Context and question: In 1930, Paul Dirac proposed a model of the vacuum as an infinite sea of particles possessing negative energy, called the Dirac sea. This theory helped refine the predictions of his earlier formulated Dirac equation, and successfully predicted the existence of the positron, confirmed two years later. Werner Heisenberg's uncertainty principle formulated in 1927, predict a fundamental limit within which instantaneous position and momentum, or energy and time can be measured. This has far reaching consequences on the "emptiness" of space between particles. In the late 20th century, so-called virtual particles that arise spontaneously from empty space were confirmed.
What did Heisenberg predict the existence of in 1930?
Answer: unanswerable
Context and question: In contrast, Roman expansion into Spain and Gaul occurred as a mix of alliance-seeking and military occupation. In the 2nd century BC, Roman involvement in the Greek east remained a matter of alliance-seeking, but this time in the face of major powers that could rival Rome. According to Polybius, who sought to trace how Rome came to dominate the Greek east in less than a century, this was mainly a matter of several Greek city-states seeking Roman protection against the Macedonian kingdom and Seleucid Empire in the face of destabilisation created by the weakening of Ptolemaic Egypt. In contrast to the west, the Greek east had been dominated by major empires for centuries, and Roman influence and alliance-seeking led to wars with these empires that further weakened them and therefore created an unstable power vacuum that only Rome could fill. This had some important similarities to (and important differences from) the events in Italy centuries earlier, but this time on a global scale.
What effect did the weakening of Ptolemaic Egypt have on nearby areas?
Answer: destabilisation
Context and question: Even during the war, Eritrea developed its transportation infrastructure by asphalting new roads, improving its ports, and repairing war-damaged roads and bridges as a part of the Warsay Yika'alo Program. The most significant of these projects was the construction of a coastal highway of more than 500 km connecting Massawa with Asseb, as well as the rehabilitation of the Eritrean Railway. The rail line has been restored between the port of Massawa and the capital Asmara, although services are sporadic. Steam locomotives are sometimes used for groups of enthusiasts.
How many km of war-damaged roads has Eritrea fixed?
Answer:
unanswerable