Millions of years ago, a huge asteroid hit what is now the Yucatan Peninsula in Mexico. The global forests and grasslands burned. The smoke from the resulting fires marks one of the greatest extinctions in Earth’s history, including not just dinosaurs but also fish, plankton, ammonites, and plants. A decade-long Ice Age ensued. A war with just a few of the world’s thousands of nuclear weapons targeted on densely populated cities could plunge Earth into the same types of conditions that the dinosaurs experienced. A war involving Russia, NATO, and the United States could kill billions of people. And what is the U.S. doing? It is upgrading and modernizing all components of its nuclear weapons arsenal at a cost of over a trillion dollars.  With the possibility of nuclear war, humans may end up like the dinosaurs.