How does gravitational lensing account for Einstein’s Cross?

I subscribe to several StackExchange lists ( and receive regular emails notifying me of current questions posted on the forum. I highly recommend the site, particularly for the computer programming forums, but also for the relatively high quality of content offered by members of many of the other forums as well. In the Physics forum I came across this explanation of how gravitational lensing can produce the sort of effect we see here:Einstein's Cross
image courtesy of Wikipedia
This astronomical object has been given the common name “Einstein’s Cross” for some obvious and some not-necessarily-obvious reasons! The ‘Cross’ part of the name is easily understood, but why ‘Einstein’s’? Because we’re not seeing the original object here. What we see are four nearly identical images of an object nearly exactly in-line with and hidden behind that object in the middle! For an interesting and in-depth explanation of how this works, I refer you to the Physics StackExchange forum. It’s totally fascinating!
Einstein's Cross - Math
(diagram reproduced here from the StackExchange site)

Here’s the link to the in-depth explanation: