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.

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.

Men in Space

by Conroy

A few weeks ago I was at the Kennedy Space Center at Cape Canaveral, Florida. Only days before, the long delayed final mission of Shuttle Discovery had ended with a successful landing in Florida, but already Endeavor was on the launch pad, surrounded in its pre-launch sheath. The Endeavor launch, scheduled for April 19 (weather and mechanical integrity permitting of course), will be either the ultimate or penultimate flight of the Space Shuttle Program depending on some final Congressional budget decisions. This is the end of an era for American manned space flight.

The Shuttle Program has been ferrying humans to an from low Earth orbit since 1981, and is ending because the shuttle fleet (or what's left of the shuttle fleet) is aging and shuttle missions are expensive. Once shuttle flights end, NASA will rely on the Russian Soyuz rockets and space craft for transport to and from the International Space Station. It is hoped that in the near future, commercial spacecraft will be available for low Earth orbit missions. We'll see what the next few years bring, but at this point in time, with the preeminent symbol of both NASA and manned space flight soon to be a piece of history, we can ask ourselves what next for NASA? On an even broader scale, what next for the story of men in space?