In video published Wednesday, Cosmos host Neil deGrasse Tyson was asked on his Star Talk radio show whether an alien species could “consist of pure thought or energy and nothing we would recognize as a body or mass.”

“I don’t see why not,” he replied. “Except that mass is energy, and energy is mass, so I can imagine an alien species that is energy. I can imagine it — I can allow my brain to accept the possibility of it — but I don’t know how to portray it.”

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“However, it’s hard to create form out of energy,” he continued. “When energy becomes matter, you can make molecules, and things and objects and brains. Without [form], energy’s amorphous, and it may be harder to make amorphous life than material life.”

Co-host Eugene Mirman responded, “But could you eat it? Could you eat a being made of energy?”

“Actually,” deGrasse Tyson replied, “since the only point of humans eating is to give ourselves energy and nourishment, if there is an alien made of energy, you wouldn’t have to eat it, you’d just have to absorb it.”

Watch the entire exchange on Star Talk below.