scientists say spacecraft travelling that fast particles hit photons of light . This would cause interstellar aliens to leave light signatures in their orbits . But travelling so fast means there will be significant interference from photons . A collision with a single dust grain would release particles equal to kilograms ( 250 lb ) of exploding TNT .
Engineers say spacecraft travelling that fast would hit photons of light . This would cause interstellar aliens to leave light signatures in their wake . But travelling so fast means there will be significant drag from photons . A collision with a single dust grain would release energy equal to 5291lbs ( 2,400kg ) of exploding TNT .