Tech News
Overfishing Has Caused Cod To Halve in Body Size Since 1990s, Study Finds
science - Posted On:2025-06-25 17:00:00 Source: slashdot
Overfishing has led to a collapse in the eastern Baltic cod population, but over the past three decades the size of the fish themselves has also been dramatically and mysteriously shrinking. From a report: Now scientists have uncovered genomic evidence that intensive fishing has driven rapid evolutionary changes that have contributed to these fish roughly halving in average body length since the 1990s. The "shrinking" of cod, from a median mature body length of 40cm in 1996 to 20cm in 2019, has a genetic basis and human activities have left a profound mark on the population's DNA, the study concluded. [...] The dramatic shrinking of cod has been a source of concern for several decades, but it was not clear to what extent the phenomenon has been driven by environmental factors such as hypoxic conditions caused by algal blooms, pollution and more extreme marine seasonal temperature changes. [...] The study used an archive of tiny ear bones, called otoliths, of 152 cod, caught in the Bornholm Basin between 1996 and 2019. Otoliths -- a bit like tree rings -- record annual growth, making them valuable biological timekeepers. Read more of this story at Slashdot.
Ars Live: What’s up with the sudden surge in temperatures?
Science - Posted On:2025-06-25 15:30:00 Source: arstechnica
On Thursday, we encourage you to join us for a live chat with Zeke Hausfather, a climate scientist and researcher at Berkeley Earth. We'll talk a bit about how he got into climate science and ended up at Berkeley Earth and the role that organization plays in the world of climate science. It was launched by a physicist who was somewhat skeptical of the work being done by climate scientists, but it has evolved into one of the key groups that does the math needed to track the planet's temperatures.
For the past couple of years, those temperatures have seen a remarkable rise to record highs, at one point setting a yearlong string where every month set a record for the warmest instance of that month on record. The rise leaves us at risk of exceeding key climate targets much earlier than expected and has left the climate science community scrambling to explain the intensity of the heat. So we plan to ask Zeke a bit about what scientists are thinking about the dramatic nature of these changes, attempts to explore the relationship between temperatures, and things like tipping points and individual weather events.
And all that leads to the key question: What does this tell us about where our climate is likely to go over the rest of this century?
Stem Cell Treatment May Cure Severe Type 1 Diabetes, Study Finds
science - Posted On:2025-06-25 11:30:00 Source: slashdot
A groundbreaking stem cell treatment developed by Vertex Pharmaceuticals has allowed 10 out of 12 patients with severe type 1 diabetes to stop insulin therapy after one year. While the trial included some side effects and two unrelated deaths, the results mark a major step forward and have progressed to phase 3 clinical testing. ScienceAlert reports: The pancreas's islet cells are responsible for maintaining most of our bodies' insulin levels. Donor transplants of healthy versions of these cells have shown promise in treating type 1 diabetes in the past, but multiple donors are required, and donors are rare. So University of Toronto surgeon Trevor Reichman and colleagues infused 12 patients with islet cells derived from human stem cells in a treatment known as zimislecel. The patients also received immunosuppressive treatment before and after their zimislecel infusion. The islets not only produced insulin inside their bodies, but they did so at safe levels, reducing the patients' dependence on costly doses of insulin. "These findings showed that zimislecel islet cells were functional and self-regulated appropriately," the researchers write in their paper. The mild to moderate side-effects, including decreased kidney function and the anticipated drop in immune cells, were all linked with the immunosuppressive therapy. Sadly, two additional participants died during the trial; one from an infection arising from surgery and the other from complications due to an unrelated condition. As there were no serious adverse events attributed to the new islet cell therapy, the clinical trials are have progressed into phase 3. "These findings provide evidence that pancreatic islets can be effectively produced from pluripotent stem cells and used to treat type 1 diabetes," Reichman and team conclude. The research has been published in the journal NEJM. Read more of this story at Slashdot.
Researchers Discover How Caffeine Could Slow Cellular Aging
science - Posted On:2025-06-25 03:15:00 Source: slashdot
alternative_right shares a report from Phys.Org: In new research published by scientists studying fission yeast�"a single-celled organism surprisingly similar to human cells�"researchers found that caffeine affects aging by tapping into an ancient cellular energy system. A few years ago, the same research team found that caffeine helps cells live longer by acting on a growth regulator called TOR (target of rapamycin). TOR is a biological switch that tells cells when to grow, based on how much food and energy is available. This switch has been controlling energy and stress responses in living things for over 500 million years. But in their latest study, the scientists made a surprising discovery: Caffeine doesn't act on this growth switch directly. Instead, it works by activating another important system called AMPK, a cellular fuel gauge that is evolutionarily conserved in yeast and humans. "When your cells are low on energy, AMPK kicks in to help them cope," explains Dr. Charalampos (Babis) Rallis, Reader in Genetics, Genomics and Fundamental Cell Biology at Queen Mary University of London, the study's senior author. "And our results show that caffeine helps flip that switch." Interestingly, AMPK is also the target of metformin, a common diabetes drug that's being studied for its potential to extend human lifespan together with rapamycin. Using their yeast model, the researchers showed that caffeine's effect on AMPK influences how cells grow, repair their DNA, and respond to stress -- all of which are tied to aging and disease. The study has been published in the journal Microbial Cell. Read more of this story at Slashdot.
Discovery of HMS Endeavour wreck confirmed
Science - Posted On:2025-06-24 18:15:01 Source: arstechnica
Back in 2022, we reported on the Australian National Maritime Museum's (ANMM) announcement that its researchers had confirmed that a shipwreck proposed as a likely candidate in 2018 is indeed the remains of the HMS Endeavour. However, the Rhode Island Marine Archaeology Project (RIMAP)—the museum's research partner in the project—promptly released a statement calling the announcement premature. RIMAP insisted that more evidence was needed.
The final report is now available, and both RIMAP and ANMM say they have confirmed that the wreck is indeed the Endeavour. (You can read the full report here.) “The timbers are British timbers. The size of all the timber scantlings are almost identical to Endeavour, and I’m talking within millimeters—not inches, but millimeters," Kieran Hosty, an ANMM archaeologist who co-wrote the report, told The Independent. “The stem scarf is identical, absolutely identical. This stem scarf is also a very unique feature—we’ve gone through a whole bunch of 18th-century ships' plans, and we can’t find anything else like it.”
As previously reported, Endeavour Captain James Cook's first voyage (1768–1771) was, in part, a mission to observe and record the 1769 transit of Venus across the Sun. The observation was part of a combined global effort to determine the distance of the Earth from the Sun. Those observations proved less conclusive than had been hoped, but during the rest of the voyage, Cook was able to map the coastland of New Zealand before sailing west to the southeastern coast of Australia—the first record of Europeans on the continent's Eastern coastline.
Discovery of HMS Endeavor wreck confirmed
Science - Posted On:2025-06-24 17:00:01 Source: arstechnica
Back in 2022, we reported on the Australian National Maritime Museum's (ANMM) announcement that its researchers had confirmed that a shipwreck proposed as a likely candidate in 2018 is indeed the remains of the HMS Endeavour. However, the Rhode Island Marine Archaeology Project (RIMAP)—the museum's research partner in the project—promptly released a statement calling the announcement premature. RIMAP insisted that more evidence was needed.
The final report is now available, and both RIMAP and ANMM say they have confirmed that the wreck is indeed the Endeavor. (You can read the full report here.) “The timbers are British timbers. The size of all the timber scantlings are almost identical to Endeavour, and I’m talking within millimeters—not inches, but millimeters," Kieran Hosty, an ANMM archaeologist who co-wrote the report, told The Independent. “The stem scarf is identical, absolutely identical. This stem scarf is also a very unique feature—we’ve gone through a whole bunch of 18th-century ships' plans, and we can’t find anything else like it.”
As previously reported, Endeavour Captain James Cook's first voyage (1768–1771) was, in part, a mission to observe and record the 1769 transit of Venus across the Sun. The observation was part of a combined global effort to determine the distance of the Earth from the Sun. Those observations proved less conclusive than had been hoped, but during the rest of the voyage, Cook was able to map the coastland of New Zealand before sailing west to the southeastern coast of Australia—the first record of Europeans on the continent's Eastern coastline.
Noise Pollution Harms Health of Millions Across Europe, Report Finds
science - Posted On:2025-06-24 17:00:01 Source: slashdot
More than 110 million people across Europe suffer high levels of health-damaging noise pollution, according to a report. The resulting physiological stress and sleep disturbance leads to 66,000 early deaths a year and many cases of heart disease, diabetes and depression. The Guardian: The report, from the European Environment Agency (EEA), focuses on noise from cars, trains and aeroplanes and found that 20% of the population of the European Economic Area (EEA) were affected. Separate research, using a slightly lower threshold for dangerous noise pollution, found that 40% of the UK population were exposed to harmful transport noise. Seventeen million people endure particularly high noise pollution -- "long-term, high-annoyance" -- and almost 5 million suffer "severe" sleep disturbance. Fifteen million children live in areas of harmful noise. The harm to health from noise is greater than that from higher-profile risks including secondhand tobacco smoke or lead exposure, and incurs an economic cost of almost $116bn a year, the analysis found. The damage to health is likely to be an underestimate, the researchers said. Using the World Health Organization's stricter threshold for risky noise pollution gives an estimate of 150 million people across Europe exposed. The EU's target to cut the number of people chronically disturbed by transport noise by 30% by 2030 will not be met without further action, the researchers said. Read more of this story at Slashdot.
Researchers get viable mice by editing DNA from two sperm
Science - Posted On:2025-06-23 18:45:00 Source: arstechnica
For many species, producing an embryo is a bit of a contest between males and females. Males want as many offspring as possible, and want the females to devote as many resources as possible to each of them. Females do better by keeping their options open and distributing resources in a way to maximize the number of offspring they can produce over the course of their lives.
In mammals, this plays out through the chemical modification of DNA, a process called imprinting. Males imprint their DNA by adding methyl modifications to it in a way that alters the activity of genes in order to promote the growth of embryos. Females do similar things chemically but focus on shutting down genes that promote embryonic growth. In a handful of key regions of the genome, having only the modifications specific to one sex is lethal, as the embryo can't grow to match its stage of development.
One consequence of this is that you normally can't produce embryos using only the DNA from eggs or from sperm. But over the last few years, researchers have gradually worked around the need for imprinted sites to have one copy from each parent. Now, in a very sophisticated demonstration, researchers have used targeted editing of methylation to produce mice from the DNA of two sperm.
PhD Graduates Far Exceed Academic Job Openings
science - Posted On:2025-06-23 17:45:00 Source: slashdot
The number of doctoral graduates globally has grown steadily over recent decades, creating a massive imbalance between PhD holders and available academic positions. Among the 38 OECD countries, new doctorate holders almost doubled between 1998 and 2017. China's doctoral enrollment has exploded from around 300,000 students in 2013 to more than 600,000 in 2023. This growth has forced PhD graduates into non-academic careers at unprecedented rates. A 2023 study of more than 4,500 PhD graduates in the United Kingdom found over two-thirds were employed outside academia. In South Africa, 18% of more than 6,000 PhD graduates reported difficulty finding jobs related to their expertise. Some countries have begun adapting their doctoral programs. Japan, Germany and the United Kingdom now offer training and paid internships during doctoral studies, including "industrial PhD" programs where students conduct research in collaboration with companies. Read more of this story at Slashdot.
Scientists Use Bacteria To Turn Plastic Waste Into Paracetamol
science - Posted On:2025-06-23 16:15:00 Source: slashdot
Bacteria can be used to turn plastic waste into painkillers, researchers have found, opening up the possibility of a more sustainable process for producing the drugs. From a report: Chemists have discovered E coli can be used to create paracetamol, also known as acetaminophen, from a material produced in the laboratory from plastic bottles. "People don't realise that paracetamol comes from oil currently," said Prof Stephen Wallace, the lead author of the research from the University of Edinburgh. "What this technology shows is that by merging chemistry and biology in this way for the first time, we can make paracetamol more sustainably and clean up plastic waste from the environment at the same time." Writing in the journal Nature Chemistry, Wallace and colleagues report how they discovered that a type of chemical reaction called a Lossen rearrangement, a process that has never been seen in nature, was biocompatible. In other words, it could be carried out in the presence of living cells without harming them. The team made their discovery when they took polyethylene terephthalate (PET) -- a type of plastic often found in food packaging and bottles -- and, using sustainable chemical methods, converted it into a new material. Read more of this story at Slashdot.
Caps of Glass Bottles Contaminate Beverages With Microplastics
science - Posted On:2025-06-23 15:30:00 Source: slashdot
Microplastics are present in all beverages, but those packaged in glass bottles contain more microplastic particles than those in plastic bottles, cartons or cans. This was the surprising finding of a study conducted by the Boulogne-sur-Mer unit of the ANSES Laboratory for Food Safety. The scientists hypothesised that these plastic particles could come from the paint used on bottle caps. Water and wine are less affected than other beverages. These findings have highlighted a source of microplastics in drinks that manufacturers can easily take measures to address. Read more of this story at Slashdot.
Crunch time—we’ll soon find out if Amazon’s launch providers are up to the job
Science - Posted On:2025-06-23 14:00:01 Source: arstechnica
For the second time in two months, United Launch Alliance sent a batch of 27 broadband Internet satellites into orbit for Amazon on Monday morning.
Just like the last flight on April 28, an Atlas V rocket lifted off from Cape Canaveral, Florida, and delivered Amazon's satellites into an on-target orbit roughly 280 miles (450 kilometers) above Earth. This was the second launch of a full load of operational satellites for Amazon's Project Kuiper, a network envisioned to become a competitor to SpaceX's Starlink.
The Atlas V launched at 6:54 am EDT (10:54 UTC) on Monday, a week after ULA scrubbed the mission's first countdown to address a problem with the rocket's Russian-made RD-180 main engine. With that issue resolved, ULA's launch team gave a "go" for Monday morning's sunrise liftoff.
Sailing the fjords like the Vikings yields unexpected insights
Science - Posted On:2025-06-23 10:00:01 Source: arstechnica
If you want to learn more about how and where the Vikings sailed, making the journey through the fjords yourself in replica boats is a practical, hands-on approach to achieving that end. Greer Jarrett, an archaeologist at Lund University in Sweden, has spent the last three years doing just that, sailing more than 5,000 kilometers along known Viking trade routes in open, spare-rigged clinker boats similar to those used by the Vikings.
Not only has Jarrett learned a great deal about the boats themselves, he also identified four possible havens along the Norwegian coast, part of what may have been a decentralized network that played a crucial role in trade and travel during that period. And those ports are located farther out to sea than other major ports and hubs known to date, according to a paper he published in the Journal of Archaeological Method and Theory.
It's just the latest intriguing discovery enabled by the growing field of experimental archaeology, whereby researchers seek to reverse-engineer all manner of ancient technologies. Experimental archaeologists have, for instance, built their own versions of Early Upper Paleolithic adzes, axes, and chisels. The resulting fractures and wear enabled them to develop new criteria for identifying the likely functions of ancient tools. Others have tried to cook like the Neanderthals, concluding that flint flakes were surprisingly effective for butchering birds, and that roasting the birds damages the bones to such an extent that it's unlikely they would be preserved in the archaeological record.
This archaeologist built a replica boat to sail like the Vikings
Science - Posted On:2025-06-23 09:15:00 Source: arstechnica
If you want to learn more about how and where the Vikings sailed, making the journey through the fjords yourself in replica boats is a practical, hands-on approach to achieving that end. Greer Jarrett, an archaeologist at Lund University in Sweden, has spent the last three years doing just that, sailing more than 5,000 kilometers along known Viking trade routes in open, spare-rigged clinker boats similar to those used by the Vikings.
Not only has Jarrett learned a great deal about the boats themselves, he also identified four possible havens along the Norwegian coast, part of what may have been a decentralized network that played a crucial role in trade and travel during that period. And those ports are located farther out to sea than other major ports and hubs known to date, according to a paper he published in the Journal of Archaeological Method and Theory.
It's just the latest intriguing discovery enabled by the growing field of experimental archaeology, whereby researchers seek to reverse-engineer all manner of ancient technologies. Experimental archaeologists have, for instance, built their own versions of Early Upper Paleolithic adzes, axes, and chisels. The resulting fractures and wear enabled them to develop new criteria for identifying the likely functions of ancient tools. Others have tried to cook like the Neanderthals, concluding that flint flakes were surprisingly effective for butchering birds, and that roasting the birds damages the bones to such an extent that it's unlikely they would be preserved in the archaeological record.
'Unprecedented' Detail: Vera Rubin Space Telescope Releases First Images from Its 3,200-Megapixel Camera
science - Posted On:2025-06-23 08:00:00 Source: slashdot
Perched in Chile's Andes mountains, "A revolutionary new space telescope has just taken its first pictures of the cosmos," reports National Geographic — "and they're spectacular." Formerly known as the Large Synoptic Survey Telescope, it's expected to bring "unprecedented detail" to space photography: The observatory has a few key components: A giant telescope, called the Simonyi Survey Telescope, is connected to the world's largest and highest resolution digital camera. Rubin's 27-foot primary mirror, paired with a mind-boggling 3,200-megapixel camera, will repeatedly take 30-second exposure images of vast swaths of the sky with unrivaled speed and detail. Each image will cover an area of sky as big as 40 full moons. Every three nights for the next 10 years, Rubin will produce a new, ultra-high-definition map of the entire visible southern sky. With this much coverage, scientists hope to create an updated and detailed "movie" they can use to view how the cosmos changes over time.... For the next decade, Rubin will capture millions of astronomical objects each day — or more than 100 every second. Ultimately, it's expected to discover about 17 billion stars and 20 billion galaxies that we've never seen before... When the observatory begins science operations in earnest later in 2025, its instruments will yield a deluge of astronomical data that will be too overwhelming to process manually. (Each night, the observatory will generate around 20 terabytes of data.) Astronomers expect high-quality observations taken with the telescope will help map out the structure of the universe, find comets and potentially hazardous asteroids in our solar system, and detect exploding stars and black holes in distant galaxies. The observatory will also examine the optical counterparts of gravitational wave events — ripples in the fabric of space caused by some of the most energetic processes in the cosmos. By studying these events, astronomers hope to uncover the secrets of the invisible forces that shape the universe like dark matter and dark energy. "Already, in just over 10 hours of test observations, the observatory has discovered 2,104 never-before-seen-asteroids," reports NPR, "including seven near-Earth asteroids, none of which pose any danger..." The basic idea is that the data "should let astronomers catch transient phenomena that they otherwise wouldn't know to look for, such as exploding stars, asteroids, interstellar objects whizzing in from other solar systems, and maybe even the movement of a giant planet that some believe is lurking out in our own solar system, beyond Pluto." The telescope is a joint project between the U.S. Energy Department and its National Science Foundation — and it will stream a special live broadcast of its first images today at 11 a.m. EDT (1500 GMT) on their official YouTube channel (also simulacast at Space.com). Read more of this story at Slashdot.
Tiny Orange Beads Found By Apollo Astronauts Reveal Moon's Volcanic Past
science - Posted On:2025-06-22 12:45:01 Source: slashdot
"When Apollo astronauts stumbled across shimmering orange beads on the moon, they had no idea they were gazing at ancient relics of violent volcanic activity," writes ScienceDaily. These glass spheres, tiny yet mesmerizing, formed billions of years ago during fiery eruptions that launched molten droplets skyward, instantly freezing in space. Now, using advanced instruments that didn't exist in the 1970s, scientists have examined the beads in unprecedented detail. The result is a remarkable window into the moon's dynamic geological history, revealing how eruption styles evolved and how lunar conditions once mirrored explosive events we see on Earth today... Analyses of orange and black lunar beads have shown that the style of volcanic eruptions changed over time. "It's like reading the journal of an ancient lunar volcanologist," said Ryan Ogliore [an associate professor of physics at Missouri's Washington University, which has a large repository of lunar samples that were returned to Earth]. "The beads are tiny, pristine capsules of the lunar interior..." says Ogliore. "We've had these samples for 50 years, but we now have the technology to fully understand them..." "The very existence of these beads tells us the moon had explosive eruptions, something like the fire fountains you can see in Hawaii today." Thanks to Slashdot reader alternative_right for sharing the news. Read more of this story at Slashdot.
A Cracked Piece of Metal Self-Healed In Experiment That Stunned Scientists
science - Posted On:2025-06-22 10:45:00 Source: slashdot
alternative_right writes: We certainly weren't looking for it. What we have confirmed is that metals have their own intrinsic, natural ability to heal themselves, at least in the case of fatigue damage at the nanoscale.' While the observation is unprecedented, it's not wholly unexpected. In 2013, Texas A&M University materials scientist Michael Demkowicz worked on a study predicting that this kind of nanocrack healing could happen, driven by the tiny crystalline grains inside metals essentially shifting their boundaries in response to stress... That the automatic mending process happened at room temperature is another promising aspect of the research. Metal usually requires lots of heat to shift its form, but the experiment was carried out in a vacuum; it remains to be seen whether the same process will happen in conventional metals in a typical environment. A possible explanation involves a process known as cold welding, which occurs under ambient temperatures whenever metal surfaces come close enough together for their respective atoms to tangle together. Typically, thin layers of air or contaminants interfere with the process; in environments like the vacuum of space, pure metals can be forced close enough together to literally stick. Read more of this story at Slashdot.
People with Severe Type 1 Diabetes are Cured in Small Trial of New Drug
science - Posted On:2025-06-22 00:45:00 Source: slashdot
"A single infusion of a stem cell-based treatment may have cured 10 out of 12 people with the most severe form of Type 1 diabetes," reports the New York Times. "One year later, these 10 patients no longer need insulin. The other two patients need much lower doses." The experimental treatment, called zimislecel and made by Vertex Pharmaceuticals of Boston, involves stem cells that scientists prodded to turn into pancreatic islet cells, which regulate blood glucose levels. The new islet cells were infused and reached the pancreas, where they took up residence. The study was presented Friday evening at the annual meeting of the American Diabetes Association and published online by The New England Journal of Medicine... Patients in the study began to need less insulin within a few months of being infused with new islet cells, and most stopped needing the hormone altogether at about six months [said Dr. Trevor Reichman, director of the pancreas and islet transplant program at University Health Network, a hospital in Toronto, and first author of the study]. He added that patients' episodes of hypoglycemia went away within the first 90 days of treatment. If the study continues to show positive results, the company expects to submit an application to the FDA next year. "For the short term, this looks promising" for severely affected patients like those in the study," said Dr. Irl B. Hirsch, a diabetes expert at the University of Washington who was not involved in the study. But patients in the trial had to stay on drugs to prevent the immune system from destroying the new cells. Suppressing the immune system, he said, increases the risk of infections and, over the long term, can increase the risk of cancer... Patients may have to take the immunosuppressant drugs for the rest of their lives, the Vertex spokesperson said. Read more of this story at Slashdot.
Casino Lights Could Be Warping Your Brain To Take Risks, Scientists Warn
science - Posted On:2025-06-21 18:30:01 Source: slashdot
ScienceAlert reports: Casino lighting could be nudging gamblers to be more reckless with their money, according to a new study, which found a link between blue-enriched light and riskier gambling behavior. The extra blue light emitted by casino decor and LED screens seems to trigger certain switches in our brains, making us less sensitive to financial losses compared to gains of equal magnitude, researchers from Flinders University and Monash University in Australia found... The researchers think circadian photoreception, which is our non-visual response to light, is playing a part here. The level of blue spectrum light may be activating specific eye cells connected to brain regions in charge of decision-making, emotional regulation, and processing risk versus reward scenarios. "Under conditions where the lighting emitted less blue, people tended to feel a $100 loss much more strongly than a $100 gain — the loss just feels worse," [says the study's lead author, a psychologist at the Flinders Health and Medical Research Institute]. "But under bright, blue-heavy light such as that seen in casino machines, the $100 loss didn't appear to feel as bad, so people were more willing to take the risk...." That raises some questions around ethics and responsibility, according to the researchers. While encouraging risk taking might be good for the gambling business, it's not good for the patrons spending their cash. One professor involved in the study reached this conclusion. "It is possible that simply dimming the blue in casino lights could help promote safer gambling behaviors." The research has been published in Scientific Reports. Thanks to Slashdot reader alternative_right for sharing the news. Read more of this story at Slashdot.
Psyche keeps its date with an asteroid, but now it’s running in backup mode
Science - Posted On:2025-06-21 14:45:01 Source: arstechnica
A NASA spacecraft bound for an unexplored metal-rich asteroid has reignited its plasma thrusters, continuing its cruise deeper into the Solar System after switching to a backup fuel line.
The $1.4 billion Psyche mission, built to explore an asteroid with the same name, has four electric thrusters fueled by xenon gas. Psyche's solar electric propulsion system is more fuel efficient than conventional rocket thrusters, and it works by flowing xenon through an electromagnetic field, which ionizes the gas and expelling the ions at high speed to produce thrust.
The plasma engines generate lower thrust than chemical rocket engines, but they can accumulate years of run time over the course of a mission, enabling a spacecraft to make significant changes in its velocity to steer its way through space.