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Science
Some questions sit just on the edge of known physics. Others are clean applications of a formula you already met in school. Science experiments on IfSketch keep those two kinds of question separate: if we are extrapolating, we say so. If we are calculating, you can see the inputs.
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- What If Humans Didn't Need Sleep? At 8 hours a night, sleep takes about 26.7 years by age 80. Here's what you'd gain.
- What If You Could Stop Time? A story-style thought experiment, honest about the physics that gets in the way.
- What If Humans Could Breathe Underwater? Breathing is only half of it: depth still costs about one atmosphere every ten metres.
- What If Humans Could Fly? A hover-power estimate from your weight and wingspan, and why muscle-powered flight is borderline.
- What If Gravity Stopped? Weight vanishes but speed doesn't, so the Earth goes straight, the air expands and you float.
Featured in Science
What If Gravity Stopped?
Weight vanishes; velocity does not. Earth goes straight, air expands, people float. A thought experiment with a timer.
Explore this experimentExperiments in Science
10 interactive experiments.
What If Gravity Stopped?
Weight vanishes; velocity does not. Earth goes straight, air expands, people float. A thought experiment with a timer.
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What If Humans Could Breathe Underwater?
Gills would need about 47 litres of seawater a minute at rest, and depth still adds about one atmosphere every 10 metres.
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What If Humans Didn't Need Sleep?
At 8 hours a night, sleep takes about 26.7 years by age 80. See your own figure, and what real sleepless records show.
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What If Humans Could See Infrared?
Set a long-wavelength cutoff and use Wien's law. Body heat peaks near 10 μm, not in near-IR superhero vision.
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What If Humans Could Fly?
A hover-power estimate from weight and wingspan. Muscle-powered human flight is borderline; history agrees, barely.
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What If Sound Travelled Twice as Fast?
Scale 343 m/s and watch thunder delay, conversation lag and a concert hall shrink in time — not in bricks.
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What If Light Travelled Slower?
Slow light as a local delay, then admit that changing c globally would break atoms. Slow glass and a new c are different ideas.
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What If You Fell Through the Earth?
Uniform-density Earth, no friction: about 42 minutes to the other side. With friction, you do not oscillate.
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What If You Could Stop Time?
A narrative thought experiment. If time stopped, light would not move and you could not see. The walking-distance numbers are a story, labelled as one.
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What If You Travelled at the Speed of Sound?
343 m/s at sea level, about 295 m/s at 11 km. Distance is speed × time. A boom is a shock, not a jet performance sim.
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How the science experiments work
Each one changes a single thing, like the speed of sound, gravity or your need for sleep, and follows what a simple, open model says happens next. You can see the inputs and change them. Where the page is calculating from a known formula it shows you the numbers, and where it's reaching beyond known physics it says so.
Which one to try first
If you want the most personal one, start with not needing sleep: it turns your own nights into years. For pure curiosity, stopping time and falling through the Earth are the classics. And if you've ever wondered whether people could fly or breathe underwater, those pages walk through how far the maths gets you.
Thought experiments, not predictions
Here's the thing: these are ways to build intuition, not forecasts. The models are deliberately simple so you can follow every step, and real physics and biology are messier. Every page lists its sources and assumptions, so you can see exactly where the numbers come from.