Where Do Black Holes Lead?

(THIS ARTICLE IS COURTESY OF LIVE SCIENCE)

 

Where Do Black Holes Lead?

Artist's impression of a black hole.

Where does a black hole go?
(Image: © All About Space magazine)

So there you are, about to leap into a black hole. What could possibly await should — against all odds — you somehow survive? Where would you end up and what tantalizing tales would you be able to regale if you managed to clamor your way back?

The simple answer to all of these questions is, as Professor Richard Massey explains, “Who knows?” As a Royal Society research fellow at the Institute for Computational Cosmology at Durham University, Massey is fully aware that the mysteries of black holes run deep. “Falling through an event horizon is literally passing beyond the veil — once someone falls past it, nobody could ever send a message back,” he said. “They’d be ripped to pieces by the enormous gravity, so I doubt anyone falling through would get anywhere.”

If that sounds like a disappointing — and painful — answer, then it is to be expected. Ever since Albert Einstein’s general theory of relativity was considered to have predicted black holes by linking space-time with the action of gravity, it has been known that black holes result from the death of a massive star leaving behind a small, dense remnant core. Assuming this core has more than roughly three-times the mass of the sun, gravity would overwhelm to such a degree that it would fall in on itself into a single point, or singularity, understood to be the black hole’s infinitely dense core.

Related: 9 Ideas About Black Holes That Will Blow Your Mind

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The resulting uninhabitable black hole would have such a powerful gravitational pull that not even light could avoid it. So, should you then find yourself at the event horizon — the point at which light and matter can only pass inward, as proposed by the German astronomer Karl Schwarzschild — there is no escape. According to Massey, tidal forces would reduce your body into strands of atoms (or ‘spaghettification’, as it is also known) and the object would eventually end up crushed at the singularity. The idea that you could pop out somewhere — perhaps at the other side — seems utterly fantastical.

What about a wormhole?

Or is it? Over the years scientists have looked into the possibility that black holes could be wormholes to other galaxies. They may even be, as some have suggested, a path to another universe.

Such an idea has been floating around for some time: Einstein teamed up with Nathan Rosen to theorise bridges that connect two different points in space-time in 1935. But it gained some fresh ground in the 1980s when physicist Kip Thorne — one of the world’s leading experts on the astrophysical implications of Einstein’s general theory of relativity — raised a discussion about whether objects could physically travel through them.

“Reading Kip Thorne’s popular book about wormholes is what first got me excited about physics as a child,” Massey said. But it doesn’t seem likely that wormholes exist.

Indeed, Thorne, who lent his expert advice to the production team for the Hollywood movie Interstellar, wrote: “We see no objects in our universe that could become wormholes as they age,” in his book “The Science of Interstellar” (W.W. Norton and Company, 2014). Thorne told Space.com that journeys through these theoretical tunnels would most likely remain science fiction, and there is certainly no firm evidence that a black hole could allow for such a passage.

Artist’s concept of a wormhole. If wormholes exist, they might lead to another universe. But, there’s no evidence that wormholes are real or that a black hole would act like one.

(Image credit: Shutterstock)

But, the problem is that we can’t get up close to see for ourselves. Why, we can’t even take photographs of anything that takes place inside a black hole — if light cannot escape their immense gravity, then nothing can be snapped by a camera. As it stands, theory suggests that anything which goes beyond the event horizon is simply added to the black hole and, what’s more, because time distorts close to this boundary, this will appear to take place incredibly slowly, so answers won’t be quickly forthcoming.

“I think the standard story is that they lead to the end of time,” said Douglas Finkbeiner, professor of astronomy and physics at Harvard University. “An observer far away will not see their astronaut friend fall into the black hole. They’ll just get redder and fainter as they approach the event horizon [as a result of gravitational red shift]. But the friend falls right in, to a place beyond ‘forever.’ Whatever that means.”

Maybe a black hole leads to a white hole

Certainly, if black holes do lead to another part of a galaxy or another universe, there would need to be something opposite to them on the other side. Could this be a white hole — a theory put forward by Russian cosmologist Igor Novikov in 1964? Novikov proposed that a black hole links to a white hole that exists in the past. Unlike a black hole, a white hole will allow light and matter to leave, but light and matter will not be able to enter.

Scientists have continued to explore the potential connection between black and white holes. In their 2014 study published in the journal Physical Review D, physicists Carlo Rovelli and Hal M. Haggard claimed that “there is a classic metric satisfying the Einstein equations outside a finite space-time region where matter collapses into a black hole and then emerges from a while hole.” In other words, all of the material black holes have swallowed could be spewed out, and black holes may become white holes when they die.

Far from destroying the information that it absorbs, the collapse of a black hole would be halted. It would instead experience a quantum bounce, allowing information to escape. Should this be the case, it would shed some light on a proposal by former Cambridge University cosmologist and theoretical physicist Stephen Hawking who, in the 1970s, explored the possibility that black holes emit particles and radiation — thermal heat — as a result of quantum fluctuations.

Redshifting Star Orbiting Supermassive Black Hole Demonstrates Einstein Prediction
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“Hawking said a black hole doesn’t last forever,” Finkbeiner said. Hawking calculated that the radiation would cause a black hole to lose energy, shrink and disappear, as described in his 1976 paper published in Physical Review D. Given his claims that the radiation emitted would be random and contain no information about what had fallen in, the black hole, upon its explosion, would erase loads of information.

This meant Hawking’s idea was at odds with quantum theory, which says information can’t be destroyed. Physics states information just becomes more difficult to find because, should it become lost, it becomes impossible to know the past or the future. Hawking’s idea led to the ‘black hole information paradox’ and it has long puzzled scientists. Some have said Hawking was simply wrong, and the man himself even declared he had made an error during a scientific conference in Dublin in 2004.

So, do we go back to the concept of black holes emitting preserved information and throwing it back out via a white hole? Maybe. In their 2013 study published in Physical Review Letters, Jorge Pullin at Louisiana State University and Rodolfo Gambini at the University of the Republic in Montevideo, Uruguay, applied loop quantum gravity to a black hole and found that gravity increased towards the core but reduced and plonked whatever was entering into another region of the universe. The results gave extra credence to the idea of black holes serving as a portal. In this study, singularity does not exist, and so it doesn’t form an impenetrable barrier that ends up crushing whatever it encounters. It also means that information doesn’t disappear.

Maybe black holes go nowhere

Yet physicists Ahmed Almheiri, Donald Marolf, Joseph Polchinski and James Sully still believed Hawking could have been on to something. They worked on a theory that became known as the AMPS firewall, or the black hole firewall hypothesis. By their calculations, quantum mechanics could feasibly turn the event horizon into a giant wall of fire and anything coming into contact would burn in an instant. In that sense, black holes lead nowhere because nothing could ever get inside.

This, however, violates Einstein’s general theory of relativity. Someone crossing the event horizon shouldn’t actually feel any great hardship because an object would be in free fall and, based on the equivalence principle, that object — or person — would not feel the extreme effects of gravity. It could follow the laws of physics present elsewhere in the universe, but even if it didn’t go against Einstein’s principle it would undermine quantum field theory or suggest information can be lost.

Related: 11 Fascinating Facts About Our Milky Way Galaxy

Artist’s impression of a tidal disruption event which occurs when a star passes too close to a supermassive black hole.

(Image credit: All About Space magazine)

A black hole of uncertainty

Step forward Hawking once more. In 2014, he published a study in which he eschewed the existence of an event horizon — meaning there is nothing there to burn — saying gravitational collapse would produce an ‘apparent horizon’ instead.

This horizon would suspend light rays trying to move away from the core of the black hole, and would persist for a “period of time.” In his rethinking, apparent horizons temporarily retain matter and energy before dissolving and releasing them later down the line. This explanation best fits with quantum theory — which says information can’t be destroyed — and, if it was ever proven, it suggests that anything could escape from a black hole.

Hawking went as far as saying black holes may not even exist. “Black holes should be redefined as metastable bound states of the gravitational field,” he wrote. There would be no singularity, and while the apparent field would move inwards due to gravity, it would never reach the center and be consolidated within a dense mass.

And yet anything which is emitted will not be in the form of the information swallowed. It would be impossible to figure out what went in by looking at what is coming out, which causes problems of its own — not least for, say, a human who found themselves in such an alarming position. They’d never feel the same again!

One thing’s for sure, this particular mystery is going to swallow up many more scientific hours for a long time to come. Rovelli and Francesca Vidotto recently suggested that a component of dark matter could be formed by remnants of evaporated black holes, and Hawking’s paper on black holes and ‘soft hair’ was released in 2018, and describes how zero-energy particles are left around the point of no return, the event horizon — an idea that suggests information is not lost but captured.

This flew in the face of the no-hair theorem which was expressed by physicist John Archibald Wheeler and worked on the basis that two black holes would be indistinguishable to an observer because none of the special particle physics pseudo-charges would be conserved. It’s an idea that has got scientists talking, but there is some way to go before it’s seen as the answer for where black holes lead. If only we could find a way to leap into one.

Russia Says It Will Keep Source of Hole (and Air Leak) on Soyuz Secret— But NASA Wants to Know

(THIS ARTICLE IS COURTESY OF SPACE.COM)

 

Russia Says It Will Keep Source of Hole (and Air Leak) on Soyuz Secret— But NASA Wants to Know: Report

Russia's Soyuz MS-09 crew spacecraft is is shown docked to the International Space Station (ISS). The MS-09 carried NASA astronaut Serena M. Auñón-Chancellor, the European Space Agency's Alexander Gerst and cosmonaut Sergey Prokopyev to the ISS in June 2018.

Russia’s Soyuz MS-09 crew spacecraft is is shown docked to the International Space Station (ISS). The MS-09 carried NASA astronaut Serena M. Auñón-Chancellor, the European Space Agency’s Alexander Gerst and cosmonaut Sergey Prokopyev to the ISS in June 2018.
(Image: © NASA)

Amid reports that the Russians will keep the cause of an air leak discovered at the International Space Station in 2018 secret, NASA Administrator Jim Bridenstine has promised to speak personally with the head of the Russian space agency.

“They have not told me anything,” Bridenstine said during a Houston energy conference question session Thursday (Sept. 19), according to the Houston Chronicle. But he emphasized that he wants to keep good relations with the Russians, one of the two chief partners on the orbiting complex.

“I don’t want to let one item set [the relationship] back, but it is clearly not acceptable that there are holes in the International Space Station,” he said, referring to the 2-millimeter (0.08 inches) hole that the Expedition 56 crew found in the Soyuz MS-09 spacecraft, a crew vehicle that was docked to the station.

Bridenstine’s comments came in the wake of a report by Russia’s state-run international news agency RIA Novosti, in which Dmitry Rogozin, head of Roscosmos (the Russian space agency), suggested his agency found what created the hole last year, but would not disclose the results outside of Roscosmos.

Related: Hole That Caused Leak in Russian Spacecraft Possibly Traced to Assembly or Testing

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Space Station’s Cabin Pressure Loss Explained by NASA
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“What happened is clear to us, but we won’t tell you anything,” Rogozin said at a meeting with participants at a science conference, according to a computer-translated page from RIA Novosti’s Russian-language report on Wednesday (Sept. 18).

After NASA reported a slow drop in cabin pressure at the station on Aug. 29, 2018, the crew of Expedition 56 located the cause of the air leak in the orbital compartment of the Soyuz MS-09 spacecraft, nearly three months after the vessel arrived at the International Space Station with three new crewmembers on board.

The astronauts plugged the hole using epoxy, gauze and heavy-duty tape, and the Russians launched an investigation. In the first few weeks, Roscosmos director Dmitry Rogozin first speculated that a micrometeoroid might have punched the hole, then suggested the hole could have been drilled by a human either accidentally or deliberately.

Space station astronauts patched a small hole in the upper orbital module of the Soyuz MS-09 spacecraft (left) on Aug. 30, 2018.

(Image credit: NASA/Space.com)

NASA and Roscosmos, however, issued a joint statement in mid-September 2018 after the two agency chiefs spoke by phone. The agencies “agreed on deferring any preliminary conclusions and providing any explanations until the final investigation has been completed,” Roscosmos and NASA said in their statement.

Roscosmos is currently the only agency capable of launching crew members to space since NASA retired the space shuttle in 2011. NASA is readying American commercial crew vehicles from Boeing and SpaceX and expects to start running crewed test flights as early as this year. But for now, the Soyuz is the only way astronauts can fly to and from the International Space Station.

The two agencies are the chief partners on the space station, and have been working together to build and maintain the 21-year-old orbiting complex since the early 1990s. Bridenstine and other NASA officials have thus repeatedly emphasized the level of trust between their agency and Roscosmos, which includes several missions before ISS. NASA and the Soviet Union ran a joint mission in 1975 called Apollo-Soyuz, and the new Russian nation partnered with NASA for shuttle flights to the space station Mir between 1994 and 1998.

Follow Elizabeth Howell on Twitter @howellspace. Follow us on Twitter @Spacedotcom and on Facebook

Have a news tip, correction or comment? Let us know at [email protected]

About de Wets Wild

via About de Wets Wild

Falls Brook Falls

MaritimeMac

I finally got to visit New Brunswick’s, disputed highest waterfall. Falls Brook Falls, is 70 meters high. Having been to the other two contenders for highest, Walton-Glen-gorge-ous falls, and Third-vault-falls, I can attest this one is higher.

My friends Laura Harris, at Explorenb.ca/blog/fall-brook-falls. Has written a post about her experiences there. I though I would share it today.

Cheers from Maritimemac.

My Feature Image Photo: 1/13 sec. f/22 18 mm ISO 200 Nikon 7100- No tripod so slight blur at the top- oh well- Kelly MacKay.

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4 Longest Roads in the U.S.

(THIS ARTICLE IS COURTESY OF TRAVEL TRIVIA)

 

4 Longest Roads in the U.S.

If you love cruising the open road with your car or motorcycle on adventurous road trips, you need to travel the longest roads in the United States. You don’t have to worry about exits, except to find some great places to eat, rest, and soak up local flare. The best part about traveling on one of the longest roads is you don’t have to worry about your navigation system kicking in and interrupting you while you rock out to your favorite music or listen to an inspiring podcast. Here are the four longest roads in the U.S., so you can plan your next exciting road trip:

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U.S. Route 30, New Jersey to Oregon

U.S. Route 30, New Jersey to Oregon

Credit: peeterv/iStock

The nation’s fourth longest road and third longest U.S. highway spans 3,072 miles starting in Atlantic City, New Jersey, and ending in Astoria, Oregon. In addition to Oregon and New Jersey, U.S. 30 runs through nine more states, giving you plenty of exciting rest stops. One of the most gorgeous stretches of U.S. 30 is the Thousand Springs Scenic Byway, which runs through Idaho from Bliss through Twin Falls. This part of U.S. 30 meanders through the Snake River Canyon where you will find thousands of waterfalls, hot springs, and charming Idaho towns.

For more small towns and some historic immersion, you will find several worthwhile stops on U.S. 30 through Nebraska, called the Lincoln Highway Historical Byway. As you travel this route you will drive along the Oregon, Mormon, and California trails, as well as the transcontinental Pony Express route and Union Pacific Railroad. The largest city along U.S. Route 30 is Philadelphia, where you can visit several historical sites like the Liberty Bell, Independence Hall, Congress Hall, The Betsy Ross House, and one of the oldest streets in the U.S., Elfreth’s Alley. If you spend some time in Philadelphia, don’t forget to enjoy a world-famous Philly cheesesteak.

Interstate 90, Massachusetts to Washington

Interstate 90, Massachusetts to Washington

Credit: 4nadia/iStock

The nation’s third longest road and longest interstate runs from Boston to Seattle and spans a little more than 3,100 miles. If you drive it from end to end, it would take you about 46 hours, but with so many must-sees and must-dos along the way, it will surely take you longer. Traveling along I-90 brings you through 13 states, including Massachusetts and Washington. If it’s an urban getaway you crave, stop off in Cleveland, Ohio, to visit the Rock and Roll Hall of Fame, or head to Chicago to visit the Navy Pier, The Art Institute of Chicago, or the Museum of Science and Industry.

If you crave a smaller town feel, spend some time in Madison, Wisconsin. Located on an isthmus formed by two lakes, this capital city offers cute pubs and restaurants in the downtown area, which is also home to the University of Wisconsin. Outdoor enthusiasts won’t miss the chance to visit Yellowstone National Park when traveling farther west on I-90. Although the park is about an hour away from Livingston, Montana, I-90 is the best route to visit the geologic wonders on its north side. As you continue to drive along I-90 through Montana, Idaho, and Washington, the scenery of the Rocky Mountains and the Cascade Mountains is so breathtaking, you won’t want your trip to end.

U.S. Route 6, Massachusetts to California

U.S. Route 6, Massachusetts to California

Credit: wakr10/iStock

In comparison to the other longest roads in the United States, U.S. Route 6 lies the furthest south, primarily because the highway runs diagonally. On the east coast, U.S. 6 begins at the tip of Cape Cod in Provincetown, Massachusetts, and goes all the way to Bishop, California. If you were to drive Route 6 from start to finish, you would visit 14 states, and it would take approximately 61 hours to travel its 3,207 miles. U.S. 6 was once the longest road in the country, but after the Department of Transportation renumbered highways during the ’60s, it moved down the list. Route 6 is formally known as the Grand Army of the Republic Highway, dedicated to the Union troops who fought during the Civil War.

Unlike the other longest roads in the United States, U.S. 6 travels primarily through medium cities, small towns, and charming rural areas. The largest urban areas you can enjoy from U.S. 6 include Denver, Des Moines, and Omaha. This gives you the opportunity to explore middle America. If you are traveling with children, make sure to spend a night or two in Sandusky, Ohio, on the shores of Lake Erie. Here you can enjoy the world-famous Cedar Point Amusement Park and ride some of the biggest rollercoasters in history.

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U.S. Route 20

U.S. Route 20

Credit: M. Kaercher/iStock

Stretching for 3,237 miles from Boston to Newport, Oregon, U.S. Route 20 is the longest road in the United States. This beautiful route is packed with panoramic views and exciting attractions for those who love an epic road trip. It takes you through some of the nation’s must stunning national parks, such as Indiana Dunes National Lakeshore, Yellowstone in Wyoming, and Craters of the Moon National Monument, as it parallels I-90 for most of its length. U.S. 20 has not been converted to a four-lane highway in many areas, making this two-lane adventure the perfect opportunity to slowly meander across the United States.

On the eastern part of the route, you will find quaint and charming towns, providing a real taste of Americana with main streets that have looked the same for decades. In fact, the Massachusetts portion of Route 20 follows the old Boston Post Road used to carry mail between New York City and Boston in the 1600s and 1700s. Route 20 in New York travels through the Finger Lakes Region of the state and winds through remote areas filled with antique shops and charming bed and breakfasts. Likewise on the west coast, you will find enchanting bed and breakfasts throughout the vineyards of Oregon’s Willamette Valley.

Astronomers Have Seen Signs of “Life” at the Center of Messier 110

(THIS ARTICLE IS COURTESY OF SCITECH.COM)

 

Astronomers Have Seen Signs of “Life” at the Center of Messier 110

Messier 110

Located in the constellation Andromeda, M110 was discovered in 1773 by Charles Messier. It is a satellite galaxy of the Andromeda galaxy (M31) and a member of the Local Group, which is made up of the galaxies located closest to the Milky Way (our Milky Way is considered a member of the Local Group as well). M110 is approximately 2,690,000 light-years away from Earth and has a magnitude of 8. Credit: ESA/Hubble & NASA, L. Ferrarese et al.

Many of the best-loved galaxies in the cosmos are remarkably large, close, massive, bright, or beautiful, often with an unusual or intriguing structure or history. However, it takes all kinds to make a universe — as demonstrated by this Hubble image of Messier 110.

Messier 110 may not look like much, but it is a fascinating near neighbor of our home galaxy, and an unusual example of its type. It is a member of the Local Group, a gathering of galaxies comprising the Milky Way and a number of the galaxies closest to it. Specifically, Messier 110 is one of the many satellite galaxies encircling the Andromeda galaxy, the nearest major galaxy to our own, and is classified as a dwarf elliptical galaxy, meaning that it has a smooth and almost featureless structure. Elliptical galaxies lack arms and notable pockets of star formation — both characteristic features of spiral galaxies. Dwarf elliptical are quite common in groups and clusters of galaxies, and are often satellites of larger galaxies.

Because they lack stellar nurseries and contain mostly old stars, elliptical galaxies are often considered “dead” when compared to their spiral relatives. However, astronomers have spotted signs of a population of young, blue stars at the center of Messier 110 — hinting that it may not be so “dead” after all.

Messier 110 is featured in Hubble’s Messier catalog, which includes some of the most fascinating celestial objects that can be observed from Earth’s Northern Hemisphere. See the NASA-processed image and other Messier objects in Hubble’s Messier Catalog.

M110 is an elliptical galaxy, which means that it has a smooth and nearly featureless structure. Elliptical galaxies do not have arms or regions of star formation. They are oftentimes considered “dead” compared to spiral galaxies, and the stars in elliptical galaxies are often older than those in other galaxies. However, there is evidence that a population of young blue stars exists at the center of M110. This small elliptical galaxy has approximately 10 billion stars, as well as at least eight globular clusters (the brightest of which can be seen with large telescopes).

This Hubble observation was taken in visible and near-infrared light with the Wide Field and Planetary Camera 2. The core of M110 is seen toward the lower right of the image, with the galaxy’s globular clusters and numerous stars shown as points of light throughout the frame. Also featured in this Hubble image are large clouds of gas and dust, seen as dark splotches (one large region is located near the middle of the image and another, smaller one appears above the galaxy’s core). Hubble took these observations of M110 to study the development of globular clusters located in the galaxy.

M110 Star Chart

This star chart for M110 represents the view from mid-northern latitudes for the given month and time.
Credit: Image courtesy of Stellarium

With a telescope, M110 is fairly easy to spot near the core of the much larger and brighter Andromeda galaxy. Smaller telescopes will only reveal a faint, diffuse patch of light, while larger telescopes will unveil an oval shape with a brighter core. The best time to view M110 is during November.

Iranian Students Set to Start at U.S. Universities Are Barred From Country

(THIS ARTICLE IS COURTESY OF THE NEW YORK TIMES)

 

Iranian Students Set to Start at U.S. Universities Are Barred From Country

The students, who were mostly headed to schools in the University of California system, had visas in hand when they were blocked from their flights this month.

ImageNima Abdollahpour had planned to study electrical and computer engineering at the University of California, Davis.

At least a dozen Iranian students who were set to begin graduate programs in engineering and computer science say their visas were abruptly canceled and they were barred from their flights to the United States this month.

The sudden batch of visa cancellations, which came at a time of heightened tensions between the United States and Iran, set off a scramble by university officials, lawmakers, the students’ union and Iranian-American advocates to figure out what had happened.

The State Department said that there had been no change in policy regarding student visas, and higher education officials say that visa problems arise every fall for some of the hundreds of thousands of international students who travel to attend American colleges and universities.

But the students, most of whom were headed to schools in the University of California system, say their visas were revoked at the last minute, without any warning or explanation. Most were prevented from boarding flights in Iran, and others from boarding connecting flights in the Persian Gulf. One was detained at Boston Logan International Airport and then turned back.

Many of the students said that a State Department webpage showed their visa cases had been updated around Aug. 30, and they were prevented from boarding in early September.

All of that came before a Sept. 14 attack on two key Saudi oil installations, which has escalated a standoff between the United States and its ally Saudi Arabia against Iran.

[President Trump announced a new round of sanctions against Iran on Friday.]

A law enacted in 2012 under President Barack Obama requires the United States government to deny visas to Iranian students whose coursework would prepare them to work in the energy or nuclear sectors in their home country. Consular officials have wide discretion on how to interpret the statute and put it in place, said Jamal Abdi, the president of the National Iranian American Council, a Washington-based group.

Mark Dubowitz, the chief executive of the Foundation for Defense of Democracies, also based in Washington, said he appreciated that the 2012 law had sought to prevent knowledge gained in the United States from being used in the service of the Iranian government.

But he pointed to the difficulty in predicting how students would use technical skills that are widely sought after and applicable in many industries. He suggested a more radical approach: to overturn the Trump administration’s travel ban and require Iranian students in sensitive fields to stay in the United States after graduation.

Most Iranians cannot obtain visas to travel to the United States because of the travel ban on visitors from their country, as well as from Libya, Somalia, Syria, Yemen, North Korea and Venezuela. But there are narrow exemptions, including for students. Most of the students who were barred had been given single-entry visas, and were prepared to go years without seeing family members who would not have been able to visit them.

In phone interviews and emails, the students said they were crestfallen. Some had left high-level jobs or sold their homes, or had turned down opportunities in Europe or Canada. Most said their studies had been fully funded, and many had been slated to begin teaching or research positions in addition to their studies.

“I feel I’m damaged emotionally, financially, academically,” said Peyman, 23, who was supposed to begin a degree in electrical engineering at the University of California at San Diego. He asked to be identified only by his first name because he did not want to jeopardize his chances of getting another visa.

Peyman said that he had been barred from a connecting flight in Qatar this month and that an airline employee had scrawled “CANCELLED” across his visa in pen, saying the instructions to do so had come from the Department of Homeland Security.

The State Department does not release data on visa revocations, and the department said it could not release information about individual cases.

Mr. Abdi, the president of the National Iranian American Council, said the group normally hears about visa denials, not last-minute revocations. But new vetting procedures — including reviewing social media information from visa applicants — have been “a black box,” he said.

The student workers in the University of California system are represented by the United Automobile Workers Local 2865. Its president, Kavitha Iyengar, said in a statement that her members “do not deserve to be discriminated against.”

She said that the union often helps members who have visa issues, but that she had never seen a problem of this scope.

John A. Pérez, the chairman of the University of California system’s Board of Regents, said the university would stand with its international students “no matter where they were born — and protect them in any way we can from the unpredictable actions of this administration.”

The university’s media relations office said in a separate statement that it was working with government agencies and lawmakers to resolve the issue. It also noted that other Iranian students in the science, technology, engineering and math fields had arrived on campus before September.

A spokesman for Customs and Border Protection reiterated that there had been no change in policy. He added that the agency had the authority to cancel visas but also had policies in place “to ensure multiple layers of review when adjudicating a denial of admission.”

The White House did not immediately respond to a question about whether visa policy had been changed.

At a time when the Iranian economy is in dire condition, hobbled by American sanctions, many Iranian students pay out of pocket to visit the American embassies in Armenia or Turkey for visa interviews, in addition to paying for plane tickets and other arrangements.

Nima Abdollahpour, 23, completed his bachelor’s degree at Sharif University of Technology in Tehran, which is often called the M.I.T. of Iran, and had planned to study electrical and computer engineering at the University of California, Davis.

He said he and other students had grown frustrated as they were directed from one government agency to the next.

“I am a student who will lose another year or two of my life to find another program, as well as tons of money and energy,” he said.

Chinese scholars have also faced restrictions on visas to the United States amid tensions between the two countries, prompting educators to voice concerns about the possible impact on innovation and on researchers already in the United States. Last month, nine Chinese undergraduate students enrolled at Arizona State University were detained at Los Angeles International Airport and sent back to China without explanation.

In a statement on Thursday, Michael M. Crow, the president of Arizona State University, criticized Customs and Border Protection’s handling of the student visa process.

“They are unevenly and inappropriately making determinations that have no factual basis and that they have no experience making,” he said.

“If C.B.P. and D.H.S. do not take this problem seriously,” Mr. Crow said, “all universities need to seek review by Congress and the courts.”

More coverage of international students’ entry to the United States
Harvard Student Says He Was Barred From U.S. Over His Friends’ Social Media Posts

International Students Face Hurdles Under Trump Administration Policy

Visa Delays at Backlogged Immigration Service Strand International Students

Karen Zraick is a breaking news and general assignment reporter who writes frequently about race, gender and civil rights. She has also worked as an editor on the International desk and in news curation. @karenzraick

Chicago police officer shot on South Side

(THIS ARTICLE IS COURTESY OF WGN NEWS CHANNEL 9 OF CHICAGO)

 

Chicago police officer shot on South Side: officials

CHICAGO — A Chicago police officer was shot Saturday morning on the city’s West Englewood neighborhood, according to officials.

The officer was on the 6500 block of South Winchester Avenue around 8:40 a.m. when he was shot. Police did not release details about the shooting.

The officer was taken to Advocate Christ Medical Center in an unknown condition.

No further information was provided.

New top story from Time: Police Say 2 People Killed and 8 Injured in South Carolina Bar Shooting

World Best News

(LANCASTER, S.C.) ? Authorities say a shooting at a bar in South Carolina left two people dead and eight injured.

The Lancaster County Sherriff?s Office said in a statement that the agency was investigating a shooting at a bar early Saturday.

Two adult males were shot and killed. Four injured victims were airlifted to medical facilities for treatment. The other four people were treated at local facilities for injuries considered noncritical. None of the victims were identified. The statement said authorities were not sure whether more than one person fired a weapon.

The statement says a large crowd was at the bar when the shooting occurred.

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When did the dinosaurs roam Earth?

(THIS ARTICLE IS COURTESY OF TRIVIA GENIUS)

 

Science

When did the dinosaurs roam Earth?

The age of the dinosaurs has fascinated the modern imagination for centuries. Often, we are tempted to think of the era as an ancient time when all our favorite dinosaurs squared off against one another in a battle of survival.

However, dinosaurs ruled Earth for a period spanning hundreds of millions of years, during which world-ending events occurred, and the planet changed in ways that are almost difficult to imagine. Here is a guide to the different time periods during which the dinosaurs roamed the planet.

Mesozoic Era

Illustration of dinosaurs during the Mesozoic Era
Credit: CoreyFord/ iStock

The overall time period in which the dinosaurs lived was known as the Mesozoic Era. The Mesozoic Era lasted 180 million years, from 248 million years ago to 65 million years ago. It was preceded by the Paleozoic era, during which life began to take shape, and was followed by the Cenozoic Era, in which we live.

The Mesozoic Era is divided into three distinct time periods:

  • The Triassic Period – 248 million to 206 million years ago
  • The Jurassic Period – 206 million to 146 million years ago
  • The Cretaceous Period – 146 million to 65 million years ago

During the Mesozoic Era, mountains rose, climates shifted, and life reshaped itself multiple times.

Triassic period

Fossil of a pterosaur
Credit: AKKHARAT JARUSILAWONG/ Shutterstock

The first period of the Mesozoic era was the Triassic period. During this time, all the continents were still connected in one giant super continent, known as Pangaea. Temperatures were warmer and there were no polar ice caps.

The oceans teemed with life during this period. Turtles and fish were common, and the corals developed alongside mollusks and ammonites. Large marine reptiles were present as well, such as the plesiosaurus and ichthyosaurus.

On land, early dinosaurs and mammals evolved, and the first flying reptiles, the pterosaurs, took to the skies. There were no flowering plants or grass present during the Triassic period, but cycads, ferns and ginkgoes grew near water sources such as rivers or streams. Small forests of conifers grew in some parts of Pangaea, but for the most part, inland areas were arid deserts with little or no plant or animal life.

Jurassic period

Illustration of Brachiosaurs
Credit: Orla/ iStock

The Triassic period came to an end with a mass extinction that wiped out over 90 percent of the species on Earth. The animals that survived this event began to repopulate the planet and usher in the Jurassic period.

The Jurassic period was marked by the slow break-up of Pangaea into two smaller landmasses known as Laurasia and Gondwana. When the supercontinent split, new mountains arose in the sea, pushing the sea level up and creating a much wetter, more humid environment.

Ferns and mosses covered much of the ground while the small coniferous forest of the Triassic period expanded to cover wide swaths of the two continents.

Giant dinosaurs ruled the land, the largest of which was the plant-eating Brachiosaurs, which scientists believe could grow to be 80 feet long and 50 feet tall. These large herbivores were hunted by massive carnivores such as the Allosaurus.

The Jurassic period also saw the first birds diverge from the reptile family, and the Archaeopteryx flew above these massive dinosaurs.

Cretaceous period

Skeleton of a Tyrannosaurus Rex
Credit: DavidHCoder/ iStock

During the Cretaceous period, the continents continued to drift apart and end in the locations that we know them today. The climate became both wetter and cooler, resulting in the emergence of the polar ice caps and setting the stage for the glaciers that covered large parts of North America, Europe, and Asia in the following era.

The drifting continents resulted in increased specialization and many new types of dinosaurs. Triceratops and Iguanodon traveled in herds, feasting on the ancestors of the flowers, herbs and broad-leaved trees that populate Earth today.

These massive plant-eating animals were hunted by the famous Tyrannosaurus Rex. Snakes first developed during this time period, as well as crocodiles and turtles. Insects and pterosaurs flew in the air, and the first mammals scurried across the ground.

Despite the proliferation of life during this period, another mass extinction followed a natural disaster at the end of the Cretaceous period. While both reptiles and mammals survived in small numbers, the age of the dinosaurs came to an end.

What’s next?

Earth as viewed from space
Credit: dem10/ iStock

In light of this vast history, do you ever wonder what lies ahead for both Earth and us?