The Long Journey of Voyager 1

Voyager 1 (artist depiction)

Mankind is about the leave the solar system. Well, sort of anyway. Voyager 1, the space probe launched by NASA over 35 years ago, has reached a point in space about 18.5 billion miles from the sun, give or take. NASA, which still monitors and communicates with the probe, announced earlier this week that Voyager 1 has entered a region of space called the “magnetic highway” a boundary area where highly charged particles from deep space interact with solar particles. This region is very close to what’s been termed the heliopause, the very outside edge of the heliosphere, which is (the heliosphere) the bubble of space where the Sun’s solar wind dominates the background particles that permeate space. The heliosphere is used by cosmologists to demarcate our solar system from interstellar space.¹ One way to conceptualize the heliosphere is to think of it like the solar system’s version of Earth’s atmosphere, which encompasses us and separates us from space. The further from the Earth’s surface you get the thinner the atmosphere becomes until eventually it stops and space dominates. Same concept with the heliosphere², the further from the Sun you get the less its radiation dominates space until eventually its influence ceases altogether.

It may actually take Voyager 1 another year or two before it technically reaches interstellar space, such is the vastness of space, but still this is a good time to reflect on the spacecraft and just how far it’s travelled.

The Flights of Voyager 1 and 2

Jupiter with moon Io and Europa as photographed by Voyager 1

By a quirk of planetary orbital dynamics, in the late 1970s and 1980s the outer planets were in a favorable alignment for a space probe to observe each one at close range (they were all on the same side of the Sun). The relative position of the planets would allow for each planet’s gravity to be used to assist in redirecting the probe onto the next planet. This alignment was realized in the late 1960s and astronomers knew that this favorable positioning wouldn’t occur again for 175 years, so time was of the essence. Fortunately NASA, in the wake of the concluded Apollo lunar missions, took advantage and developed two probes, Voyager 1 and its sister craft Voyager 2, which would be sent on close-up flybys of each planet. Each probe weighed 1,500 pounds and was instrumented to observe the planets in just about any way NASA engineers could want. NASA launched both probes in late summer 1977.³ Initially, owing to post-Apollo budget cuts the two spacecraft were only going to observe Jupiter and Saturn, and indeed that’s all Voyager 1 did. It reached the Asteroid belt three months after launch, and approached Jupiter in early 1979. At its closest approach it came nearer the Jovian “surface” than the Moon is to Earth. Among other things, the Voyager probes discovered that Jupiter had rings and that its moon Io was volcanically active. Voyager 1 then headed on to Saturn. It flew by the planet in November 1980, just 77,000 miles above Saturn’s outer atmosphere. Voyager 1 not only observed Saturn, but its moon Titan and the combined gravities of these two bodies hurled the spacecraft (as planned) toward deep space. Its primary mission was over.

I was born just before Voyager 1 reached Saturn; for all intents and purposes, the probe has been racing out of the solar system for my entire life.⁴ More on this below.

Neptune as seen by Voyager 2

After the success of Voyager 1, NASA decided to direct Voyager 2 to Uranus and Neptune. Voyager 2 traveled slower than Voyager 1 (it reached Jupiter shortly after Voyager 1 and Saturn about eight months after) reaching Uranus in late 1985 and finally Neptune in mid-1989. To call the missions a success would be an understatement. Along with valuable scientific data about all of the gas giants, they provided gorgeous photographs. These are just the type of results that both advance science and fire our imaginations, exciting us to further explore and learn about space.

Both probes have enough power to operate until at least 2025. After that, barring a collision with some interstellar object, they will continue on into oblivion. Both probes include a Golden Disk that presents information about Earth and mankind (including audio recordings). The chances may be infinitesimal, but maybe sometime, millions and millions of years from now and many many light-years away, some other intelligent species will find these markers of man.

The Lessons of Voyager 1 for Deep Space Travel
I've always been interested in the stark contrast between the realities of space and the fantastic ways that space travel is portrayed in science fiction. The journey of Voyager 1 illustrates this discrepancy. Voyager 1 is one of the fastest moving manmade objects. It’s currently travelling away from the sun at more than 38,000 miles per hour, that’s over 10.7 miles every second. Even at that speed it still took it 32 years to travel from Saturn to the edge of the solar system⁵, a distance of roughly 17.6 billion miles. The nearest star to Earth is Proxima Centauri, 4.24 light-years distant. A light-year is equivalent to about 5.87 trillion miles (light travels at about 186,000 mi/s). 4.24 light-years is a bit less than 25 trillion miles. Don't bother trying to conceptualize this distance, it's far greater than anything we humans can relate to. At the current speed of Voyager 1, it would take the probe more than 75,000 years to reach that star (and to be clear, it’s not headed towards Proxima Centauri). That’s more than 1,000 lifetimes.⁶

I highlight these huge numbers to show you just how inconceivable it is for man to travel to another star system. The Apollo missions used the Saturn V rocket to accelerate the lunar spacecraft to about 25,000 miles per hour (Earth’s escape velocity). This is as fast as man has ever travelled, and had the astronauts been headed to Proxima Centauri instead of the Moon, it would have taken 114,000 years. In fact had Apollo 11 been on a mission to the stars when launched in July 1969, it would be about 9.5 billion miles from Earth by now, barely half way out of the solar system. Double, triple, multiply by tenfold the speed of human spacecraft and the time to approach the nearest stars don’t get any more reasonable.

I’ve written before about the questionable purpose of human spaceflight beyond low Earth orbit. But while I think this debate is largely academic (at least in the present fiscal climate), destinations like the Moon, maybe Mars, and perhaps thinking more fancifully, some distant moon of Jupiter or Saturn are at least thinkable. The simple reality of human existence and mortality demonstrate that no one will ever leave our solar system.

The overwhelming odds are that for thousands or even millions of years (or much longer) the Voyager spacecraft (along with the Pioneer and other distant probes) will transit through interstellar space, a virtual emptiness, passing nothing of note and experiencing nothing worth remembering. That’s no trip for humans to take and no place for humans to be.

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NOTES:

1. It worth a quick discussion of what exactly comprises the solar system: There’s the Sun at the center with all of the planets, moons, dwarf planets, asteroids, comets, and miscellaneous other space objects that orbit the Sun. Less familiar, and well beyond the orbit of Neptune is the Kuiper belt, which is like a much larger version of the Asteroid belt. Beyond that is a less cohesive collection of objects called the Scattered disc, which is where most periodic comets are believed to originate. Beyond that are the limits of the heliosphere, including the termination shock, heliosheath, heliopause, “magnetic highway” and other boundaries that mark the progressive decrease in the dominance of the Sun over surrounding space.

Beyond these traditional (and very distant) limits of the solar system there other highly scattered objects like Sedna (observed) and the Oort Cloud (hypothesized) that do/may orbit the sun over very long orbital periods.

2. This is a much simplified analogy. In reality the heliosphere is more like a combination of our atmosphere and Earth’s magnetic field, which is critical in deflecting solar radiation and is a crucial boundary separating the Earth below from space beyond.

3. Voyager 2 was actually launched two weeks before Voyager 1.

4. In 1990, Voyager 1 did take a long range picture of all the planets together (excepting Mercury and Pluto, which was still a planet then).

5. Voyager 1 picked up speed after it passed Saturn (it stole some of Saturn gravitational energy), so it left Earth slower than it’s travelling today.

6. Using the biblical three score and ten years definition of a lifetime.

Sinking Cities

by Conroy

Baltimore flooded by Hurricane Isabel

Are America’s coastal cities facing a losing battle against the sea? Consider these facts from cities all along the U.S. East Coast: In Galveston, Texas, a long sea wall shields the city from the Gulf of Mexico. The sea wall worked for a century, but in 2008 the storm surge from Hurricane Ike overtopped the wall and flooded the adjacent streets. In the early 1980s Miami-Dade County spent $50 million to rebuild the eroding shore line of Miami Beach. Similar projects, officially termed “beach nourishment”, are common all along the Atlantic seaboard¹. In some precariously narrow sections of Hatteras Island, North Carolina, far off the mainland in the state’s Outer Banks, sand bags line both sides of the state route 12 to keep the Atlantic on one side and Pamlico Sound on the other from splitting the island. Back in 2003 when Hurricane Isabel roared up the East Coast, the island was split and an emergency project was required to stop the erosion and prevent the split from becoming permanent. Hurricane Isabel continued its movement up the East Coast flooding coastal areas of Virginia and as it moved inland its powerful storm surge funneled water up the Chesapeake Bay causing widespread flooding in coastal Maryland, and putting Baltimore, including downtown, under several feet of water. The flooding even extended far up the tidal Potomac to Washington, D.C. In 2011, the storm surge from Hurricane Irene flooded parts of Brooklyn and lower Manhattan. Further north, Nantucket Island off of Cape Cod is literally eroding into the sea, taking pricey homes with it.

As these examples above demonstrate, being next to the sea has its dangers, and fighting the long-term trend of beach erosion and flooding are never-ending expensive battles. This situation is only going to get worse if a planet-wide trend continues: rising sea levels. Consider that just along the Atlantic and Gulf coasts Boston, New York, Philadelphia, Baltimore, Washington, Jacksonville, Miami and Southeast Florida, Tampa Bay, and New Orleans are situated at least in part at sea level. And it’s not just major metropolitan areas that are at risk, the low-lying shores of the Houston shipping channel, just inland from Galveston, are home to one of the nation’s largest ports and lined with the nation’s largest concentration of petroleum refining plants. Are all of these areas destined to be inundated over the next century?

Sea Levels Rising
Of course the first thing that has to be answered is: Are sea levels actually rising? And to answer that, we need to understand what sea level is. Sea level is harder to define than it may seem because of course the flowing, undulating sea never seems to have one level. However, the most basic definition is the average surface elevation of the oceans when surface fluctuations, like high and low tides are averaged out. This seems like a reasonable definition but it nevertheless can be hard to pin down. Note that the average sea level of the Atlantic end of the Panama Canal is nearly eight inches lower than at the Pacific end. Still, it’s fair to say that there is a local “sea level” for all places where land meets tidal water. Historically these levels have been measured from set gauges on land, and more recently satellites have been used to observe global sea levels.

The results of these measures seem to confirm that sea levels are indeed rising all over the world. According to the Intergovernmental Panel on Climate Change (IPCC)², global sea levels have been rising by about 1.8 millimeters per year (mm/yr.). If this estimate is in any way accurate, and indicative of a continuing trend (and not a rate that may slow or even reverse in the near future), there’s probably no need for immediate panic. At this rate it would take about 555 years for global sea levels to rise by one meter or about 170 years to rise one foot. This is hardly a catastrophic rate of increase. However, rising sea levels, whatever the rate, do pose an obvious risk to coastal areas. And many estimates, including those by the National Oceanic and Atmospheric Administration (NOAA), put the annual sea level rise much higher than the IPCC.

But what causes sea level to change? On geologic timescales, ocean bottom elevations and plate tectonics play major roles. These occur so slowly that they don’t affect us. More important are short term causes like tides, onshore winds, atmospheric pressure, surface water temperatures, evaporation, precipitation, river runoff, and in extreme cases major storm surges and tsunamis. On the longer term sea levels can change because glaciers and ice caps shrink or expand. In the first case, melt water is freed from the land and adds to the volume in the sea. In the latter case, water is trapped in ice and global sea levels drop. Another long term trend is changes in land elevation due to groundwater depletion, erosion, or general geological subsidence. But it’s the melting glaciers and ice caps that have gathered most attention in recent decades, the result, many will claim, of rising global temperatures, which is in turn the result of man-made effects to the environment.

Melt water on the Greenland Ice Sheet

Man-made or natural, rising temperatures will melt snow and ice. If the entire Greenland Ice Cap were to melt, global sea levels could rise by as much as 24 feet. If the entire Antarctic Ice Cap were to melt global sea levels would rise by 200 feet. These are extremely remote possibilities, Greenland and Antarctica are really cold places and it would take many thousands of years for them to melt. And Arctic sea ice melting would have a negligible effect on sea levels because these ice packs are already floating on the sea. More likely is increased melting of ice on the periphery of Greenland and Antarctica, which could still result in several feet of sea level rise. Also, if sea surface temperatures increase, water density decreases and its volume increases. So higher sea temperatures result in higher sea levels irrespective of the contribution of more water (melted ice). It’s worth noting that global temperatures haven’t increased over the last dozen or so years, which is directly contrary to the predictions of climate models. If global temperatures do stabilize then sea water temperatures and ice cap/glacier melting may not be as significant an issue as many fear.

Now I don’t know if or how much global sea levels may be rising. Like all earth systems, the various components that affect sea level are complicated and combine in unexpected ways. For example, increasing global temperatures will lead to increased precipitation, which, if it falls in the polar regions like Antarctica, will actually increase the thickness of the ice caps and the amount of impounded water, which would lower global sea levels. However, higher temperatures should result in greater calving and icebergs breaking away from the subpolar regions, which would raise global sea levels. How might these two trends interact and which is greater?³ When you consider all of these components there has to be question of how measurements of these global trends can even be made and how accurate models of these global systems can be. Let alone what predictions for future developments are possible.

It’s also worth noting that many of the flooding examples cited at the beginning of this post were the result of major storms, which are not in themselves indicative of sea level rise. Never in my memory had Baltimore flooded from the sea like in 2003, and the Galveston sea wall had stopped all storms, including hurricanes, for a century. There’s plenty of room for debate about whether American cities face an impending crisis from rising sea levels.

Nevertheless, even if the global climate doesn’t warm appreciably over the next century, America’s coastal cities would be negligent to not prepare for rising sea levels and ever more frequent flooding. Sea levels appear to be rising slowing but consistently and this can’t be ignored. And as we consider coastal flooding, we should first turn from the U.S. East Coast to an ancient city on the Mediterranean.

Hurricane Guesswork

by Conroy

This past week tropical storm Alberto churned off the coast of Georgia and the Carolinas, ushering in an early start to the Atlantic hurricane season [1]. For residents along the U.S. Atlantic and Gulf coasts, the hurricane season is a period of low-grade angst. There’s a relatively remote chance that coastal areas will be hammered by a truly devastating storm, but it happens. Since 1950 there have occurred, on average, 11 named storms [2], 6 hurricanes [3], and 3 major hurricanes (Category 3 or higher [4]), per year. A fraction of these, one or two hurricanes each year on average, will hit the U.S. mainland. And rarely, maybe once or twice a decade, a major hurricane makes landfall with catastrophic results, as witnessed by the deaths and damage caused by Camille, Hugo, Andrew, and Katrina, to name only the most prominent.

Recognizing the danger of hurricanes, it’s without question important to identify and follow every tropical depression as it forms, predict its storm track, warn people living in potentially affected areas as far in advance as possible, and prepare for emergency response as warranted. The news media and various local, state, and federal public agencies do the first three very well. Sadly, as vividly demonstrated by Katrina, emergency response can sometimes be hindered by bureaucratic obstacles and lack of initiative.

Hurricane Forecasting
The interest in hurricanes also leads to far more dubious types of planning and forecasting, namely the annual Atlantic Seasonal Hurricane Forecast. The most prominent of these is published as part of the Tropical Meteorology Project of Colorado State University [5], which was previously led by Professor William Gray and is now led by Professor Philip Klotzbach.

Gray and Klotzbach will explain that they use Atlantic and Pacific water temperatures, global weather patterns like El Nino and La Nina, and other climate factors to predict hurricane activity and probabilities for strikes in the Caribbean and North America. For example, this year’s forecast (from April) predicts a relatively quiet season with a total of ten named storms (tropical storms or hurricanes), four hurricanes, and two major hurricanes.  In addition, it places the probability of a hurricane making landfall somewhere along the U.S. coast at 42%.

Call me a skeptic, but I doubt the ability of anyone to accurately predict the number and intensity of Atlantic hurricanes, let alone the location of where they might develop and track, for any given season. Meteorologists can’t predict the weather for any one location with much accuracy even a week in advance. How can they predict the development of major weather systems over huge expanses of the equatorial and North Atlantic many months ahead of time (the Atlantic hurricane season usually peaks in early- to mid-September)? Add to that the fact that the dynamics of hurricane (or any tropical cyclone) formation are not entirely understood and the various factors that lead to hurricanes are specific to local weather conditions and cannot be predicted in advance.

Yet predictions are made each year, and each year they are given mention in the news. For that reason, Gray’s and Klotzbach’s forecasts deserve to be tested for their accuracy.

Bad Predictions
One way to check whether forecasts have any predictive value is to examine how previous forecasts have aligned with actual hurricane activity. This table summarizes predicted versus actual Atlantic hurricane activity from 1999 (the first year of Gray and Klotzbach forecast data available on-line) through 2011.

The God Particle

by Conroy

Part of the 17-mile-long LHC particle accelerator

Late last year there was breathless excitement within the physics community as several experiments conducted by CERN [1] at the Large Hadron Collider [2] under Geneva seemed to hint at the presence of a fundamental, and as yet entirely theoretical, particle: the Higgs boson. What is this particle and why did these experiments so energize physicists? The short, simple answer is that the Higgs boson is the particle associated with the Higgs field, which is hypothesized to be a ubiquitous quantum “field”. Think of it as a force or condition throughout all of space that matter interacts with. It is theorized that Higgs bosons interact with other fundamental particles (electrons, quarks, etc.) to give them mass. If detected, the Higgs boson would further validate the so called Standard Model of particle physics, one of the core theories of how the universe (the fundamental particles and forces) is structured.

The news from CERN quickly spread to the general news media and Newsweek jumped to exclaim on a cover headline that the experiments hinted at, “The Meaning of the Universe.” Other publications picked up on the Higgs boson’s nickname as “the God particle”. These headlines and reactions create the impression that this discovery, if confirmed [3], would explain many of the remaining questions in theoretical physics and provide the answers to those eternal questions that have puzzled mankind for millennia. So would it?

The Profound Questions
The Higgs boson would explain why particular particles have a specific mass. Mass is a fundamental feature of matter and explaining how mass “works” would be a tremendous breakthrough. The results would also be important in the understanding of mass-less particles like photons. But the discovery would hardly answer the even more fundamental questions about the nature of the universe, such as:

• What is the universe?
• Where did it come from?
• Why does it have the structure and forces that it does?
• Is there anything outside of the universe?
• What is the universe’s fate?

Let’s come back to these.

Everything to (Practically) Nothing

The Milky Way

There’s a terrific website – scaleofuniverse.com – that provides an interactive depiction of the size of the universe and everything in it. It’s a way to conceptualize just how inconceivably vast the totality of the universe is, and how absurdly infinitesimal are its fundamental parts. Let’s take a quick scan of this reality. Make a fist and stare at it, image it is the entire universe and you’re looking at it like God:

• Our universe is estimated to be 93 billion light years across. Light, traveling at 186,000 miles per second, would take 93 billion years to cover the current expanse of the universe.
• We can observe about 14 billion of these light years, the approximate time that light has had to travel since time began (14 billion years ago, give or take). The universe inflated faster than light a short time after the Big Bang.
• We zoom way way in to our galaxy, the Milky Way, one out of hundreds of billions, and a mere 120,000 light years across, 0.0000086 times the distance of the observable universe.
• We focus further, much further, to our solar system, which including the Oort Cloud, is 0.15 light years across, 1.5 trillion kilometers, or 0.0000013 times the distance of the whole Milky Way.
• We continue closer and see the dim Sun from Pluto, nearly six billion kilometers distant, 0.004 times the diameter of the Oort Cloud.
• We pass Jupiter, 800 million kilometers from the Sun, 0.125 times the distance from Pluto to the Sun.
• We see the Sun, shining nuclear-bomb bright, one star out of hundreds of billions in our galaxy, nearly 1.4 million kilometers across, 0.0018 the distance to Jupiter.
• We close in on the Earth, one planet of likely hundreds of billions in the Milky Way, almost 13,000 kilometers in diameter, just a spec compared to the Sun.
• We see China spread 4,000 kilometers across the Earth’s surface.
• We see Mount Everest standing nearly 9 kilometers tall.
• We see a man standing on the summit, less than 2 meters (6 feet) tall.
• He steps on a snowflake a centimeter (.01 meters) across.
• And wishes on an eyelash 0.1 millimeters (.0001 meters) thick, just about as thin as the human eye can detect.
• His heart vigorously pumps blood through his veins and he rapidly exhales moist air, red blood cells and air droplets, both about 0.00001 meters across.
• The moisture includes water molecules 0.0000000003 (3x10^-10) meters across.
• Each molecule includes two hydrogen atoms, each just 0.00000000003 (3x10^-11) meters across.
• The nucleus of those atoms is 0.00000000000001 (1x10^-14) meters across.
• The proton inside the nucleus is 0.000000000000001 (1x10^-15) meters across.
• The quarks [4] inside the proton (and the electron circling the nucleus) are 0.000000000000000001 (1x10^-18) meters across.
• Preons, the building blocks of quarks are 0.000000000000000000001 (1x10^-21) meters across.
• Neutrinos, the ghostly particles the fly virtually untouched through all of matter are smaller yet, just 0.000000000000000000000001 (1x10^-24) meters across.
• And finally to the smallest of the smallest, the theoretical strings and Plank length (the “minimum” length of anything) at 0.00000000000000000000000000000000001 (1x10^-35) meters across.

I doubt the human mind can truly conceptualize the size of anything on scales larger than the solar system or smaller than a cell (I can’t anyway). We can see the Sun and have sent space probes past Pluto. We can see the thickness of a piece of paper and understand its even smaller constituent parts. Yet the great unanswered questions lie beyond these narrow boundaries of observation and intuition.

Day and Night

by Conroy

A day/night map of the world

Just a few days ago, September 23rd to be precise, was the September equinox. The date when the sun passes the Equator on its southward journey to the Tropic of Capricorn. Or to put it in a more accurate way, the date (and time) during our planet's revolution of the sun when the Earth's axis of rotation is directly perpendicular to the imaginary line connecting the centers of the Earth and sun. After this date the southern hemisphere is tilted toward the sun (and the northern hemisphere tilted away). From our terrestrial perspective, for the next few months the sun will head ever more southward until the December solstice (December 22 in 2011), when it will reach its southern limit and begin its journey back north, passing the equator for the March equinox (March 20, 2012), and reaching its northern limit at the June solstice (June 22, 2012). Only to head back south again, repeating the cycle, forever.

This familiar cycle, corresponding to the seasonal variation that is such a distinctive feature of life, especially in temperate climates, has always fascinated me. The alternation between summer and winter, light and dark, has directly affected where and how humans live.

Time Travel Silliness

by Conroy

The latest time travel entertainment

In a couple of weeks Fox will air Terra Nova, the most expensive television program in history. The show's premise is that future civilization can only be saved by sending humans back 85 million years into the past. I have no idea what in this extinct period is going to save humanity (I'm assuming that will be the ultimate outcome of the show), but such a setting does allow for dinosaurs (plentiful in the trailer) and undoubtedly many other obstacles challenging to modern man. Whatever the details, the program is just the latest in an unbroken string of high profile television shows, movies, and literature based on time travel. Or what I like to call the tired time travel conceit. Tired and preposterous. (It's right up there for me with all those movies where one person's consciousness gets switched into another person's body, or the unending end of the world apocalypse stories.)

The idea of time travel has been around for centuries (if not longer) and its use in fiction became prevalent in the nineteenth century, when the genre was adumbrated by Dickens in A Christmas Carol, then explicitly used by Mark Twain in A Connecticut Yankee in King Arthur's Court, and perhaps most famously in H.G. Wells' The Time Machine. And these are just the more noteworthy examples. In time, time travel has become even more popular, unfortunately.

Now don't get me wrong, I like science fiction. And I know the whole point of the genre is to take humans to places and times different from the here and now. After all, isn't the point to remove people from the familiar and surround characters with radically different conditions in order see with fresh eyes the realities of the human condition? Or at least pose the relevant questions in a different light? That's the core of science fiction and it makes for some great stories and ideas...but time travel? Really, come on.

Time Travel and Paradoxes

The Terminator sent from the future

One well known example of what drives me crazy about time travel stories is from the Terminator. In the story a war between humans and machines is being fought in the not-too-distant future. The machines utilize time travel to send back an android (excuse me, "cybernetic organism") "terminator" to kill Sarah Connor, the mother of John Connor the human leader, before he was conceived. If the android succeeds then Connor will never be born and the human rebels will be leaderless (I guess). To stop the Terminator, Connor sends back a human to protect his young mother. In the process of the movie, the human protector, Kyle Reese, impregnates Connor's mother -- with Connor. This is a classic example of what is known as a predestination paradox. Reese travels back in time on orders from John Connor, impregnates Connor's mother, who then gives birth to John Connor. If Reese is never sent back, Connor can never be born, and the adult Connor cannot order Reese to go back and protect his mother. There are other examples of this just from the Terminator and its sequels.