This is another clear cut example of mindless sheep blindly believing whatever they are told. I mean seriously, who here can say that they've been in space? No-one? Right. That's what I thought. You all just believe what you're told like good little boys and girls.
If the Earth was spherical, you would be able to measure this curvature using very large bodies of water. But attempts have been made at places such as Lake Tahoe and the Salton Sea and absolutely no curvature can be detected. Also, consider the fact that the Nile river falls a little less than a single foot over a distance of 1000 miles. Obviously this fact is completely incompatible with the idea of a "spherical" Earth.
As for Astronauts, even if they have been into space (which I seriously doubt due to the overwhelming amount of compelling evidence to suggest that not only did this not in fact happen, but that is completely impossible*) curvature is exactly what you would expect to see when looking at a flat Earth from such an altitude due to the laws of perspective concerning the human eye.
In summary, check your facts (like I have) before you go spouting what you don't realize is absolute nonsense. I would have expected more from sciforums members. I would have thought that you guys, above and beyond everyone else, would have been open minded enough to discover the obvious and fatal inconsistencies inherent in "Spherical Earth Theory". Remember, a scientific theory is essentially no different than any theory that any random person could come up with in the sense that it HAS NOT BEEN PROVEN.
Finally, there are thousands of people in the world who believe that the Earth is flat. That's not many compared to the almost 7 billion people on the planet, but it reminds of those advertisements on TV in which it is stated that "9 out of 10 doctors recommend..." etc etc. When I see this I always think that maybe that one doctor was the truly brilliant one and maybe the other 9 were like, pretty average. Maybe that one doctor understood something that the others didn't, and had an excellent reason to NOT recommend the particular product. So, seriously consider that for a minute. Maybe those thousands of people actually understand something that the rest of you don't.
*Anyone who has seen that "Did we really go to the moon?" documentary will know for a fact that there are various scientific reasons why it is impossible for human beings to even reach orbit let alone remain in actual space for long enough to have study the Earth from such a vantage point.
So there you go. Be careful what you ask for. You may just get it.