By the time the universe returns to its present size, it will be contracting at quite a pace, halving its dimensions in about three and a half billion years and accelerating all the time. The fun really starts about ten billion years after this point, however, when the rise in temperature of the cosmic background heat radiation will have become a serious threat. By the time the temperature has risen to about 300K, a planet like the Earth would have difficulty divesting itself of heat. It would begin relentlessly warming up. First, any ice caps or glaciers would melt, then the oceans would start to evaporate. Gradually, the red glow would turn yellow and then white, until the fierce heat radiation bathing the universe would threaten the stars themselves. Unable to radiate away their energy, the stars would build up heat inside and explode. Space would become filled with hot gas-plasma-glowing fiercely and getting hotter all the time. The temperature rises to millions, then billions of degrees, matter that occupies vast regions of space today is squeezed into tiny volumes. The mass of a galaxy occupies a space just a few light-years across. The last three minutes have arrived. The handiwork of the big bang, and of generations of stars in creating heavy chemical elements, is undone in less time than it takes to read a page. Atomic nuclei-stable structures that may have endured for trillions of years-are irreversibly smashed. With the exception of black holes, all other structures have long since been seared into nonexistence. The universe now has an elegant but sinister simplicity. It has but seconds to live. Black holes begin to merge with each other, their interiors little different from the general collapsing state of the universe itself. In the final moments, gravity becomes the all-dominant force, mercilessly crushing matter and space. The curvature of spacetime increases ever faster. Larger and larger regions of space are compressed into smaller and smaller volumes. According to conventional theory, the implosion becomes infinitely powerful, crushing all matter out of existence and obliterating every physical thing, including space and time themselves, at a spacetime singularity(ltm119b)