True or False Science Facts

Explore true or false facts about physics, chemistry, light, sound, materials and numbers. Read a statement, then open its answer and explanation

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The metal gallium melts in a person's hand
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True
Gallium melts at about 29.8 degrees Celsius, which is below the normal body temperature of 37 degrees
Source: en.wikipedia.org
Water drops skitter across a very hot pan instead of boiling away at once
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True
Above about 193 degrees Celsius a drop rides on a cushion of its own vapor that insulates it from the metal
Source: en.wikipedia.org
During a partial solar eclipse, gaps in leaves cast tiny crescent Suns on the ground
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True
Each small gap works as a pinhole and casts an image of the partly covered Sun, so the light under a tree forms crescents
Source: eclipse.gsfc.nasa.gov
The roar in a seashell is the sound of the sea trapped inside
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False
The shell's cavity resonates and amplifies background noise from around you, which sounds like waves
Source: en.wikipedia.org
Bathtubs always drain counterclockwise north of the equator and clockwise south of it
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False
Earth's rotation is far too weak at that scale, so the basin's shape and the leftover motion of the water set the swirl
Source: en.wikipedia.org
Crushing a wintergreen mint in the dark gives off small flashes of blue light
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True
Crushed sugar crystals release tiny electric sparks, and wintergreen oil turns their ultraviolet light into blue
Source: en.wikipedia.org
Leaving a fridge door open in a closed room makes the room warmer, not cooler
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True
A fridge pumps heat out of its inside and also turns electricity into heat, so it adds more heat to the room than it removes
Source: van.physics.illinois.edu
Stretching a rubber band quickly makes it slightly warmer
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True
Stretching rubber raises its temperature a little, and letting it snap back quickly cools it by the same amount
Source: en.wikipedia.org
NASA's JPL navigates spacecraft with pi rounded to just 15 decimal places
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True
For its highest-accuracy work, interplanetary navigation, JPL uses 3.141592653589793, which is 15 decimals of pi
Source: jpl.nasa.gov
The white clouds above power plant cooling towers are largely smoke
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False
The plume is warm, saturated air whose water vapor condenses in cooler air, much like your breath on a cold day
Source: en.wikipedia.org
Old window panes are thicker at the bottom because glass slowly flows downhill
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False
Old panes are uneven because of how they were made, and once solid, glass does not flow noticeably
Source: en.wikipedia.org
Radiocarbon dating can tell the age of dinosaur fossils
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False
Carbon-14 dating works only up to about 50,000 years, and dinosaur fossils are millions of years older
Source: en.wikipedia.org
A glass Prince Rupert's drop survives hammer blows on its bulb but bursts if the tail breaks
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True
Its surface is locked in strong compression, so the bulb resists blows, but breaking the tail releases the tension inside and the drop shatters to powder
Source: en.wikipedia.org
The repeating decimal 0.999... is exactly equal to the number 1
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True
0.999... is the sum of the infinite series 9/10 + 9/100 + 9/1000 and so on, which equals exactly 1
Source: math.hmc.edu
In a room of 23 people, it is more likely than not that two share a birthday
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True
With 23 people there are 253 pairs to compare, which pushes the chance of a shared birthday just past 50%
Source: en.wikipedia.org
Humid air is heavier than dry air at the same temperature and pressure
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False
Water vapor molecules are lighter than the nitrogen and oxygen they replace, so moist air is slightly less dense than dry air
Source: en.wikipedia.org
However large the sheet, paper cannot be folded in half more than 7 times
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False
Britney Gallivan folded a 1,200 m roll of toilet paper in half 12 times, showing the limit depends on the paper's length
Source: en.wikipedia.org
Chemically pure water can conduct electricity as well as salt water does
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False
Pure water has almost no ions and is an excellent insulator, at only about 0.055 µS/cm, and dissolved salts make it conduct
Source: en.wikipedia.org
A wing lifts because air above it must meet the air below at the rear edge at the same moment
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False
NASA calls this equal-transit idea wrong, and the air over the top actually reaches the rear edge before the air below
Source: grc.nasa.gov
Stainless steel is never attracted to a magnet
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False
Ferritic, martensitic and duplex stainless steels are magnetic, and only austenitic grades are usually non-magnetic
Source: en.wikipedia.org

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