When you walk outside and look at the horizon, you can’t immediately tell that the Earth is round. That’s because we can’t observe it on a scale that really gives us an honest look at the whole Earth.
Of course when we leave the surface, it becomes clearer. Likewise, if we can take certain measurements from different vantage points, geometry can tell us a lot about the size of our planet. Eratosthenes did this in ancient Egypt, over two millennia ago.
Ethan Siegel, in his typically great fashion, tells you all about if we can use similar methods to measure the shape of our universe at Starts With A Bang.
1 million Earths
Have you ever tried to visualize how many Earth’s would fit in the Sun? The Sun’s diameter is roughly 100 times larger than the Earth’s so, in volume, that means around 100x100x100 (1 million) Earth’s fit within the Sun. 1 million is a large number and can be tricky to imagine. The Universe Awareness Project in Germany have created this ball of Earth’s to show exactly that. Each small blue ball represents the Earth. The plastic sphere represents the Sun.
Image credit: UNAWE DE/Stuart
How The Universe Works
Star size comparisons.