TV tonight: 'This is Us,' Legends' guest stars

American Experience: Rachel Carson
PBS, 8 ET/PT

As debate rages over the proper response to climate change, American Experience profiles Rachel Carson, who helped give birth to the modern American environmental movement. A scientist and writer, Carson’s best-selling 1962 book Silent Spring awakened the nation to the damage being done to wildlife by pesticides — and to the impact our actions were having on the environment in general.

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DC’s Legends of Tomorrow
CW, 9 ET/PT

This struggling (but already renewed) superhero show moves to a new day and time with an outing that sends the Legends back to 1967 to rescue their former leader, Rip (Arthur Darvill). While the story eventually works itself around to a clever salute to the power of art, the episode as a whole may still leave you wishing the show itself was more artful. There are some fine TV performers here, Neal McDonough, John Barrowman, Brandon Routh, Dominic Purcell and Victor Garber chief among them. But their work tends to get lost among the less riveting performances and the routine action sequences that surround them. This is one show where less, and fewer, might be more.

This Is Us
NBC, 9 ET/PT

The season’s biggest, and most pleasant, surprise offers what the producers promise is a “big episode.” Sounds like an hour fans won’t want to miss — not that they would, anyway.