Scientific mediation is designed to bring out the nonscientific biases that lead scientists to opposite conclusions based on the same scientific knowledge.
Scientific mediation is an idea in response to having a scientific committee composed of experts write a report that poses some solutions to some technological or scientific problem, such a report often papers over the differences or else it might have a majority report and a minority report.
We know that the dark matter has to be pretty cold - moving so slowly that its motion hardly matters - and that allows us to predict in great detail the large scale structure of the universe.
Dark matter is the vast majority of the mass of the entire universe. It’s the mass that holds all galaxies together, and in fact, led to the formation of galaxies. And it also holds clusters together and it made the most important contribution to the organization of the structure of the universe.
Joel Primack: Just as the universe ended its exponential expansion rather abruptly, we’re going to have to do the same thing.
We know that at the beginning of the Big Bang, or depending on how you like to think of it, in the moment just before the Big Bang, the universe underwent a very, very rapid expansion, an exponential expansion. That means that in any given unit of time the universe expanded by a factor of two, and then in the same amount of time, another factor of two and then another factor of two, and so forth. This is explosive growth. And during that period, the skeleton on which the universe would later form, the skeleton of the distribution of galaxies and clusters of galaxies and so forth, was laid down by quantum fluctuations.
most accurate cosmological simulation of the evolution of the large-scale structure of the universe yet
Something I’ve recently been working on is the large scale structure of the universe. We’ve done what I think is generally regarded as the best simulation so far of the very large scale structure of the universe. We’re calling them the Bolshoi Simulations, from the Russian word for grand, great, big. And there’s no question these simulations are all of those adjectives.
But this was just a question of taking the best currently available data and using a huge amount of super computer time and generating a big simulation, a whole suite of big simulations. But the problem that we’re really working on now, and that I think we can largely solve over the next decade, is the origin and evolution of galaxies, including our own home galaxy, the Milky Way.
Probably, a lot of people are impressed by these beautiful images that we get from Hubble Space Telescope, and they think that we must, by now, understand how galaxies work. But the fact is that we don’t. We don’t even understand how stars form. There’s many different classes and theories of how stars form, and we don’t even know which class is right. And if we don’t understand star formation and evolution, we can hardly understand how galaxies form. The actual process of galaxy formation involves ordinary matter, mostly hydrogen and helium at the earliest stages, coming together to make stars and through some mysterious process that isn’t well understood, forming gigantic black holes. Super massive black holes, we call them, with masses of millions to billions of times the mass of our own sun, end up at the centers of all the big galaxies.
The formation process of these supermassive black holes results in the release of an enormous amount of energy. Sometimes we see this as what we call quasars. But even between the quasar phases, there’s still a lot of energy coming out of these massive black holes. That energy interacts and helps to form the galaxies and how the energy from the stars and the stellar evolution process and the super nova that occur at the end of the lives of the massive stars. How all of this interacts to form the galaxies is a big unsolved problem. And the solution is going to involve a combination of wonderful new observations, including with the new Wide Field Camera 3 installed by the astronauts on Hubble Space Telescope in 2009, in the last visit to Hubble and other space telescopes. I hope the James Webb Space Telescope will be launched later this decade and give us wonderful new insights to the early stages of galaxy formation.
Joel R. Primack is a professor of physics and astrophysics at the University of California, Santa Cruz and is a member of the Santa Cruz Institute for Particle Physics.
Primack specializes in the formation and evolution of galaxies and the nature of the dark matter that makes up most of the matter in the universe. After helping to create what is now called the "Standard Model" of particle physics, Primack began working in cosmology in the late 1970s, and he became a leader in the new field of particle astrophysics. His 1982 paper with Heinz Pagels was the first to propose that a natural candidate for the dark matter is the lightest supersymmetric particle. He is one of the principal originators and developers of the theory of Cold Dark Matter, which has become the basis for the standard modern picture of structure formation in the universe. With support from the National Science Foundation, NASA, and the Department of Energy, he is currently using supercomputers to simulate and visualize the evolution of the universe and the formation of galaxies under various assumptions, and comparing the predictions of these theories to the latest observational data.
With Nancy Abrams, he is the author of The View from the Center of the Universe: Discovering Our Extraordinary Place in the Cosmos (Riverhead/Penguin, 2006) and The New Universe and the Human Future: How a Shared Cosmology Could Transform the World (Yale University Press, 2011).