1) The highest-grossing concert tour of all time is U2's "360° Tour," which earned over $735 million in ticket sales.

2) Sushi is a traditional Japanese dish made of vinegared rice combined with various ingredients, such as raw or cooked seafood, vegetables, and nori (seaweed). It is known for its artful presentation and delicate flavors, and has gained immense popularity worldwide. Sushi can take many forms, including nigiri (hand-pressed rice topped with ingredients) and maki (rolled sushi wrapped in seaweed), and is often enjoyed with soy sauce, wasabi, and pickled ginger.

3) The Earth's core is primarily composed of iron and nickel and is as hot as the surface of the sun.

4) The concept of proportional representation, used in some electoral systems, aims to ensure that political parties' representation in government aligns more closely with the proportion of votes they receive from the electorate.