A new estimate of the local expansion rate — the Hubble constant, or H0 (H-naught) — reinforces that discrepancy.

Using a relatively new and potentially more precise technique for measuring cosmic distances, which employs the average stellar brightness within giant elliptical galaxies as a rung on the distance ladder, astronomers calculate a rate — 73.3 kilometers per second per megaparsec, give or take 2.5 km/sec/Mpc — that lies in the middle of three other good estimates, including the gold standard estimate from Type Ia supernovae. This means that for every megaparsec — 3.3 million light years, or 3 billion trillion kilometers — from Earth, the universe is expanding an extra 73.3 ±2.5 kilometers per second. The average from the three other techniques is 73.5 ±1.4 km/sec/Mpc.

Perplexingly, estimates of the local expansion rate based on measured fluctuations in the cosmic microwave background and, independently, fluctuations in the density of normal matter in the early universe (baryon acoustic oscillations), give a very different answer: 67.4 ±0.5 km/sec/Mpc.

Astronomers are understandably concerned about this mismatch, because the expansion rate is a critical parameter in understanding the physics and evolution of the universe and is key to understanding dark energy — which accelerates the rate of expansion of the universe and thus causes the Hubble constant to change more rapidly than expected with increasing distance from Earth. Dark energy comprises about two-thirds of the mass and energy in the universe, but is still a mystery.

For the new estimate, astronomers measured fluctuations in the surface brightness of 63 giant elliptical galaxies to determine the distance and plotted distance against velocity for each to obtain H0. The surface brightness fluctuation (SBF) technique is independent of other techniques and has the potential to provide more precise distance estimates than other methods within about 100 Mpc of Earth, or 330 million light years. The 63 galaxies in the sample are at distances ranging from 15 to 99 Mpc, looking back in time a mere fraction of the age of the universe.

“For measuring distances to galaxies out to 100 megaparsecs, this is a fantastic method,” said cosmologist Chung-Pei Ma, the Judy Chandler Webb Professor in the Physical Sciences at the University of California, Berkeley, and professor of astronomy and physics. “This is the first paper that assembles a large, homogeneous set of data, on 63 galaxies, for the goal of studying H-naught using the SBF method.”

Ma leads the MASSIVE survey of local galaxies, which provided data for 43 of the galaxies — two-thirds of those employed in the new analysis.

The data on these 63 galaxies was assembled and analyzed by John Blakeslee, an astronomer with the National Science Foundation’s NOIRLab. He is first author of a paper now accepted for publication in The Astrophysical Journal that he co-authored with colleague Joseph Jensen of Utah Valley University in Orem. Blakeslee, who heads the science staff that support NSF’s optical and infrared observatories, is a pioneer in using SBF to measure distances to galaxies, and Jensen was one of the first to apply the method at infrared wavelengths. The two worked closely with Ma on the analysis.

“The whole story of astronomy is, in a sense, the effort to understand the absolute scale of the universe, which then tells us about the physics,” Blakeslee said, harkening back to James Cook’s voyage to Tahiti in 1769 to measure a transit of Venus so that scientists could calculate the true size of the solar system. “The SBF method is more broadly applicable to the general population of evolved galaxies in the local universe, and certainly if we get enough galaxies with the James Webb Space Telescope, this method has the potential to give the best local measurement of the Hubble constant.”

The James Webb Space Telescope, 100 times more powerful than the Hubble Space Telescope, is scheduled for launch in October.

Giant elliptical galaxies

The Hubble constant has been a bone of contention for decades, ever since Edwin Hubble first measured the local expansion rate and came up with an answer seven times too big, implying that the universe was actually younger than its oldest stars. The problem, then and now, lies in pinning down the location of objects in space that give few clues about how far away they are.

Astronomers over the years have laddered up to greater distances, starting with calculating the distance to objects close enough that they seem to move slightly, because of parallax, as the Earth orbits the sun. Variable stars called Cepheids get you farther, because their brightness is linked to their period of variability, and Type Ia supernovae get you even farther, because they are extremely powerful explosions that, at their peak, shine as bright as a whole galaxy. For both Cepheids and Type Ia supernovae, it’s possible to figure out the absolute brightness from the way they change over time, and then the distance can be calculated from their apparent brightness as seen from Earth.

The best current estimate of H0 comes from distances determined by Type Ia supernova explosions in distant galaxies, though newer methods — time delays caused by gravitational lensing of distant quasars and the brightness of water masers orbiting black holes — all give around the same number.

The technique using surface brightness fluctuations is one of the newest and relies on the fact that giant elliptical galaxies are old and have a consistent population of old stars — mostly red giant stars — that can be modeled to give an average infrared brightness across their surface. The researchers obtained high-resolution infrared images of each galaxy with the Wide Field Camera 3 on the Hubble Space Telescope and determined how much each pixel in the image differed from the “average” — the smoother the fluctuations over the entire image, the farther the galaxy, once corrections are made for blemishes like bright star-forming regions, which the authors exclude from the analysis.

Neither Blakeslee nor Ma was surprised that the expansion rate came out close to that of the other local measurements. But they are equally confounded by the glaring conflict with estimates from the early universe — a conflict that many astronomers say means that our current cosmological theories are wrong, or at least incomplete.

The extrapolations from the early universe are based on the simplest cosmological theory — called lambda cold dark matter, or ?CDM — which employs just a few parameters to describe the evolution of the universe. Does the new estimate drive a stake into the heart of ?CDM?

“I think it pushes that stake in a bit more,” Blakeslee said. “But it (?CDM) is still alive. Some people think, regarding all these local measurements, (that) the observers are wrong. But it is getting harder and harder to make that claim — it would require there to be systematic errors in the same direction for several different methods: supernovae, SBF, gravitational lensing, water masers. So, as we get more independent measurements, that stake goes a little deeper.”

Ma wonders whether the uncertainties astronomers ascribe to their measurements, which reflect both systematic errors and statistical errors, are too optimistic, and that perhaps the two ranges of estimates can still be reconciled.

“The jury is out,” she said. “I think it really is in the error bars. But assuming everyone’s error bars are not underestimated, the tension is getting uncomfortable.”

In fact, one of the giants of the field, astronomer Wendy Freedman, recently published a study pegging the Hubble constant at 69.8 ±1.9 km/sec/Mpc, roiling the waters even further. The latest result from Adam Riess, an astronomer who shared the 2011 Nobel Prize in Physics for discovering dark energy, reports 73.2 ±1.3 km/sec/Mpc. Riess was a Miller Postdoctoral Fellow at UC Berkeley when he performed this research, and he shared the prize with UC Berkeley and Berkeley Lab physicist Saul Perlmutter.

MASSIVE galaxies

The new value of H0 is a byproduct of two other surveys of nearby galaxies — in particular, Ma’s MASSIVE survey, which uses space and ground-based telescopes to exhaustively study the 100 most massive galaxies within about 100 Mpc of Earth. A major goal is to weigh the supermassive black holes at the centers of each one.

To do that, precise distances are needed, and the SBF method is the best to date, she said. The MASSIVE survey team used this method last year to determine the distance to a giant elliptical galaxy, NGC 1453, in the southern sky constellation of Eridanus. Combining that distance, 166 million light years, with extensive spectroscopic data from the Gemini and McDonald telescopes — which allowed Ma’s graduate students Chris Liepold and Matthew Quenneville to measure the velocities of the stars near the center of the galaxy — they concluded that NGC 1453 has a central black hole with a mass nearly 3 billion times that of the sun.

To determine H0, Blakeslee calculated SBF distances to 43 of the galaxies in the MASSIVE survey, based on 45 to 90 minutes of HST observing time for each galaxy. The other 20 came from another survey that employed HST to image large galaxies, specifically ones in which Type Ia supernovae have been detected.

Most of the 63 galaxies are between 8 and 12 billion years old, which means that they contain a large population of old red stars, which are key to the SBF method and can also be used to improve the precision of distance calculations. In the paper, Blakeslee employed both Cepheid variable stars and a technique that uses the brightest red giant stars in a galaxy — referred to as the tip of the red giant branch, or TRGB technique — to ladder up to galaxies at large distances. They produced consistent results. The TRGB technique takes account of the fact that the brightest red giants in galaxies have about the same absolute brightness.

“The goal is to make this SBF method completely independent of the Cepheid-calibrated Type Ia supernova method by using the James Webb Space Telescope to get a red giant branch calibration for SBFs,” he said.

“The James Webb telescope has the potential to really decrease the error bars for SBF,” Ma added. But for now, the two discordant measures of the Hubble constant will have to learn to live with one another.

“I was not setting out to measure H0; it was a great product of our survey,” she said. “But I am a cosmologist and am watching this with great interest.”

Co-authors of the paper with Blakeslee, Ma and Jensen are Jenny Greene of Princeton University, who is a leader of the MASSIVE team, and Peter Milne of the University of Arizona in Tucson, who leads the team studying Type Ia supernovae. The work was supported by the National Aeronautics and Space Administration (HST-GO-14219, HST-GO-14654, HST GO-15265) and the National Science Foundation (AST-1815417, AST-1817100).

In the 1950s in the Northern Hemisphere, the four seasons arrived in a predictable and fairly even pattern. But climate change is now driving dramatic and irregular changes to the length and start dates of the seasons, which may become more extreme in the future under a business-as-usual climate scenario.

“Summers are getting longer and hotter while winters shorter and warmer due to global warming,” said Yuping Guan, a physical oceanographer at the State Key Laboratory of Tropical Oceanography, South China Sea Institute of Oceanology, Chinese Academy of Sciences, and lead author of the new study in Geophysical Research Letters, AGU’s journal for high-impact, short-format reports with immediate implications spanning all Earth and space sciences.

Guan was inspired to investigate changes to the seasonal cycle while mentoring an undergraduate student, co-author Jiamin Wang. “More often, I read some unseasonable weather reports, for example, false spring, or May snow, and the like,” Guan said.

The researchers used historical daily climate data from 1952 to 2011 to measure changes in the four seasons’ length and onset in the Northern Hemisphere. They defined the start of summer as the onset of temperatures in the hottest 25% during that time period, while winter began with temperatures in the coldest 25%. Next, the team used established climate change models to predict how seasons will shift in the future.

The new study found that, on average, summer grew from 78 to 95 days between 1952 to 2011, while winter shrank from 76 to 73 days. Spring and autumn also contracted from 124 to 115 days, and 87 to 82 days, respectively. Accordingly, spring and summer began earlier, while autumn and winter started later. The Mediterranean region and the Tibetan Plateau experienced the greatest changes to their seasonal cycles.

If these trends continue without any effort to mitigate climate change, the researchers predict that by 2100, winter will last less than two months, and the transitional spring and autumn seasons will shrink further as well.

“Numerous studies have already shown that the changing seasons cause significant environmental and health risks,” Guan said. For example, birds are shifting their migration patterns and plants are emerging and flowering at different times. These phenological changes can create mismatches between animals and their food sources, disrupting ecological communities.

Seasonal changes can also wreak havoc on agriculture, especially when false springs or late snowstorms damage budding plants. And with longer growing seasons, humans will breathe in more allergy-causing pollen, and disease-carrying mosquitoes can expand their range northward.

Going to extremes

This shift in the seasons may result in more severe weather events, said Congwen Zhu, a monsoon researcher at the State Key Laboratory of Severe Weather and Institute of Climate System, Chinese Academy of Meteorological Sciences, Beijing, who was not involved in the new study.

“A hotter and longer summer will suffer more frequent and intensified high-temperature events — heatwaves and wildfires,” Zhu said. Additionally, warmer, shorter winters may cause instability that leads to cold surges and winter storms, much like the recent snowstorms in Texas and Israel, he said.

“This is a good overarching starting point for understanding the implications of seasonal change,” said Scott Sheridan, a climate scientist at Kent State University who was not part of the new study.

It is difficult to conceptualize a 2- or 5-degree average temperature increase, he said, but “I think realizing that these changes will force potentially dramatic shifts in seasons probably has a much greater impact on how you perceive what climate change is doing.”

Scientists at the University of Washington and the University of Central Florida inoculated 126 species of plants in the sunflower family with powdery mildew, growing 500 plants from seeds that were collected from the wild and provided from the USDA germplasm network. Through this large-scale study, they were able to measure the various plants’ susceptibility to powdery mildew.

“We observed that the amount of disease present on a host can be dependent on where that host lies on the tree of life — that is, the evolutionary history of a host can predict how susceptible that host is to disease,” explained Michael Bradshaw, a plant pathologist involved with the study.

They also measured common plant traits, such as biomass, trichome density, and chlorophyll content, and found that none of them were associated with the disease, underscoring the unimportance of commonly assessed host plant traits in powdery mildew severity and pointing further to the role that evolutionary history plays in plant susceptibility to disease.

“Any tools we can use to predict the severity of a disease can be valuable and improve management guidelines. Especially with fungal pathogens, where there is often a large lag time between the introduction of a pathogen and the formation of an epidemic,” Bradshaw said. “I am hopeful that this research could spur future work and provide ideas and techniques for other researchers studying the evolution of disease.”

This research provides information on species of sunflower plants that are resistant to powdery mildew disease, which can be beneficial to breeding programs. Bradshaw also hopes that this study will inspire other studies that mine the genome of different plant species involved to potentially locate genes involved with resistance.

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Materials provided by American Phytopathological Society. Note: Content may be edited for style and length.

A meta-analysis in The Lancet Global Health, consisting of 48,000 people from 17 studies, found that those with more severe vision impairment had a higher risk of all-cause mortality compared to those that had normal vision or mild vision impairment.

According to the data, the risk of mortality was 29% higher for participants with mild vision impairment, compared to normal vision. The risk increases to 89% among those with severe vision impairment.

Importantly, four of five cases of vision impairment can be prevented or corrected. Globally, the leading causes of vision loss and blindness are both avoidable: cataract and the unmet need for glasses.

The study’s lead author, Joshua Ehrlich, M.D., M.P.H., sought to better understand the association between visual disabilities and all-cause mortality.

The work complements some of Ehrlich’s recent research, also in The Lancet Global Health Commission on Global Eye Health, that highlighted the impact of late-life vision impairment on health and well-being, including its influence on dementia, depression, and loss of independence.

“It’s important these issues are addressed early on because losing your vision affects more than just how you see the world; it affects your experience of the world and your life,” says Ehrlich. “This analysis provides an important opportunity to promote not only health and wellbeing, but also longevity by correcting, rehabilitating, and preventing avoidable vision loss across the globe.”

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Materials provided by Michigan Medicine – University of Michigan. Original written by Jordyn Imhoff. Note: Content may be edited for style and length.

A long-running summer program at Rice University and elsewhere that trains high school girls in basic physics concepts has proven successful in helping them thrive when they take on full courses the next year.

When leaders of Rice’s two-week day camp looked at similar programs beyond Houston, they found participants scored 3% better in high school physics than their counterparts who did not have the equivalent summer experience.

“That doesn’t seem like a lot, but it’s really hard to move the needle on student outcomes, so 3% is significant,” said Carolyn Nichol, an assistant research professor in the Department of Chemistry and director of the Rice Office of STEM Engagement (R-STEM).

The results are detailed in an open-access study by Nichol, lead author Ericka Lawton, and co-authors Carrie Obenland and Matthew Cushing of R-STEM and Christopher Barr of the Rice Office of Research in the American Physics Society journal Physical Review Physics Education Research.

The study is one of two led and recently released by Nichol. The other analyzes the effect of long-term professional development for teachers in engineering education. That study by Nichol, lead author Christina Crawford of R-STEM and co-author Obenland appears in the Journal of STEM Outreach.

The high school study collected years’ worth of generalized data from participating districts for students who studied chemistry but did not participate in a camp, and the same data for those who did. That gave researchers a baseline to compare results for the same set of students after they all took high school physics.

“There wasn’t a self-selection bias where people could say, ‘Oh, girls who go to a physics camp in June already like physics,'” she said, noting Rice and its counterparts typically recruit students from underserved schools. “The girls who were part of the study were matched so their chemistry scores were the same. We didn’t base this on girls who were already accelerating in science.”

The study was based on a philanthropic effort by Rice alumna and trustee Wanda Gass ’78, an engineer who helped develop the first commercially viable digital signal processor during her career at Texas Instruments. She subsequently founded the nonprofit Design Connect Create to encourage girls to pursue STEM (science, technology, engineering, math) studies.

Design Connect Create runs summer camps for multiple school districts across Texas. Nichol said the study is great validation for the physics program that will ideally lead to similar courses in other science-oriented topics.

“When I talk to these girls at Rice, and often they really don’t want to be here,” she said. “They’re very quiet at the start because for the most part, they are being forced to come by their parents. But by the end, they form really wonderful bonds with the other girls. Within two weeks, they are sharing skills and become trusting of each other.

“I think that’s the real reason they go back and are successful in physics,” Nichol said. “They just get this confidence that they can do it.”

The second study sought to show the value of professional development for teachers whose coursework touches on engineering topics but who are not, themselves, engineers. The researchers followed up with teachers who took the 45-hour graduate level course at Rice in 2018 and 2019 to see how they incorporated engineering into their classrooms.

The study found that, based on a set of attributes for adult self-motivation, teachers showed significant improvement in overall self-efficacy — the belief in their own ability to succeed — in engineering instruction.

“I’m an engineer because my dad was an engineer,” said Nichol, who has a doctorate in chemical engineering. “We want engineering in K-12 classrooms because a lot of kids don’t have role models, and we want them to understand that an engineer is somebody who designs and creates new things.”

She said the program that best exemplifies what Rice offers is the NanoEnvironmental Engineering for Teachers course, which gives participants rigorous hands-on experience working on water sustainability projects. The course, a collaboration with the Rice-based and National Science Foundation-backed Nanotechnology Enabled Water Treatment Center, is also offered at Arizona State and the University of Texas at El Paso.

Lawton is associate director for educational leadership and STEM initiatives, Obenland is a lecturer and associate director for outreach and research, Crawford is associate director for science and engineering and Cushing is executive director of R-STEM. Barr is director of assessment and evaluation of STEM programs in the Office of Research.

High operations and maintenance costs and low population density in some rural areas result in prohibitively high service fees — even for a subscriber-owned cooperative structured to prioritize member needs over profits, the analysis found.

Decades ago, cooperatives were key to the expansion of electric and telephone service to underserved rural areas, spurred by New Deal legislation providing low-interest government grants and loans. Public funding for rural broadband access should similarly consider its critical role supporting economic development, health care and education, said Todd Schmit, associate professor in the Charles H. Dyson School of Applied Economics and Management.

“The New Deal of broadband has to incorporate more than building the systems,” Schmit said. “We have to think more comprehensively about the importance of getting equal access to these technologies.”

Schmit is the co-author with Roberta Severson, an extension associate in Dyson, of “Exploring the Feasibility of Rural Broadband Cooperatives in the United States: The New New Deal?” The research was published Feb. 13 in Telecommunications Policy.

More than 90% of Americans had broadband access in 2015, according to the study, but the total in rural areas was below 70%. Federal programs have sought to help close that gap, including a $20.4 billion Federal Communications Commission initiative announced last year to subsidize network construction in underserved areas.

Schmit and Severson studied the feasibility of establishing a rural broadband cooperative to improve access in Franklin County in northern New York state, which received funding for a feasibility study from the U.S. Department of Agriculture’s Rural Business Development Program.

The researchers partnered with Slic Network Solutions, a local internet service provider, to develop estimates of market prices, the cost to build a fiber-to-the-home network, operations and maintenance costs, and the potential subscriber base — about 1,600 residents — and model a cooperative that would break even over a 10-year cycle.

Federal and state grants and member investment would cover almost the entire estimated $8 million construction cost, so that wasn’t a significant factor in the analysis, the researchers said.

But even with those subsidies, the study determined the co-op would need to charge $231 per month for its high-speed service option — 131% above market rates. At that price, it’s unlikely 40% of year-round residents would opt for high-speed broadband as the model had assumed, casting further doubt on its feasibility.

The $231 fee included a surcharge to subsidize a lower-speed service option costing no more than $60 — a restriction the construction grants imposed to ensure affordability. Without that restriction, the high-speed price would drop to $175 and the low-speed climb to $105.

“In short,” the authors wrote, “grants covering investment and capital construction alone do not solve the rural broadband problem, at least in our study area.”

As an alternative — though not one available in Franklin County — Schmit and Severson examined the possibility of an existing rural electric or telecommunications co-op expanding into broadband. They would gain efficiencies from already operating infrastructure such as the poles that would carry fiber lines. In that scenario, the high-speed price improved to $144 a month — still 44% above market rates.

“These systems are very costly to operate and maintain,” Schmit said, “particularly in areas like we looked at that are very low density.”

The feasibility improves with growth in a coverage area’s density and “take rate,” or percentage of potential subscribers signing up at different speeds, according to the analysis. But in Franklin County, the researchers determined a startup co-op would need 14 potential subscribers per mile to break even over 10 years — more than twice the study area’s actual density.

To better serve such areas, Schmit and Severson said, policymakers should explore eliminating property taxes on broadband infrastructure and payments to rent space on poles owned by regulated utilities, which respectively accounted for 16% and 18% of the proposed co-op’s annual expenses. Those measures reduced an expanding rural utility co-op’s high-speed fee to 25% above market rates, a level members might be willing to pay, the authors said.

“Consideration of the public benefits of broadband access arguably needs to be added to the equation,” they wrote. “The case was made for electricity and telephone services in the 1930s and similar arguments would seem to hold for this technology today.”