Distant points of light – quasars – show us the intervening universe in silhouette. The result is a map of the gas in and between galaxies, expanding with space.

At night, the sky is dark. This familiar fact has some remarkable implications for the history and structure of the universe.

We explain science, both the idealised version to which scientists aspire, and the real version that involves actual human beings. If you are a cosmic revolutionary, who wants to replace the prevailing big bang theory with their own ideas, we explain the importance of mathematical models, publishing, peer review and presentation of your ideas. In particular, we show how to make scientist's human motivations work in your favour.

The big bang theory is not perfect. We lay out the most serious shortcomings, and the observations in the near future that will continue to test it.

Uniform light at just a few degrees above absolute zero bathes the universe, pointing to a time in the past when the universe was hotter and denser.

The universe is smooth on the largest scales, with roughly the same number of galaxies in every large cosmic neighbourhood. But the standard history of the universe won't allow any process to smooth out an initially smooth universe. An addition to the standard model, called cosmic inflation, aims to fill this void.

The farther we look, the more slowly the light from exploding stars (supernovae) fades. This tells us that the expansion of space affects even light, which arrives at Earth more spread out.

The universe has a remarkably consistent elemental composition: about 75% hydrogen, 24% helium, and 1% heavier elements. Stars, for all their element-producing abilities, cannot have created these abundances. This points to another cosmic oven, in the universe’s hotter past.

The farther we look, the redder the light from galaxies appears. This fact points to a remarkable feature of our universe: it is not static. It is expanding.

Various alternatives to the big bang model have been proposed, both inside and outside the scientific literature. We review some examples, and show how they deal (or not) with the evidence of astronomy.

Congenital diaphragmatic hernia (CDH) is a life-threatening surgically correctable congenital birth defect (3/10 000 live-born babies) [1]. Survival chances are dependent on the presence of associated malformations and severity of lung hypoplasia. Mortality remains up to 30% [2]. In the previous chapter we have outlined how fetuses with the suspicion of CDH should be assessed, using genetic testing and modern imaging techniques. Individualized prognosis of isolated CDH can be made prenatally by measurement of lung size, the presence of the liver in the thorax, and the side of the defect [3]. Patients with predicted poor prognosis are ideal candidates for an intervention that may improve the outcome. Such intervention is not aiming at repairing the diaphragmatic defect, as it can be easily closed after birth: it rather should reverse pulmonary hypoplasia (i.e. stimulate lung growth) before birth. Historically this was attempted by anatomical repair of the defect in utero, yet results were suboptimal [4].

• Intracranial pressure (ICP) can be measured by a monitor placed into one of the lateral ventricles; in the subarachnoid, subdural, or epidural spaces; or in the brain parenchyma.
• ICP monitors should be placed in a patient’s nondominant hemisphere (e.g. right hemisphere in a right-handed person).
• Kocher’s point is the external skin landmark most commonly used for insertion; at this point, the catheter trajectory to the frontal horn of the lateral ventricle avoids bridging veins, the superior sagittal sinus, and the motor strip. Kocher’s point is located 2 cm anterior to the coronal suture at the mid-pupillary line (2–3 cm lateral to midline). The coronal suture is approximately 11–12 cm from the base of the nose.
• Alternative sites for placement include Keen’s point, which is located 2.5 cm posterior and superior to the top of the ear (posterior-parietal), a Frazier burr hole (occipital-parietal), and Dandy’s point (occipital).

Twin reversed arterial perfusion sequence (TRAP) is a rare anomaly unique to monochorionic (MC) multiple pregnancies. It is estimated to affect 2.5% of MC pregnancies or 1 in 10 000 pregnancies [1]. TRAP more commonly occurs in monoamniotic than in diamniotic pregnancies, but because diamniotic twins are more common, most TRAP cases are seen in a diamniotic setting. TRAP consists of the combination of a normal-looking twin who pumps blood towards a severely abnormal co-twin. This normal twin is therefore called the ‘pump twin.’ The severely abnormal twin usually does not have a functional heart, hence also the name acardiac twin.