I don’t know much about physics or math. My claim to Einsteinian expertise pretty much begins and ends with The Photo. It hangs on my study wall, framed alongside the letter inviting my father to visit Albert Einstein at his home in Princeton. I never tire of looking at it, because it tells a great American story.

There’s my dad, who arrived at Ellis Island in 1904 at six months of age with his mother (to join his father, who had come earlier, fleeing the Czar’s army). Now a thoroughly American gentleman, he’s impeccably dressed in the latest haberdashery circa 1950. His expression and stance signal he’s bursting with pride to be in the living room of the great man’s house on Mercer Street.

Next to him is Einstein—another European immigrant who’d fled oppression—looking the polar opposite of my dapper dad and the very model of a modern genius: rumpled pants, baggy sweater, iconically tangled mane.

They’d met to talk about practical strategies for acting against ethnic and religious hatreds and genocide—a vision born out of the lessons of the Holocaust. Their common goals connected a world-renowned scientist and a New Jersey lawyer who was a grass-roots activist for political reform and racial equality.

So, what I know about relativity owes nothing to scientific knowledge and everything to the lessons of human connection: Sometimes, the movement of things seems to slow to a molasses-like pace, when people feel isolated and marginalized from the levers of change; then there are times when events seem to accelerate, as people come together to make it happen.

Lately, the pace of positive change has picked up at the National Housing Institute, in sync with movements on the grass-roots and national levels.

In a few short months, NHI has launched a redesigned Shelterforce, a state-of-the-art interactive Web site (www.nhi.org and www.shelterforce.org), and a new group blog, www.Rooflines.org. In a matter of weeks, Rooflines’ bloggers have created a conversation that takes NHI far beyond bricks and mortar to the questions that will determine how we revitalize communities in the 21st century. I urge you to visit Rooflines and add your own momentum through your comments.

When I inaugurated Rooflines in early May, I said that it felt like the country is moving out of 40 years in the political wilderness.

In so many ways, the energy is coalescing both in the electoral arena and at the grass-roots level to address the chronic economic, social, and environmental problems that have left the majority of Americans dispirited and yearning for a new set of national priorities.

Charged by that same arc, NHI has reaffirmed its commitment to the examination of the American housing crisis and advocacy for social and economic equity that has spurred us for more than 33 years. And we’ve expanded our purview to include the environmental, educational, and public-health issues that challenge the vitality of communities.

One of the leaders of the reinvigorated progressive movement is Van Jones, founder of Green for All. He’s quoted in Ted Wysocki’s article (on page 15 of this issue’s cover package), saying “We are on the cusp of incredible change.” Green for All’s program for joining the drive for social and economic equity with the goal of environmentally sustainable practices in community development and green-collar job training in low-income communities is accelerating that transformation, as is Majora Carter’s pathbreaking work through Sustainable South Bronx (The Green New Deal , Shelterforce’s interview with Carter, starts on page 8).

Carter and Jones—along with the Democratic Party’s standard-bearer, Barack Obama—exemplify the kind of high-impact leadership that can vault us forward toward diverse, vibrant communities in a more just and equitable society. I have no doubt that Dad and Prof. Einstein would have been on board for this exciting ride.