“Mars once was wet and fertile. It’s now bone dry,” said Cosmos host, Neil deGrasse Tyson, “Something bad happened on Mars. I want to know what happened on Mars so that we may prevent it from happening here on Earth.”
In the fall of 1967, Princeton’s great quantum physicist, John Archibald Wheeler was giving a lecture on pulsars at a conference where he was arguing that we should consider the possibility that the center of a pulsar is a gravitationally completely collapsed object. He remarked that one couldn’t keep saying “gravitationally completely collapsed object” over and over. That we needed a shorter descriptive phrase. “How about black hole?” asked someone in the audience, giving birth to the name of one of the most paradoxical objects in the universe.
“In the end, the most improbable and hence the most puzzling aspect of space is its very existence. The simple fact that we live in an apparently smooth and regular three dimensional world represents one of the greatest challenges to the developing quantum theory of gravity,” wrote physicist Lee Smolin in Three Roads To Quantum Gravity. “If you look around at the world seeking mystery, you may reflect that one of the biggest mysteries is that we live in a world in which it is possible to look around, and see as far as we like. The great triumph of the quantum theory of gravity may be that it will explain to us why this is so.”
On Tuesday we wrote that Mars tugs at the human imagination like no other planet. “It’s there,” said astronaut Buzz Aldrin, “waiting to be reached.” Today, NASA launched the Perseverance rover that will, if all goes as planned, touch down at the Jezero Crater landing site in February 2021 as a robotic explorer. Jezero, a 45-kilometre-wide crater is home to the remains of an ancient river delta. NASA researchers have detected deposits of hydrated silica from previous flybys –a mineral that’s especially good at preserving microfossils and other signs of past life.
“In less than a hundred years, we have found a new way to think of ourselves,” observed Stephen Hawking. “From sitting at the center of the universe, we now find ourselves orbiting an average-sized sun, which is just one of millions of stars in our own Milky Way galaxy.” Some of the oldest stars in the universe are found in ancient globular clusters that orbit around the plane, the nucleus, of our home galaxy, which is circled by 150 globular clusters, harboring hundreds of thousands, and sometimes millions of stars, formed very early in the vast halo surrounding the embryonic Milky Way before it flattened to form the spiral disc.
