Blockbuster Science

by David Siegel Bernstein

  A HOPEFULLY TRUE STORY: A TALE OF APPLICATION

  First the bad news: given the vast time scale of space travel, we humans most likely will not make it out of our solar system, at least anytime soon. The good news is that this isn't the end of short-term space projects. They just won't involve human bodies. I'm talking about sending technology.

  In 2016, Yuri Milner and Stephen Hawking announced an initiative called Breakthrough Starshot.16 They intend to develop high-speed nanocrafts (sometimes called nano-spacecrafts or nanoprobes) and send them to the Alpha Centauri star system. Once there, the nanocrafts will relay all types of information including photographs of Proxima b, our nearest earthlike neighbor.

  If these tiny crafts can be limited to around a gram in weight then, given the physics of fuel to weight travel, these little guys could be accelerated to a significant proportion of the speed of light. The fuel of choice would be light itself.

  A nanocraft could be a protective graphite shell equipped with a microprocessor, radio transceiver, and navigation gyroscope. The tiny craft would then be tethered to lightweight, highly reflective solar sails measuring only a few meters in area. Of course, the sails would be designed to absorb just enough light to get the job done. We wouldn't want them to burn up the craft that they are carrying.

  Now, before these nanocrafts can make their interstellar journey, we need to somehow get them outside of our atmosphere (I'm assuming they are built here on Earth). We could launch them with conventional rockets and deploy them in space. Boring. I'd love to see them sent up in a space elevator and launched from a space station, but maybe that's just me.

  However they achieve orbit, a ground-based laser array would target the sails and accelerate them to speeds about 20 percent of the speed of light. Once at speed, the solar sails would fold up to become antennas. During the approximate twenty-five-year voyage to Proxima b, the nano-fleet could perform additional scientific tasks. Some could coast past Jupiter's moon Enceladus and sample the water plumes. Others could zip to Pluto (the flight would only take three days).

  Only four years after they arrive at Proxima b, we would start receiving messages from our intrepid space explorers. All in all, not too shabby a cosmic project…and one that can be completed within a human lifespan.

  PARTING COMMENTS

  The sky (space) is the limit. Actually, the limit is the speed of light, but I don't want to ruin the moment, so continue looking at stars.

  It might not be geology, but aerospace science rocks. We can travel inside our atmosphere in jets (turbo/ram/scram) or, if you like the retro thing, a prop plane. If your intent is to travel between planets, chemical rockets, solar sails, nuclear propulsion (but not launched from the earth), and ion engines are your ticket out of here. If we move from the practical to the theoretical, you could imagine flying starships equipped with antimatter engines, or electromagnetic drives, or warp drives (each less feasible than the last).

  What is your substance, whereof are you made, that millions of strange shadows on you tend?

  —William Shakespeare, “Sonnet 53”

  Just in case you aren't sick of hearing it yet, here is a reminder: gravity is a force that attracts objects with mass to one another. I'm going to climb a mountain (actually a molehill) to drop some Newtonian mechanics on you.

  According to Newton's law of gravity, the attraction between the objects is directly proportional to their respective masses and inversely proportional to the distance between them. If you are standing on Earth, the downward force on you is 9.8 meters/second2 (32 feet/sec2). On the moon, the force is one-sixth of what it is on Earth. This is because the size (mass) of the moon is smaller than Earth's.

  So, if you weigh 150 pounds on Earth, your weight on the moon is a very svelte twenty-five pounds. On Jupiter, which is eleven times larger than Earth, your weight would be 355 pounds. The good news is that at each location your mass has not changed. The bad news is that it sounds like your weight fluctuates a lot. The force pressing down on you is different when you are on planets with a different mass than Earth.

  For completeness, the whole distance part of Newton's law gravity follows an inverse square rule. If the distance between a spacecraft and Earth is doubled, the force of attraction between them falls to a quarter of what it was at the closer distance. Inversely proportional means that when one rises, the other decreases.

  SO, WHAT IS MASS?

  I hope you are convinced that mass isn't weight. Mass is the actual stuff contained in your body. Mass is also everything around us that is made up of atoms. Everything you see or breathe is made up of stuff. How do we measure mass? It is tricky, after all, to count all the protons inside an object. There is a much (relatively speaking) simpler answer. All you need is to have the object wave at you.

  Nope, not a joke. That's what scientists aboard the International Space Station (ISS) have objects do when they want to measure its mass. About 205 miles above your head, the ISS has a contraption that suspends objects by springs on a tray. This, cleverly enough, is called a mass-on-spring oscillator.

  Why the oscillator part? Because the mass of the object is measured by determining the rate at which it oscillates. The greater the mass of an object, the slower its oscillation rate will be. This allows scientists to measure mass without all the weighty baggage of gravity.

  WHY DO WE HAVE MASS?

  Your body is made up of atoms that are made up of electrons, quarks, and a lot of empty space. Since electrons and quarks have very little mass (and space has none), why do you? If you are hungry for more information about quarks and electrons, give the first interlude a read (or a reread). The interlude includes a must-read description of the four universal forces, one of which is, quite shockingly, called electromagnetism.

  This is important. Your electromagnetic field is what allows you to believe that you are solid. The Standard Model, our current best theory of almost everything, includes the Higgs field. This energy field permeates all of space. Envision it as thick honey spread throughout the cosmos.

  As a fundamental particle enters the field (this process is called an interaction), the particle gets stickier and heavier as it struggles to pass through. This sticky heaviness translates into mass. But not all particles have the same experience. Neutrinos, for example, pass through the Higgs honey without getting too messy. Therefore, they have virtually no mass to show for their journey. Light doesn't care for the taste of honey, so light photons snub the field entirely.

  The Higgs field was theorized in 1964 and finally observed by experiment in 2013 at the Large Hadron Collider (LHC) at CERN.1 (By the way, the LHC is amazing because to date it is the most powerful human-made accelerator ever built.) Only when atoms interact with the Higgs field do they obtain mass.

  WHAT MAKES DARK MATTER AND DARK ENERGY SO…UM…DARK?

  If you only knew the power of the Dark Side.

  —Darth Vader, from Star Wars: Episode V—The Empire Strikes Back

  Ordinary matter, which is composed of atoms with quarks and electrons, makes up 4 percent of the universe.2 This type of matter makes up you plus all the matter of anything you interact with. What about the other 96 percent? Unseen, but it exists. Twenty-three percent of it is dark matter. The remaining 73 percent is known as dark energy. Scientists might not completely understand dark matter and dark energy, but their existence answers a couple of the big cosmological questions. How did our universe form galaxies? Why is the speed of the universe's expansion increasing?

  Dark matter cannot be observed directly because it emits no light, defying electromagnetism. And, as far as scientists currently know, its only friend is gravity. Without dark matter, the amount of gravity hanging around would have been insufficient for galaxies to form.

  In the early days, gravity acted as a scaffold around which the structure of the universe developed. Dense, clumpy regions of dark matter created gravitational dimples into which more and more normal matter flowed as the universe aged. This normal
material formed stars, which then coalesced to form galaxies. Thank you, dark matter.

  Dark energy is the unseen force that tries to resist dark matter's natural desire to clump together over large distances. This repulsive force is built into the fabric of spacetime (those who believe space can be quantized, meaning it is not continuous, will say the quantum vacuum). It is therefore evenly distributed and not clumpy like dark matter.

  Dark energy and dark matter are competitors in a tug-of-war. Early on, dark matter was winning. As the universe expanded, dark energy became the gorilla on the rope, and the rate of expansion sped up.

  IS THERE EVIDENCE OF DARK MATTER?

  The gravitational interactions of dark matter with normal visible matter are irrefutable evidence for its existence. This is indirect evidence, which is fine and nice, but scientists sometimes like things to be direct, especially if the theory is to be consistent with the Standard Model of physics. Scientists are working diligently on testable theories. To date, none of their proposed candidate particles have been detected.

  The leading contender to explain what dark matter may be is a type of particle called WIMPs (weakly interacting massive particles). WIMPs are thought to only interact with ordinary matter only via gravity and the weak nuclear force. WIMPs are a natural extension of the Standard Model of physics. The model predicts that they were created shortly after the big bang.

  Another hypothetical particle to explain dark matter is called the axion. This electrically neutral particle could produce the amount of matter currently inferred. These particles are far smaller than WIMPs and were originally predicted to solve a complicated problem associated with the strong nuclear force. As happenstance would have it, it also has the correct properties to be a good candidate for dark matter.

  A different answer to dark matter might be sterile neutrinos. Neutrinos, found in the Standard Model, are created after atomic decay. Sterile neutrinos are large hypothetical versions. They are predicted to have no electric charge, so they wouldn't be able to interact with normal matter, but they would be able to interact with gravity. Their effect on gravity would make it appear as if extra unseen matter existed in the universe.

  All three particle types can be tested. That's science! However, at the time of this writing, physicists have yet to find any of these particles.

  SOMETIMES SUBSTANCES LIKE TO CHANGE THEIR OUTFITS BEFORE GOING OUT

  In grade school, students are traditionally taught the three states of matter: solid, liquid, and gas. If you see a grade schooler, you can say, “You are missing two. There are five states (or phases) of matter.” I have listed them below. The boundary between these states depends on how active the molecules are.

  Solid. This state occurs when particles cozy up close to each other. They are very snug with little movement, meaning they exhibit very little kinetic energy (energy from motion).

  Liquid. This is the state when the particles say to each other, “Whoa, back off a bit, but stay in the friend zone.” This arrangement keeps them close enough to flow around each other but not close enough to form shapes. Because this state holds some distance between the particles, there is more room for them to dance around. Ergo, more kinetic energy.

  Gas. This is the state where the particles realize that they aren't real friends but just acquaintances. They stand far enough away from each other to express themselves actively (free-style dance) and have a lot of kinetic energy.

  Plasma. This state is like that cousin who rarely comes to visit. You know the particles are out there, but they don't come into contact with you often. Particles in this state are highly charged, which makes them jump about a lot. They have extreme kinetic energy. If you use electricity to ionize neon gas (or any of the noble gasses), it phases into plasma and glows. Our sun is in a plasma state.

  Bose-Einstein condensates (BECs). This type of matter occurs when the particles come very near to stopping all movement and have almost no kinetic energy. The atoms begin to clump together and form superatoms. Superatoms arise when groups of atoms get clingy and form a single atom. In an experiment conducted with BECs, the speed of photons (light) were slowed.3 Speaking of Bose-Einstein condensates, let's get weird but stay real. Imagine an artificial quantum matter supersolid. I can't. My mind doesn't work that way. I have a few mental tricks for quantum mechanics but this, not so much. A supersolid is rigid like crystal but simultaneously acts as a superfluid, a fluid that flows without friction.

  This is a real thing. Using lasers, two separate teams (the Swiss Federal Institute of Technology4 in Zurich and MIT5 in the United States) of scientists nudged the quantum state of a BEC, which is a superfluid, to behave simultaneously like a solid.

  The hand is the tool of tools.

  —Aristotle

  Just about anything your great-great-grandparents made for themselves or bought was mostly formed from wood, cotton, wool, brick, and iron. Few of the elements found on the modern periodic table of elements were used in production a century ago. Think of an element as an ingredient used by nature and chefs (chemists) to make materials. Today we use these ingredients to make a lot of new and exotic materials that would blow a nineteenth-century engineer's mind.

  Of course, we could have done that with dynamite. Nitroglycerin did exist back then, but I was speaking figuratively. Our creation of ceramics, plastics, semiconductors, fiberglass (glass made up of glass fiber), metamaterials, and a lot of other wild stuff described in this chapter just didn't exist until very recently. Nowadays we also make stuff using ingredients that aren't found on the current periodic table of elements.

  WHAT IS MATERIAL ENGINEERING?

  Material engineering is the creation of materials. It has existed since Australopithecus garhi flaked off bits from rocks to form crude tools about three million years ago. A millennium later, the Stone Age really started hopping. It had a good long run before petering out about ten thousand years ago. During this period, the key materials for tools were stone, bone, and animal skin. Copper, tin, and gold were all known during the Stone Age, but they were predominantly used ornamentally because they were too soft for use as tools.

  The Bronze Age kicked off in China about 1,700 BCE. At that point, someone discovered that copper and tin could be combined to form bronze, a very strong metal resistant to rust. Iron was common enough, but it ranked low in popularity. It was not much harder than bronze, but it was difficult to melt. You can melt bronze in a pot while you need a furnace system to work with iron. So the people of this era decided, why bother?

  Only some did bother. And because of them, everything changed when they stumbled upon a new material. It turns out if you add just a dash of carbon to iron, steel is formed. The discovery probably happened accidently by repeatedly putting iron back into the fire to work on it. Each time it returned to the coals, a bit more carbon was added.

  Because steel is stronger than bronze, less of it is needed to forge sturdy tools or weapons, making them a lot lighter. Steel also holds an edge better than bronze, a perk for weapons and tools. This Iron Age began in 1,200 BCE in the Middle East and spread to southeastern Europe and China around 600 BCE. Bronze was still widely used for objects like statues and fountains because it resisted rust better than objects made of iron. These three ages can overlap quite a bit depending on the location.

  ARE ANY NEW MATERIALS UNDER DEVELOPMENT NOW?

  The discovery and use of new materials is occurring faster today than during any other time in history. Today's material engineers are always searching for ways to create new materials with specialized characteristics. For example, a material imaginatively named SAM2X5-630 has the characteristics of glass but is stronger than steel.1

  If this sounds a lot like the fictional transparent aluminum container used to contain the Earth-saving whales in the movie Star Trek IV: The Voyage Home, then you get the idea. There is a lot of cool potential for this material. Not only is it a glass-like metal, but it is also very elastic. Satellites made from this mater
ial would be able to deflect meteors. Possibly of more interest to you, your smartphone would be nearly indestructible and would bounce when you dropped it.

  Google is working on developing smart contact lenses that will use flexible electronics to display a diabetic's glucose levels.2 Soon silicon will be replaced with cheap, flexible materials for solar cells and computer displays. Want to make an athlete (perhaps yourself) happy? Offer her smart clothing such as running shorts with a tiny embedded accelerometer to sense movement and adapt to a runner's stride. Or a shirt that helps a player's tennis swing.

  SPEAKING OF ATHLETES, HERE ARE A COUPLE OF (LITERALLY) COOL PROOFS OF CONCEPT

  Thanks to those pesky laws of thermodynamics, anytime we cool air, we create heat through the energy used to create cooling. Turn on an air conditioner to cool your bedroom, and the motor heats up. This is also true of material science. Unsure what the laws of thermodynamics are all about? You won't be (I hope) after you read their formal description in chapter 21.

  If you wear a cotton shirt while being chased by Daleks down endless hallways, your heart pounds away and there is a good chance that your body is overheating. Your shirt absorbs the radiation emitted from your body (which cools you down) and stores the heat. An alternative would be to wear a high-tech shirt that uses your own sweat to keep you cool.

  Researchers at Stanford University are studying a new material called nanoporous polyethylene,3 which, unlike cotton, lets the heat radiation escape. Additionally, unlike the high-tech wicking shirt you might have worn on your last ten-kilometer run, it doesn't need sweat to keep you cool.