It’s come a long way since then. In 1995, just 14% of U.S. adults used the internet. 42% had never even heard of the internet, and an additional 21% were vague on the concept—”it has something to do with computers, right?”
Now: 87% of adults use the internet. 81% have a computer, 90% have a cell phone, and 46% say it would be very hard to give up the internet.
We’ve got a new report out today that looks at 15+ years of data showing the rapid growth/overall impact of the internet, in honor of the upcoming 25th anniversary of the web.
Could you imagine your life without the internet? What do you think it’d be like?
Accretion flows are ubiquitous in astrophysics: they occur around protostars, accreting compact objects in binary systems, and supermassive black holes at the cores of galaxies. Much of professor James M. Stone's work has concerned studies of the local hydrodynamic and magnetohydrodynamics (MHD) processes that can lead to outward angular momentum transport in accretion disks. As computers become more powerful, previous studies of local patches of an accretion flow are being expanded into global studies that encompass the entire disk.
Accretion flows that cannot cool via emission of radiation become vertically thick and nearly spherical. Thus, they are intrinsically multidimensional. To study the structure and evolution of non-radiative accretion flows, 2D (axisymmetric) hydrodynamical simulations were performed using a non-uniform grid that spanned more than two decades in radius.
The most striking property of the flow is the large fluctuations produced by strong convection. Convective eddies transport a lot of mass both inwards and outwards, but the net mass accretion rate is very small and set by the properties of the flow near the inner boundary. A vanishingly small accretion rate may help to explain the deficit of high energy emission observed from accreting compact sources.
While understanding the properties of hydrodynamical accretion flows is important, it is generally agreed that angular momentum transport is in fact mediated by magnetic stresses. Thus, repeating the global simulations of non-radiative accretion flows with MHD calculations is vital.
History classes in the U.S. – at least in Holly’s and my experience – focus much of their discussion of the civil rights movement on things African-Americans were not allowed to do before it happened. Most of the context relates to segregated restrooms, schools and bus seats, and on restrictions on voting. But there’s a whole other side to that story: the things that only African-Americans were allowed to do. After the abolition of slavery, whole industries hired exclusively African-American workers in order to maintain a sort of plantationesque veneer. This pattern continued to subjugate black people long after slavery was over.
This episode talks about one of those jobs, and the organization that helped make their lives better: the sleeping car porters and the union they formed in the 1920s. This union, the Brotherhood of Sleeping Car Porters, became an important force in the larger context of the civil rights movement.
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