After about the 3rd century B.C., no one really thought the earth was flat. that idea became popular with the publication of The Life and Voyages of Christopher Columbus by Washington Irving.
There is, however, a Flat Earth Society, which sprang from interpretations of biblical passages by one Samuel Rowbotham, who took part in public debates with the scientists during much of the 19th Century. The debacle was reminiscent of the flack Charles Darwin endured for his Origin of Species. While Rowbotham's legacy dwindled into obscurity in the mid-20th century, Darwin's legacy, as we all know, lives on with the support of empirical data from scientific research.
Now, it seems Samuel Rowbotham missed the mark on a cosmic level. Scientists now say that while the Earth is obviously not flat, the universe IS.
Astronomically, this "flatness" refers to geometrical constants existing in the cosmos-namely, that light travels in straight lines. Einstein suggested the universe was curved, and it most likely was for a short time after the Big Bang, but now scientists have proven to within a couple of percentage points of certainty, that the expansion of the universe is a very real event, and is expected to continue indefinitely, since there isn't enough matter to make it collapse again into a repeat performance of the great Singularity AKA the Big Bang scientists speak of.
To say that the universe we see is all the universe that IS, however, would be a cosmic understatement. The geometrical "flatness" to which this discovery refers is based on Euclidean geometry and in the context of the "observable" universe. If you're small enough, on a big enough surface, it will always look flat. Thus, we exist in a dimension of time, but time does not exist outside the purview of this universe. Time exists completely in the whole of our universe, so things a billion light years away from us is in a sense "the future"-but it's more complicated than that. Just like when you drive your car down the highway, your final destination exists, even if you haven't reached it yet, and it might take a long period of time to get there. Time, in other words, exists all at once, even when we can't fathom it, nor have any experience of it outside our own past or present. The future is still there.
We know that when the universe was formed from a gas cloud that began to rotate, it was easier for matter to collect on the poles, since centripetal force would push them away at the center belt around the spinning cloud. Thus, this spherical cloud would eventually collapse and expand outward, exponentially, to create our solar system. This is the "flatness" of the Universe. It just means that it's not folded up on itself as it would be if it were spherical, and not flat like a compact disc, but flat like something round that has been mashed down. But parallel lines remain parallel, and triangles always have 180 degrees.
Remember making a round ball with Silly Putty, when you were a kid? And how you'd flatten it with your palm? The universe is sort of like that. What once was curved, now is flat. Now, with your hands, you can pull this squished ball of Silly Putty in all directions, stretching it-that's like the expansion of the universe.
And that's not necessarily suggesting any supreme entity had a "hand" in it. The laws of nature and science took care of that as a matter of course. Just like they did in evolution. Who says the Big Bang wasn't God Himself exploding in a Swan Song of Ultimate creation?
So, FlatHeads rejoice. You have the universe on your side, now.