The universe is constantly sending us his story. For example: information about what happened for a long time, long long ago, contained in the long-lasting radio waves that are ubiquitous throughout the universe, probably contain the details of how the first stars and black holes were formed. There is a problem, however. Due to our atmosphere and the noisy radio signals generated by modern society, we cannot read them from Earth.
That’s why NASA is in the early stages of planning what it would take to build an automated research telescope on the far side of the moon. One of the most ambitious proposals would be to Lunar crater radio telescope, the largest (by far) full aperture radio telescope dish in the universe. Another duo of projects, called Other side and FarView, would connect a vast array of antennas – ultimately more than 100,000, many of which are built on the moon itself and made from its surface material – to pick up the signals. The projects are all part of NASA’s Institute for Advanced Concepts (NIAC) program, which rewards innovators and entrepreneurs with funding to advance radical ideas in the hopes of creating groundbreaking aerospace concepts. Although still hypothetical and years from reality, the results of these projects could reshape our cosmological model of the universe.
“With our telescopes on the moon, we can invert the radio spectra we record and infer the properties of the very first stars for the first time,” said Jack Burns, cosmologist at the University of Colorado Boulder and co-investigator and scientific manager for FarSide and FarView. “We care about those early stars because we care about our own origins – I mean, where are we from? Where does the Sun come from? Where does the Earth come from? The Milky Way?”
The answers to these questions come from a dark time in the universe about 13.7 billion years ago.
When the universe cooled about 400,000 years after the Big Bang, the first atoms, neutral hydrogen, released their photons in a burst of electromagnetic radiation that scientists can still see today. This cosmic diffuse background, or CMB, was first detected in 1964. Today, scientists use complex tools like the European Space Agency’s Planck probe to detect its minute fluctuations, which create an instant view of the distribution of matter and energy in the young universe. Scientists can also go about a hundred million years to study much of the roughly 13 billion years since the first stars were formed, or “Cosmic Dawn,” using visual data gleaned from starlight by telescopes like Hubble (and soon, the improved James Webb). They allow us to see so far that we are literally looking into the past.
After the initial Big Bang fireball faded into the CMB, but before the first stars started to burn, there was a period when almost no light was emitted into the universe. Scientists call this period of no visible or infrared light “the age of cosmic darkness.” At that time, it seems likely that the universe was very simple, consisting mostly of neutral hydrogen, photons, and dark matter. Evidence of what happened during this period could help us understand how dark matter and dark energy, which our best estimates make up about 95% of the mass of the universe, are yet largely invisible to us and still don’t really understand. – shaped his training.
There are clues to what happened during the Cosmic Dark Ages, hidden in hydrogen, which still makes up the majority of known matter in the universe. Every time the electron spin of a hydrogen atom switches, it emits a radio wave at a specific wavelength: 21 centimeters. But those wavelengths released during the Cosmic Dark Ages are not actually 21 centimeters long by the time they reach Earth. Because the universe is rapidly expanding, the wavelengths of hydrogen also expand, or “redshift,” extending as they travel vast distances. This means that the length of each wave works like a timestamp: the longer the wave, the older it is. By the time they reach Earth, they are rather ten or even 100 meters long, with frequencies below the FM band.