After the 11 September 2001 attacks on the United States, border controls were tightened and it became much more difficult for scientists to enter the US. Scientists argue that science requires the free flow of ideas, and that if scientists cannot move freely across international borders, science will suffer.
Some science students wishing to study in the US have had to wait months for a visa. But the State Department, which oversees visa policy accepts that scientists have had to wait too long for visas, but says that the situation is now improving.
