The planetarium darkens. You look up expectantly. It's time for a twenty-five minute journey to the beginning of time and space, the Big Bang. Why do scientists think that our Universe was born in a Big Bang? Why is the Universe dark? The story unfolds, accompanied by superb images and visualizations. This is Dark Universe, and it's a real treat.
The people behind Dark Universe
The American Museum of Natural History in New York created the show in collaboration with some other organizations and the services of a dream team. The script is by Timothy Ferris, my favorite astronomy writer. The evocative music of Robert Miller adds to the film's power. The National Center for Supercomputing Applications and the San Diego Supercomputer Center, using scientific data, were behind the animations. Director Carter Emmart has a string of high-class planetarium films to his credit.
I've commented before on narration of planetarium shows by Hollywood stars. They're good, but they're actors. I have no complaints in this respect about Dark Universe. It's presented by broadcaster, author, astrophysicist, and Director of the Hayden Planetarium, Neil deGrasse Tyson. He may be using a script, but this is a man who knows what he's talking about.
The story doesn't start at the beginning of time. It starts in the 1920s at Mount Wilson in California where Edwin Hubble was studying the spectra of galaxies. If the spectrum of a celestial object is shifted towards the red end of the spectrum, it's moving away from us.
Hubble found that the galaxies were all moving away from us. The farther away they were, the faster they were receding. It's what you would see if space itself were expanding. The expansion is represented by a wonderful scene that was like an animated abstract painting. (In reality, we can't see the expansion.)
Yet if the Universe is expanding now, it must have been smaller in the past. At the very beginning, all the matter and energy of the Universe would be compressed into something smaller than an atom. When this bitsy Universe exploded, it was incredibly hot – much hotter than a star. But it expanded, and as it expanded, it cooled and evolved. This is the Big Bang theory.
Big Bang theory - deuterium
The superhot new Universe was a plasma of positive protons, negative electrons, neutral neutrons, and photons (particles of light). A proton is the nucleus of ordinary hydrogen. Deuterium is a heavier kind of hydrogen - it formed, along with a couple of other light elements, while the Universe was still hot. All the other elements were made much later by stars.
The Big Bang theory says how much ordinary hydrogen and how much deuterium were made in the Big Bang. NASA's Galileo mission released a probe into Jupiter's atmosphere to measure the hydrogen and deuterium there, because Jupiter's strong gravity should have held on to the elements that were present when the Solar System formed. The film lets you feel as if you were there as the probe heads into Jupiter's atmosphere. And the outcome? The ratio of hydrogen to deuterium was as predicted by the theory.
Light from the Universe's infancy
Atoms had simply been positive nuclei when it was too hot to form stable neutral atoms. But about 380,000 years after the Big Bang, it was cool enough for the nuclei and electrons to form atoms, and for the photons to escape. There was a suggestion that these photons were still around. However the Universe had been expanding and cooling for billions of years, so the radiation would be cold and only detectable as microwaves.
In the 1960s, while a group of astronomers discussed how they might detect this microwave radiation, Arno Penzias and Robert Wilson discovered it by accident while working on the Horn Antenna at Bell Labs in New Jersey.
“Dark cosmic sea of invisible stuff”
You may wonder, with all those stars around, why the show is about a dark Universe. It's because only 5% of the Universe is the matter that we see around us. Another 25% is dark matter, matter that has a gravitational effect, but can't be seen. The way it was distributed in the early Universe has determined the evolution of the structure of the Universe. There's a wonderful animation showing how this might have occurred.
And the rest of the Universe? Its expansion seems to be speeding up. No one knows what the cause is, so they've called it dark energy.
I've given you a few highlights of the show, but there's much more to see, and I'd have liked to see even more. If it could have been longer, we might have seen what the current data suggest about the future of the Universe.
I was fortunate to see Dark Universe at the Hayden Planetarium in New York. But if you have a local planetarium – or might visit one while on vacation – check to see if it's showing there. It's well worth seeing.
NOTE: I paid for entry to the planetarium with my own funds.