Category: chemistry

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Biology Brain Science chemistry particle physics physics

How Old Are You?: How The Atomic Age Solved One of Biology’s Greatest Mysteries

atomicbomb

By Bradley Stockwell

My two favorite arenas of academia are science and history, and the more I study the two, the more I see how interwoven they really are. There’s no greater example of this than something called the “bomb pulse”. Whether you know it or not, lurking inside of you is a piece of Cold War history—even if you weren’t alive at the time—and it is this little memento that finally solved one of biology’s most elusive secrets: How old are you? And I don’t mean how many times has the cellular clump of mass known as you swung around the sun, but how old are the individual cells that make up that mass? Your skin cells, heart cells, neurons—your body is constantly renewing itself with new cells and it is only as of 2002 that we began to have a definitive answer for how old each one was. With this post, my intentions are twofold. One: I want to tell you about one of the greatest scientific discoveries of the 21st century, and two: I’m hoping that by wrapping them in this titillating story, I can also slip in a few basic principles of nuclear chemistry. With that said, let’s begin!

Between 1945 and 1963, over four hundred nuclear bombs were detonated, unleashing an untold number of extra neutrons into the atmosphere. Some of these neutrons found their way into nitrogen atoms, causing them to eject a proton. If you’re familiar with some basic chemistry, when a seven-proton nitrogen atom loses a proton, it becomes a six-proton carbon atom. However, because these carbon atoms still have two extra neutrons from when they were nitrogen, they become something called an isotope, a variant of an element which differs in neutrons, but has the same amount of protons. In this case, these slightly more massive and radioactive isotopes become an isotope of carbon called carbon-14.

When I say radioactive, all I mean is that the atom’s nucleus is unstable; that it is emitting energy in the form of ejected subatomic particles or energetic light waves to stabilize itself until it becomes a stable isotope, or a completely new element altogether. This radioactive decay comes in three main forms: alpha, beta and gamma. Alpha decay—which only happens with heavy elements like uranium—is the ejection of something physicists call an alpha particle, but chemists just call it a helium atom, a bundle of two protons and two neutrons. In fact, almost all the helium here on Earth came from this type of decay. Think about that the next time your sucking down a helium balloon; you’re inhaling the atomic leftovers of uranium, thorium and other heavy, radioactive elements. Beta minus decay is the ejection of an electron and beta plus decay is the ejection of the electron’s antiparticle, the positron. Gamma decay is the emission of an extremely energetic light wave called a gamma ray and it is often emitted in conjunction with alpha and beta decay.

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The time it can take for a radioactive element to reach a stable form can be anywhere from instantaneous to far longer than the age of the universe. Because individual atoms decay unpredictably, the way in which we measure this loss is through probability, or something called a half-life. This is the time it takes for half a quantity of radioactive material to decay into a more stable form. This is not to say if you have four radioactive atoms, in x amount of time you’ll have two necessarily, but more that each individual radioactive atom has a fifty percent chance that it will decay to a more stable form in x amount of time. For example, carbon-14, the star of our story, has a half-life of 5,730 years. This means if you had a pound of it, after 5,730 years you’d have a half pound of carbon-14 and half a pound of nitrogen-14, carbon-14’s more stable form. Then after another 5,730 years you’d have a quarter pound of carbon-14 and three-quarters pound of nitrogen-14, and so forth. This is how carbon dating works; by measuring the relative portions of carbon-12 and carbon-14 in a sample of organic matter, archeologists are able to determine its age.

carbon14Dating

The period between 1945 and 1963 in which all this atomic testing was happening is now called the “bomb pulse” by the scientific community. It was called this because the amount of carbon-14 in the atmosphere was doubled during this period from all those free neutrons crashing into nitrogen. In 1963, when the Soviet Union, the U.K. and the U.S. agreed to the Limited Test Ban Treaty which prohibited all above-ground detonations, the amount of carbon-14 began to decrease by half every eleven years and will eventually be depleted somewhere around 2030 to 2050. This isn’t because the carbon-14 is decaying into nitrogen-14 (remember the half-life of carbon-14 is 5,730 years), but because it is being absorbed by the life inhabiting our planet, which includes us. Although carbon-14 is an altered carbon atom—a carbon isotope, it still behaves like a carbon atom because it is the number of protons in an atom that determines its chemical behavior, while the number of neutrons determines its mass; and like a regular carbon atom, these carbon-14 atoms have been binding to oxygen, forming CO2, which is sucked up by plants during photosynthesis and then fed to the rest of us through the food chain. Like the plants, our bodies too can’t tell the difference between carbon and carbon-14, so for the last seventy-plus years all this extra carbon-14 has been used by every living creature to build new cells, proteins and DNA.

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While our bodies can’t tell the difference between carbon and carbon-14 (because they have the same amount of protons), scientists can because of their slight difference in mass (remember carbon-14 has two extra neutrons). The difference in mass is measureable through a technique called mass spectrometry, which sorts atoms by weight. Without getting too technical, an instrument called a mass spectrometer strips atoms of some of their electrons and launches them into a magnetic field, which alters the atoms’ course, and because of inertia, heavier atoms take a wider path than lighter ones. By measuring how many atoms travel along certain paths, scientists can determine how much of a specific atom—in this case a carbon-14 atom—is in a sample.

So what does this have to do with determining a cell’s age? Well for a long time nothing. But somewhere around 2002, Krista Spalding, a postdoc at the Karolinska Institute in Stockholm, Sweden, wanted to challenge the longtime doctrine that said the human brain couldn’t create any new neurons after the age of four. There had been growing evidence that the adult hippocampus—a seahorse-shaped region deep in the brain that is important for memory and learning—could regenerate neurons, but no one knew for sure. Spalding and her postdoc advisor, Jonas Frisén, had a hunch that the “bomb pulse” period could somehow offer a solution and it did, culminating in a paper by Spalding, Frisén and their team published in June 2013, which conclusively found that the hippocampus did produce approximately 700 to 1,400 new neurons per day, and these neurons last twenty to thirty years. How you ask? Well there’s an episode of Radiolab (a wonderful science podcast I recommend you all listen to) that has a much more colorful version of Spalding and Frisén’s journey here, but because I know I’m probably already pushing your attention spans, I’ll just give a brief overview. You see, atmospheric scientists have been measuring the amount of carbon-14 and other elements in the atmosphere every two weeks since the late 1950s, giving us an extremely accurate timetable of how much carbon-14 is and was in the atmosphere at any given time after. By correlating this data to the amount of carbon-14 found in a cell’s DNA (while other molecules are regularly refreshed throughout a cell’s life, DNA remains constant), researchers can determine not just the age of a hippocampal neuron, but any cell. So by accident, the nuclear age finally shed light on when tissues form, how long they last and how quickly they’re replaced.

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You—and every other living organism—are continually creating new cells. Cells that make up your skin, hair and the lining of your gut are constantly being replaced, while others, like cells that make up the lens of your eye, the muscles of your heart and the neurons of the cerebral cortex, have been with you since birth and will stay with you until you die.

So why is this so important? Well firstly, it gives us a key insight into the mechanisms behind many neurodegenerative diseases such as amyotrophic lateral sclerosis (Lou Gehrig’s disease), Parkinson’s, Alzheimer’s, Huntington’s and many more. Really we’ve only just begun to dig into this Pandora’s box so to speak, and unfortunately time is limited (well unless we start blowing up a bunch of atomic weapons again, but let’s hope humanity has moved past this) because, as I said, this measureable spike of carbon-14 in our atmosphere from the “bomb pulse” will eventually be depleted somewhere between 2030 and 2050.

Despite what the “bomb pulse” is and will offer to scientific research, isn’t it cool just knowing which cells have been at the party of you the longest? Or that like the rings of a tree, or the sedimentary layers of rock, our bodies too tell the story of our times? With that, until next time, stay curious my friends.

 

 

Categories
chemistry particle physics Quantum Mechanics technology

How Pencil Lead and Sticky Tape Won a Nobel Prize

 

pencil_lead_and_tape

By Bradley Stockwell

First off, I want to apologize to all of my six followers to this blog. I know I left you in anxious anticipation over my follow-up post to Climate Change Part I on future green technologies. However, after three months of procrastination, I confess I still haven’t written it. I’m sorry, but I’m easily distracted and while attempting to assemble it I came across a story too good not to tell about a fascinating material called graphene. Graphene is the thinnest, strongest and stiffest material on Earth; it conducts electricity and heat better than any other known material; it is transparent and two-dimensional and is the basis for all future technologies and A.I. At the moment, its potential of applications looks limitless. Oh did I mention it was discovered with nothing more than pencil lead and tape? They even gave the guys who discovered it the 2010 Nobel Prize in Physics. Shit, if I knew it was that easy I could’ve scratched Nobel prize in physics off the bucket list a long time ago.

So what is graphene exactly then? In short, it’s a sheet of pencil lead (graphite) an atom thick. But to understand how we arrived at the discovery of graphene, we need to tell another story, the story of carbon. Graphene is an allotrope of carbon which simply means it’s one possible way to structure carbon atoms. The carbon atom has six protons and typically six neutrons in its nucleus. Sometimes the nucleus has eight neutrons, in which case the carbon atom is known as carbon-14. Carbon-14 is unstable, meaning it radioactively decays, but the decay is consistent over long periods of time. Because this form of carbon is found in many materials, measuring its presence gives us a way to age materials—or what is known as carbon dating. Carbon-14 however is not an allotrope of carbon, it is what is known as an isotope, something covered in detail in a previous post, Flight of the Timeless Photon.

Allotrope formation is dependent on the electrons of a carbon atom and the way in which they bond to other carbon electrons. Carbon has six electrons, two of which are buried in its innermost shell near the nucleus, and four in its outermost shell which are called valence electrons. It is these four outermost electrons—and a ton of heat and pressure—that make the difference between a lump of coal and a diamond, another allotrope of carbon. In diamond, a carbon atom’s four valence electrons are bonded with four other carbon valence electrons. This produces an extremely stiff crystalline structure. In fact, a typical diamond is made up of about a million billion billion atoms (1 with 24 zeros after it) all perfectly arranged into a single pyramidal structure, which is key to its extraordinary strength. But diamond is not the strongest and most stable allotrope of carbon. Although DeBeers may want you to think otherwise, a diamond is not forever; every diamond in existence is actually slowly turning into graphite. The process however takes billions of years so no need to worry about your wedding ring just yet.

Graphite is not a crystalline structure like diamond, but planes of carbon atoms connected in a hexagonal pattern, with each plane having an extremely strong and stable structure—stronger and more stable than diamond. Some of you may be asking, is this not the same graphite we write with and grind up into fine powder lubricants? Yes indeed it is, and the conundrum of descriptives can be blamed on electrons. In diamond, a carbon atom shares its four valence electrons with four other carbon atoms, whereas in graphite it shares its electrons with only three (see graphic below). This results in graphite having no electrons left over to form strong bonds between layers, leaving it up to something called van der Waals forces, a weak set of forces generated by fluctuations in a molecular electric field. Basically it’s the universal glue of matter and is something all molecules naturally possess. Because these forces are so weak is why you’re able to write with graphite—a.k.a. pencil lead. As you press your pencil to paper, you’re breaking the van der Waals forces, allowing layers of graphite to slide across one another and deposit themselves on a page. If it weren’t for the weak van der Waals bonds, pencil lead would be stronger than diamond and this is behind the advent of carbon fiber. Carbon fiber is spun graphite, lathered in an epoxy glue to overcome the weak van der Waals forces. Restriction of van der Waals forces is also behind the phenomenality of graphene.

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Since graphene is a single layer of graphite one atom thick, there is no need to worry about weak van der Waals forces. By default this makes graphene the strongest and thinnest material known to man. Also, because its carbon atoms are not structured in a crystalline lattice like diamond, which leaves no free electrons, it also conducts electricity and heat better than any known material. This means because of its transparency and thinness, we could literally add touch sensitivity to any inanimate object and possibly entire buildings. It also allows for something called Klein tunneling, which is an exotic quantum effect in which electrons can tunnel through something as if it’s not there. Basically it means it has the potential to be an electronic dynamo and may someday replace silicon chips and pave the way for quantum computing. Graphene was purely hypothetical until 2004 when Andre Geim and Konstantin Novoselov discovered it. As stated in the title of this post, they discovered it with nothing more than a lump of graphite and sticky tape. They placed the tape on the graphite and peeled off a layer. They then took another piece of tape and stuck it to the piece of tape with the graphite layer and halved the layer. They continued to do this until they were left with a layer of graphite one atom thick. I’m not exaggerating the simplicity of the procedure in any way. Watch the video below and you can replicate the experiment yourself, the only catch is you need an electron microscope to confirm you indeed created graphene. Until next time my friends, stay curious.

Categories
Alien Life Astronomy Biology chemistry science

The 3 Most Likely Places We’ll Find Alien Life in Our Lifetimes

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By Bradley Stockwell

If we are ever to find alien life in our lifetimes, there is no doubt that it will most likely be within our own solar system. And I’m not talking about little green men (sorry about the misleading picture), but more likely microbial alien life. In April of this year, NASA’s chief scientist, Ellen Stofan said, “I believe we are going to have strong indications of life beyond Earth in the next decade and definitive evidence in the next 10 to 20 years.”

This is quite shocking considering a little over a decade ago we thought the search for extraterrestrial life was all but dead. For many years scientists narrowly confined the search to something called the “habitable zone”, or informally known as the Goldilocks zone (I like this name better). This is the area within a star system that’s close enough to a star to allow liquid water, but not so close as to boil it away. Because Earth is our only reference for life, it was once thought that liquid water was an essential ingredient to the porridge of it; but as we’ll see later, even now that is being questioned.

Nevertheless our best hope still lies with liquid water and the only places thought to have, or had it at one time, was Earth and Mars. Unsurprisingly these are also the only two planets within our own solar system’s Goldilocks zone. Since Mars has yet to yield any signs of life, the chances of finding alien life in our solar system once seemed pretty grim. However very recent and very credible evidence is showing there is most likely oceans of liquid water far from where we thought it should be in our solar system. Because of this and continuing research on how life forms, the race is back on to find alien life in our solar system and here are the three most likely places we’ll find it.

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Enceladus and its geyser spray 

1. Enceladus

Enceladus is a small, ice-covered moon of Saturn. Although some may disagree, I list this as the most likely place for three reasons: warm liquid water, organics and the ease of access. In 2005, NASA’s Cassini spacecraft photographed geysers of frozen water shooting up from cracks on the surface of Enceladus. It is almost certain the culprit of these geysers is reservoirs of liquid water beneath the frozen surface formed by something called tidal flexing. Basically there’s this sort of gravitational tug-of-war between Enceladus, its neighboring moons and Saturn itself. These interactions stretch and contract the moon, creating heat which causes the ice beneath the surface to melt and form liquid water. Additionally, Cassini’s instruments also detected organic compounds like methane in the geyser spray and where there’s warm water—speculated to be near boiling temperatures—and organics, there’s the possibility of life. Life has formed in very similar conditions near hydrothermal vents here on Earth. However what really sets Enceladus apart is how easily it would be to snatch up evidence of life if it’s there. Whatever exists in those subsurface water reservoirs is continually being shot up by geysers into space and all we’d have to do is fly by and grab it with a spacecraft. There’d be none of the complications of landing robot drillers on the surface like other icy-moon candidates. Unfortunately, partly due to NASA’s shrinking planetary science budget, there are no planned missions to explore Enceladus.

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2. Europa

Europa is another ice-covered moon a little smaller than our own orbiting Jupiter. Like Enceladus and Europa’s two neighboring moons, Callisto and Ganymede, it most likely has liquid water beneath its surface caused by tidal flexing between it, Jupiter and other Jovian satellites. Possibly there’s more water here than in all of Earth’s oceans. It is also speculated that the oceans contain salt because the moon has a magnetic field which means it’s electrically conductive; something fresh water is not. With water, salt and carbon-based organic compounds from comets that have inevitably hit the moon, you’ve got quite the recipe for life. While salt hasn’t been directly detected yet, a probe mission has been proposed for 2025 that will answer all questions about the moon’s chemical makeup. If this chemical makeup is considered life-friendly it will be all the more reason to send a lander to Europa. The problem however lies then with how to drill through 10 miles (16 km) of extremely hard ice. Nevertheless drilling through 10 miles of ice to reach water seems more promising than drilling through the at least 60 miles (100 km) of rock covering Callisto’s and Ganymede’s water.

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Titan is the only other place in our solar system to have rain and liquid lakes. It is also the only moon to have a dense atmosphere. 

3. Titan

Titan, Saturn’s largest moon and the second-largest in the solar system, would be my favorite outcome for alien life because it would completely rewrite our recipe book for life and expand the possibility of it immensely throughout the rest of the universe. Honestly I was tempted to list it as first, but I felt obligated to give preference to at least two water-bearing moons first. Other than Earth, Titan is the only known place in our solar system where it rains and there are liquid lakes. It is also the only moon in the solar system to have a dense atmosphere. Granted the rain and lakes are made of liquid ethane and methane, but ethane and methane are both saturated hydrocarbons—a.k.a. life-making stuff—and the atmosphere is largely made up of nitrogen just like here on Earth. On Earth ethane and methane are gases, but because the temperature on Titan averages about -290 Fahrenheit (-179 Celsius), they come in all three states of matter—liquid, solid and gas. There’s also a whole methane cycle analogous to Earth’s water cycle which creates similar Earthly weather patterns on Titan.

Just because organic compounds found one way to form into life here on Earth, doesn’t mean that there aren’t a multitude of other ways—in fact I refuse to believe so. In 2010 Sarah Horst of the University of Arizona found all five nucleotide bases (the building blocks of DNA and RNA) and amino acids (the building blocks of protein) among the compounds produced when energy was applied to a combination of gases like those found in Titan’s atmosphere. It was the first time nucleotide bases and amino acids had been found in such an experiment without the presence of liquid water. In 2013 NASA did an experiment of their own and also concluded that complex organic chemicals could arise on Titan based on simulations of the Titan atmosphere. If life were to exist on Titan, it would most likely inhale hydrogen in place of oxygen and metabolize with acetylene instead of glucose and exhale methane instead of carbon dioxide.

The other thing Titan has going for it over the two former candidates is we already know how to get robot landers to the surface because we’ve done it before. In 2005 the Cassini spacecraft dropped the Huygens probe and you can see how eerily similar the surface looks to Earth in this video here. Unfortunately as of right now there are no planned return trips to Titan.

Until next time my friends, stay curious.

 

Categories
Astrophysics Biology chemistry Life Lessons particle physics physics religion science spirituality

The Spirituality of Science

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An obviously very doped-up me after my colonoscopy 

By Bradley Stockwell

To spare you of the intimate details, I’ll just say recently I’ve had some ‘digestive issues’. Two weeks ago I had a colonoscopy to check out these issues. Although I realized the possibility that they may be caused by something serious such as cancer, when my doctor presented me with that reality, it dug in a lot more than I thought. Fortunately, it seems this world is stuck with me a little longer for all my biopsies came out okay. However during the five days in which I had to wait to hear these results, I couldn’t help but contemplate my own mortality and what death means to me as an atheist.

For lack of a better label, I am an atheist but I am not spiritual-less. I find a deep sense of sanctity and humility in the scientific observations of nature. To make clear, this post is not intended to degrade or disprove anyone’s religious faith. The world is richly diverse in beliefs, cultures and opinions and I think that’s a necessary and beautiful thing. What I do have a problem with is the contention surrounding the subject of faith and I in no part want to contribute to it. The reason I love physics so much is it seeks to find unity amongst division and I apply that same philosophy in all facets of my life. Simply, I’m presenting how I sleep at night without believing in a god(s) or an afterlife because it is an honest question I’m frequently asked.

The primary source of my peace of mind comes from the laws of thermodynamics which describes how energy behaves. The first law, the conservation of energy, states energy cannot be created nor destroyed. This law was exampled in a previous post, Flight of The Timeless Photon, on how the photon (aka energy) is transformed from hydrogen proton mass into the life-providing sunshine we all know. The energy we consume, and consequently life, is all sourced from the sun. And the sun’s energy is sourced from the matter within the universe and to find out where the universe’s energy is sourced, we would’ve had to been around during The Big Bang. However according to multiverse theorists, it’s a good chance that it may have come from the matter of a previous universe which was chopped up and scrambled by a black hole into energy. Regardless, the point I’m trying to make is energy is immortal. It is the driver of the circle of life not just here on Earth but in the entire universe. As special as you think you are, you are nothing more than a temporary capsule of mass for energy to inhabit. Death is nothing more than a dispersion of this energy and this is what I take consolation in. When I die, all the energy that was me, my personality—my soul, my body even, still remains in this world. I’m not gone; just less ordered. I am a part of what keeps the arrow of time moving forward as the universe naturally moves from a higher state of order towards a lower—the second law of thermodynamics.

The universe is very cyclical. Life and death are just different stopping points on a grand recycling process. Matter, like our bodies, is created and recycled and energy, like our souls, is immortal and transferred. If you’re familiar with Dharmic beliefs, this probably sounds familiar. It’s funny how the world’s oldest religion, Hinduism, seemed to grasp these concepts thousands of years before science did. While I’m not a practicing Hindu, nor do I plan to be, if forced to choose it would be the closest to my belief system due to the many correlations I find between it and science. One correlation I was most awestruck by was the concept of Brahman to the laws of thermodynamics (aka the laws of energy) mentioned above. According to belief, Brahman is the source of all things in the universe including reality and existence. Everything comes from Brahman and everything returns to Brahman. Brahman is uncreated, external, infinite and all-embracing. You could substitute the word energy for Brahman and get a simple understanding of the applications of the first and second laws of thermodynamics.

If you can’t fathom the thought of an afterlife as some form of your current self, I can understand that. Once again I’m not here to convince you differently, I’m just presenting my viewpoint. However in regards to the value of life, I do hope to convince you that there is no deeper appreciation than through the eyes of science. I only stress this to debunk the perpetuated myth that science somehow devalues the beauty of this world by picking it apart. Once again, the reason I love physics is it widens the perspective of my existence through unifying the universe’s many diverse creations and movements. It connects me to the infinitely larger cosmos above yet also to the infinitely smaller universes below. I have an atomic connection to the stars, a chemical connection to the earth, a biological connection to life and a genetic connection to my fellow humans. When you see the world on so many dimensions, I can personally attest that suddenly everything becomes very interesting. Even the things we don’t give much thought to, like sunshine, weather, the way in which water ripples, or why your friend’s beer overflows when you smack the top of it with yours, become regularly appreciated with a new sense of awe and curiosity. The world becomes much more absorbing than anything a smartphone or television can provide and you find yourself wanting to experience everything it can offer. There’s no greater feeling than the intercourse between knowledge and experience. This perspective is perfectly captured by one of my idols, the great physicist Richard Feynman.

 “I have a friend who’s an artist and has sometimes taken a view which I don’t agree with very well. He’ll hold up a flower and say “look how beautiful it is,” and I’ll agree. Then he says “I as an artist can see how beautiful this is but you as a scientist take this all apart and it becomes a dull thing,” and I think that he’s kind of nutty. First of all, the beauty that he sees is available to other people and to me too, I believe. Although I may not be quite as refined aesthetically as he is … I can appreciate the beauty of a flower. At the same time, I see much more about the flower than he sees. I could imagine the cells in there, the complicated actions inside, which also have a beauty. I mean it’s not just beauty at this dimension, at one centimeter; there’s also beauty at smaller dimensions, the inner structure, also the processes. The fact that the colors in the flower evolved in order to attract insects to pollinate it is interesting; it means that insects can see the color. It adds a question: does this aesthetic sense also exist in the lower forms? Why is it aesthetic? All kinds of interesting questions which the science knowledge only adds to the excitement, the mystery and the awe of a flower. It only adds. I don’t understand how it subtracts.”

When I finally do say goodbye to this world, I hope my friends and family will realize this is not actually the case. Everything that was me is still very much a part of this world, just partaking in a different dimension of it. The energy contained within my body will go back into the earth so that it can provide new life to the flora and fauna which kept me alive as I dined on them throughout my own life. Every joule of energy that was me will be released back into this world to live life anew. And will the unique combination of matter the winds of energy deposited as Bradley Stockwell be forgotten? Well I hope I will have done something impactful enough to be remembered by history, but if not, I can always depend on my beloved light particle, the photon, to ensure my existence will mean something. Explained in detail in my previous post, A Crash Course in Relativity and Quantum Mechanics, according to relative velocity time dilation, the photon’s existence is timeless relative to ours because it moves at the speed of light. A funny thing happens to time at the speed of light—it ceases to exist, at least relative to our perception of time. That is of course until I interrupt this so-called photon’s path by absorbing it as heat and become that photon’s entire existence; forever altering the universe. And this is not the only way the photon will preserve my existence. I of course don’t absorb all the photons I come into contact with—some of them bounce off me and are collected in the photon detectors (aka the eyes) of my friends and family members. These photons then create electromagnetically charged webs of neurons, better known as memories. Well until next time, stay curious my friends!

 

Categories
Biology chemistry particle physics physics science

Flight of the Timeless Photon

sunshinelove

By Bradley Stockwell

One of my favorite stories in all of physics is the story of sunlight because it touches on such a wide range of concepts. I apologize for the length of this post, but I guarantee you’ll be enlightened on many terms you probably hear thrown around a lot, but not a lot of people understand. Also, we learned in my previous post some of the important uses of light, but didn’t address the most important use of all, life!

Sunlight’s story, along with almost everything in the universe (we’ll ignore something called dark matter for now), begins with a hydrogen atom. Hydrogen is the most elementary and abundant element in the universe, hence the reason it is element one on the periodic table. Also because it’s comprised of one positively charged particle called a proton, which makes up its nucleus, and one negatively charged particle called an electron, which orbits around that single-proton nucleus. Within the sun, or any star, there is a process called nuclear fusion which transforms hydrogen into all 92 elements found in nature. Every grain of matter that makes up our physical world is forged in the heart of stars and is released when they begin to die. Not all stars produce all 92 elements however, like our sun will never get hot enough to fuse enough atoms together to produce heavy metals like gold. When I say heavy, what I am referring to is the element’s mass. The more sub-atomic particles shoved into an element’s nucleus, the heavier it is. Stars of different sizes produce different elements, but all stars begin with fusing hydrogen into helium as our sun is currently doing.

Within the sun’s core, hydrogen atoms are sped up from high amounts of energy, or heat, created by the force of the star’s mass on itself and collide at very high speeds, fusing them together to make helium. The sun has to smash four hydrogen atoms together to make one helium atom. The radioactive elements created in the steps in between are called hydrogen isotopes. Two hydrogen atoms make the stable isotope deuterium, three, the unstable isotope tritium, and four a helium atom. The difference between a stable and an unstable isotope is the even pairing of protons and neutrons (we’ll get to what a neutron is soon) in the nucleus. An even pairing, like one proton and one neutron (deuterium), is stable, but an uneven pairing, like one proton and two neutrons (tritium) is not and eventually falls apart into stable isotopes because it is too energetic to stay together. This ‘falling apart’ is known as radioactive decay.

 

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Two hydrogen atoms make the stable isotope deuterium, three, the unstable isotope tritium, and four a helium atom.

If you’re a fan of The Simpsons, you may remember the Springfield baseball team was called The Isotopes. This was in reference to the town’s nuclear power plant, in which a forced and more violent version of this process occurs called nuclear fission. Typically uranium nuclei are loaded up with extra neutrons until it reaches what is called critical mass. Once critical mass is reached, the nuclei split and large amounts of energy are released because they can’t hold this new influx of neutrons. It’s kind of like your friend who drinks too much at a bar then spews all over the place. This neutron ‘spewing’ is what provides us with electrical power. While the process releases energy, it also leaves varying forms of unstable uranium isotopes that decay naturally into stable isotopes over sometimes hundreds of years. This is because uranium is such a heavier element in comparison to hydrogen, which its isotopes decay rather quickly. These radioactive leftovers are still highly energetic and emit damaging gamma and x-ray waves (we learned what these were in my previous post) and that is why containment is so crucial. My apologies for this nuclear fission tangent, but one should know the difference between fusion and fission. Fusion brings atoms together, fission rips them apart.

So back to the story of sunlight. When the sun does finally manage to smash four hydrogen atoms together, two of the hydrogen’s protons lose mass in the process and become neutrally charged particles called neutrons, making a total of two protons and two neutrons in the new helium nucleus with two orbiting electrons, one for each proton. The expelled proton mass, which eventually will become our beloved sunlight, is given off as energy in the form of highly energetic electromagnetic radiation (a.k.a. light) known as gamma rays. This is an excellent example of Einstein’s famous equation for energy, E=mc2, at work. What this equation says is mass (m) can be converted to energy (E). If you’ve ever tried to lose weight, the same concept applies. You’re trying to convert your mass into energy to lose it. However things on a quantum level work in funny ways. The neutron instead of being less massive actually becomes more massive than it was when it was a proton. This can be blamed on particles within protons and neutrons called quarks and how they behave; something I’ll leave for another post. The ‘C’ part of the equation stands for the speed of light constant which is just something that needs to be added formulaically in order to receive a correct calculation and we’ll get to why later.

We learned in my previous post that electromagnetic radiation is made of particles called photons. These newly created gamma ray photons are at first far too dangerous for earthly consumption. However after tens of thousands of years of being passed around between densely packed atoms within the sun, the photons tire out a bit until they become less energetic visible light photons, or what we call sunshine. Even traveling at the speed of light, photons can take up to a million years to escape the sun; a distance of 432,000 miles from core to surface. While this may seem like a long distance, compare it to the 93 million miles photons travel in only 8 minutes and it becomes apparent how abated those photons are by being continually absorbed and emitted by the soup of atoms within the sun. However once they hit the empty vacuum of space, they have a straight shot to Earth.

When photons finally enter Earth’s atmosphere, some of them are absorbed by tiny pores on plants’ leaves called stomata that convert those photons into chemical energy. This is done by the synthesizing of hydrogen atoms from water in the plant with carbon dioxide in the air to create sugars. This process, I’m sure you’re familiar with, is called photosynthesis. Since plants only use the hydrogen from water, they emit the remaining oxygen as a waste product and we literally breathe their shit. The sugar is stored and later converted into kinetic energy to allow the plant to function. This sugar however can be transferred to a creature that eats the plant and a creature that eats that creature and so forth. Animals (including us) extract energy from these sugars by reacting them with the oxygen they breathe and exhale the remaining carbon dioxide from the sugars so that another plant can use it to create more sugar and oxygen for them to consume.

So next time you look up at the sun (not directly!), think about what’s going on inside there. Think about everything nuclear fusion gives you; air, food— the very matter you’re made of, and say thanks. And as the sunlight warms your skin, think about the tens of thousands of years it took for those photons to reach it. And here’s another interesting fact to blow your mind on; for those photons, you are their entire existence! Well at least within our idea of existence. This is where the ‘C’ (the speed of light constant) in E=mc2 comes into play. The photon, which is energy, travels at the speed of light and that is why that speed needs to be figured into every calculation for energy. It is ‘constant’. And according to Einstein’s theory of relativity, time slows down the faster you move relative to another object until it completely stops at the speed of light. The photon’s time, relative to ours, doesn’t exist. The photon is considered timeless . . . well at least until it’s brought into our reality when you absorbed it as heat. I’ll segue this into my next post which will be on the theory of relativity and quantum mechanics. Until then, stay curious my friends!