Hypothetical Space Shuttle at Epsilon Eridani. Credit for base image: NASA

Once again I have drifted off thinking about the size and scale of space–the things in it and the distances between them–and once again have brought pen and paper, math, and a spreadsheet to bear on the question: are the stars in our destiny, or is the notion of physically reaching them (in person, at least) beyond the available realities?

With all of the science fiction stories devised to get their characters to other stars not only within their lifetimes, but sometimes within a few paltry days, it’s easy to think of interstellar travel as something we might eventually get around to, given the technology, time, and money. We just need to figure out how warp drive or hyperspace work, and how to exploit them, and we’re off!

But putting teleportation and wormhole expressways and their ilk on the shelf labeled, “Cool, but probably just fancy” for a moment, what are the Newtonian-Einsteinian requirements to get us to, say, the nearest known extrasolar planet, which orbits the star Epsilon Eridani, 10.4 light years away from us? It’s a gas giant planet larger than Jupiter and orbits well beyond its star’s habitable zone, but it’s a planet after all, and we star-seekers just love planets.

Now the math that will get us there. I had to assume a mass for our would-be starship, conservatively chosen as 2000 metric tons, or about the weight of the Space Shuttle. In reality that’s far too small a ship for any human interstellar journey, unless the crew are all frozen. And keep in mind, my calculation does not take into account the weight of any fuel we need to carry with us. I’m also choosing a top cruising (coasting) speed of one-tenth the speed of light, or 30,000 kilometers per second. A tenth light speed is pretty darned fast, but not so fast that we need to worry much about relativistic mass—that is, the increase in the spaceship’s effective mass when traveling a significant fraction of the speed of light.

If our engines can produce thrust sufficient to accelerate our 2000 ton spaceship at a rate of “1 gee”, or one Earth-gravity equivalent (~10 meters per second, per second), then to achieve a velocity of one-tenth light speed we’ll need to run those engines for about 35 days, non-stop. We should assume our engines are powered by nuclear fusion or even antimatter reaction (possible future technologies that today present technical challenges, but which aren’t on that shelf of sci-fi fancy).

The energy required for this 1-gee, 35-day engine burn of our 2000 ton spaceship is about 900,000,000,000,000 (yes, 900 trillion) MegaJoules, or 250 trillion kilowatt-hours. That’s the same amount of energy required to launch 20 million normal Space Shuttle flights to low Earth orbit, or almost twice the world’s annual energy consumption. And that’s just to get this little ship accelerated to cruising speed. We’d need another like amount of energy to slow it down to its destination in the Epsilon Eridani system.

As for how long the trip would take, forgetting the 35 days spent getting up to speed and the 35 days spent slowing down again, traveling 10.4 light years at one-tenth the speed of light would take 104 years, one way. (Although, moving at a tenth light speed, the trip would only feel like 103.5 years due to relativistic effects.)

What about the weight of fuel required to do the job? Forget normal rocket fuel; we’d need the energy contained in about 20 billion tons of it just to get to cruising speed—and that doesn’t take into account the mass of the fuel itself, which would also need to be accelerated. Two-thousand ton spacecraft + 20 billion tons of fuel = not practical.

If our engine is powered by hydrogen fusion, we may only need about 3000 tons of fuel (and I’m assuming our fuel is also our propellant—the mass we need to fling out of the engine to accelerate the ship by reaction force; probably not a conservative assumption, in reality).

And if we could use antimatter as our fuel, as does the Starship Enterprise, releasing energy by mixing equal parts antimatter with normal matter, we could carry in our fuel tanks as little as 5 tons of the stuff (plus, I think, 5 tons of normal matter to react with) to achieve cruising speed.

And of course double the fuel amounts if you plan to come to a stop at your destination, 104 years from now.

In summary: tiny cramped ship, 20 tons of antimatter/matter fuel to pack the necessary 500 trillion kilowatt-hours of energy, and 104 years to delivery you to the fabulous Epsilon Eridani system with its one known super-Jupiter sized planet. Anyone interested? Or should we leave space travel to the robot crowd….

Artist concept of AMS-2 mounted on the ISS.

The Alpha Magnetic Spectrometer 2 (AMS-2), like other space-borne observatory satellites, will make its observations outside of Earth's atmosphere, attached to the International Space Station—but unlike "conventional" satellite observatories such as the Hubble Space Telescope, Kepler, and the Solar Dynamics Observatory, AMS-2 will not observe electromagnetic radiation (light), but rather cosmic rays.

Cosmic rays are energetic, electrically charged subatomic particles whizzing through space, originating from various places such as the Sun, distant stars and supernovae, and other high-energy sources from the most distant reaches of the known Universe. Most cosmic rays are simply high-speed protons (hydrogen nuclei) and alpha particles (helium nuclei). Less than 1% of cosmic rays are heavier atomic nuclei, and electrons. All of these particles are things familiar to us on Earth, the main differences being their exotic origins and their extremely high speeds—often approaching the speed of light.

A tiny fraction of cosmic rays are exotic particles indeed: antimatter, in the form of positrons (the positively charged antimatter counterpart of electrons) and anti-protons.

What is AMS-2 looking for? In a nutshell, it's looking for what we cannot see…. Only about 5% of the Universe is composed of "ordinary" matter—the stuff we are made of, and which we can see with telescopes out in the universe by virtue of the light it emits: stars, galaxies, nebulae, giant molecular clouds, and more.

An estimated 95% of the Universe's bulk is made up of "dark" stuff—dark matter (about 20%) and dark energy. Some of this dark matter may be accounted for by massive objects that we can't see, such as black holes, but the primary constituent probably consists of exotic particles that defy direct detection. A number of particles that fit this bill have been theorized, like neutrinos, and more recently neutralinos. In theory, interactions between neutralinos should produce charged particles in the form of cosmic rays that AMS-2 should be able to detect. If it does, then we'll have observational evidence for the existence of this exotic particle, which would shed some light onto some of the Universe's dark mystery….

AMS-2 will also look for antimatter. The Big Bang theory (the theory, not the TV show) of the formation of the Universe suggests that there should be equal parts matter and its counterpart antimatter, but so far we've mostly seen only the former. While there are positrons and anti-protons flying about that can be accounted for by processes involving nuclear interactions, if AMS-2 can detect a more complex anti-particle, like an anti-helium nucleus (an atom composed of two anti-protons, two anti-neutrons, and two positrons), then we'll have an example of antimatter that formed by more complex processes than a random nuclear collision or decay.

AMS-2's "lens" is not made of glass, but of magnetic fields. Conventional telescopes bend and focus light with glass lenses or curved mirrors, but AMS-2 will observe electrically charged cosmic rays, which can be collected and sorted with magnetic force. AMS-2 will count cosmic rays, determine what types of particles they are, and how much energy they possess (how fast they are moving).

From Earth's surface observing cosmic rays is nearly impossible, at best. The particles interact with the nuclei of atoms in our atmosphere, forming a different subatomic particle and a burst of "secondary" cosmic radiation—which can be detected by ground-based instruments, but only as "second hand" news. In fact, it is cosmic ray interactions with ordinary carbon (carbon 12) in Earth's atmosphere that transform them into the radioisotope carbon 14, which scientists take advantage of to determine how long a sample of formerly living material has been dead (as in carbon dating).

So, stay tuned for news on what scientists discover as they peer into the very dark darkness of a currently unknown realm of existence. Should be exciting….

37.8148 -122.178

With the demolition of the Bevatron, a chapter of the Bay Area's high-level physics research comes to a close.

One of the places they came to ask those questions was Lawrence Berkeley National Laboratory, in the Berkeley hills.

Stewart Loken is a physicist with Lawrence Berkeley National Laboratory, and every day on his way to work he passes by a decrepit-looking building about the size and shape of a small sports stadium. Its windows are knocked out, there's a junk pile of old doors and pipes in front. It's called the Bevatron.

Listen to the QUEST radio story Goodbye to the Bevatron.

With the demolition of the Bevatron, a chapter of the Bay Area's high-level physics research comes to a close.

“This was the highest energy accelerator in the world,” says Loken, pointing to the ruins. “It was commissioned with a single goal in mind, which was to produce experimental evidence of the existence of the anti-proton.”

To understand – or at least, approach understanding — the anti-proton, you have to back up, all the way up to the event that physicists consider the very beginning of the universe, 14 billion years ago: The big bang.

“Any model of the big bang that makes any sense to us creates equal amounts of matter and antimatter from the vacuum,” says Persis Drell, who directs the SLAC National Accelerator Lab, at Stanford.

Some of the Bevatron’s waste was radioactive, and had to be hauled to hazardous waste sites, such as in Kettleman City.

Drell says matter is pretty straightforward. It's what makes up your coffee cup, your brain, the visible universe. But for every subatomic particle that makes up matter, there’s a matching particle, an anti-particle, with the opposite electrical charge.

“When you create matter, you always create an equal amount of antimatter,” Drell says.

Scientists knew the anti-matter had to be out there, but for the most part, they couldn't see it. So, they decided to look for one type of anti-matter in particular, the anti-proton.

“The anti-proton was the thing that would confirm the fact that there is an antimatter world, in addition to the matter world that we see every day,” says Stewart Loken.

In other words, if scientists could produce an anti-proton, it would mean that our understanding of the Big Bang, and the makeup of our universe was basically on the right track. If not, well, it was back to square one.

So, they built the Bevatron to test their theory.

Five Nobel Prizes were won based on work at the Bevatron, including the 1959 nobel Prize in Physics, for the discovery of the anti-proton.

The experiment began with a thin cloud of hydrogen gas. First, scientists extracted protons from the hydrogen atoms, and injected them into the accelerator chamber. As the protons whipped around and around the chamber they went faster and faster, until they approached the speed of light.

“You want to get to high enough energy that when particles smash together, you can turn that energy into the production of new particles,” says Loken.

Which is exactly what happened. As the particles approached light speed, the Bevatron performed a feat Einstein himself described with the equation E=MC2: That mass and energy are different manifestations of the same thing.

Since mass and energy are essentially interchangeable, the Bevatron was able to transform matter into energy, and energy back into even more matter… including, in 1955, for the first time ever, antimatter.

“We smashed proton against proton and in the end we had proton, proton, antiproton and another proton to balance it out,” Loken says.

This work won Bevatron scientists the 1959 Nobel Prize in physics. It was the first of four Nobels to come from research done here – as well as new insights into things like radiation treatment for cancer, and how to keep astronauts safe from radiation in space.

But by the late 1980s, the Bevatron had become obsolete. In 1993, it closed its doors for good.

Taking down the Bevatron is a huge endeavor. When it's finally demolished, in 2011, it will have cost the country 50 million dollars. Part of the expense will be from removing a protective layer of concrete blocks that kept scientists safe from radiation released by the accelerator. Now, those blocks must be hauled away to hazardous waste sites.

As for the work that in some ways began here… much of it has moved to the Large Hadron Collider in Cern, Switzerland. Where scientists – including from Berkeley – are trying to get a better understanding of how the universe began.

37.8768 -122.251

Inside the Bevatron. Credit: Lawrence Berkeley National Lab.

Much as I tried to get Stewart Loken to wax poetic about the demise of the Bevatron, the truth is that he – and, I'll bet, a lot of scientists – just don't think that way.

As Loken put it, "science never stands still." However many Nobel prizes the Bevatron produced, this old, defunct particle accelerator is really just taking up space; its demolition, and replacement with a new, up-to-the-minute research facility, is, Loken feels, the best way to honor the work done here. Plans aren't finalized, but it's likely the facility to replace the Bevatron will forward work done at Lawrence Berkeley National Lab's Advanced Light Source (which, by the way, produces light a billion times brighter than the sun).

The new facility – described here – would allow scientists to watch "electrons joining forces, atoms snapping together within millionths of a billionth of a second, the real time of chemical reactions."

But that's a long way off. First, demolition workers must contend with a major disposal challenge, including getting rid of radioactive waste produced during experiments at the Bevatron. Some neighbors are concerned about the prospect of hauling the stuff through Berkeley's residential areas. Others have called for the Bevatron to be preserved as a national landmark.

But demolition is already underway, and picking up speed, thanks in part to $1.2 billion recently bestowed on federal research labs across the country under the American Recovery and Reinvestment Act. The Lab describes the environmental impacts of the Bevatron demolition project here.

See the Bevatron today and in its heyday – watch the "Goodbye to the Bevatron" slideshow online.

37.877657 -122.25111