Can humans travel through wormholes in space?
Two new studies examine ways we could engineer human wormhole travel.
Marcelo Gleiser is a professor of natural philosophy, physics, and astronomy at Dartmouth College. He is a Fellow of the American Physical Society, a recipient of the Presidential Faculty Fellows Award from the White House and NSF, and was awarded the 2019 Templeton Prize. Gleiser has authored five books and is the co-founder of 13.8, where he writes about science and culture with physicist Adam Frank.
- Sci-fi movies and books love wormholes—how else can we hope to travel through interstellar distances?
- But wormholes are notoriously unstable; it's hard to keep them open or make them big enough.
- Two new papers offer some hope in solving both of these issues, but at a high price.
Imagine if we could cut paths through the vastness of space to make a network of tunnels linking distant stars somewhat like subway stations here on Earth? The tunnels are what physicists call wormholes, strange funnel-like folds in the very fabric of spacetime that would be—if they exist—major shortcuts for interstellar travel. You can visualize it in two dimensions like this: Take a piece of paper and bend it in the middle so that it makes a U shape. If an imaginary flat little bug wants to go from one side to the other, it needs to slide along the paper. Or, if there were a bridge between the two sides of the paper the bug could go straight between them, a much shorter path. Since we live in three dimensions, the entrances to the wormholes would be more like spheres than holes, connected by a four-dimensional "tube." It's much easier to write the equations than to visualize this! Amazingly, because the theory of general relativity links space and time into a four-dimensional spacetime, wormholes could, in principle, connect distant points in space, or in time, or both.
A wormhole connecting two points in space.
Credit: TDHster via Adobe Stock
The idea of wormholes is not new. Its origins reach back to 1935 (and even earlier), when Albert Einstein and Nathan Rosen published a paper constructing what became known as an Einstein-Rosen bridge. (The name 'wormhole' came up later, in a 1957 paper by Charles Misner and John Wheeler, Wheeler also being the one who coined the term 'black hole.') Basically, an Einstein-Rosen bridge is a connection between two distant points of the universe or possibly even different universes through a tunnel that goes into a black hole. Exciting as the possibility is, the throats of such bridges are notoriously unstable and any object with mass that ventures through it would cause it to collapse upon itself almost immediately, closing the connection. To force the wormholes to stay open, one would need to add a kind of exotic matter that has both negative energy density and pressure—not something that is known in the universe. (Interestingly, negative pressure is not as crazy as it seems; dark energy, the fuel that is currently accelerating the cosmic expansion, does it exactly because it has negative pressure. But negative energy density is a whole other story.)
If wormholes exist, if they have wide mouths, and if they can be kept open (three big but not impossible ifs) then it's conceivable that we could travel through them to faraway spots in the universe. Arthur C. Clarke used them in "2001: A Space Odyssey", where the alien intelligences had constructed a network of intersecting tunnels they used as we use the subway. Carl Sagan used them in "Contact" so that humans could confirm the existence of intelligent ETs. "Interstellar" uses them so that we can try to find another home for our species.
If wormholes exist, if they have wide mouths, and if they can be kept open (three big but not impossible ifs) then it's conceivable that we could travel through them to faraway spots in the universe.
Two recent papers try to get around some of these issues. Jose Luis Blázquez-Salcedo, Christian Knoll, and Eugen Radu use normal matter with electric charge to stabilize the wormhole, but the resulting throat is still of submicroscopic width, so not useful for human travel. It is also hard to justify net electric charges in black hole solutions as they tend to get neutralized by surrounding matter, similar to how we get shocked with static electricity in dry weather. Juan Maldacena and Alexey Milekhin's paper is titled 'Humanly Traversable Wormholes', thus raising the stakes right off the bat. However, they are open to admitting that "in this paper, we revisit the question [of humanly traversable wormholes] and we engage in some 'science fiction.'" The first ingredient is the existence of some kind of matter (the "dark sector") that only interacts with normal matter (stars, us, frogs) through gravity. Another point is that to support the passage of human-size travelers, the model needs to exist in five dimensions, thus one extra space dimension. When all is set up, the wormhole connects two black holes with a magnetic field running through it. And the whole thing needs to spin to keep it stable, and completely isolated from particles that may fall into it compromising its design. Oh yes, and extremely low temperature as well, even better at absolute zero, an unattainable limit in practice.
Maldacena and Milekhins' paper is an amazing tour through the power of speculative theoretical physics. They are the first to admit that the object they construct is very implausible and have no idea how it could be formed in nature. In their defense, pushing the limits (or beyond the limits) of understanding is what we need to expand the frontiers of knowledge. For those who dream of humanly traversable wormholes, let's hope that more realistic solutions would become viable in the future, even if not the near future. Or maybe aliens that have built them will tell us how.
A new paper reveals that the Voyager 1 spacecraft detected a constant hum coming from outside our Solar System.
Voyager 1, humanity's most faraway spacecraft, has detected an unusual "hum" coming from outside our solar system. Fourteen billion miles away from Earth, the Voyager's instruments picked up a droning sound that may be caused by plasma (ionized gas) in the vast emptiness of interstellar space.
Launched in 1977, the Voyager 1 space probe — along with its twin Voyager 2 — has been traveling farther and farther into space for over 44 years. It has now breached the edge of our solar system, exiting the heliosphere, the bubble-like region of space influenced by the sun. Now, the spacecraft is moving through the "interstellar medium," where it recorded the peculiar sound.
Stella Koch Ocker, a doctoral student in astronomy at Cornell University, discovered the sound in the data from the Voyager's Plasma Wave System (PWS), which measures electron density. Ocker called the drone coming from plasma shock waves "very faint and monotone," likely due to the narrow bandwidth of its frequency.
While they think the persistent background hum may be coming from interstellar gas, the researchers don't yet know what exactly is causing it. It might be produced by "thermally excited plasma oscillations and quasi-thermal noise."
The new paper from Ocker and her colleagues at Cornell University and the University of Iowa, published in Nature Astronomy, also proposes that this is not the last we'll hear of the strange noise. The scientists write that "the emission's persistence suggests that Voyager 1 may be able to continue tracking the interstellar plasma density in the absence of shock-generated plasma oscillation events."
Voyager Captures Sounds of Interstellar Space www.youtube.com
The researchers think the droning sound may hold clues to how interstellar space and the heliopause, which can be thought of as the solar's system border, may be affecting each other. When it first entered interstellar space, the PWS instrument reported disturbances in the gas caused by the sun. But in between such eruptions is where the researchers spotted the steady signature made by the near-vacuum.
Senior author James Cordes, a professor of astronomy at Cornell, compared the interstellar medium to "a quiet or gentle rain," adding that "in the case of a solar outburst, it's like detecting a lightning burst in a thunderstorm and then it's back to a gentle rain."
More data from Voyager over the next few years may hold crucial information to the origins of the hum. The findings are already remarkable considering the space probe is functioning on technology from the mid-1970s. The craft has about 70 kilobytes of computer memory. It also carries a Golden Record created by a committee chaired by the late Carl Sagan, who taught at Cornell University. The 12-inch gold-plated copper disk record is essentially a time capsule, meant to tell the story of Earthlings to extraterrestrials. It contains sounds and images that showcase the diversity of Earth's life and culture.
A team of scientists managed to install onto a smartphone a spectrometer that's capable of identifying specific molecules — with cheap parts you can buy online.
- Spectroscopy provides a non-invasive way to study the chemical composition of matter.
- These techniques analyze the unique ways light interacts with certain materials.
- If spectrometers become a common feature of smartphones, it could someday potentially allow anyone to identify pathogens, detect impurities in food, and verify the authenticity of valuable minerals.
The quality of smartphone cameras has increased exponentially over the past decade. Today's smartphone cameras can not only capture photos that rival those of stand-alone camera systems but also offer practical applications, like heart-rate measurement, foreign-text translation, and augmented reality.
What's the next major functionality of smartphone cameras? It could be the ability to identify chemicals, drugs, and biological molecules, according to a new study published in the Review of Scientific Instruments.
The study describes how a team of scientists at Texas A&M turned a common smartphone into a "pocket-sized" Raman and emission spectral detector by modifying it with just $50 worth of extra equipment. With the added hardware, the smartphone was able to identify chemicals in the field within minutes.
The technology could have a wide range of applications, including diagnosing certain diseases, detecting the presence of pathogens and dangerous chemicals, identifying impurities in food, and verifying the authenticity of valuable artwork and minerals.
Raman and fluorescence spectroscopy
Raman and fluorescence spectroscopies are techniques for discerning the chemical composition of materials. Both strategies exploit the fact that light interacts with certain types of matter in unique ways. But there are some differences between the two techniques.
As the name suggests, fluorescence spectroscopy measures the fluorescence — that is, the light emitted by a substance when it absorbs light or other electromagnetic radiation — of a given material. It works by shining light on a material, which excites the electrons within the molecules of the material. The electrons then emit fluorescent light toward a filter that measures fluorescence.
The particular spectra of fluorescent light that's emitted can help scientists detect small concentrations of particular types of biological molecules within a material. But some biomolecules, such as RNA and DNA, don't emit fluorescent light, or they only do so at extremely low levels. That's where Raman spectroscopy comes into play.
Raman spectroscopy involves shooting a laser at a sample and observing how the light scatters. When light hits molecules, the atoms within the molecules vibrate and photons get scattered. Most of the scattered light is of the same wavelength and color as the original light, so it provides no information. But a tiny fraction of the light gets scattered differently; that is, the wavelength and color are different. Known as Raman scattering, this is extremely useful because it provides highly precise information about the chemical composition of the molecule. In other words, all molecules have a unique Raman "fingerprint."
Creating an affordable, pocket-sized spectrometer
To build the spectrometer, the researchers connected a smartphone to a laser and a series of plastic lenses. The smartphone camera was placed facing a transmission diffraction grating, which splits incoming light into its constituent wavelengths and colors. After a laser is fired into a sample, the scattered light is diffracted through this grating, and the smartphone camera analyzes the light on the other side.
Schematic diagram of the designed system.Credit: Dhankhar et al.
To test the spectrometer, the researchers analyzed a range of sample materials, including carrots and bacteria. The laser used in the spectrometer emits a wavelength that's readily absorbed by the pigments in carrots and bacteria, which is why these materials were chosen.
The results showed that the smartphone spectrometer was able to correctly identify the materials, but it wasn't quite as effective as the best commercially available Raman spectrometers. The researchers noted that their system might be improved by using specific High Dynamic Range (HDR) smartphone camera applications.
Ultimately, the study highlights how improving the fundamentals of a technology, like smartphone cameras, can lead to a surprisingly wide range of useful applications.
"This inexpensive yet accurate recording pocket Raman system has the potential of being an integral part of ubiquitous cell phones that will make it possible to identify chemical impurities and pathogens, in situ within minutes," the researchers concluded.
- Lawrence Kohlberg's experiments gave children a series of moral dilemmas to test how they differed in their responses across various ages.
- He identified three separate stages of moral development from the egoist to the principled person.
- Some people do not progress through all the stages of moral development, which means they will remain "morally undeveloped."
Has your sense of right and wrong changed over the years? Are there things that you see as acceptable today that you'd never dream of doing when you were younger? If you spend time around children, do you notice how starkly different their sense of morality is? How black and white, or egocentric, or oddly rational it can be?
These were questions that Lawrence Kohlberg asked, and his "stages of moral development" dominates a lot of moral psychology today.
The Heinz Dilemma
Kohlberg was curious to see how and why children differed in their ethical judgements, and so he gave roughly 60 children, across a variety of ages, a series of moral dilemmas. They were all given open-ended questions to explain their answers in order to minimize the risk of leading them to a certain response.
For instance, one of the better-known dilemmas involved an old man called Heinz who needed an expensive drug for his dying wife. Heinz only managed to raise half the required money, which the pharmacists wouldn't accept. Unable to afford it, he has only three options. What should he do?
(a) Not steal it because it's breaking the law.
(b) Steal it, and go to jail for breaking the law.
(c) Steal it, but be let off a prison sentence.
What option would you choose?
Stages of Moral Development
From the answers he got, Kohlberg identified three definite levels or stages of our moral development.
Pre-conventional stage. This is characterized by an ego-centric attitude that seeks pleasure and to prevent pain. The primary motivation is to avoid punishment or claim a reward. In this stage of moral development, "good" is defined as whatever is beneficial to oneself. "Bad" is the opposite. For instance, a young child might share their food with a younger sibling not from kindness or some altruistic impulse but because they know that they'll be praised by their parents (or, perhaps, have their food taken away from them).
In the pre-conventional stage, there is no inherent sense of right and wrong, per se, but rather "good" is associated with reward and "bad" is associated with punishment. At this stage, children are sort of like puppies.
If you spend time around children, do you notice how starkly different their sense of morality is? How black and white, or egocentric, or oddly rational it can be?
Conventional stage. This stage reflects a growing sense of social belonging and hence a higher regard for others. Approval and praise are seen as rewards, and behavior is calibrated to please others, obey the law, and promote the good of the family/tribe/nation. In the conventional stage, a person comes to see themselves as part of a community and that their actions have consequences.
Consequently, this stage is much more rule-focused and comes along with a desire to be seen as good. Image, reputation, and prestige matter the most in motivating good behavior — we want to fit into our community.
Post-conventional stage. In this final stage, there is much more self-reflection and moral reasoning, which gives people the capacity to challenge authority. Committing to principles is considered more important than blindly obeying fixed laws. Importantly, a person comes to understand the difference between what is "legal" and what is "right." Ideas such as justice and fairness start to mature. Laws or rules are no longer equated to morality but might be seen as imperfect manifestations of larger principles.
A lot of moral philosophy is only possible in the post-conventional stage. Theories like utilitarianism or Immanuel Kant's duty-focused ethics ask us to consider what's right or wrong in itself, not just because we get a reward or look good to others. Aristotle perhaps sums it up best when he wrote, "I have gained this from philosophy: that I do without being commanded what others do only from fear of the law."
How morally developed are you?
Kohlberg identified these stages as a developmental progression from early infancy all the way to adulthood, and they map almost perfectly onto Jean Piaget's psychology of child development. For instance, the pre-conventional stage usually lasts from birth to roughly nine years old, the conventional occurs mainly during adolescence, and the post-conventional goes into adulthood.
What's important to note, though, is that this is not a fatalistic timetable to which all humans adhere. Kohlberg thought, for instance, that some people never progress or mature. It's quite possible, maybe, for someone to have no actual moral compass at all (which is sometimes associated with psychopathy).
More commonly, though, we all know people who are resolutely bound to the conventional stage, where they care only for their image or others' judgment. Those who do not develop beyond this stage are usually stubbornly, even aggressively, strict in following the rules or the law. Prepubescent children can be positively authoritarian when it comes to obeying the rules of a board game, for instance.
So, what's your answer to the Heinz dilemma? Where do you fall on Kohlberg's moral development scale? Is he right to view it is a progressive, hierarchical maturing, where we have "better" and "worse" stages? Or could it be that as we grow older, we grow more immoral?
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