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The current Holocene epoch is considered to be a time period of relatively stable climate compared to earlier geological periods. Still, some significant changes in temperature and sea level did occur. These climatic fluctuations include the Medieval Warm Period and the Little Ice Age, and more recently global warming. Temperature data for the 20th century shows a strong warming from about 1970 to the present day, typically associated with...more
Today's lecture is our second and final lecture on time travel, or more precisely, temporal data structures. Here we will study retroactive data structures, which mimic the "plastic timeline" model of time travel. For example, in Back to the Future, Marty goes back in time, makes changes, and returns to the present that resulted from those changes and all the intervening years. In a partially retroactive data structures, the user can go ba...more
This lecture tells the story of visual satire in London, a city in which caricature flourished like no other. Throughout the 18th and 19th centuries, the people of London have been both amused and outraged by the thousands of social and political satires in paint, paint and engravings which have variously and humorously described London and its people. The enormous body of cartoon images range from the specific to the general: from caricat...more
This lecture is about a cool data structure for maintaining rooted trees (potentially very unbalanced) in O(log n) time per operation. The operations include linking two trees together by adding an edge, and cutting an edge to split a tree into two trees, so the data structure is called link-cut trees. This result is our first solving a dynamic graph problem (where in general we can insert and delete edges); next lecture will see other sol...more
In this lecture, Professor Holloway discusses how race influenced public policy by examining some of the key cultural symbols of the past few decades, all in an effort to answer the question: how is race used in our society? Professor Holloway discusses Bill Clinton's policies in particular, honing in on his ability to connect with the African American community, the controversy surrounding Lani Guinier's cabinet appointment, and his Natio...more
In this lecture, Professor Holloway documents the "Great Migration," beginning in the first decade of the twentieth century and continuing with increasing pace until the mid-1920s. During this time, black Americans relocated from the rural South to the urban North. This general shift in the population marked a moment of self-determination for African Americans, demonstrating that they were prepared to leave behind the lives they had made i...more
The early 1970s marked a moment of social confusion, violence, and cultural excitement carried over from the late 1960s. In this lecture, Professor Holloway canvasses some of the political turmoil of this era and the ways that it was reflected in popular culture. By examining musical achievements like Marvin Gaye's album, What's Going On?, and some of Stevie Wonder's songs recorded around this time, it becomes clear that black cultural pro...more
Professor Freeman discusses when we can consider a revolution to have ended, arguing that a revolution is finally complete when a new political regime gains general acceptance throughout society - and that, for this reason, it is the American citizenry who truly decided the fate and trajectory of the American Revolution. Yet, in deciding the meaning of the Revolution, the evolving popular memory of its meaning counts as well. Founders like...more
More Detail about Activation Records - Layout of Memory During a Function Call, How the Return Address of a Function is Stored on the Stack, Example Showing How an Activation Record is Constructed on the Stack, Setting Up Function Parameters on the Stack, Using the Call Instruction to Jump to the Function, Cleaning Up at the End of a Function and Using the RET Instruction and the Saved Return Address to Return to the Original Function, Gen...more
This lecture continues our theme of dynamic graphs. Beyond surveying results for several such problems, we'll focus on dynamic connectivity, where you can insert and/or delete edges, and the query is to determine whether two vertices are in the same connected component (i.e., have a path between them). We'll cover a few different results for this problem: Link-cut trees (from last lecture) already solve trees in O(lg n). Euler-tour trees ...more
Work by Wöhler and Liebig on benzaldehyde inspired a general theory of organic chemistry focusing on so-called radicals, collections of atoms which appeared to behave as elements and persist unchanged through organic reactions. Liebig's French rival, Dumas, temporarily advocated radicals, but converted to the competing theory of types which could accommodate substitution reactions. These decades teach more about the psychology, sociology, ...more
The first lecture is about "persistence" (which corresponds to the "branching universe" model of time travel). On the one hand, we'd like to remember all past versions of our data structure ("partial persistence"). On the other hand, we'd like to be able to modify past versions of our data structure, forking off a new version ("full persistence"). Surprisingly, both of these goals are achievable with only a constant-factor overhead, in a f...more
