Experts decide to try knocking an asteroid off course
Before the next big, dangerous, incoming rock arrives.
- A NASA/ESA project plans to try and change the path of an extraterrestrial body.
- The target is the moon of a binary asteroid almost 7 million miles away.
- Science is getting serious about planetary defense.
It's a ready-made sci-fi trope: Authorities discover an asteroid racing toward the earth on track to wipe out everything we hold dear. Plus us. In the midst of the panic, an unusually attractive, resolute nobody grabs the public's attention: "I have an idea so crazy it just might work. We can fire a rocket at the demon rock and maybe, just maybe, knock it off course and save the Earth." Cue the popcorn and two hours of your life you'll never get back.
But maybe the hero's crazy idea could work. Of course, you wouldn't want to wait until it has to work to find out. So that's exactly what an international group of 130 scientists tasked with developing our planetary defenses have resolved to do: They're making plans to fire a spacecraft at a distant object to see if the kinetic impact can change its trajectory.
The AIDA project is a collaboration between NASA and the ESA (European Space Agency). "AIDA" is short for "Asteroid Impact and Deflection Assessment." In September, participants met to hash out the details in Rome. ESA's Ian Carnelli explains why: "Today, we're the first humans in history to have the technology to potentially deflect an asteroid from impacting the Earth. The key question that remains to be answered is, are the technologies and models that we have good enough to actually work? Before you drive a car, you need to have an insurance policy. Well, AIDA is the insurance policy for planet Earth."
The project actually involves two phases: The DART spacecraft will crash into an asteroid, and Hera will follow a few years later to assess the results.
The DART asteroid nudger
NASA is in charge of DART, or "Double Asteroid Redirection Test." In July 2021, the DART satellite, a half-ton chunk of metal, will be launched toward a known asteroid, 65803 Didymos, which is actually a binary object comprised of its main, larger 780-meter body and a smaller, 160-meter moonlet, AKA "Didymoon," that orbits it. It's Didymoon that's DART's target.
"[Didymos] is not on a path to collide with Earth," says Nancy Chabot, director of the mission, "and therefore poses no current threat to the planet, but its binary nature enables DART's kinetic impactor demonstration." It presents an opportunity to test DART and measure its effect in a controlled way since it will hit a satellite already in orbit around another object. In addition, Didymoon will be visible from ground telescopes as it passes in front of and behind the larger body.
The vehicle carrying DART will utilize two new acronymed technologies. One is a solar electric propulsion system first deployed during the decade-old Dawn mission to study protoplanets Vesta and Ceres. This system is called NEXT-C, or "NASA Evolutionary Xenon Thruster-Commercial." The other innovation is a new spacecraft-guidance algorithm called SMART-Nav, for "Small-body Maneuvering Autonomous Real-Time Navigation." Hitting such a distant target is no small matter, says Chabot: "One of DART's main challenges is to reliably target and squarely impact the small moonlet, 6.8 million miles away from Earth."
After a 16-month journey, in September 2022, just before hitting Didymoon, DART will release a small camera-bearing cubesat from Italy, the LICIACube, which will capture images of the 14,700 mph collision.
Just a slight alteration of the moonlet's path — even a fraction of a degree — will be enough to verify DART's success.
Series of radar images of Didymos and Didymoon, taken at Arecibo November 23, 24 and 26, 2003.
Image source: NASA/Naidu et al., AIDA Workshop, 2016
Two years after DART, the ESA's Hera will take off for a journey to Didymos that won't reach its destination until 2028. It'll have an autonomous navigation system onboard to help it reach the asteroid whose orbit will hopefully have changed a little by then, thanks to DART.
Hera contains a pair of cubesats, one of which will map the impact area on Didymoon using a high-resolution camera, LIDAR, and a thermal imager as the craft orbits the asteroid. The other will attempt to land on the satellite for an up-close crash-scene analysis. If successful, Didymoon will be the smallest object on which humans have ever landed.
Hera at Didymos
Image source: ESA–ScienceOffice.org
Back here on Earth
In the face of impending climate change, some find the idea of planetary defense quixotic. Still, its participants assert there's no reason not to use advancing technologies to do what we can to ensure humanity's long-term survival in the face of recognized potential future threats. As Carnelli puts it, "Planetary defense is really a worldwide endeavor. Besides just the technology and the science, AIDA is also a really good experiment in terms of collaboration between scientists and agencies around the world. It's the sort of thing that would be needed were an asteroid on a collision course for Earth."
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The idea of 'absolute time' is an illusion. Physics and subjective experience reveal why.
- Since Einstein posited his theory of general relativity, we've understood that gravity has the power to warp space and time.
- This "time dilation" effect occurs even at small levels.
- Outside of physics, we experience distortions in how we perceive time — sometimes to a startling extent.
Physics without time<p>In his book "The Order of Time," Italian theoretical physicist Carlo Rovelli suggests that our perception of time — our sense that time is forever flowing forward — could be a highly subjective projection. After all, when you look at reality on the smallest scale (using equations of quantum gravity, at least), time vanishes.</p><p style="margin-left: 20px;">"If I observe the microscopic state of things," writes Rovelli, "then the difference between past and future vanishes … in the elementary grammar of things, there is no distinction between 'cause' and 'effect.'"</p><p>So, why do we perceive time as flowing <em>forward</em>? Rovelli notes that, although time disappears on extremely small scales, we still obviously perceive events occur sequentially in reality. In other words, we observe entropy: Order changing into disorder; an egg cracking and getting scrambled.</p><p>Rovelli says key aspects of time are described by the second law of thermodynamics, which states that heat always passes from hot to cold. This is a one-way street. For example, an ice cube melts into a hot cup of tea, never the reverse. Rovelli suggests a similar phenomenon might explain why we're only able to perceive the past and not the future.</p><p style="margin-left: 20px;">"Any time the future is definitely distinguishable from the past, there is something like heat involved," Rovelli wrote for the <a href="https://www.ft.com/content/ce6ef7b8-429a-11e8-93cf-67ac3a6482fd" target="_blank"><em>Financial Times</em></a>. "Thermodynamics traces the direction of time to something called the 'low entropy of the past', a still mysterious phenomenon on which discussions rage."</p>
The strange subjectivity of time<p>Time moves differently atop a mountain than it does on a beach. But you don't need to travel any distance at all to experience strange distortions in your perception of time. In moments of life-or-death fear, for example, your brain would release large amounts of adrenaline, which would speed up your internal clock, causing you to perceive the outside world as moving slowly.<br></p><p>Another common distortion occurs when we focus our attention in particular ways.</p><p style="margin-left: 20px;">"If you're thinking about how time is <em>currently</em> passing by, the biggest factor influencing your time perception is attention," Aaron Sackett, associate professor of marketing at the University of St. Thomas, told <em><a href="https://gizmodo.com/why-does-time-slow-down-and-speed-up-1840133782" target="_blank">Gizmodo</a></em>.<em> "</em>The more attention you give to the passage of time, the slower it tends to go. As you become distracted from time's passing—perhaps by something interesting happening nearby, or a good daydreaming session—you're more likely to lose track of time, giving you the feeling that it's slipping by more quickly than before. "Time flies when you're having fun," they say, but really, it's more like "time flies when you're thinking about other things." That's why time will also often fly by when you're definitely <em>not</em> having fun—like when you're having a heated argument or are terrified about an upcoming presentation."</p><p>One of the most mysterious ways people experience time-perception distortions is through psychedelic drugs. In an interview with <a href="https://www.theguardian.com/books/2018/apr/14/carlo-rovelli-exploding-commonsense-notions-order-of-time-interview" target="_blank"><em>The Guardian</em></a>, Rovelli described a time he experimented with LSD.</p><p style="margin-left: 20px;">"It was an extraordinarily strong experience that touched me also intellectually," he said. "Among the strange phenomena was the sense of time stopping. Things were happening in my mind but the clock was not going ahead; the flow of time was not passing any more. It was a total subversion of the structure of reality."<br></p><p>It seems few scientists or philosophers believe time is completely an illusion.</p><p style="margin-left: 20px;">"What we call <em>time</em> is a rich, stratified concept; it has many layers," Rovelli told <em><a href="https://physicstoday.scitation.org/do/10.1063/PT.6.4.20190219a/full/" target="_blank">Physics Today</a>.</em> "Some of time's layers apply only at limited scales within limited domains. This does not make them illusions."</p>What <em>is</em> an illusion is the idea that time flows at an absolute rate. The river of time might be flowing forever forward, but it moves at different speeds, between people, and even within your own mind.
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Controversial physics theory says reality around us behaves like a computer neural network.
- Physicist proposes that the universe behaves like an artificial neural network.
- The scientist's new paper seeks to reconcile classical physics and quantum mechanics.
- The theory claims that natural selection produces both atoms and "observers".
Vanchurin interview:<span style="display:block;position:relative;padding-top:56.25%;" class="rm-shortcode" data-rm-shortcode-id="539759cbfd8fcd5b6ebf14a3b597b3f9"><iframe type="lazy-iframe" data-runner-src="https://www.youtube.com/embed/bmyRy2-UhEE?rel=0" width="100%" height="auto" frameborder="0" scrolling="no" style="position:absolute;top:0;left:0;width:100%;height:100%;"></iframe></span>
Vanchurin on “Hidden Phenomena”:<span style="display:block;position:relative;padding-top:56.25%;" class="rm-shortcode" data-rm-shortcode-id="18886ffd5e5840bb19d4494212f88d82"><iframe type="lazy-iframe" data-runner-src="https://www.youtube.com/embed/2NDVdNwsHCo?rel=0" width="100%" height="auto" frameborder="0" scrolling="no" style="position:absolute;top:0;left:0;width:100%;height:100%;"></iframe></span>Vitaly Vanchurin speaking at the 6th International FQXi Conference, "Mind Matters: Intelligence and Agency in the Physical World." The Foundational Questions...
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