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Astronomy & Astrophysics JUNE/JULY 2020 | SCIENTIFICAMERICAN.COM Space&Physics Plus: DOUBTS ABOUT DARK A Lopsided MATTER’S EXISTENCE Universe? IN THE HEARTS OF A new x-ray survey of NEUTRON distant galaxies suggests STARS that the universe is expanding unevenly APOLLO 13: 50 YEARS WITH COVERAGE FROM LATER FROM THE SPACE EDITOR &PHYSICS Your Opinion Matters! Help shape the future of this digital magazine. Let us know what you think of the stories within these pages by emailing us: [email protected]. LIZ TORMES The Beautiful, Irregular Universe In my eighth-grade science class, our teacher explained to us the Doppler effect: that objects moving away from us would display stretched-out sound or light waves, whereas objects moving toward us would show crunched-up sound or light waves. The instructor cited as an example that astronomers could determine whether cosmological objects are moving toward or away from Earth depending on if their light waves were stretched out (redshifted for longer wavelengths) or were shorter wavelengths (blueshifted). This captured my imagination immediately, and I pictured an ever expanding universe spreading out away from Earth evenly like the ripples formed by dropping a stone in a pond. And indeed, measurements of the cosmic microwave background radiation suggest that the uni- XXL); SURVEY verse spread evenly following the big bang. But now, as senior editor Lee Billings reports in this issue’s cover story, the expansion of the universe may not be uniformly distributed but may be occurring more rapidly in certain regions OPTICAL (see “Do We Live in a Lopsided Universe?”). As with much astronomical research, it sometimes takes years to see below the surface of what we thought we understood. Elsewhere in this issue, one candidate source of dark matter is at risk of being ruled out (see “Milky Way Dark Matter CFHT-LS); ( Signals in Doubt after Controversial New Papers”), and be sure to check out some of the Hubble Space Telescope’s most famous images, such as the Eagle Nebula, the Lagoon Nebular, and others (see “A Birthday Message from the X-RAYS Hubble Telescope”). Dive in! On the Cover Andrea Gawrylewski A new x-ray survey Senior Editor, Collections of distant galaxies [email protected] suggests that the universe is expanding unevenly ESA AND XMM-NEWTON ( 2 June-July 2020 WHAT’S Volume 3 • No. 3 INSIDE OPINION 31. A Sobering Astronomical Reminder from COVID-19 We should be grateful for the conditions that allow us to exist at all, because they won’t last forever 33. A Birthday Message from the Hubble Telescope I’m turning 30, and it’s GETTY IMAGES been an amazing journey so far PASIEKA PASIEKA NASA 38. Life as We Don’t NEWS 8. Will String Theory 13. Universe Creates FEATURES Know It 4. Are We Ready Finally Be Put to the All Elements in the 15. Do We Live in a Lopsided Universe? If we’re going to find for Quantum Experimental Test? Periodic Table in A new study of galaxy clusters suggests the extraterrestrials, we need Computers? Physicists have found 10 Minutes cosmos may not be the same in all directions to stop assuming they’ll Hardware hasn’t caught a way the theory might Originally published in 18. Milky Way Dark Matter Signals in Doubt think like humans up with theory, but we’re limit the cosmic inflation July 1948 after Controversial New Papers 40. Remembering already lining up many that is thought to 13. This Black Hole New analyses question whether mysterious Freeman Dyson previously intractable have expanded the Collision Just Made gamma-ray and x-ray light in the galaxy actually In our conversations, he problems for when early universe Gravitational Waves stems from an invisible mass ventured far and wide it does 10. Antimatter Even More 21. The Strange Hearts of Neutron Stars across science, literature 6. Astronomers May Discovery Reveals Interesting Space observations are poised to reveal more and politics, offering Have Captured the Clues about the An unprecedented about the center of one of the universe’s most unorthodox ideas with a First Ever Image of Universe’s Beginning signal from unevenly enigmatic objects bracing self-confidence Nearby Exoplanet New evidence from sized objects gives 27. Apollo 13 at 50 Years: Looking Back Proxima C neutrinos points to one astronomers rare insight at the Mission’s Lost Lunar Science It could be an unpreced- of several theories into how black holes spin Its commander Jim Lovell and pilot Fred Haise ented view of a world about why the cosmos reflect on their fateful, flawed voyage to the moon in the closest planetary is made of matter and system to our own, not antimatter but uncertainties aplenty remain 3 NEWS A recent paper by Google claiming Google achieved this milestone Gate-based quantum computers Are We Ready that a quantum computer performed against the backdrop of a more operate using logic gates, but in for Quantum a specific calculation that would sobering reality: Even the best contrast with classical computers, Computers? choke even the world’s fastest gate-based quantum computers today they exploit inherent properties of classical supercomputer has raised can only muster around 50 qubits. A quantum mechanics such as super- GETTY IMAGES Hardware hasn’t caught up with many more questions than it an- qubit, or quantum bit, is the basic piece position, interference and entangle- theory, but we’re already lining up swered. Chief among them is this: of information in quantum computing, ment. Current quantum computers many previously intractable When full-fledged quantum comput- analogous to a bit in classical comput- are so noisy and error-prone that the problems for when it does ers arrive, will we be ready? ing but so much more. information in its quantum state is lost YUICHIRO CHINO 4 NEWS within tens of microseconds through them on quantum computers. Simu- Current quantum computers are so noisy a mechanism called decoherence and lating quantum physics is the app for and error-prone that the information through faulty gates. quantum computers. They’re not in its quantum state is lost within tens of Still, researchers are making going to be helping you stream video demonstrable, if slow, progress on your smartphone. If large, fault- microseconds through a mechanism called toward more usable qubits. Perhaps tolerant quantum computers can be decoherence and through faulty gates. in 10 years, or 20, we’ll reach the goal built, they will enable us to probe the of reliable, large-scale, error-tolerant strange world of quantum mechanics quantum computers that can solve a to unprecedented depths. It follows model of the quantum computer, the methods in one of the first wide range of useful problems. different rules than the world we which establishes how it will harness small-scale quantum simulations When that day comes, what should observe in our everyday lives and yet quantum mechanics to perform a ever done of a system of electrons, we do with them? underpins everything. useful computation. Researchers in a nuclear magnetic resonance We’ve had decades to prepare. On a big enough quantum comput- write quantum algorithms to perform quantum information processor. In the early 1980s American physicist er, we could simulate quantum field a task or solve a problem using that Others have also followed up on Paul Benioff published a paper theories to study the most fundamen- model. These are basically a se- our work and recently simulated demonstrating that a quantum- tal nature of the universe. In chemistry quence of quantum gates together simple quantum field theories on the mechanical model of a Turing ma- and nanoscale research, where with a measurement of the quantum noisy intermediate-scale quantum chine—a computer—was theoretically quantum effects dominate, we could state that provides the desired computers available today and in possible. Around the same time, investigate the basic properties of classical information. laboratory experiments. Richard Feynman argued that simulat- materials and design new ones to So, for instance, Grover’s algorithm As we wait for the hardware to ing quantum systems at any useful understand mechanisms such as shows a way to perform faster catch up with theory, researchers in scale on classical computers would unconventional superconductivity. searches. Shor’s algorithm has proved quantum information science will always be impossible because the We could simulate and understand that large quantum computers will continue to study and implement problem would get far, far too big: the new chemical reactions and new one day be able to break computer quantum algorithms useful for the required memory and time would compounds, which could aid in security systems based on RSA, a currently available noisy, fault-ridden increase exponentially with the volume drug discovery. method widely used to protect, for machines. But many of us are also of the quantum system. On a quantum By diving deep into mathematics instance, e-mail and financial Web taking a longer view, pushing theory computer, the required resources and information theory, we already sites worldwide. deep into the intersection of quantum would scale up far less radically. have developed many theoretical In my research, my colleagues and physics, information theory, complexi- Feynman really launched the field tools to do these things, and the I have demonstrated very efficient ty and mathematics and opening up of quantum computing when he algorithms are farther along than the algorithms to perform useful compu- new frontiers to explore, once we suggested that the best way to study technology to build the actual ma- tations and study physical systems. have the quantum computers to take quantum systems was to simulate chines. It all starts with a theoretical We have also demonstrated one of us there.
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