Gary Steigman, Who Teased Out the Universe’s Dark Secrets, Dies at 76

[JSngry]

https://www.nytimes.com/2017/04/27/science/space/gary-steigman-died-big-bang-astrophysicist.html

Dr. Steigman was one of the ringleaders of cosmology in an era in which astronomy and particle physics were merging. It was a time when scientists were asking giant questions about the cosmos — like why there are matter and galaxies — and seeking answers in the relationships between quantum particles, formed when the universe was a split-second old and ablaze with energies beyond the dreams of earthly particle accelerators...

According to all the laws of physics, when the universe was born in the Big Bang, elementary particles and their antimatter evil-twin opposites — with opposite charges and spins — should be produced in equal, counterbalancing amounts. But all that astronomers could see in the present-day universe was matter. Where did the antimatter go? Were there antimatter stars and galaxies hiding out there?

In his thesis, Dr. Steigman showed that a universe with equal amounts of matter and antimatter would not work. The universe, he concluded, must have become unbalanced in favor of matter in its earliest moments.

Cosmologists are still struggling to understand how that happened....

In collaboration with Dr. Schramm and others, Dr. Steigman continued to refine the Big Bang calculations and investigate their potential consequences for the universe.

One important result of their calculations was a determination that the amount of atomic matter in the universe fell far short of the amount needed to reverse its expansion and cause it to fall back together some day in a Big Crunch. This contradicted reigning theories that the universe was right on the border between eternal expansion and eventual collapse — a so-called flat universe.

In 1980, Dr. Steigman wrote a paper suggesting that huge neutrinos left over from the Big Bang might comprise the missing mass needed to flatten the cosmos. It was one of the first proposals for what became known as dark matter.

He, Dr. Turner and Lawrence Krauss, now at Arizona State, went on to write a prophetic paper in 1984 suggesting that all problems in cosmology could be solved by adopting an old idea — invented by Einstein in 1917 and later abandoned by him — known as the cosmological constant, a long-range cosmic repulsion force.

In 1999, two teams of astronomers discovered that the universe was expanding faster and faster with time, not slowing down, under the influence of some “dark energy” that appeared to behave exactly like Einstein’s cosmological constant.

In 2011, they won the Nobel Prize in Physics.

Amazing...