|MadSci Network: Physics|
I haven't seen Event Horizon, so I'll restrict my comments to Contact. First off, it's a great movie! As a radio astronomer myself, I thought it was not only reasonably accurate, but also captured the "feel" of being a radio astronomer.
The Machine in Contact was designed to open up an Einstein-Rosen bridge. (This was perhaps not made all that clear in the movie, but it is in the novel.) The primary purpose of an E-R bridge is to allow faster-than-light travel (though it could allow for time travel). In Contact, Ellie Arroway ultimately travels to the center of the Milky Way galaxy in less than 18 hours. Without an E-R bridge, it would take a minimum of about 25 000 years.
One of Carl Sagan's concerns in writing Contact was to write an authentically science fiction novel. That is, a fictional story that was as scientifically accurate as was possible. He contacted Kip Thorne, a well-known theoretical physicist, who worked out the details of how Arroway could travel a long distance at a faster than light speed.
So is a Contact-like Machine possible? To the best of our knowledge, there is nothing in the laws of physics that prevents a machine from being constructed which could open an E-R bridge. (In fact, one of the questions that Sagan asked Thorne was, Could a sufficiently advanced civilization figure out a way to bypass the light-speed limit?) Scientifically such a machine is possible. The technology for such a machine is way beyond anything we are capable of doing, and probably will remain so for the foreseeable future. At this point, our fastest space probes travel at something like 1/10000 the speed of light. It is highly unlikely that we will be able to create, anytime soon, an E-R bridge that will take us even to the nearest star.
This distinction between science and technology is a useful one. Our basic scientific understanding of the Universe, as described by the theories of general relativity and quantum electrodynamics, hasn't changed much in the past 30 years or so. (That doesn't mean that we don't know a lot more since then, just that the basic theories of QED and GR are unchanged.) What has changed in the past 30 years has been our level of technology.
For more details on Contact (if you haven't already read the book!), check out the book Carl Sagan's Universe, edited by Terzian and Bilson.
Try the links in the MadSci Library for more information on Physics.