It is always cool to repeat classic experiments. How many of us know the radius of the Earth because we determined it on our own? I haven't done this, at least not yet. For all my life I have just ...

I don't know where he got this idea (surely not from the internet), but Eratosthenes estimated the radius of the Earth by looking at two shadows at two different locations on the Earth. This diagram ...

The Earth's tail is known as the "magnetotail". Though it is generally a permanent feature, it is at the whims of the solar ...

Astronomers may be ready to explain our universe's lack of exoplanets twice the radius of Earth. When you purchase through links on our site, we may earn an affiliate commission. Here’s how it works.