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IN BRIEF

A new paper asserts that a physical body might be able to pass through a wormhole in spite of the extreme tidal forces that are at play.

A physical object, such as a person or a spacecraft, could theoretically make it through a wormhole in the centre of a black hole, and maybe even access another universe on the other side, physicists have suggested.

In what looks like the logical extension of the plot of Interstellar – where astronauts try to hunt down another universe after the catastrophic effects of climate change destroy Earth – physicists have modelled what would happen to a chair, a scientist, and a spacecraft, if each one ended up inside the spherical wormhole of a black hole.

“What we did was to reconsider a fundamental question on the relation between the gravity and the underlying structure of space-time,” said one of the team, Diego Rubiera-Garcia from the University of Lisbon in Portugal.

“In practical terms, we dropped one assumption that holds in general relativity, but there is no a priori reason for it to hold in extensions of this theory.”

So let’s take a step back first, and go through some of the basics. According to Einstein’s theory of general relativity, at the centre of a black hole lies a singularity – the point at which the forces of gravity are at their most intense, and time and space effectively end.

Watch: What are Wormholes?

If an object approaches the event horizon, it would be crushed in one direction, and stretched in another, thanks to the extreme tidal forces of gravity at play inside a black hole. If the object stays intact long enough to make it to the centre of a black hole, it will be infinitely long and thin: basically, it’s been spaghettified beyond recognition.

Physicists have been playing around with the assumption of a singularity in the centre of a black hole for years, because until we can actually prove it exists, there could be any number of possibilities that still work – in theory.

Earlier this year, physicists from the University of Cambridge in the UK argued that there’s no reason why a singularity necessarily has to be on the inside of a black hole. They suggest that in a universe with five or more dimensions – which isn’t out of the question for us – a ‘naked’ singularly could exist, which is not bound by an event horizon.

Of course, this would mean big, huge things for our current understanding of how the laws of physics govern our Universe, because it basically needs Einstein’s theory of general relativity to be wrong.

“If naked singularities exist, general relativity breaks down,” said one of the team, Saran Tunyasuvunakool, back in January. “And if general relativity breaks down, it would throw everything upside down, because it would no longer have any predictive power – it could no longer be considered as a standalone theory to explain the Universe.”

If you feel you are in a black hole, don’t give up. There’s a way out.

Einstein being wrong isn’t out of the question, either. Stephen Hawking has been battling for decades with the way general relativity appears to clash with quantum mechanics in black holes – a problem known as the information paradox.

So assuming that the stipulations of general relativity aren’t set in stone, the new study from Rubiera-Garcia’s team argue that if you remove singularity from a black hole, what you get in the centre instead is a finite-sized wormhole.

Then, they figured out what could happen if various objects – a chair, a scientist, and a spacecraft – made it beyond the event horizon and into the wormhole. These objects are referred to as ‘observers’.

They modelled these observers as an aggregation of points connected by physical or chemical interactions that hold everything together as the object travels along a geodesic line. A geodesic line is simply the path in spacetime that a free-falling object follows.

“Each particle of the observer follows a geodesic line determined by the gravitational field,” says Rubiera-Garcia. “Each geodesic feels a slightly different gravitational force, but the interactions among the constituents of the body could nonetheless sustain the body.”

Publishing in the journal Classical and Quantum Gravity, the researchers demonstrate this by showing how the time spent by a light ray in a round trip between two parts of the body is always finite.

This means that finite forces, no matter how strong, could compensate for the impact of the gravitational field near and inside the wormhole on a physical body travelling through it.

“Thus, different parts of the body will still establish physical or chemical interactions and, consequently, cause and effect still apply all the way across the throat of the wormhole,” they explain.

So while the theory of general relativity predicts that an object approaching a black hole will be crushed along one direction and stretched along another infinitely, if we assume that the centre of a black hole is a wormhole with a finite radius, the object can only be crushed just as much as the size of the wormhole.

This means according to Rubiera-Garcia’s hypothesis, an object could survive a journey through a wormhole and make it out the other side – and potentially to another universe – technically intact, but it would be crushed to the size of the finite wormhole. At least it’s not completely destroyed, right?

“For a theoretical physicist, the suffering of observers is admissible (one might even consider it part of an experimentalist’s job) but their total destruction is not,” Rubiera-Garcia and his team quip in an opinion piece.

Until we figure out how to actually see a black hole, all of this is going to remain well and truly in the realm of pure hypotheticals. But we’re beginning to see how black holes might not be the horrible, existence-obliterating death traps we thought they were.

As Hawking said at a conference back in August 2015 about his solution to the information paradox: “The message of this lecture is that black holes ain’t as black as they are painted. They are not the eternal prisons they were once thought. … If you feel you are in a black hole, don’t give up. There’s a way out.”

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Credit: Reid Wiseman/NASA

If you want a job protecting Earth from threats from outer space — or even protecting Mars from us — NASA has an opening for you — sort of. The job of planetary protection officer generated quite a bit of buzz last week, when the public learned that a role seemingly out of a science fiction novel was actually a bonafide NASA job. But the position has nothing to do with protecting Earth from little green men, but a whole lot to do with important interplanetary science.

A primary task of the officer is to make sure that during NASA missions earthly microbes don't contaminate potentially habitable environments. And should a mission bring back samples from outer space, the officer is tasked with making sure that dust, or rocks, or whatever is brought back from outer space doesn't contaminate us.

John Rummel, a biology professor at East Carolina University, held the position twice, first between 1990 and 1993 and again from 1998 to 2006.

"The planetary protection job was mostly challenging in that it was not just important for each mission to do the right — required by requirements — thing, but to know why they were doing it, and why it was important to do a good job," Rummel said. "From that aspect, the job was definitely worth it. But as to 'rewards,' those were mostly internal."

Rummel explained that the planetary protection office reports to the associate administrator for each mission, who oversees the cost of the project. That means recommendations made by the officer are often judged in the context of whether or not they will cost the administrator more money — a vexing problem many of us might easily understand from our own work experiences.

Rummel's time as planetary protection officer coincided with the restart of NASA's Mars program.

After the successful twin Viking landings of the 1970s, a few famous searching-for-life experiments came up empty. NASA shifted its attention to other locations in the solar system, and Mars didn't get a launch opportunity until the failed Mars Observer mission in 1992.

A slew of missions followed, however, including the Mars Pathfinder mission that made it all the way to the surface in 1996 and deployed a mini-rover – Sojourner. Several other landing and orbiting missions followed — some successful, others not.

Fifteen years ago, Sojourner rolled down a specially engineered ramp to leave the first ever rover tracks on Mars.

Those missions wouldn't have been possible without the approval of the planetary protection officer, who ensured that Sojourner and other Martian spacecraft were sterile enough to prevent microbes from taking root in potentially life-friendly areas. One of Rummel's first tasks in 1990 was to look at the risk of contamination on Mars and how scientific understanding had changed since the days of the Viking missions.

"I knew people would like to go back and land on Mars, but I also knew we didn't have current advice," Rummel said.

So he assisted in the drafting of a 1992 report – Biological Contamination of Mars. The report concluded that a large part of the surface was "extremely inhospitable to terrestrial life" and for that reason, future missions would not need to be sterilized as much as the Viking missions.

But changes in landing technology meant that NASA had to be extra mindful of different scenarios for its missions. Pathfinder, for example, was supposed to fall to the surface using airbags. If the airbags failed, the mission would need to withstand a fall and possible burial in the soil of up to 1.5 meters (5 feet) without exposing possible Earth microbes to the Martian environment.

Recurring slope lineae in Raga Crater on Mars. Such features have been suggested as "special regions" where life may be present. This image is also from the Mars Reconnaissance Orbiter HiRISE camera

(NASA/JPL-Caltech/University of Arizona)

NASA has seen extensive evidence of briny water flow in recurring slope lineae, which are features that develop on the slopes of craters. Rummel, among others, speculated about recurring slope lineae as early as 2002. While researchers have long observed the formations, it was only in 2015 that NASA had strong enough evidence to say the formations are probably due to liquid water on the surface.

Rummel warned against sending Curiosity to investigate a nearby recurring slope lineae. The materials on the rover's surface could not be thoroughly sterilized with UV radiation due to their properties. And inside the rover is a warm electronics box that could melt any ice with which the box comes into contact.

Rummel was also part of early-stage planning for a "sample return" mission to bring pieces of Mars back to Earth, in collaboration with the French space agency CNES. While that mission never went forward, NASA has left the door open for future sample return missions. The next Mars rover, called Mars 2020, is expected to leave "caches" of interesting material behind for future missions to potentially pick up and bring back to Earth, when we presumably know a little more about how to protect ourselves.

Of course, Mars wasn't the only target of note back in the 1990s when Rummel began his work. NASA already had a Jupiter probe — called Galileo — and was about to launch Cassini, which has now been orbiting Saturn since 2004. Those missions confirmed some intriguing Voyager mission results from the 1970s and 1980s, showing that some of the moons are icy and potentially habitable.

Rummel remembers modifying the planetary protection plan for Galileo as evidence emerged that a liquid ocean might lie underneath Europa's icy surface.

At the end of Galileo's mission, an option was included to deliberately crash the probe into Io or Jupiter, just in case it happened to fall into Europa, damaging a potentially habitable environment underneath the ice. Because the mission planners were uncomfortable with changing Galileo's orbit to fall into Io, they went for a Jupiter extermination — collecting science all the way down.

NASA said the job posting has generated "a lot of excitement," including from Jack Davis a fourth grader from New Jersey and self-described "Guardian of the Galaxy." In a letter to the agency, Davis said he was fit for the job because his sister thought he was an alien, among other qualifications.

Although the planetary protection officer is no intergalactic warrior, it's a position that clearly provokes the imagination of skywatchers young and old.

Originally published on Seeker.