Cosmic strings are theoretical fault lines in the universe, defective links between different regions of space created in the moments after the Big Bang. They are defects in the fabric of the universe, a byproduct of the universe cooling in the first instants after the Big Bang, like thousands of small hairline fractures. They have no width or height, and are also incredibly dense. A string that’s just a mile long would weigh considerably more than Earth. They pack quite a gravitational pull on anything that passes near them, enabling objects attached to a cosmic string to travel at incredible speeds and benefit from time dilation. Yes!