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By NASA
u0022The really interesting thing to me is how time theoretically acts strangely around black holes. According to Albert Einstein’s theory of gravity, black holes change the flow of time,u0022 said Jeremy Schnittman, Goddard research astrophysicist. u0022So much of how we experience the world is based on time, time marching steadily forward. Anything that changes that is a fascinating take on reality.u0022u003cstrongu003eu003cemu003eCredits: NASA’s Goddard Space Flight Center / Rebecca Rothu003c/emu003eu003c/strongu003e Name: Jeremy Schnittman
Formal Job Classification: Research astrophysicist
Organization: Gravitational Astrophysics Laboratory, Astrophysics Division (Code 663)
What do you do and what is most interesting about your role here at Goddard? How do you help support Goddard’s mission?
I try to understand the formation and properties of black holes. I also help develop ideas for new missions to study black holes.
What drew you to astrophysics?
I always liked science and math. The great thing about astrophysics is that it involves a little bit of everything – math, computer programming, physics, chemistry and even philosophy to understand the big picture, the enormity of space.
I have a B.A. in physics from Harvard, and a Ph.D. in physics from MIT. I came to Goddard in 2010 after two post-doctoral fellowships.
Explore how the extreme gravity of two orbiting supermassive black holes distorts our view. In this visualization, disks of bright, hot, churning gas encircle both black holes, shown in red and blue to better track the light source. The red disk orbits the larger black hole, which weighs 200 million times the mass of our Sun, while its smaller blue companion weighs half as much. Zooming into each black hole reveals multiple, increasingly warped images of its partner. Watch to learn more.
Credits: NASA’s Goddard Space Flight Center/Jeremy Schnittman and Brian P. Powell
Download high-resolution video and images from NASA’s Scientific Visualization Studio As an astrophysicist, what do you think about?
I think of myself as a computational physicist as opposed to an experimental or observational physicist. I write many computer programs to do computer simulations of black holes. I also do a lot of theoretical physics, which is pencil and paper work. I think a lot about equations and math to understand black holes.
What is most philosophical about black holes to me is not so much what people most often think about, that their gravity is so strong that even light cannot escape. The really interesting thing to me is how time theoretically acts strangely around black holes. According to Albert Einstein’s theory of gravity, black holes change the flow of time. If you could get close enough to a black hole, theoretically you could go back and forth in time. All our experiments and observations seem to indicate that is how black holes might behave.
So much of how we experience the world is based on time, time marching steadily forward. Anything that changes that is a fascinating take on reality.
Related Link: Gravity Assist: Black Hole Mysteries, with Jeremy Schnittman What do you tell the people you mentor?
I mentor undergraduate, graduate, and post graduate students in astrophysics. Since we are working remotely, I have students from all over the country. I help them with their research projects which mostly relate to black holes in some way. I also offer career advice and help them with their work-life balance. When possible, family comes first.
There are more people coming out of graduate school in astrophysics than there are jobs, so there are going to be many people who will not work for NASA or as a professor. Fortunately, there are a lot of other fascinating, related jobs, and I help guide the students there.
What do you do for fun?
I have a woodshop in our basement where I build furniture, dollhouses, toys, and other items for gifts. As a theoretical physicist, I don’t get to work in a lab. So it is nice to have some hands on experience.
I do a lot of hiking and cycling to exercise. I also enjoy spending time with my family.
Who is your favorite author?
Andy Weir is probably my favorite sci-fi author. I also love the epic naval historical fiction by Patrick O’Brian.
Who inspires you?
My childhood hero, who is still my scientific hero, is Albert Einstein. The more I work in astrophysics, the more he impresses me. Every single one of his predictions that we have been able to test has proven true. It may be a while, but someday I hope we prove his theories about time travel.
Also, I admire Kip Thorne, an American physicist from Cal Tech and recent Nobel laureate, who is “the man” when it comes to black holes. He is also a really nice, good guy, a real mensch. Very humble and down-to-earth. He is always extremely patient, kind and encouraging especially to the younger scientists. He is a good role model as I transition from junior to more senior status.
What is your one big dream?
I make a lot of predictions, so it would be exciting if one of my theories was proven correct. Hopefully someday.
By Elizabeth M. Jarrell
NASA’s Goddard Space Flight Center, Greenbelt, Md.
Conversations with Goddard Conversations With Goddard is a collection of question and answer profiles highlighting the breadth and depth of NASA’s Goddard Space Flight Center’s talented and diverse workforce. The Conversations have been published twice a month on average since May 2011. Read past editions on Goddard’s “Our People” webpage.
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Last Updated Feb 10, 2025 Related Terms
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By European Space Agency
Image: This Copernicus Sentinel-2 image highlights part of the São Francisco River in eastern Brazil. View the full article
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By NASA
1 min read
Preparations for Next Moonwalk Simulations Underway (and Underwater)
NASA Marshall will hold a candle-lighting ceremony and wreath placement at 9:30 a.m. CST. The ceremony will include remarks from Larry Leopard, associate director, and Bill Hill, director of Marshall’s Office of Safety and Mission Assurance. NASA/ Krisdon Manecke NASA’s Marshall Space Flight Center in Huntsville, Alabama, invites media to attend its observance of the agency’s Day of Remembrance at 9:30 a.m. CST Thursday, Jan. 23, in the lobby of Building 4221.
Day of Remembrance honors the members of the NASA family who lost their lives while furthering the cause of exploration and discovery.
The event will include brief remarks from NASA Marshall leaders, followed by a candle lighting and moment of silence for the crews of Apollo 1 and space shuttles Challenger and Columbia. Speakers will include:
Larry Leopard, associate director, technical. Bill Hill, director, Office of Safety and Mission Assurance. Media interested in attending the event must confirm by 12 p.m. Wednesday, Jan. 22, with Molly Porter at: molly.a.porter@nasa.gov.
The agency will also pay tribute to its fallen astronauts with special online content, updated on NASA’s Day of Remembrance, at:
https://www.nasa.gov/dor/
Molly Porter
Marshall Space Flight Center, Huntsville, Ala.
256-424-5158
molly.a.porter@nasa.gov
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Last Updated Jan 21, 2025 EditorBeth RidgewayContactMolly Portermolly.a.porter@nasa.govLocationMarshall Space Flight Center Related Terms
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By NASA
NASA’s Dawn spacecraft captured this image of Vesta as it left the giant asteroid’s orbit in 2012. The framing camera was looking down at the north pole, which is in the middle of the image.NASA/JPL-Caltech/UCLA/MPS/DLR/IDA Known as flow formations, these channels could be etched on bodies that would seem inhospitable to liquid because they are exposed to the extreme vacuum conditions of space.
Pocked with craters, the surfaces of many celestial bodies in our solar system provide clear evidence of a 4.6-billion-year battering by meteoroids and other space debris. But on some worlds, including the giant asteroid Vesta that NASA’s Dawn mission explored, the surfaces also contain deep channels, or gullies, whose origins are not fully understood.
A prime hypothesis holds that they formed from dry debris flows driven by geophysical processes, such as meteoroid impacts, and changes in temperature due to Sun exposure. A recent NASA-funded study, however, provides some evidence that impacts on Vesta may have triggered a less-obvious geologic process: sudden and brief flows of water that carved gullies and deposited fans of sediment. By using lab equipment to mimic conditions on Vesta, the study, which appeared in Planetary Science Journal, detailed for the first time what the liquid could be made of and how long it would flow before freezing.
Although the existence of frozen brine deposits on Vesta is unconfirmed, scientists have previously hypothesized that meteoroid impacts could have exposed and melted ice that lay under the surface of worlds like Vesta. In that scenario, flows resulting from this process could have etched gullies and other surface features that resemble those on Earth.
To explore potential explanations for deep channels, or gullies, seen on Vesta, scientists used JPL’s Dirty Under-vacuum Simulation Testbed for Icy Environments, or DUSTIE, to simulate conditions on the giant asteroid that would occur after meteoroids strike the surface.NASA/JPL-Caltech But how could airless worlds — celestial bodies without atmospheres and exposed to the intense vacuum of space — host liquids on the surface long enough for them to flow? Such a process would run contrary to the understanding that liquids quickly destabilize in a vacuum, changing to a gas when the pressure drops.
“Not only do impacts trigger a flow of liquid on the surface, the liquids are active long enough to create specific surface features,” said project leader and planetary scientist Jennifer Scully of NASA’s Jet Propulsion Laboratory in Southern California, where the experiments were conducted. “But for how long? Most liquids become unstable quickly on these airless bodies, where the vacuum of space is unyielding.”
The critical component turns out to be sodium chloride — table salt. The experiments found that in conditions like those on Vesta, pure water froze almost instantly, while briny liquids stayed fluid for at least an hour. “That’s long enough to form the flow-associated features identified on Vesta, which were estimated to require up to a half-hour,” said lead author Michael J. Poston of the Southwest Research Institute in San Antonio.
Launched in 2007, the Dawn spacecraft traveled to the main asteroid belt between Mars and Jupiter to orbit Vesta for 14 months and Ceres for almost four years. Before ending in 2018, the mission uncovered evidence that Ceres had been home to a subsurface reservoir of brine and may still be transferring brines from its interior to the surface. The recent research offers insights into processes on Ceres but focuses on Vesta, where ice and salts may produce briny liquid when heated by an impact, scientists said.
Re-creating Vesta
To re-create Vesta-like conditions that would occur after a meteoroid impact, the scientists relied on a test chamber at JPL called the Dirty Under-vacuum Simulation Testbed for Icy Environments, or DUSTIE. By rapidly reducing the air pressure surrounding samples of liquid, they mimicked the environment around fluid that comes to the surface. Exposed to vacuum conditions, pure water froze instantly. But salty fluids hung around longer, continuing to flow before freezing.
The brines they experimented with were a little over an inch (a few centimeters) deep; scientists concluded the flows on Vesta that are yards to tens of yards deep would take even longer to refreeze.
The researchers were also able to re-create the “lids” of frozen material thought to form on brines. Essentially a frozen top layer, the lids stabilize the liquid beneath them, protecting it from being exposed to the vacuum of space — or, in this case the vacuum of the DUSTIE chamber — and helping the liquid flow longer before freezing again.
This phenomenon is similar to how on Earth lava flows farther in lava tubes than when exposed to cool surface temperatures. It also matches up with modeling research conducted around potential mud volcanoes on Mars and volcanoes that may have spewed icy material from volcanoes on Jupiter’s moon Europa.
“Our results contribute to a growing body of work that uses lab experiments to understand how long liquids last on a variety of worlds,” Scully said.
Find more information about NASA’s Dawn mission here:
https://science.nasa.gov/mission/dawn/
News Media Contacts
Gretchen McCartney
Jet Propulsion Laboratory, Pasadena, Calif.
818-287-4115
gretchen.p.mccartney@jpl.nasa.gov
Karen Fox / Molly Wasser
NASA Headquarters, Washington
202-358-1600
karen.c.fox@nasa.gov / molly.l.wasser@nasa.gov
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Last Updated Dec 20, 2024 Related Terms
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By NASA
Download PDF: Statistical Analysis Using Random Forest Algorithm Provides Key Insights into Parachute Energy Modulator System
Energy modulators (EM), also known as energy absorbers, are safety-critical components that are used to control shocks and impulses in a load path. EMs are textile devices typically manufactured out of nylon, Kevlar® and other materials, and control loads by breaking rows of stitches that bind a strong base webbing together as shown in Figure 1. A familiar EM application is a fall-protection harness used by workers to prevent injury from shock loads when the harness arrests a fall. EMs are also widely used in parachute systems to control shock loads experienced during the various stages of parachute system deployment.
Random forest is an innovative algorithm for data classification used in statistics and machine learning. It is an easy to use and highly flexible ensemble learning method. The random forest algorithm is capable of modeling both categorical and continuous data and can handle large datasets, making it applicable in many situations. It also makes it easy to evaluate the relative importance of variables and maintains accuracy even when a dataset has missing values.
Random forests model the relationship between a response variable and a set of predictor or independent variables by creating a collection of decision trees. Each decision tree is built from a random sample of the data. The individual trees are then combined through methods such as averaging or voting to determine the final prediction (Figure 2). A decision tree is a non-parametric supervised learning algorithm that partitions the data using a series of branching binary decisions. Decision trees inherently identify key features of the data and provide a ranking of the contribution of each feature based on when it becomes relevant. This capability can be used to determine the relative importance of the input variables (Figure 3). Decision trees are useful for exploring relationships but can have poor accuracy unless they are combined into random forests or other tree-based models.
The performance of a random forest can be evaluated using out-of-bag error and cross-validation techniques. Random forests often use random sampling with replacement from the original dataset to create each decision tree. This is also known as bootstrap sampling and forms a bootstrap forest. The data included in the bootstrap sample are referred to as in-the-bag, while the data not selected are out-of-bag. Since the out-of-bag data were not used to generate the decision tree, they can be used as an internal measure of the accuracy of the model. Cross-validation can be used to assess how well the results of a random forest model will generalize to an independent dataset. In this approach, the data are split into a training dataset used to generate the decision trees and build the model and a validation dataset used to evaluate the model’s performance. Evaluating the model on the independent validation dataset provides an estimate of how accurately the model will perform in practice and helps avoid problems such as overfitting or sampling bias. A good model performs well on
both the training data and the validation data.
The complex nature of the EM system made it difficult for the team to identify how various parameters influenced EM behavior. A bootstrap forest analysis was applied to the test dataset and was able to identify five key variables associated with higher probability of damage and/or anomalous behavior. The identified key variables provided a basis for further testing and redesign of the EM system. These results also provided essential insight to the investigation and aided in development of flight rationale for future use cases.
For information, contact Dr. Sara R. Wilson. sara.r.wilson@nasa.gov
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