#Universe sandbox 2 life likelihood free

Indeed, the predictions of the theory have survived all tests to date. Astronomers are not sure, for example, how the galaxies were formed, but there is no reason to think the process did not occur within the framework of the big bang.

At present, there are no fundamental challenges to the big bang theory, although there are certainly unresolved issues within the theory itself. The major claim of the theory is that in the largescale average the universe is expanding in a nearly homogeneous way from a dense early state. Our best efforts to explain this wealth of data are embodied in a theory known as the standard cosmological model or the big bang cosmology. Satellites detect the cosmic background radiation left over from the early stages of expansion, providing an image of the universe on the largest scales we can observe. Particle accelerators probe the basic physics of the high-energy environment of the early universe.

Modern telescopes on the ground and in space detect the light from galaxies billions of light-years away, showing us what the universe looked like when it was young. This knowledge comes from decades of innovative experiments and theories. Our understanding of the genesis and evolution of the universe is one of the great achievements of 20th-century science. Fifteen billion years from now stars like our sun will be relatively rare, making the universe a far less hospitable place for observers like us. Over time the formation of stars has consumed the supply of gas in galaxies, and hence the population of stars is waning. Our solar system is relatively young: it formed five billion years ago, when the universe was two thirds its present size. When the universe was half its present size, nuclear reactions in stars had produced most of the heavy elements from which terrestrial planets were made. By the time the universe had expanded to one fifth its present size, the stars had formed groups recognizable as young galaxies.

The neutral atoms then began to coalesce into gas clouds, which later evolved into stars. Neutral atoms appeared in abundance only after the expansion had continued for 300,000 years and the universe was 1,000 times smaller than it is now. Conditions were still too hot, however, for atomic nuclei to capture electrons. All of this occurred within the first minute of the expansion. After the universe had grown by another factor of 1,000, protons and neutrons combined to form atomic nuclei, including most of the helium and deuterium present today.

#Universe sandbox 2 life likelihood free

When the universe had expanded an additional 1,000 times, all the matter we can measure filled a region the size of the solar system.Īt that time, the free quarks became confined in neutrons and protons. By the time the temperature had dropped to 100 million times that of the sun’s core, the forces of nature assumed their present properties, and the elementary particles known as quarks roamed freely in a sea of energy. He describes these ideas in this article, which he co-wrote for Scientific American in 1994.Īt a particular instant roughly 15 billion years ago, all the matter and energy we can observe, concentrated in a region smaller than a dime, began to expand and cool at an incredibly rapid rate. Editor’s Note (10/8/19): Cosmologist James Peebles won a 2019 Nobel Prize in Physics for his contributions to theories of how our universe began and evolved.