The future universe will be very different from the one we know. In about 3 billion years, our galaxy will collide with the Andromeda galaxy. The two galaxies might merge into one large galaxy, or they might rip each other apart. As the universe continues to expand, most scientists believe that 100 billion years from now all galaxies will be so far away from each other that it will not be possible to observe one from another. Between 100 billion years and trillions of years from now, star formation will gradually slow down and cease. Then as stars, brown dwarfs and even black holes die and exhaust their fuel many trillions of years from now, there will eventually be nothing but cold, scattered fundamental particles at very great distances from each other.