Through the WormholePhysics Graduate Student Shawn Westmoreland and His Work to be Featured in Television Show Through the Wormhole with Morgan Freeman to Air in Summer of 2013 on Science  

 

 

Last June, physics graduate student Shawn Westmoreland got a call from Hollywood. “I was contacted by producers from the television show Through the Wormhole with Morgan Freeman,” Shawn said, "they wanted me to make an appearance on a future episode because they read a paper that Louis Crane and I wrote back in 2009, which they liked a lot." This paper, entitled ‘Are black hole starships possible?’ speculated that humans will someday venture to the stars in massive starships powered by tiny black holes.

 

“I agreed to do the show because I've always been interested in doing science popularization for television, but never really had the opportunity." Shawn said. Working with television was a very enjoyable and educational experience for him. He worked closely with the writers on crafting a mutually agreeable script over email until filming the segment with a small crew in California on July 25. “I would love to do more television in the future. I hope there will be more opportunities for me.” Shawn said.

 

Shawn WestmorelandSo what is the physical basis for black hole powered propulsion? “As Stephen Hawking famously argued, black holes aren't really black," Shawn explained, “a black hole emits thermal radiation, called Hawking radiation, and the temperature turns out to be inversely proportional to the mass of the black hole.” Louis and Shawn imagined a starship attached to a parabolic reflector. According to their scheme, a very hot black hole is placed at the focus of the reflector and Hawking radiation pushes the ship forward. Meanwhile, another reflector reflects a portion of the Hawking radiation back towards the black hole, which pushes the black hole forward along with the ship. “This is not fundamentally any different from the way that ordinary chemical rockets work,” Shawn pointed out. “Essentially, we're talking about using black holes as fuel instead of chemicals. Although setting up a black hole starship would be a tedious balancing act, at the end of the day it all comes down to the conservation of momentum. As long as a net momentum is expelled out the back of the ship, the ship will move forward. That's how a rocket works. The advantage of using black hole fuel is that, thanks to the Hawking effect, black holes convert their mass into energy with practically 100% efficiency. When chemical rocket fuel is combusted, on the other hand, only about 15 billionths of a percent of the fuel mass is converted into energy. Although chemical rockets can get us around the Solar System, we'll need something much more powerful, like a black hole engine, if we want to visit extrasolar planets.”

 

A corollary to Hawking's famous result on black hole radiation is that black holes don't last forever. Since black holes emit radiation, they will gradually lose mass and evaporate. Louis and Shawn found that there was a fairly narrow range of black holes which would last long enough and be powerful enough for interstellar travel. “We calculated that black holes between 1 and 4 million tons have the right power-to-mass ratio to accelerate themselves up to a significant fraction of the speed of light within a human lifetime. A black hole under 1 million tons would evaporate itself away too fast. A black hole over 4 million tons would be overweight and underpowered."

 

“A black hole with a mass of 1.8 million tons would last about 100 years and would output about 17 million billion watts of power,” Shawn said. “That's about 1000 times the amount of power that the entire world currently consumes on average. What's really mind boggling is that this incredible power source is 300 times smaller than a proton!”

 

Shawn said that he was very keen on making it clear that the idea of a black hole starship is very speculative and that many unsolved theoretical and engineering problems remain. Even if black hole starships are possible, it will be a few centuries before we could actually start to build one. “I understand that the public loves speculation. Obviously, I enjoy speculation too,” Shawn said, “but I think it's hugely important, in fact a moral obligation, to clearly balance speculation with scientific skepticism when talking to the public. I did my best to achieve this.”

 

Shawn's segment of Through the Wormhole will air in early summer of 2013 on the Science channel. 

 

See a copy of the paper ‘Are black hole starships possible?’.