The speed of light is not fast enough.
Even integer multiples of the speed of light are not fast enough.
Even if you had a ship that could do 10 times the speed of light, getting to a star 40 light years away, a relatively short, ‘neighborhood’ distance in galactic terms, it would still take 4 years to traverse the distance and 4 to get back home.
Unless and until man invents some ‘Star Trek’ type of propulsion system that will allow us to travel the stars in comfort and luxury, then we, as a species are essentially locked within our own solar system.
And so is everyone else in the universe...................
The article isn't about sending humans to Alpha Centauri, it's about sending a probe there. Besides being the nearest star cluster, Alpha's very similar to our own Sun, oh, and I think that's where Spock's ancestors live ;^); Proxima is a red dwarf and the closest of the bunch.