Say for example, how far away coul I get from my nearest capital city, Dublin, without coming back the other way? I initially thought to find out the diameter of the Earth and just divide by two, but isn’t it true that the Earth is not a perfect sphere? In which case, half the diameter would not be accurate. Is there a distance calculator available on the internet?

The Earth’s diameter at the equator is only 25 miles greater than the diameter at the poles, so it isn’t much of an issue. You can do the math.

equator = 7926 miles

polar = 7901 miles

Well if you go with mankind, then the moon is the current limit - though they all returned, but they didn’t have to.

First of all, you forgot about pi. That being said, all you have to do is find your exact coordinates and reverse them.

Of course you didn’t stipulate that you’re looking for the **most direct **answer. You could leave Dublin and wander around in a Dublin-centric spiral for a kazillion years, without ever returning or getting closer.

“Can you tell me the quickest way to Dublin?”

“Well, for one thing, I wouldn’t start from here.”

If you work it as a spiral, you can go several 100s of thousands of miles without “returning.”

I think the most straight forward answer is obvious.

Half way.

You want half the circumference (assuming a sphere), not half the diameter!