\n<\/p>\n
Amid simmering anxiety about the future of federally funded science, the U.S. government has quietly withdrawn support for cosmology\u2019s next premier project, an experiment that would have given us the best read yet of the strangest chapter in our cosmic origin story.<\/p>\n
Called CMB-S4\u2014or Cosmic Microwave Background Stage 4\u2014the project would have used a suite of new radio telescopes, constructed in Antarctica and Chile, to search the big bang\u2019s faint, ancient afterglow for new clues about the universe\u2019s earliest moments. First conceived in 2013 and repeatedly ranked as a top priority by the nation\u2019s astronomers and physicists, the project carried an estimated $900-million price tag, which was set to be roughly split between U.S. Department of Energy and the National Science Foundation (NSF).<\/p>\n
Yet in a terse, unsigned statement to project leaders on July 10, the two agencies declared they had \u201cjointly decided that they can no longer support the CMB-S4 project.\u201d<\/p>\n
If you’re enjoying this article, consider supporting our award-winning journalism by subscribing. By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today.<\/p>\n
\u201cWe knew things weren\u2019t looking good,\u201d says John Carlstrom of the University of Chicago, the project\u2019s principal investigator. \u201cThey had warned us that it was not the time to start any big projects, given all the budget areas and all the uncertainty. But whether they would continue to drag us out or have a clean break or try to do something\u2014that was unknown.\u201d<\/p>\n
Without federal support, Carlstrom says, the project is essentially canceled. Although abrupt, the decision follows years of concern about the decay of U.S. Antarctic scientific infrastructure, exacerbated by hesitations from both agencies about starting big new projects in the face of ongoing federal budget uncertainty.<\/p>\n
Still, the decision \u201cis a tremendous loss for science and also for the U.S. as the leader in science. It\u2019s a big blow to the community,\u201d says Hitoshi Murayama, a physicist at the University of California, Berkeley, and chair of the once-a-decade Particle Physics Project Prioritization Panel, which in 2023 ranked CMB-S4 as the highest priority for construction. The project also received a high ranking in 2021 from the U.S. astronomy and astrophysics community via a similar but separate process, the Decadal Survey on Astronomy and Astrophysics 2020 (Astro2020) .<\/p>\n
\u201cIf the agencies are really saying it\u2019s over, scientifically, that\u2019s awful,\u201d says Joel Parriott, the American Astronomical Society\u2019s director of external affairs and public policy. \u201cAnd for the people involved, that\u2019s devastating.\u201d<\/p>\n
The universe burst into existence some 13.8 billion years ago, and the unfolding sweep of cosmic evolution eventually led to us.<\/p>\n
\u201cWhat kind of universe created intelligent beings that can go and look at the first instants and understand how everything evolved?\u201d Carlstrom says.<\/p>\n
Perhaps the most curious aspect of that beginning is the wealth of circumstantial evidence suggesting that in the first minuscule moments after the big bang, the universe underwent an almost inconceivably exponential expansion\u2014a ballooning so violent it shook the fabric of the newborn cosmos. This \u201ccosmic inflation\u201d would have left indelible ripples in spacetime called primordial gravitational waves. Today they would be visible as subtle, swirly fingerprints in the big bang\u2019s relict radiation. Known as the cosmic microwave background, or CMB, that radiation is a diffuse light that permeates all of space. CMB-S4\u2019s flagship objective was to detect those signature swirls in the CMB and clinch the case for cosmic inflation.<\/p>\n
\u201cThere are a few different signatures that would be consistent with inflation, and some of them we\u2019ve already seen,\u201d says Jo Dunkley, an astrophysicist at Princeton University. \u201cBut the tensor fluctuation\u2014these gravitational waves\u2014they would be much stronger evidence than we currently have.\u201d<\/p>\n
First observed in 1965, the CMB has become a treasure trove for cosmologists, who use it to look back in time and study the characteristics of the very early universe. But even after 60 years of observations, we\u2019ve only scratched the surface of what\u2019s possible to see in this faint light. With CMB-S4 and other next-generation observatories, scientists have aimed for multiple breakthroughs, ranging from precisely measuring the energies at play in the first instants of creation to constraining the properties of dark energy, the still-mysterious force that drives the universe\u2019s accelerating expansion. Along the way, almost as a bonus, advanced CMB studies could also reveal new particles, clarify the nature of known ones (such as neutrinos) and identify the earliest seeds of sprawling galaxy clusters and other large-scale cosmic structures.<\/p>\n
A key signal of cosmic inflation would be patterns of swirling ripples imprinted on the cosmic microwave background by primordial gravitational waves. The swirls seen here, however, in data from the BICEP2 telescope, ultimately proved to be contamination from dust in our own galaxy.<\/p>\n
Science History Images\/Alamy Stock Photo<\/p>\n
\u201cThe CMB is a way that we might learn about physics at scales that are completely inaccessible in any other way,\u201d says David Spergel, a theoretical astrophysicist and president of the Simons Foundation.<\/p>\n
To definitively detect\u2014or rule out\u2014those inflation-scrawled swirls, scientists need to make very deep and detailed observations of the CMB. That\u2019s something best done from space, above Earth\u2019s turbulent, troublesome atmosphere, following in the footsteps of a few earlier CMB-focused satellites from NASA and the European Space Agency. Today such a mission would cost billions of dollars, however, and wouldn\u2019t be amenable to upgrades or enduring operations. Seeking the swirls is feasible (and cheaper) from Earth\u2014presuming you\u2019re able to stare for a long time at the same patch of sky through an exceptionally stable and dry column of air.<\/p>\n
Antarctica, despite its logistical challenges, is one of the very few places on the planet where that\u2019s possible. \u201cThe South Pole is particularly outstanding in that regard,\u201d says Rachel Mandelbaum, a physicist at Carnegie Mellon University, who served on multiple high-profile expert panels that recommended prioritizing CMB-S4. \u201cIf you\u2019re at the pole, as the Earth is rotating, you\u2019re still looking at the same patch of sky.\u201d<\/p>\n
That would make the U.S.\u2019s Amundsen-Scott South Pole Station a natural hosting site for CMB-S4. And in fact, it is already home to a couple of other CMB projects: the South Pole Telescope and the BICEP Array. (Incidentally, the BICEP Array predecessor BICEP2 made its own claim of detecting smoking-gun swirls in the CMB in 2014, although those putative features were soon shown to instead be the work of contaminating dust in our own Milky Way.)<\/p>\n
At the South Pole, with a new five-meter aperture microwave telescope plus an array of nine smaller telescopes and state-of-the-art detectors, CMB-S4 would take an ultradeep look at roughly 3 percent of the sky. It would be much more sensitive than all of its predecessors and more easily able to cut through any contaminating dust.<\/p>\n
To add to CMB-S4\u2019s utility and allure, the project also planned to include two new six-meter telescopes on the summit of Cerro Toco in Chile\u2019s Atacama Desert. High, dry and with a stable atmosphere above, that site is already home to the Simons Observatory, a newly operational set of telescopes that are conducting similar cosmological observations. The additional CMB-S4 telescopes would make nightly observations of huge swaths of galaxy-studded sky in an effort to map visible matter, better understand the dark universe and catch astrophysical transient events in action.<\/p>\n
Altogether, there would have been 550,000 detectors spread between CMB-S4\u2019s two sites, giving the project an unprecedented chance to hunt for clues of cosmic inflation in the universe\u2019s oldest light.<\/p>\n
\u201cI\u2019m kind of mesmerized by how much science there still is to get from the CMB,\u201d says Suzanne Staggs, a physicist at Princeton University and co-director of the Simons Observatory. \u201cIt provides a unique opportunity to understand the early universe.\u201d<\/p>\n
With such a compelling science case\u2014and such strong support from multiple authoritative panels planning the near future of U.S. research\u2014CMB-S4 seemed almost inevitable for a time. \u201cThis project has scientifically been through about every appraisal that it could be, with glowing reviews,\u201d Parriott says.<\/p>\n
Optimistically, the team hoped it might be able to start construction at the two sites in the near future. Then delays started piling up, and a series of rude awakenings began.<\/p>\n
Despite its status as a scientific priority, CMB-S4\u2019s not-so-glowing fate may have been foretold years ago. Chief among its challenges was that prized South Pole location because, while the pole might be ideal for astronomy, it\u2019s not the easiest place on Earth to build and operate sophisticated science facilities. Antarctica is the coldest, driest, windiest, most remote continent on Earth; it demolishes infrastructure without even trying.<\/p>\n
And NSF, which manages the U.S. Antarctic program on behalf of the government, has known for more than a decade that the existing facilities are in desperate need of maintenance. \u201cIf someone hasn\u2019t been following this for a while, they might assume that this is the government pulling back from all kinds of projects,\u201d says Mitch Ambrose, director of science policy news at the American Institute of Physics. \u201cBut in the case of CMB-S4, I think there\u2019s a longer history in terms of the challenges with the infrastructure in Antarctica that have been brewing.\u201d<\/p>\n
In 2011 the White House and NSF convened a panel to evaluate the logistical challenges associated with maintaining U.S. scientific leadership in Antarctica. The panel\u2019s report, released after visits to three Antarctic research stations, noted that activities there \u201care very well managed but suffer from an aging infrastructure\u201d and are hamstrung by \u201cthe lack of a capital budget,\u201d which it described as \u201ca situation that no successful corporation would ever permit to persist.\u201d<\/p>\n
\u201cThe status quo is simply not an option,\u201d the report continued, after noting such deficiencies as a warehouse where forklifts fall through the floor, buildings with gaps so large that snow blows inside and the repeated forced choice between repairing a roof or conducting a science experiment.<\/p>\n
A report from the U.S. National Academy of Sciences followed and also identified the need to shore up crucial Antarctic infrastructure. NSF, correspondingly and with a limited budget, began planning some upgrades. Then 2020 and the COVID pandemic came along, with disruptions to site access and supply chain issues that sent price tags through those crumbling roofs.<\/p>\n
\u201cA lot of that planning really went off the rails during the pandemic in a major way,\u201d Parriott says. \u201cAs somebody who\u2019s spent a lot of time thinking about the U.S. Antarctic program, it\u2019s kind of heartbreaking to see what\u2019s become of it.\u201d<\/p>\n
Since then NSF has struggled to make the required upgrades\u2014a situation that became an ominous portent for projects like CMB-S4. In 2023 the agency paused new projects at the South Pole. In May 2024 NSF definitively told CMB-S4 that the South Pole was off-limits; buildings were sinking into the snow, electrical power was insufficient, and there wasn\u2019t enough room to house essential personnel. As a result, NSF officially declined to move the project toward its next design milestone.<\/p>\n
\u201cWhen the announcement came out a year ago, I was completely shocked,\u201d Staggs says.<\/p>\n
Afterward NSF and the DOE had a simple question for CMB-S4: Could the project proceed without the South Pole site? What if Chile was the only option?<\/p>\n
On June 4 the collaboration submitted a proposal to both agencies that outlined a path forward in Chile at roughly half the cost of the original plan. By constructing one large telescope plus a smaller array of dishes at Cerro Toco and leaning heavily on data-sharing and collaborations with the South Pole Telescope, the Simons Observatory and others, the CMB-S4 collaboration reckoned it could still achieve its scientific objectives, albeit more slowly and less robustly.<\/p>\n
\u201cIn the June plan, the idea was: \u2018Okay, we\u2019re scaling back; we\u2019re working with these other experiments so that allows us to build less.\u2019 And the expectation was that we could get telescopes on the air as early as 2032 … with combined results in 2040, 2041,\u201d Carlstrom says. \u201cYou know, when I started this [in 2013], I thought, \u2018This is going to be great; we\u2019ll get on the air in 2020, and I can retire in 2025.\u201d<\/p>\n
Staggs, the Simons Observatory\u2019s co-director, says both projects\u2019 leaders met multiple times over the past year to talk about the revised plan.<\/p>\n
\u201cEven prior to that, because there was always a plan for part of the CMB-S4 to be in Chile, we had envisioned that eventually the two projects would be working very closely together, at least operationally, but with no details laid out yet,\u201d Staggs says. \u201cAnd we were sort of hoping we would be starting on that right around now\u2014because, with the news that they would need to move to Chile, it seemed it was going to be a good opportunity for us to work together more.\u201d<\/p>\n
But under intense and mounting budgetary pressures, a balance sheet filled with fixed costs for operating cherished existing facilities and a backlog of other projects awaiting construction, the agencies decided to withdraw anyway.<\/p>\n
The agencies \u201cjust had really hard choices to make,\u201d Ambrose says. \u201cThis is the biggest tension point here: the community seems to really want this thing, and yet the agencies aren\u2019t willing to do it.\u201d<\/p>\n
Knocked down hard, scientists who had planned on CMB-S4\u2019s success are now focused on getting back up\u2014and charting a new path forward.<\/p>\n
\u201cIt\u2019s not that the search for primordial gravitational waves won\u2019t happen; it just won\u2019t advance as rapidly as we had hoped,\u201d Spergel says. \u201cI hope this ends up being an opportunity to rethink how we do the science and not a decision to step away from doing what is really exciting and compelling science.\u201d<\/p>\n
In a statement sent to Scientific American, a DOE spokesperson reiterated that \u201cthe scientific case for CMB exploration is strong and compelling\u201d and said that the agency \u201cplans to continue supporting CMB research,\u201d which is described as a core component of the DOE\u2019s high-energy physics program. That includes investigating opportunities to make near-term upgrades to existing experiments at the South Pole and in Chile. (NSF declined to provide comment.)<\/p>\n
\u201cIf these existing projects weren\u2019t there at all, that would be also a different situation,\u201d Dunkley says. \u201cWe\u2019ll have to see how things evolve on that front: How much upgrading or continuation of the projects that are already running can be achieved?\u201d<\/p>\n
One possible solution, Spergel says, is to build as much as possible in Chile to do as much science as possible from there\u2014and then pivot to the South Pole if needed.<\/p>\n
Another possibility that most U.S. researchers seem less eager to mention is to effectively cede leadership in CMB studies to other nations. Japan\u2019s space agency, for instance, is leading development of LiteBIRD (Light Satellite for the Study of B-mode Polarization and Inflation from Cosmic Background Radiation Detection), a space-based CMB mission, for launch in the early 2030s. And on the Tibetan Plateau, China\u2019s Ali Cosmic Microwave Background Polarization Telescope (AliCPT) has recently completed the first of two planned construction phases, with scientific observations soon to begin. The U.S. is involved in both efforts, chiefly via hardware contributions from the federal National Institute of Standards and Technology, but only plays a supporting role. Despite continued U.S. support for CMB experiments in Chile, perhaps the long-sought confirmation of the strangest chapter of cosmic history will come from elsewhere.<\/p>\n
\u201cWe\u2019ll get there eventually,\u201d Carlstrom says. \u201cIt\u2019s just going to be much harder to do without the South Pole, much harder to do without substantial new instrumentation wherever you are, including Chile.\u201d<\/p>\n","protected":false},"excerpt":{"rendered":"
Amid simmering anxiety about the future of federally funded science, the U.S. government has quietly withdrawn support for cosmology\u2019s next premier project, an experiment that would have given us the best read yet of the strangest chapter in our cosmic origin story. Called CMB-S4\u2014or Cosmic Microwave Background Stage 4\u2014the project would have used a suite<\/p>\n","protected":false},"author":1,"featured_media":11901,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[58],"tags":[5413,5414,747,2973,370,188,694,811],"class_list":{"0":"post-11900","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-science","8":"tag-cmbs4","9":"tag-cosmic","10":"tag-ends","11":"tag-inflation","12":"tag-project","13":"tag-study","14":"tag-support","15":"tag-u-s"},"_links":{"self":[{"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=\/wp\/v2\/posts\/11900","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=11900"}],"version-history":[{"count":0,"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=\/wp\/v2\/posts\/11900\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=\/wp\/v2\/media\/11901"}],"wp:attachment":[{"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=11900"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=11900"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=11900"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}