Interstellar travel is significantly more difficult than spaceflight within our solar system, because the distances involved are vast.
For example, at its farthest, Mars is about 20 light-minutes away from Earth, and even Pluto is only about 4 light-hours distant. But the nearest star to the sun, Proxima Centauri, is more than 4 light-years from Earth, meaning a vehicle traveling at light-speed would take 4 years to arrive.
Since the fastest spaceships ever built can't even approach light speed, a probe or manned vessel would take many, many years to reach even the nearest stars.
That's why the 100-Year Starship initiative, a project started with seed money from the Defense Advanced Research Projects Agency (DARPA ), has targeted the goal of developing a vehicle that could reach another star in 100 years.
Toward that end, the independent, non-governmental 100 Year Starship organization is hosting its public symposium Sept. 13 through Sept. 16 at the Hyatt Regency in Houston. Speakers include symposium chair Mae Jemison, the first female African American astronaut, as well as astronomer Jill Tarter, a co-founder of the Search for Extraterrestrial Intelligence (SETI) Institute, Johnnetta B. Cole, director of the Smithsonian Museum of African Art, space journalist Miles O'Brien, and photographer Norman Seeff.