Human knowledge and tricks with percentages

A bit of a self-indulgent post today.  (OK, even more self-indulgent than usual.)

Suppose your destination is 100 miles away and you've travelled 20 miles. One day you travel another 10 miles, so you have travelled half as much again: you've increased the distance you have travelled by 50%.  Or, in that day, you have gone from having covered 20% of your total distance to having travelled 30%, so you have got 10% closer to your destination.

On another journey your destination is 1000 miles away and you've travelled 20 miles. Again, one day you travel another 10 miles, so you have travelled half as much again: you've increased the distance you have travelled by 50%.  But in this case, in that day, you have gone from having covered 2% of your total distance to having travelled 3%, so you have got 1% closer to your destination.

Then, destination 1000,000 miles away, still increase the distance you've travelled by 50%, but only get 0.001% closer.

But what if your destination is infinitely far away?  Do you get any closer however far you travel? So are you really travelling at all?

Is that what human knowledge is like?  Certainly we know lots more about the universe than we did 1000 years ago, but are we any closer to understanding the universe?

Update: see later post