The Human Body
The remarkable machine you live in, from your bones to your immune system.
What is the largest organ of the human body?
No telescope required. These ten questions cover the essentials of our cosmic neighbourhood — and a few facts that surprise almost everyone.
Our solar system is a handful of planets and a great deal of empty space, all held in place by the Sun, which holds more than 99 percent of the whole system's mass. This quiz covers the essentials and a few facts that surprise most people: that Venus, not Mercury, is the hottest planet because of a runaway greenhouse effect; that Jupiter is more massive than every other planet combined; that Uranus rolls around its orbit tipped almost on its side. You will meet the largest moon, Ganymede, which is bigger than the planet Mercury, and Pluto, reclassified as a dwarf planet in 2006. None of it needs a telescope or a physics degree, and every answer comes with a short explanation of why it is true.
Every question in this quiz is listed below with its correct answer and the reasoning behind it. Play first if you would rather not see the answers — or read through as a study sheet.
Play it insteadAnswer: C. Mercury
Why: Mercury orbits at an average distance of about 58 million kilometres from the Sun.
Answer: C. Jupiter
Why: Jupiter is so massive that its mass is more than twice that of all the other planets combined.
Answer: B. Mars
Why: Iron oxide — essentially rust — on its surface gives Mars its reddish colour.
Answer: D. Saturn
Why: Saturn's bright rings are made mostly of countless pieces of ice and rock.
Answer: A. Ganymede
Why: Ganymede, a moon of Jupiter, is even larger than the planet Mercury.
Answer: B. Uranus
Why: Uranus has an axial tilt of about 98 degrees, so it essentially rolls around its orbit.
Answer: B. The Sun
Why: The Sun holds about 99.8% of the entire system's mass, keeping everything in orbit.
Answer: D. Venus
Why: A runaway greenhouse effect makes Venus hotter than Mercury, with surface temperatures around 465°C.
Answer: D. Pluto
Why: The International Astronomical Union redefined "planet" in 2006, reclassifying Pluto as a dwarf planet.
Answer: B. About 8 minutes
Why: Light travels the roughly 150 million km from the Sun to Earth in about 8 minutes and 20 seconds.
Each correct answer awards 10 XP. There is zero point penalty for incorrect guesses, encouraging learning through exploration.
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What is the largest organ of the human body?
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