The following letter was sent to the MIT community today by President L. Rafael Reif. To the members of the MIT community, Every day brings fresh evidence that our society has arrived at a turning point. For years, the nation has grown increasingly unstable, the predictable result of tolerating severe economic and racial inequalities. This spring, the sudden crisis of Covid-19 highlighted and magnified those inequalities. And through a cascade of horrific killings of Black Americans, including the public killing of George Floyd, the long crisis of systemic racial injustice…