NY to Sydney in two hours? Coming soon

Scramjets, which could make the world a lot smaller--but not necessarily safer--may get off the ground sooner than expected. The peak speed of the fastest jets is currently Mach 3, but engines that break Mach 6 are being tested--and new technologies develop faster than expected. But the breakthrough that could get you around the world in two hours could also be adapted for killer missiles.

Read the full story on Popsci.com: The Hypersonic Age is near.