\def\GWslide{\slide{Fusion - milestones}{
\twocolumns{0.5\tw}{
Fission
\bi
\im a
\ei
\credit{wiki/Timeline of nuclear fusion}{https://en.wikipedia.org/wiki/Timeline_of_nuclear_fusion}
}{0.5\tw}{Fusion
\bi
\im 1929-1939:  How fusion powers the stars.
\im 1952: Hydrogen bomb Ivy Mike.
\im 1997: JET 16 MW fusion energy for $\sim$ 4s.
\ei
\credit{wiki/Timeline of nuclear fusion}{https://en.wikipedia.org/wiki/Timeline_of_nuclear_fusion}
}
}}