A recent article from Wired.com walks readers through a clever experiment: with just a few LEGO bricks, a smartphone, and a friend at a distant location, you can estimate the radius of the Earth, much like the ancient Greek scholar Eratosthenes did around 240 BC.
Here’s the gist: build two identical vertical structures from LEGO bricks. Place one at your location and another a significant distance away (ideally at least 100 km). At the same moment, under sunny conditions, measure the length of the shadow cast by each device. Using the height of your LEGO tower and the shadow length, compute the sun-angle above the horizon via the formula θ = arctan(height/shadow length).
Once you have the angular difference between the two sites and know the straight-line distance between them (easily obtained from a map or car odometer), you can estimate Earth’s radius using simple geometry. With careful measurement, you can derive a value close to the accepted mean radius of about 6,371 km.
The article highlights why LEGO works well for this: the uniformity of pieces ensures both devices are effectively identical. No fancy instruments, no advanced sensors, just basic materials, sunlight, and math.
For STEM learners or DIY-minded folks, this experiment offers a hands-on reminder: fundamental concepts such as planetary size can be probed with creative analog methods. It also underlines that curiosity, geometry, and simple tools still hold power in understanding our world.