We are on the threshold of a new era. With SIM, we will have the capability, for the first time in history, to find New Worlds in our stellar neighborhood. By New Worlds, I mean planets such as our Earth, planets of the right size, and orbiting their parent stars at the right distance.
The urgency of continuing the SIM project is best expressed in the words of the late Carl Sagan in his book, Contact. On page 36, the protagonist of the novel, Dr. Arroway, is arguing the case for SETI, the Search for ExtraTerrestrial Intelligence. Those words, I believe, apply equally to SIM. Here is the relevant quote -
"This is the time to be optimistic. If we lived in any previous time of human history, we could wonder about this all our lives, and we couldn't do a thing to find the answer. But this time is unique. ....Wouldn't you be ashamed of your civilization if we were able to listen and didn't have the gumption to do it?"
SIM will not listen. Rather, it will look. However, the message is the same. This is a special time in which we now live. As a species, we are poised to find, and map, nearby Earths. This is not the time to pause, to turn our backs on the challenge that we face. With the data from SIM, we will be able to answer the question of whether there are Worlds, like our own, circling the nearest stars. As Sagan wrote in Contact,
"Can you think of a more important question?"