The gecko’s remarkable ability to regenerate its tail in the space of a month could help scientists figure out how to heal spine injuries in humans, and it’s all down to the regenerative ability of stem cells.
Scientists studying gecko tails at the cellular level – how they detach when under pressure, and how they grow back again – have found a particular group of stem cells known as radial glial cells are responsible for growing the tail back.
As gecko tails hold much of their spinal cord, the team from the University of Guelph in Canada thinks that studying these radial glial cells and their behaviour could give us a better understanding of how spinal cords could eventually be prompted to grow back in human bodies.
“To many scientists, [geckos] are the ultimate forms of regenerating species,” one of the researchers, Matthew Vickaryous, told Claire Maldarelli at Popular Science.
The study looked at tail regeneration in leopard geckos, which surrender their tails relatively easily when faced with a predator – the researchers could literally pinch the tails to get them to fall away.
When that happens, the radial glial cells start multiplying and generating a variety of proteins to respond to the injury. Like other stem cells, they can morph into different types of cells depending on what the body needs.
In fact, there’s already been promising research looking at how stem cells could be coaxed into regenerating parts of the spinal cord in mammals.
The researchers also noticed a blood clot forming when the gecko’s tail was detached, sealing the injury. By blocking that clot with a piece of skin, the tail regeneration process was stopped.
That suggests there’s something about the open wound that passes the right signals back to the gecko that the tail needs replacing. It’s possible that the scar tissue that forms around spinal injuries in humans works like the skin placed on the gecko tails, somehow preventing regrowth.
The scar tissue that human bodies produce is important in reducing inflammation, but the gecko seems to do fine without it, leaving the researchers to wonder if this could be a clue as to how they can regenerate extra limbs so quickly.
“This absence of a scar is a big feature, we think, that permits them to regrow,” Vickaryous told Popular Science.
The next question is why the human body forms scar tissue rather than growing new cells. Humans have plenty of radial glial cells as developing foetuses, but these disappear as the body develops, so replacing them could be one future option for treatment.
We’re still a long way from translating these findings into something that might work for spinal cord injuries, but it’s another step towards that goal, like the research from earlier this year looking at reconnecting sensory neurons in the spine.
What’s more, we’ve also seen recent research into manipulating wound healing so that scar tissue doesn’t form – by changing the protein signalling in lab tests, the researchers were able to regenerate normal skin.
If we can eventually figure out a way to prompt stem cells in the spine into regrowing the right kind of tissue, we might have the gecko to thank.
“As the closest living regeneration-competent relatives of mammals, reptiles such as geckos provide novel opportunities to probe the mechanisms leading to successful functional recovery following spinal cord injury,” conclude the researchers.
We’re all familiar with the idea of solar sails to explore the Solar System, using the light pressure from the Sun. But there’s another propulsion system that could harness the power of the Sun, electric sails, and it’s a pretty exciting idea.
A few weeks ago, I tackled a question someone had about my favorite exotic propulsion systems, and I rattled off a few ideas that I find exciting: solar sails, nuclear rockets, ion engines, etc. But there’s another propulsion system that keeps coming up, and I totally forgot to mention, but it’s one of the best ideas I’ve heard in awhile: electric sails.
As you probably know, a solar sail works by harnessing the photons of light streaming from the Sun. Although photons are massless, they do have momentum, and can transfer it when they bounce off a reflective surface.
In addition to light, the Sun is also blowing off a steady stream of charged particles – the solar wind. A team of engineers from Finland, led by Dr. Pekka Janhunen, has proposed building an electric sail that will use these particles to carry spacecraft out into the Solar System.
To understand how this works, I’ll need to jam a few concepts into your brain.
First, the Sun. That deadly ball of radiation in the sky. As you probably know, there’s a steady stream of charged particles, mainly electrons and protons, zipping away from the Sun in all directions.
Astronomers aren’t entirely sure how, but some mechanism in the Sun’s corona, its upper atmosphere, accelerates these particles on an escape velocity. Their speed varies from 250 to 750 km/s.
Solar Wind Power
The solar wind travels away from the Sun, and out into space. We see its effects on comets, giving them their characteristic tails, and it forms a bubble around the Solar System known as the heliosphere. This is where the solar wind from the Sun meets the collective solar winds from the other stars in the Milky Way.
The solar wind does cause a direct pressure, like an actual wind, but it’s incredibly weak, a fraction of the light pressure a solar sail experiences.
But the solar wind is negatively charged, and this is the key.
An electric sail works by reeling out an incredibly thin wire, just 25 microns thick, but 20 kilometers long. The spacecraft is equipped with solar panels and an electron gun which takes just a few hundred watts to run.
By shooting electrons off into space, the spacecraft maintains a highly positive charged state. As the negatively charged particles from the Sun encounter the positively charged tether, they “see” it a huge obstacle 100 meters across, and crash into it.
By imparting their momentum into the tether and spacecraft, the ions accelerate it away from the Sun.
The amount of acceleration is very weak, but it’s constant pressure from the Sun and can add up over a long period of time. For example, if a 1000 kg spacecraft had 100 of these wires extending out in all directions, it could receive an acceleration of 1 mm per second per second.
In the first second it travels 1 mm, and then 2 mm in the next second, etc. Over the course of a year, this spacecraft could be going 30 km/s. Just for comparison, the fastest spacecraft out there, NASA’s Voyager 1, is merely going about 17 km/s. So, much faster, definitely on an escape velocity from the Solar System.
One of the downsides of the method, actually, is that it won’t work within the Earth’s magnetosphere. So an electric sail-powered spacecraft would need to be carried by a traditional rocket away from the Earth before it could unfurl its sail and head out into deep space.
I’m sure you’re wondering if this is a one-way trip to get away from the Sun, but it’s actually not. Just like with solar sails, a electric sail can be pivoted. Depending on which side of the sail the solar wind hits, it either raises or lowers the spacecraft’s orbit from the Sun.
Strike the sail on one side and you raise its orbit to travel to the outer Solar System. But you could also strike the other side and lower its orbit, allowing it to journey down into the inner Solar System. It’s an incredibly versatile propulsion system, and the Sun does all the work.
Although this sounds like science fiction, there are actually some tests in the works. An Estonian prototype satellite was launched back in 2013, but its motor failed to reel out the tether. The Finnish Aalto-1 satellite was launched in June 2017, and one of its experiments is to test out an electric sail.
We should find out if the technique is viable later this year.
The HERTS Mission
It’s not just the Finns who are considering this propulsion system. In 2015, NASA announced that they had awarded a Phase II Innovative Advanced Concepts grant to Dr. Pekka Janhunen and his team to explore how this technology could be used to reach the outer Solar System in less time than other methods.
The Heliopause Electrostatic Rapid Transit System, or HERTS spacecraft would extend 20 of these electric tethers outward from the center, forming a huge circular electric sail to catch the solar wind. By slowly rotating the spacecraft, the centrifugal forces will stretch the tethers out into this circular shape.
With its positive charge, each tether acts like a huge barrier to the solar wind, giving the spacecraft an effective surface area of 600 square kilometers once it launches from the Earth. As it gets farther, from Earth, though, its effective area increases to the equivalent of 1,200 square km by the time it reaches Jupiter.
When a solar sail starts to lose power, an electric sail just keeps accelerating. In fact, it would keep accelerating out past the orbit of Uranus.
If the technology works out, the HERTS mission could reach the heliopause in just 10 years. It took Voyager 1 35 years to reach this distance, 121 astronomical units from the Sun.
But what about steering? By changing the voltage on each wire as the spacecraft rotates, you could have the whole sail interact differently on one side or the other to the solar wind. You could steer the whole spacecraft like the sails on a boat.
In September 2017, a team of researchers with the Finnish Meteorological Institute announced a pretty radical idea for how they might be able to use electric sails to comprehensively explore the asteroid belt.
Instead of a single spacecraft, they proposed building a fleet of 50 separate 5-kg satellites. Each one would reel out its own 20 km-long tether and catch the Sun’s solar wind. Over the course of a 3-year mission, the spacecraft would travel out to the asteroid belt, and visit several different space rocks. The full fleet would probably be able to explore 300 separate objects.
Each spacecraft would be equipped with a small telescope with only a 40 mm aperture. That’s about the size of a spotting scope, or half a pair of binoculars, but it would be enough to resolve features on the surface of an asteroid as small as 100 meters across. They’d also have an infrared spectrometer to be able to determine what minerals each asteroid is made of.
That’s a great way to find that $ 10 trillion asteroid made of solid platinum.
Because the spacecraft would be too small to communicate all the way back to Earth, they’d need to store the data on board, and then transmit everything once they came past our planet 3 years later.
The planetary scientists I’ve talked to love the idea of being able to survey this many different objects at the same time, and the electric sail idea is one of the most efficient methods to do it.
According to the researchers, they could do the mission for about $ 70 million, bringing the cost to analyze each asteroid down to about $ 240,000. That would be cheap compared to any other method proposed of studying asteroids.
Space exploration uses traditional chemical rockets because they’re known and reliable. Sure they have their shortcomings, but they’ve taken us across the Solar System, to billions of kilometers away from Earth.
But there are other forms of propulsion in the works, like the electric sail. And over the coming decades, we’re going to see more and more of these ideas put to the test. A fuel free propulsion system that can carry a spacecraft into the outer reaches of the Solar System? Yes please.
I’ll keep you posted when more electric sails are tested.
You wake up, get ready for work, have some toast and coffee with your spouse, then wave goodbye. It’s your typical workday. There is, however, something unusual: your beloved has been dead for many years. You didn’t have breakfast with your spouse – but rather with a simulation of your spouse.
The simulation lives in a virtual environment, perhaps accessed by a device such as the Oculus Rift. A digital bereavement company has captured and analysed torrents of data about your husband to create a digital likeness. His voice, his gait, his idiosyncrasies and mannerisms, the undulations of his laugh – all are replicated with near-perfect similitude. Spending time with your digitally reborn spouse has become a part of your daily routine.
Death is often viewed as the great leveller that marks the cessation of experience. But perhaps this needn’t be the case. Even if the dead can’t interact with us anymore, we can still interact with a simulation of them. It was the death of my father that inspired me to embark on a project to make this fantasy a reality.
Two hundred years ago, most people didn’t have access to a picture of their dearly departed, and a few decades ago the same could be said for any film of a person. Yet, soon, simulations could be able to accurately imitate those who have died so that we can continue to interact with them as if they continued to live. As emerging technologies conspire to make simulations of the dead a part of our lives, this possibility is no longer the realm of science fiction.
With smartphones, the quantified-self movement and massive online data collection, one can get a passably accurate view of how a person behaves. This type of data collection would be the basis of creating simulations of the deceased. Humans have a natural tendency to ascribe agency – indeed personality – to animate objects, so creating a convincing simulation might not be as hard as it first seems. Consider Eliza, a computer program with a few lines of code created in the 1960s which could convince people that they were talking to a psychotherapist. And bots have been getting more sophisticated still ever since.
One immediate objection is that a simulation is never going to be as rich as the real thing. But this is akin to saying that a chess program is not going to be able to play chess in the same artful manner that a human champion does. While IBM’s Deep Blue had an exhaustive search-based chess-playing architecture that was less than elegant, it did accomplish the task of defeating the greatest chess grandmaster who ever lived.
If our hypothetical simulation can pass the deceased person’s version of the Turing test, then we have accomplished the task of having experiences of the dead. Don’t get hung up on ascribing intelligence or consciousness to the software. If the only goal is to have the experience of interacting with a person who is now deceased, then the metaphysics of personal identity is irrelevant. Will such a system have a soul? Will it be conscious? At best, these question are irrelevant and, at worst, they distract us from actually attempting to build simulations. My project focuses on making experiences of a deceased person possible – but not necessarily experiences with the deceased.
Simulations can be thought of as the next step in the evolution of bereavement. Whether it is by writing eulogies, building memorials, creating tombs or simply keeping a photograph on the nightstand, cultures have different ways of remembering and mourning – but they always do remember and mourn. One of the great appeals of religion is the promise of reunion with the departed in one form or another. Simulations hold the possibility that the living are no longer permanently cut off from the dead.
These simulations will also change how we relate to the living. Imagine if you didn’t have to say goodbye forever to anyone (that is, until you yourself die). A friend’s death would be met with bereavement and deep sadness, of course. But at any moment in the future you would still be able to spend time laughing and reminiscing with a simulation so similar to your friend that it would be difficult to tell the two apart.
At the same time, a world where you can interact freely with idealised simulations of other people could have a deleterious effect on real-world relationships. Why interact with your petulant uncle in real life when you can interact with an idealised, and much more fun, version of him in the digital world? After all, bots can be muted and their bothersome traits simply deleted. Why bother with the living if the dead can provide comfort and personality tailored to our whims?
New and unexpected patterns of behaviour might also emerge. Perhaps simulations will allow people to hold grudges even after a person has died, continuing to combat a bot that is only ever a click away. Alternatively, one might wait for the other’s demise and let go of grudges later on so that they can deal with a more pleasant version of that person. The only difference is that it will not be a person that they are interacting with but rather a simulacra.
If we don’t start a discussion about the possibility and viability of simulations of the deceased now, then they will be thrust upon us when we’re not ready for them in the near future. The road will be fraught with moral dilemmas and questions about the human condition. Soon, the line that divides the living from the dead might not be so clear.
Muhammad Aurangzeb Ahmad
This article was originally published at Aeon and has been republished under Creative Commons.
Starting on November 3rd, Verizon customers who want to stream full 4K video on their phones can finally do so. Just two months ago, the company had split its unlimited plans into two tiers; one capped streaming at 480p, while the more expensive one… Engadget RSS Feed
Within the next decade, planes could be capable of traveling across the country by hypersonic flight in less than an hour—all it would take is some boron nitride.
A key factor for a vehicle to maintain extremely high speeds is the intense amount of heat generated during travel; for example, the now-retired supersonic Concorde aircraft experienced temperatures of up to 260°F at its lazy cruising speed of 1,534 miles per hour. As such, the materials used to build these aircraft must also be able to withstand very high heat, in addition to being structurally stable and lightweight. A study conducted by researchers from NASA and Binghamton University investigated the properties of nanotubes made using boron nitride, a combination of boron and nitrogen. The study revealed it could potentially be used to make hypersonic travel—speeds above 4,000 miles per hour—possible.
Currently, carbon nanotubes are used in aircraft due to their strength and ability to withstand temperatures up to 400 degrees Celsius (752 degress Fahrenheit). Boron nitride nanotubes (BNNTs), however, can withstand up to 900 degrees Celsius (1652 Fahrenheit). They can also handle high amounts of stress, and are much more lightweight than their carbon counterparts.
The Price of Air Travel
The problem with using BNNTs is their cost. According to Binghamton University Associate Professor of Mechanical Engineering Changhong Ke, coating an aircraft with BNNTs would run a very high price tag.
“NASA currently owns one of the few facilities in the world able to produce quality BNNTs,” said Ke. “Right now, BNNTs cost about $ 1,000 per gram. It would be impractical to use a product that expensive.”
Despite the high production cost, it’s possible prices will decrease, and production increase, after more studies detail the material’s usefulness. Carbon nanotubes were around the same price 20 years ago, but are now between $ 10 and $ 20 per gram. Ke believes something similar will happen with BNNTs.