The Space Force would constitute the sixth branch of the US armed forces.

The news: During a meeting with the National Space Council today, President Donald Trump directed the Department of Defense and the Pentagon to begin work on the creation of the Space Force. He stated, “‘We are going to have the Air Force and we’re going to have the Space Force, separate but equal.”

Some background: This isn’t the first time Trump has brought up this idea. He has continued to express interest in the idea during visits to West Point and in speeches to military members.

What would a Space Force do? Few details have been mentioned so far, but Trump spoke of the new branch as a way to prevent “China and Russia and other countries leading us” in space. What is certain, though, is that a space-bound military force would be exorbitantly expensive. Military missions outside our atmosphere, manned or unmanned, would require a tremendous amount of resources. And space is a place humanity has largely attempted to keep peaceful so far, raising questions of whether something like this sends the right message to other countries—or other planets.