Exploring space is one of humanity’s most hopeful activities. By going out into the great unknown of the Universe, we hope to extend our reach, find new resources and life forms, while solving many of our earthly problems. But going to space is not something to take for granted—it can actually become impossible. There is a scenario, called the Kessler Syndrome, that can cause the end of all space exploration and dramatically impact our daily lives.
In 1978, the NASA scientist Donald J. Kessler proposed that a chain reaction of exploding space debris can end up making space activities and the use of satellites impossible for generations. He predicted that the number of objects that we keep launching into Low Earth Orbit (LEO) can create such a dense environment above the planet that inevitable collisions could cause a cascading effect. The space junk and shrapnel generated by one collision could make further collisions much more possible. And if you have enough collisions, the amount of space debris could overwhelm the orbital space entirely.
What makes that situation possible is the fact that there are millions of micrometeoroids as well as man-made debris that is already orbiting Earth. The danger posed by even a small fragment that’s traveling at high speeds is easy to see. As calculated by NASA, a 1-centimeter “paint fleck” traveling at 10km/s (22,000 mph) can cause the same damage as a 550-pound object traveling 60 miles per hour on Earth. If the size of the shard was increased to 10 centimeters, such a projectile would have the force of 7 kilograms of TNT. Now imagine thousands of such objects flying around at breakneck speeds and crashing into each other.
Distribution of debris around Earth. (Credit: ESA)
If a chain reaction of exploding space junk did occur, filling the orbital area with such dangerous debris, the space program would indeed be in jeopardy. Travel that goes beyond the LEO, like the planned mission to Mars, would be made more challenging but still conceivably possible.
What would, of course, be affected if the Kessler Syndrome’s worst predictions came to pass, are all the services that rely on satellites. Core aspects of our modern life—GPS, television, military and scientific research—all of that would be under threat.
NASA experienced a small-scale Kessler Syndrome incident in the 1970s when Delta rockets that were left in orbit started to explode into shrapnel clouds. This inspired Kessler, an astrophysicist, to show that there is a point when the amount of debris in an orbit gets to critical mass. At that point, the collision cascading would start even if no more things are launched into space. And once the chain of explosions begins, it can keep going until the orbital space can no longer be used.
Space junk. (Credit: Shutterstock)
In Kessler’s estimate, it would take 30 to 40 years to get to such a threshold. NASA says that its experts caution that we are already at critical mass in the low-Earth orbit, which is about 560-620 miles (900 to 1,000 kilometers) out.
According to NASA estimates, the Earth’s orbit currently has 500,000 pieces of space debris up to 10cm long, over 21,000 pieces of debris longer than 10cm, and more than 100 million pieces of space debris smaller than 1cm.
A 2009 incident dubbed the Cosmos-Iridium collision featured a space collision between Russian and American communication satellites that provided a preview of potential attractions in the massive debris field it created. The accident resulted in more than 2,000 pieces of relatively large space junk.
While there are some safety measures being taken, like the Space Surveillance Network run by the military, the sheer amount of stuff already floating in space makes the domino effect of explosions a likely possibility.
Check out this video about the Kessler Syndrome that features Don Kessler himself. And here’s Kessler’s original paper on the subject, titled 'Collision Frequency of Artificial Satellites: The Creation of a Debris Belt'.
Some scientists have studied near death experiences (NDEs) to try to gain insights into how death overcomes the brain. What they've found is remarkable, a surge of electricity enters the brain moments before brain death. One 2013 study out of the University of Michigan, which examined electrical signals inside the heads of rats, found they entered a hyper-alert state just before death.
Scientists are beginning to think an NDE is caused by reduced blood flow, coupled with abnormal electrical behavior inside the brain. So the stereotypical tunnel of white light might derive from a surge in neural activity. Dr. Sam Parnia is the director of critical care and resuscitation research, at NYU Langone School of Medicine, in New York City. He and colleagues are investigating exactly how the brain dies.
Our cerebral cortex is likely active 2–20 seconds after cardiac arrest. Credit: Getty Images.
In previous work, he's conducted animal studies looking at the moments before and after death. He's also investigated near death experiences. “Many times, those who have had such experiences talk about floating around the room and being aware of the medical team working on their body," Dr. Parnia told Live Science. “They'll describe watching doctors and nurses working and they'll describe having awareness of full conversations, of visual things that were going on, that would otherwise not be known to them."
Medical staff confirm this, he said. So how could those who were technically dead be cognizant of what's happening around them? Even after our breathing and heartbeat stops, we're conscious for about 2–20 seconds, Dr. Parnia says. That's how long the cerebral cortex is thought to last without oxygen. This is the thinking and decision-making part of the brain. It's also responsible for deciphering the information gathered from our senses.
According to Parnia during this period, "You lose all your brain stem reflexes — your gag reflex, your pupil reflex, all that is gone." Brain waves from the cerebral cortex soon become undetectable. Even so, it can take hours for our thinking organ to fully shut down.
Usually, when the heart stops beating, someone performs CPR (cardiopulmonary resuscitation). This will provide about 15% of the oxygen needed to perform normal brain function. "If you manage to restart the heart, which is what CPR attempts to do, you'll gradually start to get the brain functioning again," Parnia said. “The longer you're doing CPR, those brain cell death pathways are still happening — they're just happening at a slightly slower rate."
CPR may help retain some brain function for longer. Credit: Getty Images.
Dr. Parnia's latest, ongoing study looks at large numbers of Europeans and Americans who have experienced cardiac arrest and survived. "In the same way that a group of researchers might be studying the qualitative nature of the human experience of 'love,'" he said, "we're trying to understand the exact features that people experience when they go through death, because we understand that this is going to reflect the universal experience we're all going to have when we die."
One of the objectives is to observe how the brain acts and reacts during cardiac arrest, through the process of death, and during revival. How much oxygen exactly does it take to reboot the brain? How is the brain affected after revival? Learning where the lines are drawn might improve resuscitation techniques, which could save countless lives per year.
"At the same time, we also study the human mind and consciousness in the context of death," Parnia said, “to understand whether consciousness becomes annihilated or whether it continues after you've died for some period of time — and how that relates to what's happening inside the brain in real time."
For more on the scientific perspective on a near death experience, click here:
As he described it, “In my mind's eye I saw many, many things: children that I hadn't even had yet, friends that I had never seen but are now my friends. The thing that really stuck in my mind was playing an instrument". Then Tony landed on his head and lost consciousness.
When he came to at the hospital, he felt like a different person and didn't want to return to his previous life. Over the following weeks, the images kept flashing back into his mind. He felt that he was “being shown something" and that the images represented his future.
Later, Tony saw a picture of a saxophone and recognized it as the instrument he'd seen himself playing. He used his compensation money from the accident to buy one. Now, Tony Kofi is one of the UK's most successful jazz musicians, having won the BBC Jazz awards twice, in 2005 and 2008.
Though Tony's belief that he saw into his future is uncommon, it's by no means uncommon for people to report witnessing multiple scenes from their past during split-second emergency situations. After all, this is where the phrase “my life flashed before my eyes" comes from.
But what explains this phenomenon? Psychologists have proposed a number of explanations, but I'd argue the key to understanding Tony's experience lies in a different interpretation of time itself.
When life flashes before our eyes
The experience of life flashing before one's eyes has been reported for well over a century. In 1892, a Swiss geologist named Albert Heim fell from a precipice while mountain climbing. In his account of the fall, he wrote is was “as if on a distant stage, my whole past life [was] playing itself out in numerous scenes".
More recently, in July 2005, a young woman called Gill Hicks was sitting near one of the bombs that exploded on the London Underground. In the minutes after the accident, she hovered on the brink of death where, as she describes it: “my life was flashing before my eyes, flickering through every scene, every happy and sad moment, everything I have ever done, said, experienced".
In some cases, people don't see a review of their whole lives, but a series of past experiences and events that have special significance to them.
Explaining life reviews
Perhaps surprisingly, given how common it is, the “life review experience" has been studied very little. A handful of theories have been put forward, but they're understandably tentative and rather vague.
For example, a group of Israeli researchers suggested in 2017 that our life events may exist as a continuum in our minds, and may come to the forefront in extreme conditions of psychological and physiological stress.
Another theory is that, when we're close to death, our memories suddenly “unload" themselves, like the contents of a skip being dumped. This could be related to “cortical disinhibition" – a breaking down of the normal regulatory processes of the brain – in highly stressful or dangerous situations, causing a “cascade" of mental impressions.
But the life review is usually reported as a serene and ordered experience, completely unlike the kind of chaotic cascade of experiences associated with cortical disinhibition. And none of these theories explain how it's possible for such a vast amount of information – in many cases, all the events of a person's life – to manifest themselves in a period of a few seconds, and often far less.
Thinking in 'spatial' time
An alternative explanation is to think of time in a “spatial" sense. Our commonsense view of time is as an arrow that moves from the past through the present towards the future, in which we only have direct access to the present. But modern physics has cast doubt on this simple linear view of time.
Indeed, since Einstein's theory of relativity, some physicists have adopted a “spatial" view of time. They argue we live in a static “block universe" in which time is spread out in a kind of panorama where the past, the present and the future co-exist simultaneously.
The modern physicist Carlo Rovelli – author of the best-selling The Order of Time – also holds the view that linear time doesn't exist as a universal fact. This idea reflects the view of the philosopher Immanuel Kant, who argued that time is not an objectively real phenomenon, but a construct of the human mind.
This could explain why some people are able to review the events of their whole lives in an instant. A good deal of previous research – including my own – has suggested that our normal perception of time is simply a product of our normal state of consciousness.
In many altered states of consciousness, time slows down so dramatically that seconds seem to stretch out into minutes. This is a common feature of emergency situations, as well as states of deep meditation, experiences on psychedelic drugs and when athletes are “in the zone".
The limits of understanding
But what about Tony Kofi's apparent visions of his future? Did he really glimpse scenes from his future life? Did he see himself playing the saxophone because somehow his future as a musician was already established?
There are obviously some mundane interpretations of Tony's experience. Perhaps, for instance, he became a saxophone player simply because he saw himself playing it in his vision. But I don't think it's impossible that Tony did glimpse future events.
If time really does exist in a spatial sense – and if it's true that time is a construct of the human mind – then perhaps in some way future events may already be present, just as past events are still present.
Admittedly, this is very difficult to make sense of. But why should everything make sense to us? As I have suggested in a recent book, there must be some aspects of reality that are beyond our comprehension. After all, we're just animals, with a limited awareness of reality. And perhaps more than any other phenomenon, this is especially true of time.
Steve Taylor, Senior Lecturer in Psychology, Leeds Beckett University
This article is republished from The Conversation under a Creative Commons license. Read the original article.
