Using gravitational waves as a measure of the universe's rate of expansion could solve the biggest headache in physics, the so-called "Hubble tension." ...

Rocket Lab plans to launch its Electron rocket from Virginia's Wallops Flight Facility at midnight, Dec.18. The mission will deliver four experimental disk-shaped satellites into orbit for the U.S.

Elon Musk's SpaceX is set to launch a Falcon 9 rocket from Cape Canaveral, Florida. Here are best places to watch liftoff and what time to stream it.