Tachyons described in the Bosonic String Theory have an imaginary mass. So the square of it is negative. How does gravity laws apply to imaginary masses in the theory? Is there any explanation in the bosonic string theory for black matter and black energy ? These two questions can in fact be condensed into "Aren't black matter and black energy the ones of tachyons" (as per the string theory which recognises them of course). F.