7/

https://en.wikipedia.org/wiki/Cravat_(early)

https://en.wikipedia.org/wiki/Necktie

#4 How can vultures eat rotten meat and not get sick?

Photo by Antony Trivet from Pexels: https://www.pexels.com/photo/flock-of-vultures-eating-its-prey-6057416/

https://www.audubon.org/news/how-vultures-can-eat-rotten-meat-without-getting-sick

https://www.npr.org/sections/health-shots/2014/11/25/366545524/how-can-vultures-eat-rotten-roadkill-and-survive

https://en.wikipedia.org/wiki/Vulture

https://www.sciencefocus.com/the-human-body/what-happens-in-my-body-when-i-get-food-poisoning/

https://www.nature.com/articles/nature.2014.16345

https://www.redding.com/story/life/2017/07/26/vultures-have-ph-public-health/504630001/

#5 Why are labradors used as guide dogs?

Image By Antonio Cruz/Abr – Agência Brasil [1], CC BY 3.0 br, https://commons.wikimedia.org/w/index.php?curid=1213253

https://en.wikipedia.org/wiki/Labrador_Retriever

https://en.wikipedia.org/wiki/Guide_dog

https://www.dogsforgood.org/our-dogs/from-pup-to-partner/tiny-puppy/breeds-we-work-with/breed-focus-labrador/

https://wagwalking.com/behavior/why-are-labrador-retrievers-good-guide-dogs

#6 Why does the Earth have seasons?

Photo by Kari Korpihete: https://www.pexels.com/photo/wooden-bench-on-snow-covered-ground-11003082/

https://www.washingtonpost.com/weather/2019/06/20/summer-is-about-here-that-you-can-thank-billion-year-old-rock/

https://spaceplace.nasa.gov/seasons/en/

https://www.bbc.co.uk/bitesize/articles/zhtvscw

https://en.wikipedia.org/wiki/Giant-impact_hypothesis

https://en.wikipedia.org/wiki/Formation_and_evolution_of_the_Solar_System

Does Venus Have Seasons?

#7 How do salting and pickling preserve food?

Photo by Kristina Snowasp: https://www.pexels.com/photo/green-vegetables-in-clear-glass-jar-8978860/

https://recipes.howstuffworks.com/tools-and-techniques/salt-prevent-food-from-spoiling.htm

https://en.wikipedia.org/wiki/Curing_(food_preservation)

http://www.todayifoundout.com/index.php/2014/01/fascinating-early-history-salt/

https://en.wikipedia.org/wiki/Pickling

https://www.ncbi.nlm.nih.gov/books/NBK50952/

https://education.seattlepi.com/high-concentration-salt-cell-membrane-4414.html

Rotting

#8 How can Vantablack be so black?

Image By Surrey NanoSystems – Surrey NanoSystems, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=34139562

https://en.wikipedia.org/wiki/Vantablack

https://en.wikipedia.org/wiki/Carbon_nanotube

https://news.mit.edu/2019/blackest-black-material-cnt-0913

#9 How can an airbag inflate so quickly?

Image By Janipewter at the English Wikipedia, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=49076238

https://bda.org/news-centre/blog/Pages/Commemorating-two-pioneers-of-jaw-injury-treatment-during-WW1.aspx

https://en.wikipedia.org/wiki/Airbag

History of Airbags

https://www.racq.com.au/cars-and-driving/safety-on-the-road/car-safety-features/airbags

https://en.wikipedia.org/wiki/Gas_generator

https://www.wired.com/story/the-insane-physics-of-airbags/

#10 What causes seasickness?

Photo by Rachel Claire: https://www.pexels.com/photo/a-white-luxury-yacht-on-the-sea-6752179/

https://en.wikipedia.org/wiki/Motion_sickness

https://oceanservice.noaa.gov/facts/seasickness.html

https://www.michiganneurologyassociates.com/blog/what-are-inner-ears-and-how-do-they-affect-balance

https://en.wikipedia.org/wiki/Inner_ear

#11 How did the elevator change our lives?

Photo by Dayvison de Oliveira Silva: https://www.pexels.com/photo/corridor-of-modern-building-with-opened-elevator-doors-5733814/

https://en.wikipedia.org/wiki/Elevator

https://www.ascensionelevators.com/blog/how-elevators-changed-the-world/

https://www.bbc.com/culture/article/20140819-how-the-lift-changed-everything

https://www.abb-conversations.com/2017/02/how-elevators-changed-the-world/

https://www.worldometers.info/world-population/world-population-by-year/

#12 How does alcohol make us drunk?

Photo by Chris F: https://www.pexels.com/photo/assorted-wine-bottles-1283219/

https://www.livescience.com/10221-beer-lubricated-rise-civilization-study-suggests.html

https://www.theguardian.com/commentisfree/2018/may/16/why-does-alcohol-make-us-drunk-google

https://www.mydr.com.au/liver-and-alcohol-breakdown/

https://en.wikipedia.org/wiki/History_of_alcoholic_drinks

https://en.wikipedia.org/wiki/Ethanol

https://www.scripps.edu/newsandviews/e_20020225/koob2.html

#13 How does a gun silencer work?

Image By Cortland at English Wikipedia, Public Domain, https://commons.wikimedia.org/w/index.php?curid=2263371

https://en.wikipedia.org/wiki/Silencer_(firearms)

https://en.wikipedia.org/wiki/Sound_baffle

https://www.explainthatstuff.com/bullets.html

https://en.wikipedia.org/wiki/Lock_time

https://nationalinterest.org/blog/buzz/explained-gun-silencers-don%E2%80%99t-work-they-do-movies-177224

#14 How is leather made? Why is it so strong?

Photo by MART PRODUCTION: https://www.pexels.com/photo/jackets-on-hangers-7679725/

https://www.britannica.com/topic/leather

https://mahileather.com/blogs/news/how-is-leather-made

https://mahileather.com/blogs/news/a-brief-history-of-leather

https://www.one4leather.com/fact/fact-24

https://en.wikipedia.org/wiki/Tanning_(leather)

#15 How is food canned?

Photo by Andrea Davis: https://www.pexels.com/photo/can-goods-on-plaid-picnic-blanket-10658157/

https://www.bbc.com/news/magazine-21689069

https://www.smithsonianmag.com/smart-news/arctic-explorers-uncover-60-year-old-food-stash-180956936/

source“>https://www.questia.com/read/1G1-9009146/the-canning-process-old-preservation-technique-goes”>source</a>

https://en.wikipedia.org/wiki/Canning

#16 Where do the plus, minus, multiplication, and division symbols come from?

Photo by Pixabay: https://www.pexels.com/photo/calculator-and-pen-on-table-209224/

https://en.wikipedia.org/wiki/History_of_mathematical_notation

https://encyclopediaofmath.org/wiki/Mathematical_symbols

https://en.wikipedia.org/wiki/History_of_mathematics

https://www.fastcompany.com/3032233/the-surprisingly-short-history-of-the-plus-sign

https://www.buzzfeednews.com/article/stephaniemcneal/divisive-issue

#17 What happens when animals hibernate? Is it the same as sleeping?

Photo by Nicky Pe: https://www.pexels.com/photo/a-brown-bear-resting-on-a-rock-7287817/

https://www.nps.gov/yell/learn/nature/denning.htm

https://www.pbs.org/wgbh/nova/article/secrets-of-bear-hibernation-could-help-us-get-to-mars/

https://www.riken.jp/en/news_pubs/research_news/rr/20201225_3/index.html

https://www.science.org.au/curious/hibernation

https://en.wikipedia.org/wiki/Hibernation

#18 Why isn’t Pluto a planet?

Image By NASA https://www.nasa.gov/image-feature/the-rich-color-variations-of-pluto

https://en.wikipedia.org/wiki/Pluto#Orbit

https://en.wikipedia.org/wiki/Planets_beyond_Neptune

https://www.loc.gov/everyday-mysteries/item/why-is-pluto-no-longer-a-planet/

https://astronomy.stackexchange.com/questions/2092/what-is-the-minimum-mass-required-so-that-objects-become-spherical-due-to-its-ow

https://www.space.com/18568-how-big-is-pluto.html

https://en.wikipedia.org/wiki/Clearing_the_neighbourhood

https://en.wikipedia.org/wiki/Timeline_of_discovery_of_Solar_System_planets_and_their_moons

https://www.npr.org/2011/02/04/133498152/why-the-former-planet-pluto-got-demoted

https://socratic.org/questions/how-many-moons-in-our-solar-system-are-larger-than-pluto

#19 Are hurricanes and tornados the same thing?

Photo by Pixabay: https://www.pexels.com/photo/earth-planet-76969/

https://en.wikipedia.org/wiki/Tornado

https://timesofindia.indiatimes.com/what-is-the-difference-between-cyclone-hurricane-tornado-and-twister/articleshow/1317404.cms

https://www.livescience.com/32179-how-strong-can-a-hurricane-get.html

https://en.wikipedia.org/wiki/Tropical_cyclone

https://www.wtoc.com/2020/03/31/how-do-hurricanes-form/

https://spaceplace.nasa.gov/hurricanes/en/

#20 Do cats blink?

Photo by Krysten Merriman: https://www.pexels.com/photo/short-coated-gray-cat-20787/

https://www.sciencealert.com/you-can-build-a-rapport-with-your-cat-by-blinking-real-slow

https://www.litter-robot.com/blog/2018/10/18/why-do-cats-have-a-third-eyelid/

https://www.eyeandlasik.com/happens-blink-eye/

https://www.somatechnology.com/blog/thursday-thoughts/fast-average-blink/

https://www.petmd.com/cat/behavior/do-cats-blink

How Often Do Cats Blink?

https://en.wikipedia.org/wiki/Nictitating_membrane

https://en.wikipedia.org/wiki/Blinking

#21 How do TV remoter controllers work?

Photo by Karolina Grabowska: https://www.pexels.com/photo/person-pressing-the-button-of-a-remote-control-5202957/

https://en.wikipedia.org/wiki/Remote_control

https://www.ucl.ac.uk/culture-online/ask-expert/your-questions-answered/how-does-remote-control-work-tv

https://electronics.stackexchange.com/questions/187754/infrared-led-binary-code

https://learn.parallax.com/tutorials/robot/cyberbot/infrared-light-navigation-cyberbot/infrared-light-signals

http://www.arrl.org/files/file/ETP/TV%20remote%20decoder%20kit%20ver%202_2.pdf

https://home.howstuffworks.com/universal-remotes.htm

#22 Why was the piano invented?

Photo by Dalila Dalprat : https://www.pexels.com/photo/brown-grand-piano-with-chair-2043571/

http://bjamusicappreciation.weebly.com/uploads/1/6/2/2/16224382/what_is_the_difference_between_a_piano_and_a_harpsichord.pdf

https://en.wikipedia.org/wiki/Piano

https://en.wikipedia.org/wiki/Harpsichord

https://www.yamaha.com/en/musical_instrument_guide/piano/structure/

https://www.wqxr.org/story/how-did-piano-unseated-harpsichord-keyboard-champion/

https://www.squarepianos.com/backers.html

https://www.elbphilharmonie.de/en/mediatheque/the-harpsichord/101

#23 How do electric eels make electricity

Image By Steven G. Johnson – Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=1446721

https://www.businessinsider.com/why-electric-eels-dont-electrocute-themselves-2015-3

https://www.uwa.edu.au/science/-/media/Faculties/Science/Docs/Electric-eels.pdf

https://www.scientificamerican.com/article/how-do-electric-eels-gene/

https://en.wikipedia.org/wiki/Electric_eel

#24 What causes water mirages and heat hazes?

Image By Brocken Inaglory – Own work, Public Domain, https://commons.wikimedia.org/w/index.php?curid=10842357

http://www.mjtruiz.com/publications/2019_11_mirage.pdf

https://encyclopedia2.thefreedictionary.com/Heat+haze

http://physicsbuzz.physicscentral.com/2015/09/ask-physicist-cold-light-and-negative.html

https://www.quora.com/Why-does-light-travel-faster-in-hotter-regions-than-in-colder-ones

https://www.wsav.com/news/weather-wise-kids-what-causes-a-mirage-on-hot-days/

https://en.wikipedia.org/wiki/Refraction

https://en.wikipedia.org/wiki/Mirage

https://www.theguardian.com/news/2011/aug/17/weatherwatch-heat-haze-mirage

#25 Why is Wall Street called Wall Street?

By Fletcher6 – Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=4807995

https://en.wikipedia.org/wiki/Wall_Street

https://www.history.com/topics/us-states/wall-street-timeline

https://www.thebalance.com/wall-street-how-it-works-history-and-crashes-3306252

https://www.thestreet.com/lifestyle/history-of-wall-street

https://www.investopedia.com/ask/answers/where-does-the-name-wall-street-come-from/

https://en.wikipedia.org/wiki/Buttonwood_Agreement

https://www.investopedia.com/terms/s/security.asp

#26 How did the invention of the horse collar change society?

Photo by Mehmet Turgut Kirkgoz : https://www.pexels.com/photo/people-riding-a-horse-drawn-carriage-14077067/

https://en.wikipedia.org/wiki/Yoke

https://en.wikipedia.org/wiki/Ox

https://en.wikipedia.org/wiki/Plough

https://www.thegreatcoursesdaily.com/medieval-farming-technology-transforms-europe/

https://www.barrons.com/articles/a-hat-tip-to-the-horse-collar-1400309246

https://en.wikipedia.org/wiki/Horse_collar

#27 Why would we have evolved with our esophagus and windpipe so close together that we can choke?

Image By US ARMY MEDICAL DEPARTMENT CENTER AND SCHOOLFORT SAM HOUSTON, TEXAS 78234-6100 – https://www.militarynewbie.com/wp-content/uploads/2013/11/US-Army-medical-course-Cardiopulmonary-Resuscitation-CPR-MD0532.pdf

https://www.npr.org/templates/story/story.php?storyId=129083762

https://www.cracked.com/article_19890_5-ways-evolution-has-screwed-us-over.html

Oral Cavity’s Supposedly “Lousy” Design Is a Key to Human Speech

https://www.quora.com/Why-would-humans-evolve-to-have-food-go-down-the-same-opening-as-air-thus-making-choking-a-hazard

https://www.theatlantic.com/science/archive/2019/12/when-did-ancient-humans-start-speak/603484/

#28 Why can’t we see color at night?

Photo by Francesco Ungaro: https://www.pexels.com/photo/hallway-between-buildings-246316/

https://www.ncbi.nlm.nih.gov/books/NBK22541/

http://www.chemistry.wustl.edu/~edudev/LabTutorials/Vision/Vision.html

https://indianapublicmedia.org/amomentofscience/night-vision-humans-color.php

http://www.madsci.org/posts/archives/2000-01/949047063.Ns.r.html

https://en.wikipedia.org/wiki/Rod_cell

https://askabiologist.asu.edu/rods-and-cones

https://www.cis.rit.edu/people/faculty/montag/vandplite/pages/chap_9/ch9p1.html

https://en.wikipedia.org/wiki/Cone_cell

#29 Why will people happily wait in a queue?

Photo by Cátia Matos: https://www.pexels.com/photo/people-in-line-1604200/

https://www.scirp.org/journal/paperinformation.aspx?paperid=99238

https://www.vonage.nz/resources/articles/the-psychology-of-queuing/

https://queue-it.com/blog/psychology-of-queuing/

https://en.wikipedia.org/wiki/Queueing_theory

#30 How does a Venus flytrap know when to close?

Image By Beatriz Moisset – Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=83312055

https://en.wikipedia.org/wiki/Venus_flytrap

https://homeguides.sfgate.com/venus-flytrap-trap-flies-74657.html

https://www.countryliving.com/uk/homes-interiors/gardens/a35391400/venus-flytraps/

https://www.britannica.com/plant/Venus-flytrap

#31 Why are Neanderthals called “Neanderthals”?

Image By Charles R. Knight – http://donglutsdinosaurs.com/knight-neanderthals/

https://en.wikipedia.org/wiki/Neanderthal

https://en.wikipedia.org/wiki/Johann_Carl_Fuhlrott

https://humanorigins.si.edu/evidence/human-fossils/species/homo-neanderthalensis

https://www.nhm.ac.uk/discover/who-were-the-neanderthals.html

https://www.smithsonianmag.com/science-nature/rethinking-neanderthals-83341003/

https://www.nhm.ac.uk/discover/who-were-the-neanderthals.html

#32 Why do wounds heal with scars?

Photo by cottonbro studio: https://www.pexels.com/photo/close-up-photo-of-man-with-scar-on-his-face-7265993/

https://www.bbc.com/future/article/20161007-why-is-scar-tissue-different-to-normal-skin

https://www.nhs.uk/conditions/scars/

https://www.bbc.com/future/article/20161007-why-is-scar-tissue-different-to-normal-skin

https://en.wikipedia.org/wiki/Scar

https://www.sciencefocus.com/the-human-body/why-dont-scars-disappear-as-skin-is-shed/

#33 What are the 5 types of civilization?

Image By Kevin Gill from Los Angeles, CA, United States – A Dyson Swarm Superstructure, CC BY 2.0, https://commons.wikimedia.org/w/index.php?curid=59175426

https://futurism.com/the-kardashev-scale-type-i-ii-iii-iv-v-civilization

https://en.wikipedia.org/wiki/Kardashev_scale

https://kardashev.fandom.com/wiki/Type_V

#34 Why do ships float?

Photo by Adam Heunis: https://www.pexels.com/photo/green-cargo-ship-on-body-of-water-9296985/

https://letstalkscience.ca/educational-resources/stem-in-context/why-do-ships-float

https://www.wonderopolis.org/wonder/how-do-boats-float

https://davidson.weizmann.ac.il/en/online/askexpert/why-do-ships-float

https://physics.stackexchange.com/questions/14378/why-does-density-decide-whether-something-floats-or-sinks

#35 How do fireworks work?

Photo by Pixabay: https://www.pexels.com/photo/city-night-explosion-firework-3871/

https://en.wikipedia.org/wiki/Visco_fuse

https://en.wikipedia.org/wiki/History_of_gunpowder

https://science.howstuffworks.com/innovation/everyday-innovations/fireworks.htm

https://www.explainthatstuff.com/howfireworkswork.html

https://www.pbs.org/wgbh/nova/fireworks/anat_nf.html

http://www.jes.or.jp/mag/stem/Vol.80/documents/Vol.80,No.4,p.130-135.pdf

#36 How do kidney stones form?

Image By Whoisjohngalt – Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=116993805

https://en.wikipedia.org/wiki/Kidney_stone_disease

https://en.wikipedia.org/wiki/Kidney

https://www.nhs.uk/Livewell/Kidneyhealth/Documents/kidney%20guide.pdf

https://www.niddk.nih.gov/health-information/kidney-disease/kidneys-how-they-work

https://www.urologyhealth.org/urology-a-z/k/kidney-stones

https://www.kidneyfund.org/kidney-disease/kidney-problems/kidney-stones/

https://www.livestrong.com/article/476234-why-do-you-get-so-thirsty-when-you-eat-foods-high-in-sodium/

https://www.healthline.com/health/can-you-live-with-one-kidney#transplant

#37 Why did we start using time zones?

Image By TimeZonesBoy – US Central Intelligence Agency, Public Domain, https://commons.wikimedia.org/w/index.php?curid=22556731

https://en.wikipedia.org/wiki/Time_zone

https://en.wikipedia.org/wiki/Railway_time

https://en.wikipedia.org/wiki/History_of_rail_transport#Britain

https://www.thoughtco.com/what-are-time-zones-1435358

https://www.timeanddate.com/time/time-zones-history.html

#38 Why was the Berlin Wall first built?

Image By Neptuul – Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=37233588

https://www.history.com/topics/cold-war/berlin-wall

https://www.history.com/this-day-in-history/berlin-wall-built

https://en.wikipedia.org/wiki/Berlin_Wall

https://en.wikipedia.org/wiki/Barbed_Wire_Sunday

https://en.wikipedia.org/wiki/Walter_Ulbricht#Dismissal_and_death

https://www.independent.co.uk/life-style/history/berlin-wall-what-you-need-know-about-barrier-divided-east-and-west-9847347.html?r=41678

#39 How do broken bones heal?

Photo by Alessia Marzotto: https://www.pexels.com/photo/a-person-with-a-cast-on-her-leg-11560334/

https://en.wikipedia.org/wiki/Bone_healing

https://www.webmd.com/first-aid/ss/slideshow-break-bone-what-happens

https://www.medicalnewstoday.com/articles/318961#Cartilage-and-bone

https://www.betterhealth.vic.gov.au/health/conditionsandtreatments/bone-fractures

https://socratic.org/questions/why-is-the-skeletal-system-an-organ-system

https://www.news-medical.net/health/What-are-Osteoblasts.aspx

https://depts.washington.edu/bonebio/bonAbout/bonecells.html

#40 How does GPS know where I am?

Photo by Mike B: https://www.pexels.com/photo/turned-on-black-gps-monitor-244822/

https://en.wikipedia.org/wiki/Global_Positioning_System

http://www.nasonline.org/publications/beyond-discovery/the-global-positioning-system.pdf

https://oceanservice.noaa.gov/education/tutorial_geodesy/geo09_gps.html

https://en.wikipedia.org/wiki/Korean_Air_Lines_Flight_007

http://www.astronomy.ohio-state.edu/~pogge/Ast162/Unit5/gps.html

https://en.racelogic.support/VBOX_Automotive/01General_Information/Knowledge_Base/How_Does_GPS_Work%3F

#41 Why do we become addicted to nicotine?

Photo by Geri Tech: https://www.pexels.com/photo/a-person-holding-a-cigarette-stick-5813080/

https://en.wikipedia.org/wiki/Nicotine

https://www.swedish.org/classes-and-resources/smoking-cessation/nicotine-dependence-how-it-happens

https://en.wikipedia.org/wiki/History_of_tobacco

https://www.quit.org.au/articles/nicotine-addiction-explained/

#42 Why is the Colosseum called the “Colosseum”?

Photo by Davi Pimentel: https://www.pexels.com/photo/colosseum-rome-italy-2064827/

https://en.wikipedia.org/wiki/Colosseum

https://www.the-colosseum.net/history/h1.htm

https://en.wikipedia.org/wiki/Colossus_of_Nero

https://www.kissfromitaly.com/en/blog/how-did-the-colosseum-get-its-name

https://www.rome.net/colosseum

#43 How does an MRI work?

Photo by MART PRODUCTION: https://www.pexels.com/photo/technology-hospital-medicine-indoors-7089017/

https://en.wikipedia.org/wiki/Magnetic_resonance_imaging

https://en.wikipedia.org/wiki/History_of_magnetic_resonance_imaging

https://www.nibib.nih.gov/science-education/science-topics/magnetic-resonance-imaging-mri

https://mayfieldclinic.com/pe-mri.htm

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1121941/

https://www.sciencealert.com/it-s-probably-safe-to-get-an-mri-if-you-have-tattoos-just-in-case-you-were-worried

#44 Why is Mars red?

By Justin Cowart – Tharsis and Valles Marineris – Mars Orbiter Mission, CC BY 2.0, https://commons.wikimedia.org/w/index.php?curid=71790570

https://www.jpl.nasa.gov/edu/learn/video/mars-in-a-minute-is-mars-really-red/

https://en.wikipedia.org/wiki/Mars

https://www.cslsilicones.com/en/about/blog/item/what-causes-corrosion.html

https://en.wikipedia.org/wiki/Rust

https://www.wonderopolis.org/wonder/why-do-some-things-rust

https://science.howstuffworks.com/question445.htm

https://slate.com/news-and-politics/2004/01/why-is-mars-red.html

https://www.quora.com/What-causes-rust-to-form

https://www.rust911.com/rust/

https://skyandtelescope.org/astronomy-news/rusting-mars-without-water/

#45 Why is slime mold so awesome?

Image By Siga – Own work, Public Domain, https://commons.wikimedia.org/w/index.php?curid=2690264

https://www.pbs.org/wgbh/nova/article/slime-mold-smart-brainless-cognition/

https://www.scientificamerican.com/article/how-slime-molds-remember-where-they-ate/

https://en.wikipedia.org/wiki/Eukaryote

https://en.wikipedia.org/wiki/Slime_mold

https://www.kqed.org/science/635319/this-pulsating-slime-mold-comes-in-peace

https://www.nature.com/articles/s41598-019-50872-z

#46 Why was the teabag invented?

By Siga – Own work, Public Domain, https://commons.wikimedia.org/w/index.php?curid=2690264

https://patents.google.com/patent/US723287

https://en.wikipedia.org/wiki/Tea_bag

https://gizmodo.com/how-the-tea-bag-was-invented-1700351584

https://time.com/3996712/a-brief-history-of-the-tea-bag/

https://www.tea.co.uk/the-history-of-the-tea-bag

https://tea-shirt.co.uk/blogs/news/history-of-the-teabag

https://www.smithsonianmag.com/smart-news/ever-wonder-who-invented-tea-bag-180961469/

https://www.tea.co.uk/history-of-tea

https://en.wikipedia.org/wiki/Etymology_of_tea

#47 What exactly is yogurt?

Photo by Cats Coming: https://www.pexels.com/photo/crop-man-taking-natural-yogurt-with-spoon-from-jar-4428345/

https://www.foodunfolded.com/article/the-chemistry-behind-the-fermentation-of-yogurt

https://en.wikipedia.org/wiki/Lactobacillus_delbrueckii_subsp._bulgaricus

https://en.wikipedia.org/wiki/Streptococcus_thermophilus

https://www.scientificamerican.com/article/bring-science-home-yogurt-bacteria/

https://en.wikipedia.org/wiki/Colloid

https://brodandtaylor.com/blogs/recipes/the-science-of-great-yogurt

https://www.researchgate.net/publication/263440016_Formation_and_Physical_Properties_of_Yogurt

https://academic.oup.com/nutritionreviews/article/73/suppl_1/4/1819293

#48 Why is Earl Grey tea called Earl Grey?

Photo by Julia Sakelli: https://www.pexels.com/photo/teacup-with-tea-905485/

https://en.wikipedia.org/wiki/Earl_Grey_tea

https://web.archive.org/web/20130120184519/http://showbizandstyle.inquirer.net/lifestyle/lifestyle/view/20080723-150279/More-than-just-a-pot-of-tea

https://en.wikipedia.org/wiki/Bergamot_orange

http://www.foodsofengland.co.uk/earlgreytea.htm

http://www.historyhome.co.uk/pms/grey.htm

https://en.wikipedia.org/wiki/Charles_Grey,_2nd_Earl_Grey#Prime_minister_(1830%E2%80%931834)

https://www.teacupsfull.com/blogs/blog/the-history-of-earl-grey-tea

#49 Why are butlers called butlers?

Image By American Telephone and Telegraph Company American Telephone and Telegraph Company. Information Dept – Title: Bell telephone magazineYear: 1922 (1920s), CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=78851298

https://www.gq.com/story/rich-billionaires-butlers-servants

https://www.magnumsacademy.com/2013/05/02/history-of-butlers/

https://www.linkedin.com/pulse/evolution-butler-service-sandeep-pandey/

http://www.literary-liaisons.com/article046.htm

https://en.wikipedia.org/wiki/Buttery_(room)

https://en.wikipedia.org/wiki/Butler

#50 How do white blood cells kill pathogens?

Image By Bruce Wetzel (photographer). Harry Schaefer (photographer) – Image and description: National Cancer Institute, Public Domain, https://commons.wikimedia.org/w/index.php?curid=1243646

https://askabiologist.asu.edu/t-cell

https://www.cedars-sinai.org/newsroom/research-shows-how-white-blood-cells-detect-invaders/

https://www.sciencedaily.com/releases/2011/04/110429095229.htm

https://en.wikipedia.org/wiki/White_blood_cell

https://www.medicalnewstoday.com/articles/327446#types-and-function

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4029293/

https://www2.mrc-lmb.cam.ac.uk/viruswars/viruses.php

https://www.sciencedaily.com/releases/2006/10/061002214703.htm

#51 Where did the symbol for the Red Cross come from?

https://en.wikipedia.org/wiki/International_Committee_of_the_Red_Cross

https://en.wikipedia.org/wiki/Henry_Dunant

https://en.wikipedia.org/wiki/Battle_of_Solferino

https://www.history.com/topics/19th-century/red-cross

#52 Who won the first Nobel Peace Prize?

Image By Photograph: JonathunderMedal: Erik Lindberg (1873-1966) – Derivative of File:NobelPrize.JPG, PD-US, https://en.wikipedia.org/w/index.php?curid=58432969

https://en.wikipedia.org/wiki/Nobel_Prize

https://en.wikipedia.org/wiki/Henry_Dunant

https://www.nobelprize.org/prizes/peace/1901/dunant/facts/

https://www.nobelprize.org/prizes/peace/1901/passy/facts/

https://www.nobelpeaceprize.org/

https://www.history.com/this-day-in-history/first-nobel-prizes-awarded

https://www.nobelprize.org/prizes/lists/all-nobel-prizes/

#53 What are the blue bits in blue cheese?

Image By Coyau / Wikimedia Commons, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=38084934

https://en.wikipedia.org/wiki/Rennet

http://milkfacts.info/Milk%20Processing/Cheese%20Production.htm

https://www.washingtonpost.com/lifestyle/kidspost/ever-wondered-how-milk-becomes-cheese/2015/05/15/32abad22-ece8-11e4-8abc-d6aa3bad79dd_story.html

https://qz.com/471172/notallmolds-why-is-it-safe-to-eat-bleu-cheese/

https://www.healthline.com/nutrition/is-blue-cheese-mold#bottom-line

https://en.wikipedia.org/wiki/Stilton_cheese

https://en.wikipedia.org/wiki/Gorgonzola

https://en.wikipedia.org/wiki/Blue_cheese

https://www.thespruceeats.com/how-blue-cheese-is-made-591563

#54 Why can cats jump so high?

Photo by Gratisography: https://www.pexels.com/photo/jumping-cute-playing-animals-4602/

https://lisbdnet.com/how-high-can-a-lion-jump/

https://www.hillspet.com/cat-care/training/managing-your-cats-jumping

https://biology.stackexchange.com/questions/1116/why-is-it-that-cats-can-jump-so-high-for-their-size-compared-with-humans

https://www.bbc.com/news/magazine-17492802

https://en.wikipedia.org/wiki/Cat_righting_reflex

#55 Where does Black Friday originate?

Image By Gridprop at English Wikipedia – Public Domain, https://commons.wikimedia.org/w/index.php?curid=16773387

https://en.wikipedia.org/wiki/Black_Friday_(shopping)

https://www.visualthesaurus.com/cm/wordroutes/the-origins-of-black-friday/

https://en.wikipedia.org/wiki/Black_Friday

https://en.wikipedia.org/wiki/Black_Friday_(1869)

https://www.history.com/news/black-friday-thanksgiving-origins-history

https://www.dictionary.com/e/black-friday/

https://www.hindustantimes.com/lifestyle/festivals/black-friday-2021-what-is-black-friday-the-real-history-and-significance-explained-101637752653558.html

https://www.businessinsider.com/why-is-it-called-black-friday-2017-11

https://www.britannica.com/event/Black-Friday

#56 Why is gold so rare?

Photo by Michael Steinberg: https://www.pexels.com/photo/gold-bars-366551/

https://www.theguardian.com/notesandqueries/query/0,,-194047,00.html

https://www.investopedia.com/articles/investing/071114/why-gold-has-always-had-value.asp

https://www.sciencefocus.com/science/why-is-gold-rare/

https://en.wikipedia.org/wiki/Gold

https://money.howstuffworks.com/question213.htm

https://www.thoughtco.com/how-is-gold-formed-4683984

https://sciencing.com/rock-formations-can-gold-found-7439756.html

https://www.bbc.com/news/magazine-21969100

https://www.wtamu.edu/~cbaird/sq/2014/05/02/can-gold-be-created-from-other-elements/

https://physicstoday.scitation.org/doi/10.1063/PT.3.3815

#57 How does spot welding work and what is it used for?

Image By BMW Werk Leipzig – http://bmw-werk-leipzig.de, CC BY-SA 2.0 de, https://commons.wikimedia.org/w/index.php?curid=11928438

https://www.schuettemetals.com/blog/resistance-welding

https://en.wikipedia.org/wiki/Spot_welding

https://surehand.com/blog/welding/history-of-mig-and-spot-welding-in-car-manufacturing-industry/

https://en.wikipedia.org/wiki/Joule_heating

https://en.wikipedia.org/wiki/Electrical_resistance_and_conductance

https://askinglot.com/how-hot-does-a-spot-welder-get

https://en.wikipedia.org/wiki/Elihu_Thomson

#58 How tall could a human grow?

Image https://commons.wikimedia.org/w/index.php?curid=60346588

https://www.yourhormones.info/hormones/growth-hormone-releasing-hormone/

https://en.wikipedia.org/wiki/Growth_hormone

https://ourworldindata.org/human-height

https://en.wikipedia.org/wiki/Robert_Wadlow

https://www.nbcnews.com/id/wbna3076703

https://www.smithsonianmag.com/science-nature/cardiovascular-secrets-giraffes-180977785/

#59 Why do we say “the press” to refer to journalists and newspapers?

Photo by LT Chan: https://www.pexels.com/photo/the-press-capturing-the-events-during-a-protest-5343098/

https://en.wikipedia.org/wiki/Newspaper

https://en.wikipedia.org/wiki/Johannes_Gutenberg

https://en.wikipedia.org/wiki/Printing_press

https://en.wikipedia.org/wiki/History_of_newspaper_publishing

https://en.wikipedia.org/wiki/Newspaper_production_process

https://people.howstuffworks.com/newspaper5.htm

https://www.printingforless.com/Digital-Printing-Explained.html

https://www.britannica.com/topic/publishing/The-age-of-early-printing-1450-1550

https://timesofindia.indiatimes.com/when-and-where-was-the-first-newspaper-published/articleshow/2477418.cms

https://www.britannica.com/topic/publishing/The-first-newspapers

https://www.etymonline.com/word/press

#60 Why do birds migrate?

Photo by Brett Sayles: https://www.pexels.com/photo/flock-of-canada-geese-soaring-in-sky-during-migration-7651244/

https://en.wikipedia.org/wiki/Bird_migration

https://www.nationalgeographic.com/animals/article/bird-migration-one-of-natures-wonders-heres-how-they-do-it

https://www.sciencedaily.com/releases/2018/08/180808093901.htm

https://www.si.edu/spotlight/buginfo/winter

#61 How do antlers grow?

Photo by cmonphotography: https://www.pexels.com/photo/brown-deer-near-tree-3329812/

https://www.mossyoak.com/our-obsession/blogs/deer/antler-genesis-how-deer-grow-antlers

https://www.mossyoak.com/our-obsession/blogs/deer/mining-for-antlers-ideas-for-productive-deer-mineral-sites

https://www.reconnectwithnature.org/news-events/the-buzz/nature-curiosity-how-do-antlers-grow-so-fast

https://en.wikipedia.org/wiki/Antler

https://onlinelibrary.wiley.com/doi/10.1111/j.0014-3820.2001.tb00794.x

https://animaldiversity.org/collections/mammal_anatomy/horns_and_antlers/

#62 Why are zippers called zippers?

Photo by Pixabay: https://www.pexels.com/photo/blue-blue-jeans-canvas-casual-206365/

https://en.wikipedia.org/wiki/Elias_Howe

https://eriehistory.blogspot.com/2015/05/the-talon-zipper-company.html

https://www.thoughtco.com/history-of-the-zipper-4066245

https://en.wikipedia.org/wiki/Talon_Zipper

https://www.wonderopolis.org/wonder/who-invented-the-zipper

https://www.vintagefixation.com/blogs/frontpage/8517-the-amazing-automatic-continuous-clothing-closure

https://en.wikipedia.org/wiki/Zipper

https://en.wikipedia.org/wiki/Whitcomb_L._Judson

https://en.wikipedia.org/wiki/Gideon_Sundback

#63 Why do we feel pain when we touch cold or hot things?

Photo by Oussama Elhaidi: https://www.pexels.com/photo/burning-wood-on-the-ground-5159914/

https://www.bbc.com/future/article/20170206-why-do-we-feel-hot-and-cold-as-pain

https://en.wikipedia.org/wiki/TRPA1

https://en.wikipedia.org/wiki/Thermoreceptor

https://en.wikipedia.org/wiki/TRPM8

https://en.wikipedia.org/wiki/TRPV1

https://www.sciencefocus.com/science/when-did-humans-first-start-wearing-clothes/

https://www.uofmhealth.org/health-library/colde

https://en.wikipedia.org/wiki/Nociceptor

https://www.verywellhealth.com/how-we-feel-pain-2564638

#64 What is the difference between alternating current (AC) and direct current (DC)?

Photo by Pixabay: https://www.pexels.com/photo/cable-current-danger-distribution-236089/

https://simple.wikipedia.org/wiki/Voltaic_pile

https://en.wikipedia.org/wiki/Voltaic_pile

https://en.wikipedia.org/wiki/Alternating_current

https://learn.sparkfun.com/tutorials/alternating-current-ac-vs-direct-current-dc/all

https://www.power-and-beyond.com/whats-the-difference-between-ac-and-dc-power-a-915187/

https://en.wikipedia.org/wiki/Direct_current

https://www.dummies.com/article/technology/electronics/general-electronics/electronics-basics-what-is-alternating-current-179847

https://electronics.stackexchange.com/questions/152307/how-is-it-possible-to-have-high-voltage-and-low-current-it-seems-to-contradict/152311

#65 How can bats sleep hanging upside down?

Photo by Will Mu: https://www.pexels.com/photo/bats-hanging-upside-down-on-branches-11934278/

https://en.wikipedia.org/wiki/Bat

https://www.iowadnr.gov/About-DNR/DNR-News-Releases/ArticleID/1082/Why-do-bats-hang-upside-down

https://www.mentalfloss.com/article/574568/why-do-bats-hang-upside-down

https://www.terminix.com/blog/education/do-bats-sleep-upside-down/

https://www.batworlds.com/bat-anatomy/

https://smallscience.hbcse.tifr.res.in/how-bats-fly/

https://animals.howstuffworks.com/mammals/how-bats-land-upside-down.htm

https://en.wikipedia.org/wiki/Muscle_fatigue

https://science.howstuffworks.com/innovation/science-questions/hang-upside-down-how-long-safe-deadly.htm

#66 How much time does the Panama Canal save a ship?

Photo by Michael D. Camphin: https://www.pexels.com/photo/photo-of-ships-2906490/

https://en.wikipedia.org/wiki/Panama_Canal

https://en.wikipedia.org/wiki/History_of_the_Panama_Canal

https://www.nationalgeographic.com/history/article/140815-panama-canal-culebra-cut-lake-gatun-focus

#67 Why do we use a QWERTY keyboard?

Photo by Sathesh D: https://www.pexels.com/photo/closeup-photo-of-black-computer-keyboard-s-left-side-keys-698808/

https://www.theatlantic.com/technology/archive/2013/05/the-lies-youve-been-told-about-the-origin-of-the-qwerty-keyboard/275537/

https://www.theeditingco.com/blog/10380/the-history-of-the-qwerty-keyboard-how-it-came-to-be

https://en.wikipedia.org/wiki/QWERTY

http://kanji.zinbun.kyoto-u.ac.jp/~yasuoka/publications/PreQWERTY.html

https://www.cnet.com/news/a-brief-history-of-the-qwerty-keyboard/

https://www.thebritishacademy.ac.uk/blog/summer-showcase-2020-how-qwerty-keyboard-shapes-way-we-communicate/?gclid=CjwKCAiA78aNBhAlEiwA7B76pz750q6NsaA9Umaa9JBRjlWEz_W_6C3DihTCyzY0a9z65TctPSjkNhoCmLcQAvD_BwE

https://americasbesthistory.com/abhtimeline1829m.html

https://en.wikipedia.org/wiki/Typewriter

https://www.smithsonianmag.com/arts-culture/fact-of-fiction-the-legend-of-the-qwerty-keyboard-49863249/

#68 What is the Drake equation?

Photo by Simon BB: https://www.pexels.com/photo/silhouette-of-trees-under-purple-sky-5222117/

https://en.wikipedia.org/wiki/Pioneer_plaque

https://en.wikipedia.org/wiki/Pioneer_10

https://en.wikipedia.org/wiki/Pioneer_11

https://www.pbs.org/lifebeyondearth/listening/drake.html

https://en.wikipedia.org/wiki/Frank_Drake

https://www.seti.org/drake-equation-index

https://www.space.com/25219-drake-equation.html

https://exoplanets.nasa.gov/news/1350/are-we-alone-in-the-universe-revisiting-the-drake-equation/

#69 How does a gyroscope work?

Image By Stéphane Magnenat – Own work by uploader, subject public domain, Public Domain, https://commons.wikimedia.org/w/index.php?curid=4302903

https://en.wikipedia.org/wiki/Gyroscope

https://science.howstuffworks.com/gyroscope.htm

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5677445/

https://en.wikipedia.org/wiki/Gimbal

#70 How do animals change color?

Photo by Сергей Сёмин: https://www.pexels.com/photo/close-up-shot-of-a-chameleon-perched-on-a-tree-branch-4704637/

https://www.economist.com/the-economist-explains/2015/03/12/how-animals-change-colour

https://www.nationalgeographic.com/animals/article/color-change-camouflage-animals-explained

https://en.wikipedia.org/wiki/Chromatophore

https://theconversation.com/how-do-chameleons-and-other-creatures-change-colour-13842

https://animals.howstuffworks.com/animal-facts/animal-camouflage.htm

https://en.wikipedia.org/wiki/List_of_animals_that_can_change_color

https://en.wikipedia.org/wiki/Misumena_vatia

https://www.aquarium.co.za/blog/entry/how-does-an-octopus-change-its-colour-and-shape

Weird pupils let octopuses see their colorful gardens

https://en.wikipedia.org/wiki/Chameleon

https://ocean.si.edu/ocean-life/invertebrates/how-octopuses-and-squids-change-color

#71 How do jellyfish survive without a brain?

Photo by Thuan Vo: https://www.pexels.com/photo/a-jellyfish-with-long-tentacles-8637575/

https://en.wikipedia.org/wiki/Statocyst

https://www.visitsealife.com/london/information/news/7-things-you-didn-t-know-about-jellyfish/

https://findanyanswer.com/how-do-jellyfish-maintain-balance

https://animals.howstuffworks.com/marine-life/jellyfish.htm

https://en.wikipedia.org/wiki/Jellyfish

#72 How can whales hold their breath for so long?

Photo by Elianne Dipp: https://www.pexels.com/photo/whale-in-blue-depth-of-ocean-4696771/

https://www.nhm.ac.uk/discover/quick-questions/how-can-whales-hold-their-breath-for-so-long.html

https://en.wikipedia.org/wiki/Whale

http://scienceline.ucsb.edu/getkey.php?key=1009

https://www.healthline.com/health/alveoli-function#alveoli-function

#73 How do solar panels generate electricity?

Photo by Pixabay: https://www.pexels.com/photo/black-and-silver-solar-panels-159397/

https://en.wikipedia.org/wiki/Solar_panel

https://en.wikipedia.org/wiki/Photovoltaic_effect

https://www.livescience.com/41995-how-do-solar-panels-work.html

https://en.wikipedia.org/wiki/Concentrated_solar_power

https://en.wikipedia.org/wiki/Photon

https://www.solarreviews.com/blog/how-much-electricity-does-a-solar-panel-produce

https://sciencebusiness.net/climate-news/news/future-solar-four-problems-we-need-solve-fast

#74 Why do tectonic plates move?

Photo by Wilson Malone: https://www.pexels.com/photo/orange-and-white-traffic-pole-on-cracked-gray-asphalt-road-4558211/

https://en.wikipedia.org/wiki/List_of_tectonic_plates

https://www.nationalgeographic.org/encyclopedia/plate-tectonics/

https://www.livescience.com/37706-what-is-plate-tectonics.html

https://www.gns.cri.nz/Home/Learning/Science-Topics/Earthquakes/Earthquakes-at-a-Plate-Boundary/Tectonic-Plates-and-Plate-Boundaries

https://earthobservatory.sg/faq-on-earth-sciences/earth%E2%80%99s-mantle-made-liquid-magma

https://www.nationalgeographic.org/encyclopedia/mantle/

https://en.wikipedia.org/wiki/Mantle_convection

https://www.nationalgeographic.org/encyclopedia/plate-boundaries/

https://www.britannica.com/science/plate-tectonics/Earths-layers

https://www.geolsoc.org.uk/Plate-Tectonics/Chap2-What-is-a-Plate/Plate-Movement

https://en.wikipedia.org/wiki/Slab_pull

#75 How does a QR code work?

https://www.fastprint.co.uk/blog/quick-response-codes-what-are-they-and-how-do-they-work.html

https://www.sproutqr.com/blog/how-do-qr-codes-work

https://en.wikipedia.org/wiki/QR_code

#76 When were the first dinosaur bones found?

Image By Evolutionnumber9 – Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=94082518

https://www.nhm.ac.uk/discover/how-dinosaurs-got-their-name.html

https://en.wikipedia.org/wiki/Iguanodon

https://en.wikipedia.org/wiki/William_Buckland

https://en.wikipedia.org/wiki/Megalosaurus

https://en.wikipedia.org/wiki/Robert_Plot

https://wonderopolis.org/wonder/who-discovered-the-first-dinosaur-bone

https://www.bbc.com/news/uk-england-lancashire-31623397

https://en.wikipedia.org/wiki/Richard_Owen

https://www.discovery.com/science/First-Dinosaur-Fossil-Name

https://en.wikipedia.org/wiki/Dinosaur

https://www.scholastic.com/teachers/articles/teaching-content/when-was-first-dinosaur-discovered/

#77 How did dogs change when they were domesticated?

Photo by Pixabay: https://www.pexels.com/photo/brown-wolf-standing-on-green-grass-162256/

https://www.sciencedirect.com/topics/medicine-and-dentistry/neural-crest-cell

https://bigthink.com/life/mystery-behind-dogs-domestication-syndrome/

https://www.newscientist.com/article/2264329-humans-may-have-domesticated-dogs-by-accident-by-sharing-excess-meat/

https://www.smithsonianmag.com/science-nature/how-wolves-really-became-dogs-180970014/

https://www.pnas.org/content/118/6/e2010083118

https://www.theatlantic.com/science/archive/2016/06/the-origin-of-dogs/484976/

#78 Why were steam cars so popular in 1900?

Image By Amos Wolfe – Image from an original photograph by Amos Wolfe taken 12th August 2001. Edited to remove traces of orange fencing and traffic cones by Amos Wolfe on 22nd August 2001., CC BY-SA 2.0, https://commons.wikimedia.org/w/index.php?curid=588767

https://www.carkeys.co.uk/news/why-does-nobody-make-a-steam-powered-car

http://www.stanleymotorcarriage.com/GeneralTechnical/GeneralTechnical.htm

https://www.thoughtco.com/history-of-steam-powered-cars-4066248

https://en.wikipedia.org/wiki/History_of_steam_road_vehicles

https://en.wikipedia.org/wiki/Steam_car

https://en.wikipedia.org/wiki/Steam_engine

#79 Can dogs smell cancer?

Photo by Simon Robben: https://www.pexels.com/photo/selective-close-up-photography-of-brow-dog-looking-up-464664/

https://www.nidcd.nih.gov/health/smell-disorders

https://www.irishexaminer.com/lifestyle/arid-20462718.html

https://phoenixvetcenter.com/blog/214731-how-powerful-is-a-dogs-nose

https://vcahospitals.com/know-your-pet/how-dogs-use-smell-to-perceive-the-world

https://en.wikipedia.org/wiki/Polyamine

https://archive.uef.fi/en/web/uef-bulletin/cancer/

https://www.medicalnewstoday.com/articles/323620#overview

https://www.understandinganimalresearch.org.uk/news/research-medical-benefits/the-science-of-sniffs-disease-smelling-dogs/

#80 Why do we say Middle Ages and Dark Ages?

Photo by Pixabay: https://www.pexels.com/photo/black-steel-helmet-near-black-and-gray-handle-sword-161936/

https://en.wikipedia.org/wiki/Middle_Ages

https://en.wikipedia.org/wiki/Classical_antiquity

https://www.history.com/topics/middle-ages/middle-ages

https://www.historyextra.com/period/medieval/how-when-why-did-we-start-calling-medieval-era-name/

https://en.wikipedia.org/wiki/Leonardo_Bruni

https://www.britannica.com/biography/Leonardo-Bruni

https://en.wikipedia.org/wiki/Petrarch

https://en.wikipedia.org/wiki/Dark_Ages_(historiography)

https://en.wikipedia.org/wiki/Medieval_technology

#81 Why do whales make sounds?

Photo by Elianne Dipp: https://www.pexels.com/photo/humpback-whales-underwater-4666753/

https://www.ifaw.org/journal/are-dolphins-whales

https://oceanservice.noaa.gov/facts/light_travel.html

https://en.wikipedia.org/wiki/Dolphin

https://en.wikipedia.org/wiki/Toothed_whale

https://en.wikipedia.org/wiki/Baleen_whale

https://en.wikipedia.org/wiki/Whale_vocalization

https://oceanservice.noaa.gov/facts/whalesounds.html

https://www.awe.gov.au/environment/marine/marine-species/cetaceans/whale-dolphins-sound

#82 Why is skin waterproof?

Photo by Polina Tankilevitch: https://www.pexels.com/photo/person-washing-hands-3736403/

https://en.wikipedia.org/wiki/Human_skin

https://en.wikipedia.org/wiki/Stratum_corneum

https://en.wikipedia.org/wiki/Apocrine

https://www.aocd.org/page/SkinFacts

https://gizmodo.com/why-is-our-skin-waterproof-5906135

https://www.newscientist.com/article/dn21755-strange-fat-explains-skins-waterproof-properties/?ignored=irrelevant

https://cen.acs.org/articles/95/i7/Tracing-chemistry-household-dust.html

https://www.khanacademy.org/science/biology/macromolecules/lipids/a/lipids

https://www.ncbi.nlm.nih.gov/books/NBK26871/

https://sciencing.com/happens-nonpolar-molecules-water-8633386.html

#83 How does a quartz watch work?

Photo by 157 Industries: https://www.pexels.com/photo/close-up-photo-of-a-wristwatch-6166175/

https://www.explainthatstuff.com/quartzclockwatch.html

https://www.jcwa.or.jp/en/time/qa/qa07.html

https://tf.nist.gov/general/pdf/2276.pdf

https://en.wikipedia.org/wiki/Quartz_clock

https://en.wikipedia.org/wiki/Piezoelectricity

https://en.wikipedia.org/wiki/Quartz

https://www.autodesk.com/products/eagle/blog/piezoelectricity/

https://en.wikipedia.org/wiki/Mechanical_watch

#84 Why is London where it is?

Photo by Dominika Gregušová: https://www.pexels.com/photo/city-view-at-london-672532/

https://londonist.com/london/features/why-is-london-here

https://www.independent.co.uk/news/science/archaeology/how-london-became-britain-s-capital-has-been-revealed-for-the-first-time-a7028191.html

https://en.wikipedia.org/wiki/History_of_London

https://en.wikipedia.org/wiki/Londinium

https://en.wikipedia.org/wiki/Boudican_revolt

https://localhistories.org/a-brief-history-of-london/

https://en.wikipedia.org/wiki/Colchester

https://en.wikipedia.org/wiki/Camulodunum

#85 When did people start using money?

Photo by Pixabay: https://www.pexels.com/photo/bank-notes-banknotes-bills-cash-259234/

https://www.investopedia.com/articles/07/roots_of_money.asp

https://www.discovermagazine.com/planet-earth/when-did-people-start-using-money

https://en.wikipedia.org/wiki/History_of_money

https://en.wikipedia.org/wiki/Shekel

https://medium.com/@kasra.kaveh/the-history-of-money-and-banking-f51fbaa74a26

#86 When did people start using aircraft carriers?

Photo by Jaxon Matthew Willis: https://www.pexels.com/photo/drone-shots-of-uss-yorktown-aircraft-carrier-in-the-harbor-12485411/

https://en.wikipedia.org/wiki/History_of_the_aircraft_carrier

https://en.wikipedia.org/wiki/HMS_Furious_(47)

https://en.wikipedia.org/wiki/Eugene_Burton_Ely

https://en.wikipedia.org/wiki/HMS_Ark_Royal_(1914)

https://airandspace.si.edu/multimedia-gallery/web11687-2010640jpg

https://www.businessinsider.com/eugene-ely-navy-launched-plane-from-ship-for-first-time-in-1910-2017-11

https://www.lacrosselibrary.org/sites/default/files/u117/05-aircraft_carriers_rule_the_pacific.pdf

#87 How do stars die?

Photo by Miriam Espacio: https://www.pexels.com/photo/silhouette-photo-of-trees-during-night-time-365633/

https://www.energy.gov/science/doe-explainsnuclear-fusion-reactions

https://www.wwu.edu/astro101/a101_sun.shtml

https://en.wikipedia.org/wiki/Helium

https://en.wikipedia.org/wiki/Hydrogen

https://ptable.com/?lang=en#Properties

http://solar-center.stanford.edu/activities/FingerprintsInStarlight/Inquiry-Questions-Answers.pdf

https://en.wikipedia.org/wiki/Sun

https://en.wikipedia.org/wiki/Stellar_classification

https://en.wikipedia.org/wiki/Star

https://www.sciencefocus.com/space/how-do-stars-die/

https://www.space.com/how-do-stars-die

https://science.howstuffworks.com/star6.htm

https://www.discovery.com/science/how-stars-die–the-big-ones

#88 Why is Venice where it is?

Photo by Anastasiya Lobanovskaya: https://www.pexels.com/photo/venice-italy-804954/

https://www.britannica.com/place/Venice/In-unified-Italy

How was Venice built?

https://en.wikipedia.org/wiki/Sack_of_Rome_(410)

https://www.thetravel.com/how-was-venice-built-on-water/

https://en.wikipedia.org/wiki/History_of_the_Republic_of_Venice

https://whc.unesco.org/en/list/394

https://en.wikipedia.org/wiki/Venice

#89 How does the Large Hadron Collider work?

Photo by Ramaz Bluashvili: https://www.pexels.com/photo/the-large-hadron-collider-at-geneva-switzerland-6855582/

https://home.cern/science/accelerators/large-hadron-collider

https://home.cern/resources/faqs/facts-and-figures-about-lhc

https://en.wikipedia.org/wiki/Large_Hadron_Collider

https://science.howstuffworks.com/science-vs-myth/everyday-myths/large-hadron-collider.htm

https://theconversation.com/explainer-how-does-an-experiment-at-the-large-hadron-collider-work-42846

https://home.cern/science/accelerators/how-accelerator-works

#90 When did people in Europe start eating sugar?

Photo by Suzy Hazelwood: https://www.pexels.com/photo/close-up-photo-of-sugar-cubes-in-glass-jar-2523659/

https://en.wikipedia.org/wiki/History_of_sugar

https://www.nordzuckerireland.ie/ie/about-sugar/how-sugar-arrived-in-europe

https://www.verywellhealth.com/reduced-sugar-consumption-recommendations-5080477

https://www.etymonline.com/word/sugar

https://en.wikipedia.org/wiki/Sugar_beet

#91 How did the Rosetta stone help people decipher hieroglyphics?

Image by By © Hans Hillewaert, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=3153928

https://www.history.com/news/what-is-the-rosetta-stone

https://en.wikipedia.org/wiki/Rosetta_Stone

#92 Why do bees make honey?

Photo by Pixabay: https://www.pexels.com/photo/honeycomb-close-up-detail-honey-bee-56876/

https://en.wikipedia.org/wiki/Waggle_dance

https://journeynorth.org/tm/monarch/nectar.html

https://wonderopolis.org/wonder/how-do-bees-make-honey

https://www.sciencefocus.com/nature/how-do-bees-make-honey/

#93 Is it possible to get absolute zero?

Photo by Riccardo: https://www.pexels.com/photo/ice-river-photography-300857/

https://en.wikipedia.org/wiki/Absolute_zero

https://en.wikipedia.org/wiki/William_Thomson,_1st_Baron_Kelvin

https://en.wikipedia.org/wiki/Kelvin

https://en.wikipedia.org/wiki/Superfluidity

https://en.wikipedia.org/wiki/Bose%E2%80%93Einstein_condensate

https://www.titech.ac.jp/english/public-relations/about/stories/absolute-zero

https://en.wikipedia.org/wiki/Third_law_of_thermodynamics

https://www.smithsonianmag.com/science-nature/the-coldest-place-in-the-universe-8121922/

https://blogs.scientificamerican.com/observations/racing-toward-absolute-zero/

https://www.forbes.com/sites/startswithabang/2020/11/12/even-at-its-end-the-universe-will-never-reach-absolute-zero/?sh=4ec1cc052748

#94 What is the caliber of a gun cartridge?

Photo by Pixabay: https://www.pexels.com/photo/close-up-photography-of-brass-bullets-53224/

https://en.wikipedia.org/wiki/Caliber

https://en.wikipedia.org/wiki/Cartridge_(firearms)

https://en.wikipedia.org/wiki/Paper_cartridge

https://en.wikipedia.org/wiki/Gauge_(firearms)

https://www.pewpewtactical.com/bullet-sizes-calibers-and-types/

https://en.wikipedia.org/wiki/Smokeless_powder

https://smallwarsjournal.com/jrnl/art/complete-history-small-arms-ammunition-and-cartridges

#95 What happened to the ice industry?

Image By International Film Service, U.S. National Archives and Records Administration, Public Domain, https://commons.wikimedia.org/w/index.php?curid=16522514

https://www.materials.sandvik/en/campaigns/fridge-of-the-future/the-history-of-the-refrigerator/

https://www.livescience.com/57797-refrigerator-history.html

https://en.wikipedia.org/wiki/Refrigerator

https://en.wikipedia.org/wiki/Icebox

https://americanhistory.si.edu/blog/ice-harvesting-electric-refrigeration

https://en.wikipedia.org/wiki/Ice_trade

#96 When was the first dentist?

Photo by Pixabay: https://www.pexels.com/photo/business-care-clean-clinic-208474/

https://en.wikipedia.org/wiki/Toothbrush

https://www.dentalcareersedu.org/2017/02/why-prehistoric-humans-had-better-teeth/

https://en.wikipedia.org/wiki/Dentistry

https://www.adea.org/GoDental/Health_Professions_Advisors/History_of_Dentistry.aspx

https://en.wikipedia.org/wiki/Hesy-Ra

https://news.ku.edu/2017/06/23/analysis-neanderthal-teeth-marks-uncovers-evidence-prehistoric-dentistry

https://en.wikipedia.org/wiki/Tooth_worm

https://www.drericyao.com/History-of-Dentistry

#97 What are mail fraud and wire fraud?

Photo by sl wong: https://www.pexels.com/photo/oblong-brown-metal-mailbox-947384/

https://digitalcommons.law.ou.edu/cgi/viewcontent.cgi?article=1058&context=olr

https://www.richardhornsby.com/federal/crimes/wire-fraud.html

https://www.everycrsreport.com/reports/R41930.html

https://www.criminaldefenselawyer.com/resources/wire-fraud.htm

https://www.investopedia.com/terms/w/wirefraud.asp

https://en.wikipedia.org/wiki/Mail_and_wire_fraud

https://en.wikipedia.org/wiki/Classes_of_offenses_under_United_States_federal_law

https://www.mccabecoleman.com/blog/2019/april/the-difference-between-a-felony-and-a-misdemeano/

https://www.encyclopedia.com/law/legal-and-political-magazines/mail-federal-mail-fraud-act

http://numismatics.org/the-beginnings-of-the-secret-service/

https://www.justice.gov/usao-edny/pr/captain-and-10-members-and-associates-gambino-crime-family-plead-guilty-crimes

#98 Why is cold fusion not possible?

Image By Stevenkrivit at the English-language Wikipedia, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=5766203

https://www.nationalgeographic.com/science/article/cold-fusion-remains-elusive-these-scientists-may-revive-quest

https://en.wikipedia.org/wiki/Cold_fusion

https://www.seeker.com/5-reasons-cold-fusion-is-bunk-1767562536.html

https://www.scientificamerican.com/article/what-is-the-current-scien/

https://en.wikipedia.org/wiki/Nuclear_fusion

https://en.wikipedia.org/wiki/Main_sequence

https://en.wikipedia.org/wiki/Coulomb%27s_law

https://en.wikipedia.org/wiki/Weak_interaction

https://science.howstuffworks.com/fusion-reactor2.htm

https://www.euro-fusion.org/fusion/fusion-on-the-sun/

https://medium.com/the-infinite-universe/cold-fusion-may-not-be-fusion-2e7238f38b80

#99 What is a Lagrange point?

Image By Lagrange_points.jpg: created by NASAderivative work: Xander89 (talk) – Lagrange_points.jpg, CC BY 3.0, https://commons.wikimedia.org/w/index.php?curid=7547312

https://en.wikipedia.org/wiki/James_Webb_Space_Telescope

https://astronomy.com/magazine/ask-astro/2021/10/ask-astro-how-and-why-do-satellites-orbit-lagrange-points

https://en.wikipedia.org/wiki/Lagrange_point

https://en.wikipedia.org/wiki/Leonhard_Euler

https://en.wikipedia.org/wiki/Joseph-Louis_Lagrange

https://solarsystem.nasa.gov/resources/754/what-is-a-lagrange-point/

https://en.wikipedia.org/wiki/Centripetal_force

https://en.wikipedia.org/wiki/Orbit

https://www.space.com/30302-lagrange-points.html

https://www.esa.int/Science_Exploration/Space_Science/Herschel/L2_the_second_Lagrangian_Point

https://www.scientificamerican.com/article/what-is-a-lagrange-point/

https://flexbooks.ck12.org/cbook/ck-12-physics-flexbook-2.0/section/5.4/primary/lesson/orbital-motion-phys/

https://www.nesdis.noaa.gov/news/why-dont-satellites-fall-out-of-the-sky

https://www.physicsclassroom.com/class/circles/Lesson-4/Circular-Motion-Principles-for-Satellites

#100 Who came up with the phrase “flight or fight”?

Photo by Vinicius Altava: https://www.pexels.com/photo/scared-fox-on-gravel-ground-near-field-in-autumn-2675801/

https://en.wikipedia.org/wiki/Fight-or-flight_response

https://en.wikipedia.org/wiki/Walter_Bradford_Cannon

https://www.health.harvard.edu/staying-healthy/understanding-the-stress-response

https://en.wikipedia.org/wiki/Hypothalamic%E2%80%93pituitary%E2%80%93adrenal_axis

https://en.wikipedia.org/wiki/Amygdala

https://en.wikipedia.org/wiki/Hypothalamus

https://en.wikipedia.org/wiki/Adrenaline

https://www.pinnaclehealthchiro.com/blog/how-adrenaline-and-endorphins-can-delay-the-pain-you-feel-after-a-car-accident

#101 Why does our voice change when we inhale helium?

Photo by Natalie Bond: https://www.pexels.com/photo/woman-holding-white-and-red-balloons-3371095/

https://flexbooks.ck12.org/cbook/ck-12-physics-flexbook-2.0/section/12.2/primary/lesson/speed-of-sound-ms-ps/

https://www.tutorialspoint.com/physics_part1/physics_speed_of_sound_in_different_media.htm

https://byjus.com/physics/speed-of-sound-propagation/

https://www.theguardian.com/notesandqueries/query/0,5753,-9439,00.html

https://www.sciencefocus.com/the-human-body/why-does-helium-change-your-voice/

https://wonderopolis.org/wonder/why-does-helium-change-the-sound-of-your-voice

https://pages.mtu.edu/~suits/SpeedofSoundOther.html

https://www.ncbi.nlm.nih.gov/books/NBK534630/

#102 What is the core of Jupiter like?

Photo by @T Keawkanok: https://www.pexels.com/photo/high-definition-photo-of-jupiter-13229882/

https://www.missionjuno.swri.edu/origin?show=hs_origin_story_whats-in-jupiters-core

https://spaceplace.nasa.gov/jupiter/en/

https://en.wikipedia.org/wiki/Jupiter

https://astronomy.com/magazine/ask-astro/2020/10/ask-astro-could-jupiter-ever-become-a-star

https://www.nasa.gov/mission_pages/juno/main/index.html

#103 What is Maslow’s Hierarchy of Needs?

Image By EucalyptusTreeHugger – Own work, https://commons.wikimedia.org/w/index.php?curid=122601755

https://en.wikipedia.org/wiki/Maslow%27s_hierarchy_of_needs

https://en.wikipedia.org/wiki/Abraham_Maslow

https://www.simplypsychology.org/maslow.html

https://www.verywellmind.com/updating-maslows-hierarchy-of-needs-2795269

https://www.quora.com/How-accurate-is-the-Maslows-hierarchy-of-needs

#104 How does a pearl form?

Photo by Marta Branco: https://www.pexels.com/photo/white-pearl-ring-on-blue-surface-1395305/

https://www.jthomasjewelers.com/pages/how-pearls-are-formed

https://www.amnh.org/exhibitions/pearls/what-are-pearls/how-pearls-form

https://en.wikipedia.org/wiki/Pearl

https://www.nhm.ac.uk/discover/quick-questions/how-do-oysters-make-pearls.html

https://en.wikipedia.org/wiki/Conchiolin

https://en.wikipedia.org/wiki/Nacre

#105 How many times can you recycle something?

Photo by Magda Ehlers: https://www.pexels.com/photo/close-up-photo-of-plastic-bottles-2547565/

https://blog.nationalgeographic.org/2018/04/04/7-things-you-didnt-know-about-plastic-and-recycling/

https://en.wikipedia.org/wiki/Recycling

https://earth911.com/business-policy/how-many-times-recycled/

https://recyclenation.com/2017/06/how-many-times-can-recyclables-be-recycled/

https://www.economist.com/technology-quarterly/2007/06/09/the-truth-about-recycling

https://homeguides.sfgate.com/many-times-can-something-recycled-79191.html

https://stacker.com/stories/2682/how-long-it-takes-50-common-items-decompose

#106 When did people start using tissues?

Image CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=109417620

https://www.valmet.com/media/articles/tissue/the-history-of-tissue-products/

https://www.supplytime.com/Blogs/Blog/What-is-the-History-of-Kleenex-Facial-Tissue_111.aspx

https://en.wikipedia.org/wiki/Facial_tissue

https://en.wikipedia.org/wiki/Kimberly-Clark

https://en.wikipedia.org/wiki/Kleenex

https://www.thoughtco.com/history-of-kleenex-tissue-1992033

https://en.wikipedia.org/wiki/Washi

https://en.wikipedia.org/wiki/Japanese_tissue

https://en.wikipedia.org/wiki/Toilet_paper

https://en.wikipedia.org/wiki/History_of_paper

https://en.wiktionary.org/wiki/cellucotton

#107 How do fiber optic cables work?

Photo by Brett Sayles: https://www.pexels.com/photo/fiber-optic-switch-with-bright-connectors-in-studio-4373997/

https://electronics.howstuffworks.com/question402.htm

https://www.explainthatstuff.com/fiberoptics.html

https://en.wikipedia.org/wiki/Fiber-optic_cable

https://www.um.es/docencia/barzana/DIVULGACION/TELEFONIA/Funcionamiento_telefono.html

Fiber Optic Cable History – Fiber Optic Cables for the Telecommunications, Defense and Broadcast TV Industries – Tevelec Limited

https://en.wikipedia.org/wiki/Narinder_Singh_Kapany

https://en.wikipedia.org/wiki/John_Tyndall

https://en.wikipedia.org/wiki/Total_internal_reflection

#108 When did the CIA start?

Image By United States Federal government – Public Domain, https://commons.wikimedia.org/w/index.php?curid=981534

https://en.wikipedia.org/wiki/Central_Intelligence_Agency

https://en.wikipedia.org/wiki/History_of_the_Central_Intelligence_Agency

https://www.history.com/topics/us-government/history-of-the-cia

https://en.wikipedia.org/wiki/Roscoe_H._Hillenkoetter

https://www.washingtonpost.com/world/national-security/black-budget-summary-details-us-spy-networks-successes-failures-and-objectives/2013/08/29/7e57bb78-10ab-11e3-8cdd-bcdc09410972_story.html

#109 What is Jupiter’s Great Red Spot?

Image By Kevin Gill from Los Angeles, CA, United States – Jupiter – Great Red Spot – https://commons.wikimedia.org/w/index.php?curid=127343363

https://www.nasa.gov/feature/goddard/jupiter-s-great-red-spot-a-swirling-mystery

https://wonderopolis.org/wonder/why-is-there-a-great-red-spot-on-jupiter

https://en.wikipedia.org/wiki/Great_Red_Spot

https://www.npr.org/2021/11/09/1052773575/in-jupiters-swirling-great-red-spot-nasa-spacecraft-finds-hidden-depths

https://www.space.com/jupiter-great-red-spot-deeper-than-thought

https://www.nasa.gov/image-feature/jpl/jupiter-s-great-red-spot-a-rose-by-any-other-name

https://www.theverge.com/2021/10/28/22749095/nasa-juno-jupiter-great-red-spot-depth

#110 Why do the sun’s poles flip every 11 years?

Photo by Pixabay: https://www.pexels.com/photo/sun-fire-hot-research-87611/

https://scijinks.gov/solar-cycle/

https://en.wikipedia.org/wiki/Solar_cycle

https://scied.ucar.edu/learning-zone/sun-space-weather/sunspot-cycle

http://ibex.swri.edu/students/How_does_the_Sun.shtml

https://www.nasa.gov/feature/goddard/2016/understanding-the-magnetic-sun

https://www.psfc.mit.edu/vision/what_is_plasma

https://www.windows2universe.org/sun/sun_magnetic_field.html

https://en.wikipedia.org/wiki/Solar_wind

https://en.wikipedia.org/wiki/Heliosphere

https://www.nasa.gov/content/goddard/the-suns-magnetic-field-is-about-to-flip/

https://www.nationalgeographic.com/science/article/earth-magnetic-field-flip-poles-spinning-magnet-alanna-mitchell

3D simulations reveals why the Sun flips its magnetic field every 11 years

https://www.nasa.gov/topics/earth/features/2012-poleReversal.html

#111 What effect did the 1815 Mt. Tambora eruption have?

Image By myself – The base map was taken from NASA picture Image:Indonesia_BMNG.png and the isopach maps were traced from Oppenheimer (2003).[1], CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=1266774

https://www.nationalgeographic.com/science/article/160408-tambora-eruption-volcano-anniversary-indonesia-science

https://en.wikipedia.org/wiki/1815_eruption_of_Mount_Tambora

https://en.wikipedia.org/wiki/Year_Without_a_Summer

https://en.wikipedia.org/wiki/Sumbawa

https://en.wikipedia.org/wiki/Mount_Tambora

https://www.smithsonianmag.com/history/blast-from-the-past-65102374/

https://www.nesdis.noaa.gov/news/day-history-mount-tambora-explosively-erupts-1815

https://www.wired.com/2015/04/tambora-1815-just-big-eruption/

https://en.wikipedia.org/wiki/Volcanic_winter

https://www.scientificamerican.com/article/1816-the-year-without-summer-excerpt/

#112 Why are plants green?

Photo by Lisa Fotios: https://www.pexels.com/photo/selective-focus-photo-of-green-leafed-plant-1207958/

https://www.jic.ac.uk/blog/why-are-plants-green/

https://www.quantamagazine.org/why-are-plants-green-to-reduce-the-noise-in-photosynthesis-20200730/

https://www.ambius.com/learn/plant-doctor/why-are-plants-green/

https://www.nationalgeographic.org/encyclopedia/photosynthesis/

https://www.nationalgeographic.org/encyclopedia/chlorophyll/

https://en.wikipedia.org/wiki/Photosynthesis

https://www.britannica.com/science/photosynthesis/Energy-efficiency-of-photosynthesis

https://www.vernier.com/2018/09/04/what-are-the-best-light-sources-for-photosynthesis/

#113 Why can fish drink saltwater but we can’t?

Photo by Peter Simmons: https://www.pexels.com/photo/gray-and-silver-school-of-fish-underwater-photography-66218/

https://animals.mom.com/how-do-saltwater-fish-deal-with-osmosis-12201571.html

https://www.amnh.org/exhibitions/water-h2o-life/life-in-water/surviving-in-salt-water

https://www.divescotty.com/underwater-blog/why-saltwater-fish-cannot-live-in-freshwater-and-vice-versa.php

https://www.usgs.gov/special-topics/water-science-school/science/water-qa-why-cant-people-drink-seawater

https://www.quora.com/Why-does-salt-dry-out-cells

https://chem.libretexts.org/Courses/College_of_Marin/CHEM_114%3A_Introductory_Chemistry/13%3A_Solutions/13.10%3A_Osmosis-_Why_Drinking_Salt_Water_Causes_Dehydration

https://www.sun.ac.za/english/Lists/news/DispForm.aspx?ID=7172

https://en.wikipedia.org/wiki/Euryhaline

http://www.tristatesteelheaders.com/salmon-in-school/teacher-materials/osmoregulation-surviving-in-salt-and-fresh-water/

#114 What was Sumerian Cuneiform script?

Image By Unknown author – Public Domain, https://commons.wikimedia.org/w/index.php?curid=660521

https://www.britannica.com/topic/Sumerian-language

https://en.wikipedia.org/wiki/Sumerian_language

https://en.wikipedia.org/wiki/Sumer

https://en.wikipedia.org/wiki/Cuneiform

https://en.wikipedia.org/wiki/History_of_writing#Inventions_of_writing

https://en.wikipedia.org/wiki/Jiahu_symbols

https://en.wikipedia.org/wiki/Vin%C4%8Da_symbols

https://omniglot.com/writing/sumerian.htm

https://www.archaeology.org/issues/213-1605/features/4326-cuneiform-the-world-s-oldest-writing

https://www.worldhistory.org/cuneiform/

https://www.livescience.com/25221-drought-killed-sumerian-language.html

https://www.khanacademy.org/humanities/ancient-art-civilizations/ancient-near-east1/the-ancient-near-east-an-introduction/a/cuneiform

#115 How does a pacemaker work?

Image By Johannes Maximilian – Own work, GFDL 1.2, https://commons.wikimedia.org/w/index.php?curid=99390638

https://www.mayoclinic.org/tests-procedures/pacemaker/about/pac-20384689

https://en.wikipedia.org/wiki/Artificial_cardiac_pacemaker

https://en.wikipedia.org/wiki/Cardiac_pacemaker

https://www.bhf.org.uk/informationsupport/how-a-healthy-heart-works

https://www.heart.org/en/health-topics/arrhythmia/prevention–treatment-of-arrhythmia/pacemaker

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6261336/

#116 What causes a nuclear electromagnetic pulse (EMP)?

Photo by Pixabay: https://www.pexels.com/photo/grayscale-photo-of-explosion-on-the-beach-73909/

https://en.wikipedia.org/wiki/Nuclear_electromagnetic_pulse

https://en.wikipedia.org/wiki/Ionization

https://doh.wa.gov/sites/default/files/legacy/Documents/Pubs//320-090_elecpuls_fs.pdf

https://remm.hhs.gov/EMP.htm

https://www.renesas.com/jp/en/document/apn/overview-electromagnetic-and-lightning-induced-voltage-transients?language=en

https://www.wbdg.org/resources/high-altitude-emp-effects-protection

https://www.techtarget.com/whatis/definition/e-bomb-electromagnetic-bomb

#117 When was the first stamp?

Image By General Post Office of the United Kingdom of Great Britain and Ireland – Public Domain, https://commons.wikimedia.org/w/index.php?curid=99603

https://www.thoughtco.com/history-of-stamps-1992419

https://en.wikipedia.org/wiki/Postage_stamp

https://en.wikipedia.org/wiki/Post_office

https://en.wikipedia.org/wiki/General_Post_Office

https://about.usps.com/who/profile/history/stamps-postcards.htm

https://www.smithsonianmag.com/history/stamps-what-an-idea-148588334/

http://websites.umich.edu/~ece/student_projects/money/denom.html

https://norbyhus.dk/btpb.html

#118 Why do things taste different?

Photo by Suzy Hazelwood: https://www.pexels.com/photo/cheesecake-1126359/

https://en.wikipedia.org/wiki/Taste_bud

https://en.wikipedia.org/wiki/Taste_receptor

https://www.ncbi.nlm.nih.gov/books/NBK279408/

https://www.webmd.com/diet/features/science-how-we-taste

https://en.wikipedia.org/wiki/Taste

#119 What is the gambler’s fallacy?

Photo by Pixabay: https://www.pexels.com/photo/cards-casino-chance-chip-269630/

https://www.investopedia.com/terms/g/gamblersfallacy.asp

https://en.wikipedia.org/wiki/Gambler%27s_fallacy

https://en.wikipedia.org/wiki/Faulty_generalization#Hasty_generalization

https://thedecisionlab.com/biases/gamblers-fallacy

https://byjus.com/coin-toss-probability-calculator/

https://www.casino.org/roulette/odds/

https://www.gamblingsites.com/blog/17-facts-about-roulette-that-will-surprise-your-friends-12024/

https://www.statista.com/statistics/221031/total-worldwide-casinos-by-region/

#120 How do cows produce milk?

Photo by cottonbro studio: https://www.pexels.com/photo/white-and-brown-cow-on-brown-soil-4910809/

https://en.wikipedia.org/wiki/Dairy_cattle

https://en.wikipedia.org/wiki/Milk

https://www.organicvalley.coop/blog/from-grass-to-glass-how-do-cows-make-milk/

https://www.dairy.com.au/dairy-matters/you-ask-we-answer/is-it-true-that-cows-can-only-produce-milk-if-they-have-been-pregnant

https://www.highlightskids.com/explore/science-questions/how-do-cows-produce-milk

https://en.wikipedia.org/wiki/Lactation

https://en.wikipedia.org/wiki/Dayak_fruit_bat

https://en.wikipedia.org/wiki/Lactase_persistence

https://en.wikipedia.org/wiki/Udder

https://www.babycenter.com/baby/breastfeeding/making-breast-milk-how-your-body-produces-natures-perfect-ba_8785

https://www.groupe-esa.com/ladmec/bricks_modules/brick01/co/ZBO_Brick01_2.html

#121 How do statins work?

Photo by RODNAE Productions: https://www.pexels.com/photo/top-view-of-a-pill-organizer-8580787/

https://en.wikipedia.org/wiki/Cholesterol

https://en.wikipedia.org/wiki/High-density_lipoprotein

https://en.wikipedia.org/wiki/Low-density_lipoprotein

https://en.wikipedia.org/wiki/Very_low-density_lipoprotein

https://en.wikipedia.org/wiki/Bile_acid

https://www.heart.org/en/health-topics/cholesterol/about-cholesterol

https://www.mayoclinic.org/diseases-conditions/high-blood-cholesterol/in-depth/statins/art-20045772

https://www.nhs.uk/conditions/statins/

https://en.wikipedia.org/wiki/Statin#Available_forms

https://www.health.harvard.edu/heart-health/how-its-made-cholesterol-production-in-your-body

https://www.heartuk.org.uk/cholesterol/what-is-cholesterol

https://www.mayoclinic.org/diseases-conditions/high-blood-cholesterol/symptoms-causes/syc-20350800

https://en.wikipedia.org/wiki/List_of_cholesterol_in_foods

https://www.healthline.com/health/high-cholesterol/how-do-statins-work

#122 What problems does aging in humans cause?

Photo by Matthias Zomer: https://www.pexels.com/photo/person-holding-a-stress-ball-339620/

BBC Science Focus Magazine, January 2022

https://www.nature.com/scitable/topicpage/cells-can-replicate-their-dna-precisely-6524830/

https://www.nature.com/scitable/topicpage/dna-replication-and-causes-of-mutation-409/

https://en.wikipedia.org/wiki/Telomere

https://www.sciencefocus.com/the-human-body/what-happens-to-cells-in-our-bodies-when-they-die/

https://www.businessinsider.com/biology-of-aging-why-bodies-get-old-2018-8#cells-become-bad-at-communicating-with-one-another-9

https://www.solongevity.com/en/news-en/why-dowe-age-identify-9-biological-causes/

https://www.frontiersin.org/articles/10.3389/fendo.2018.00258/full

https://www.medicaldaily.com/scientists-have-identified-9-signs-aging-which-ones-are-affecting-you-246567

#123 What is a dwarf galaxy?

Photo by Alex Andrews: https://www.pexels.com/photo/photo-of-supernova-in-galaxy-3805983/

https://en.wikipedia.org/wiki/Dwarf_galaxy

https://en.wikipedia.org/wiki/Dwarf_elliptical_galaxy

https://en.wikipedia.org/wiki/Irregular_galaxy#dwarf_irregular_anchor

https://en.wikipedia.org/wiki/Satellite_galaxies_of_the_Milky_Way

https://en.wikipedia.org/wiki/Sagittarius_Dwarf_Spheroidal_Galaxy

https://en.wikipedia.org/wiki/Small_Magellanic_Cloud

https://esahubble.org/wordbank/dwarf-galaxy/

https://astronomy.swin.edu.au/cosmos/D/dwarf+galaxy

https://www.pnas.org/doi/10.1073/pnas.1914067116

https://www.nasa.gov/feature/goddard/2019/nasa-s-webb-to-unveil-the-secrets-of-nearby-dwarf-galaxies

https://www.cosmotography.com/images/dwarf_galaxy_dark_matter.html

https://www.quantamagazine.org/dwarf-galaxies-dim-hopes-of-dark-matter-20141025/

https://carnegiescience.edu/news/reconciling-dwarf-galaxies-dark-matter

#124 What is a Higgs boson?

Image By Bengt Nyman – Flickr: IMG_7469, CC BY 2.0, https://commons.wikimedia.org/w/index.php?curid=30047307

https://www.latimes.com/science/sciencenow/la-sci-sn-higgs-boson-nobel-explained-20131008-story.html

https://www.theguardian.com/science/video/2012/jul/03/what-is-a-higgs-boson-video

https://www.energy.gov/science/doe-explainsthe-higgs-boson

https://en.wikipedia.org/wiki/Boson

https://simple.wikipedia.org/wiki/Boson

https://www.physicsforums.com/threads/what-does-half-integer-spin-mean.881920/

https://astronomy.com/news/2020/03/the-fifth-force-what-is-it

https://home.cern/science/physics/higgs-boson

https://www.science.org.au/curious/space-time/higgs-boson

https://www.symmetrymagazine.org/article/massless-particles-cant-be-stopped

https://atlas.cern/updates/briefing/higgs-boson-s-shadow

https://home.cern/news/press-release/physics/cern-experiments-announce-first-indications-rare-higgs-boson-process

https://home.cern/science/experiments/how-detector-works

https://www.smithsonianmag.com/science-nature/how-the-higgs-boson-was-found-4723520/

#125 What is the language gene?

Image By SWISS-MODEL – https://swissmodel.expasy.org/repository/uniprot/P23258?template=6v5v, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=86391787

https://www.nationalgeographic.com/science/article/revisiting-foxp2-and-the-origins-of-language

https://www.sciencedirect.com/science/article/pii/S096098221831546X

https://en.wikipedia.org/wiki/FOXP2

https://en.wikipedia.org/wiki/KE_family

https://en.wikipedia.org/wiki/Developmental_verbal_dyspraxia

https://en.wikipedia.org/wiki/FOX_proteins

https://en.wikipedia.org/wiki/Fork_head_domain

https://www.frontiersin.org/articles/10.3389/fnbeh.2016.00197/full

https://www.nature.com/articles/news.2009.1079

Book 1 Sources