Everything Everywhere Daily: History, Science, Geography & More - The Dangers of Weightlessness and Its Solutions

Starting point is 00:00:00 The human body was built for gravity, taken away, and bones weaken, muscle shrink, fluid shift, and even your vision can change. For astronauts spending months in orbit, zero gravity isn't just strange. It's one of the greatest obstacles to living and working in space. Yet, there are solutions. It might just be a matter of exercise, or in the future, the solution might be to create artificial gravity by spinning a spacecraft. Learn more about dealing with zero gravity on this episode. of everything everywhere daily. Welcome to the I Can't Sleep Podcast with Benjamin Boster. If you're tired of sleepless nights, you'll love the I Can't Sleep podcast.

Starting point is 00:01:01 I help quiet your mind by reading random articles from across the web to bore you to sleep with my soothing voice. Each episode provides enough interesting content to hold your attention, and then your mind lets you drift off. Find it wherever you get your podcasts. That's I Can't Sleep with Benjamin Boster. As a podcaster, I'm often asked what podcasts I listen to. One of the shows I subscribe to and listen to every week is The Jordan Harbinger Show.

Starting point is 00:01:45 The Jordan Harbinger Show is the top podcast that was named Best of Apple in 2018. One of my recent favorite episodes from this summer was the interview he did with Atasa Araksa Abrahemian, who explained how wealthy people can buy second passports overseas. On the show, Jordan dives into the minds of fascinating people, including everyone from athletes, authors, scientists, mobsters, spies, and hostage negotiators. If you like this podcast, you'll probably like the variety and in-depth interviews on the Jordan Harbinger Show. You can't go wrong with adding The Jordan Harbinger Show to your rotation. It's incredibly interesting and there's never a dull show. Search for The Jordan Harbinger Show.

Starting point is 00:02:22 That's H-A-R, B as in Boy, I-N- as-N-N-N-N-N-N-N-N-N-Y-R on Apple Podcasts, Spotify, or wherever you listen to podcast. Let me start right out by noting that while the term zero gravity is the common term used for the condition that astronauts experience in orbit, it is technically incorrect. A better term might be microgravity or weightlessness. Gravity is not absent in orbit. In fact, astronauts aboard the International Space Station are still strongly affected by the Earth's gravitational field. At the International Space Station's altitude, roughly 250 miles above, of the surface of the Earth, gravity is still about 90% as strong as it is at the surface. If gravity vanished, the station would fly off in a straight line in space.

Starting point is 00:03:13 What's really happening is that the spacecraft and everything inside are all falling around the Earth together. An orbit is basically a continuous fall. Imagine throwing a ball horizontally. It will eventually fall to the ground, but if you throw it faster, it lands further away. But if you throw it fast enough, as it falls, the curvature of the Earth drops away beneath it at the same rate. The object keeps falling, but it will never hit the ground. And that is all it means to orbit something. What astronauts experience is the same thing that you would experience if you were to go skydiving. So zero gravity is a misnomer because gravity is still very much present.

Starting point is 00:03:57 What is missing isn't gravity itself, but the sensation, of weight. By all accounts, weightlessness is fun, at least initially. Outside of a few seconds of bungee jumping, I can't claim to have experienced it. However, the longer you are in a weightless environment, the more problems can arise. And the first problem that many astronauts experience is space sickness. Space sickness is the nausea, dizziness, headaches, and disorientation that many astronauts feel during their first hours or days in microgravity. It has happens because the brain receives conflicting signals. On Earth, the inner ears vestibular system uses gravity to help determine balance and direction. In orbit, that gravity cue disappears,

Starting point is 00:04:43 while the eyes still report motion and orientation. The brain has to recalibrate to a world with no true up or down. Symptoms can include nausea, vomiting, cold sweating, loss of appetite, fatigue, and trouble concentrating. It's similar to motion sickness, but it's caused by weightlessness, than by a car boat or airplane. Most astronauts adapt within a few days, although they can experience a similar readjustment problem when they return to Earth's gravity. Long-term weightlessness has problems beyond just being nauseous.

Starting point is 00:05:16 It's a serious biological problem because the human body is built around constant mechanical loading. Gravity tells your bones, muscles, blood vessels, balance organs, and even fluid distribution how to behave. remove it for months or years, and the body adapts in ways that are useful in orbit, but can be dangerous when returning to Earth. In weightlessness, the body no longer has to support itself. The legs, hips, and spine stop doing much of their normal work. Bones no longer receive the same stress signals that tell them to maintain density. Fluids no longer settle towards the lower

Starting point is 00:05:53 body, so blood and cerebo spinal fluid shift upwards towards the head. The cardiovascular system, vestibular system, eyes, immune system, and kidneys all respond to this new environment. NASA summarizes the major effects as muscle loss, bone loss, upward fluid shifts, vision problems, increased risk of

Starting point is 00:06:13 kidney stones, and cardiovascular deconditioning. In microgravity, astronauts can lose bone density, and NASA's 2025 risk summary estimates a typical loss rate of about 1 to 1.5% per month during four to six-month missions, if not adequately countered.

Starting point is 00:06:32 Astronaut Scott Kelly spent 340 days aboard the International Space Station in 2015 and 2016. After returning to Earth, he reported sore skin, rashes, flu-like symptoms, swollen legs, balance issues, and other difficulties readjusting to Earth's gravity. He also has a twin brother, and NASA did a study of him and his twin to compare what happened to him after his flight. They found changes involving gene expression, immune response, bone metabolism, body mass, and cardiovascular function, although many of these returned towards baseline after he came home. The main thing currently used to offset these problems is exercise. ISS astronauts typically use a treadmill with a harness, a stationary cycle, and a resistive exercise device that mimics weightlifting.

Starting point is 00:07:22 And this helps a lot. Modern crews were. return in far better condition than early long-duration crews did. Diet, vitamin D, medication, hydration monitoring, and medical imaging also help. However, exercise is an imperfect substitute. It takes time, requires bulky equipment, stresses joints in unnatural ways, and does not reproduce gravity's continuous whole-body effects. And it also does absolutely nothing to solve the problem of fluids shifting to your head. The ultimate solution, would be to try and replicate gravity. In many science fiction movies and TV shows,

Starting point is 00:08:02 artificial gravity is used as a plot device because filming weightlessness would be challenging and expensive. Many times it isn't even explained and people just walk around on the decks of spaceships like they were on the surface of a planet. In reality, the only solution to artificial gravity that we know of is rotation. There's no known practical machine that can generate gravity like a planet.

Starting point is 00:08:23 but a rotating structure can create an outward apparent force. Stand inside the rim of a spinning station and the floor pushes against your feet. And to you, that feels very much like weight. The basic equation for creating artificial gravity is very simple. It's angular velocity squared times the radius. And that means a station can get earth-like gravity by either spinning fast, by being very large, or by some combination of the two.

Starting point is 00:08:55 There have been some movies that have depicted such space stations. There was a rotating space station in the movie 2001 of Space Odyssey, as well as in the series for All Mankind. These are usually depicted as large rotating wheels with spokes and a central docking hub. However, there's a problem with this. A rotating station is not exactly the same as standing on Earth. When you move your head, throw an object, pour water, or climb a ladder or walk inwards towards the hub, you experience the Coriolis effect.

Starting point is 00:09:26 This makes moving objects appear to curve from the perspective of people inside the station. At low rotation rates, this is manageable, but at high rotation rates, it can become nauseating. The rule of thumb that's often cited in artificial gravity design is that around one to two revolutions per minute would be comfortable for almost everyone, while three to four RPM may be tolerable after adaptation, and higher rates become increasingly unpleasant. The exact limit is debated because we've never actually built such a space station, but the lower the RPM, the easier would be to adapt to, but it also means the space station has to be larger.

Starting point is 00:10:08 To be able to support Earth-like gravity at only 1 RPM, you would need a rotating space station with a radius, not a diameter, of 895 meters, or a little more than half a mile. And that's the radius, double it for the diameter. At 2 RPM, which is also reasonable, you'd need a radius of only 224 meters. And at 4 RPM, which might require some adjustment, you'd need a radius of about 56 meters. Of course, it might not be necessary to experience the full gravity of Earth. If you wanted to simulate the moon's gravity at 1 RPM, it would only

Starting point is 00:10:47 require a station with a radius of 148 meters or 485 feet. And if you're willing to spin it at 4 RPM, you'd need a radius of a reasonable 9.2 meters or about 30 feet. This really isn't a question of physics. It's more a matter of engineering and how you could actually build such a thing in orbit. The first one would be extremely difficult to build and would most likely be extremely expensive. A rotating space station is currently possible but difficult, and it might be more plausible if we can reduce the cost of transporting cargo to orbit even further. But that hasn't stopped people from thinking even bigger. There have been proposals for some truly enormous space stations that use rotational motion to create

Starting point is 00:11:34 artificial gravity. The Stanford Taurus is a more ambitious version of the wheel. A large donut-shaped habitat usually imagined as a space colony rather than just a space station. People live on the inner surface of the torus with the ground curving up in the distance. Its major advantage is livability. A torus can provide a large continuous landscape, neighborhoods, agriculture, and a more earth-like environment. And its large radius allows for a much slower rotation. A Stanford torus would start at maybe about one RPM and go down from there if it were even larger. However, a Stanford tourist would simply have people living on the same.

Starting point is 00:12:17 the rim of a wheel. Something that would radically expand the amount of living space that people could have is an O'Neill cylinder. An O'Neill cylinder, as the name would suggest, is a gigantic, rotating cylinder with its entire interior available for use. Princeton physicist Gerard K. O'Neill proposed enormous counter-rotating cylinders with people living on the inside surface. A cylinder could provide a vast habitable area. The classic concept features alternate. strips of land and windows with mirrors reflecting sunlight into the interior. A big advantage is scale. A cylinder can, in theory, support cities, farmland, and industry. It also has better land use geometry than a wheel does because its inner surface can be very

Starting point is 00:13:03 large. O'Neill cylinders have been shown in the movie Interstellar and in the TV show The Expanse. An alien O'Neill cylinder also plays a central role in Arthur C. Clark's book, Rendezvous with Rama. There's supposedly a movie in the works that is to be directed by Denny Villeneu, but production hasn't started yet. The theoretical length of an O'Neill cylinder could be miles long, although we have absolutely no clue how to build such a thing today. However, this theoretical idea can be taken to an even higher level. A Dyson sphere is a proposed megastructure that would completely surround a star and capture

Starting point is 00:13:43 all or some of its energy output. The usual popular image is a solid shell surrounding a star, but physicist Freeman Dyson did not originally propose such a rigid sphere. His more plausible idea was a vast swarm of orbiting solar collectors, habitats, or satellites that were surrounding a star. The best fictional representation of Dyson's idea was in Larry Dimmons' 1970 novel Ringworld.

Starting point is 00:14:09 It's an enormous artificial ring built around a star with its inner surface serving as habitable land. Unlike a rotating space station, it's not a small wheel in orbit. It's more like a slice of a Dyson sphere. A band millions of miles across that completely encircles a star at roughly the orbit of Earth. The ring rotates to create artificial gravity through centrifugal force, while the star provides light and heat. Even with such a gigantic ring, it would still be required to rotate once every nine and a half days.

Starting point is 00:14:43 It would have to move more than 38 times faster than the Earth's orbital speed around the sun in order to produce the same gravity. We have yet to build a single artificial gravity system for humans in space, so all these ideas, especially the far-out ones such as O'Neill cylinders, aren't even in the planning stages. But the problems of long-term weightlessness aren't going away. In the near term, the solution will likely be more exercise and additional mitigation. efforts, but that won't solve the problem for extremely long missions.

Starting point is 00:15:18 In the long run, rotating space stations are the cleanest conceptual solution because they attack the root cause, the absence of gravity. Maybe someday in the future, we'll have people in space who won't have to spend months just floating around. The executive producer of Everything Everywhere Daily is Charles Daniel. The associate producers are Austin Otkin and Cameron Kiefer. My big thanks go to everyone who supports the show over on Patreon. Your support helps make this podcast possible. And I also want to remind everyone about the community groups on Facebook and Discord.

Starting point is 00:15:54 That's where everything happens that's outside the podcast. And links to those are available in the show notes. As always, if you leave a review on any major podcast app or in the above community groups, you too can have it read in the show.

Everything Everywhere Daily: History, Science, Geography & More - The Dangers of Weightlessness and Its Solutions

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