article_snippet: This means a spaceship would collide with thousands of billions of  photons every second creating something known as electron-positron pairs.
article_snippet: Each of these pairs would cause drag on a spaceship. '
article_snippet: Not necessarily, according to one scientist.
article_snippet: In general one can imagine the same interactions that occur in a particle accelerator to occur between relativistic spacecraft and interstellar matter,' write the authors in the authors study.
article_snippet: Our assumption that matter-matter interactions can be dealt with when civilisation can build relativistic spacecraft may prove false and may be a barrier that will prevent space travel [at relativistic speeds],' write The engineers.
highlights_snippet: Engineers say spacecraft travelling that fast would hit photons of light .
  
highlights_snippet: But travelling so fast means there will be significant drag from photons .
  