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<jats:p>Numerical simulations have revealed two types of physical structures, made from curved spacetime, that are attached to black holes: tendexes, which stretch or squeeze anything they encounter, and vortexes, which twist adjacent inertial frames relative to each other. When black holes collide, their tendexes and vortexes interact and oscillate (a form of nonlinear dynamics of curved spacetime). These oscillations generate gravitational waves, which can give kicks up to 4000 kilometers per second to the merged black hole. The gravitational waves encode details of the spacetime dynamics and will soon be observed and studied by the Laser Interferometer Gravitational Wave Observatory and its international partners.</jats:p>

<jats:p>The popular conception of black holes reflects the behavior of the massive black holes found by astronomers and described by classical general relativity. These objects swallow up whatever comes near and emit nothing. Physicists who have tried to understand the behavior of black holes from a quantum mechanical point of view, however, have arrived at quite a different picture. The difference is analogous to the difference between thermodynamics and statistical mechanics. The thermodynamic description is a good approximation for a macroscopic system, but statistical mechanics describes what one will see if one looks more closely.</jats:p>

<jats:p>We review the likely population, observational properties, and broad implications of stellar-mass black holes and ultraluminous x-ray sources. We focus on the clear empirical rules connecting accretion and outflow that have been established for stellar-mass black holes in binary systems in the past decade and a half. These patterns of behavior are probably the keys that will allow us to understand black hole feedback on the largest scales over cosmological time scales.</jats:p>

<jats:p>The past 10 years have witnessed a change of perspective in the way astrophysicists think about massive black holes (MBHs), which are now considered to have a major role in the evolution of galaxies. This appreciation was driven by the realization that black holes of millions of solar masses and above reside in the center of most galaxies, including the Milky Way. MBHs also powered active galactic nuclei known to exist just a few hundred million years after the Big Bang. Here, I summarize the current ideas on the evolution of MBHs through cosmic history, from their formation about 13 billion years ago to their growth within their host galaxies.</jats:p>

<jats:title>Transforming Optical Transformations</jats:title> <jats:p> Recent developments in optics and materials have seen interactions between light and matter move to the subwavelength regime. <jats:bold> Pendry <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="549" related-article-type="in-this-issue" vol="337" xlink:href="10.1126/science.1220600">549</jats:related-article> ) review how transformation optics has provided a general platform for controlling and manipulating light, literally transforming the field of optics. The coordinate system that the electric and magnetic components of the light field “feel” can be transformed through materials design by giving rise to exotic optical phenomena such as cloaking, negative refraction, and energy harvesting. </jats:p>

<jats:p>Electron microscopy provides a close-up view of the ninefold-symmetric stacked rings at the base of cilia and flagella.</jats:p>

<jats:title>Big Black Holes</jats:title> <jats:p> Black holes come in two sizes: stellar-mass black holes, with masses just above that of the Sun, and supermassive black holes, with masses up to a billion times that of the Sun. The hyperluminous x-ray source HLX-1 in the spiral galaxy ESO 243-49 is the best candidate to host a black hole of intermediate mass. <jats:bold> Webb <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="554" related-article-type="in-this-issue" vol="337" xlink:href="10.1126/science.1222779">554</jats:related-article> , published online 5 July) now report the detection of transient radio emission from this source, which may represent a jet ejection event. The radio flares indicate a mass that is consistent with that of an intermediate mass black hole. Jets have been seen to emanate from both supermassive and stellar-mass black holes. Intermediate mass black holes thus seem to behave like other black holes. </jats:p>

<jats:title>So Close and So Different</jats:title> <jats:p> In our solar system, the rocky planets have very distinct orbits from those of the gas giants. <jats:bold> Carter <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="556" related-article-type="in-this-issue" vol="337" xlink:href="10.1126/science.1223269">556</jats:related-article> , published online 21 June) report on a planetary system where this pattern does not apply, posing a challenge to theories of planet formation. Data from the Kepler space telescope reveal two planets with radically different densities orbiting the same star with very similar orbital periods. One planet has a rocky Earth-like composition and the other is akin to Neptune. </jats:p>

<jats:title>Unidirectional Growth</jats:title> <jats:p> Block copolymers, in which two dissimilar polymers are covalently joined together, can be designed to form micelles in solution and can be used as self-assembling injectable gels for tissue engineering or wound healing. One challenge is to find ways to create asymmetrical structures, because normally, block addition would occur at both ends of the polymer chain. <jats:bold> Rupar <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="559" related-article-type="in-this-issue" vol="337" xlink:href="10.1126/science.1221206">559</jats:related-article> ; see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6094" page="530" related-article-type="in-this-issue" vol="337" xlink:href="10.1126/science.1225524">Pochan</jats:related-article> </jats:bold> ) devised a route to link together three diblock copolymers with a capping approach. Protecting one end during growth gave rise to asymmetrical structures. </jats:p>