It appears that CERN goofed and as a result, the video of the announcement planned for tomorrow has been leaked. (That is, unless you choose to believe their cockamamie story about multiple versions of the video having been produced.)
The bottom line: there is definitely a particle there with integer spin. Its mass is about 125 GeV. We know it decays into two photons and two Z-bosons. That’s about all we know.
The assessment is that it is either the Higgs or something altogether new.
The Tevatron may have been shut down last year but the data they collected is still being analyzed.
And it’s perhaps no accident that they managed to squeeze out an announcement today, just two days before the scheduled announcement from the LHC: their observations are “consistent with the possible presence of a low-mass Higgs boson.”
The Tevatron has analyzed ten “inverse femtobarns” worth of data. This unit of measure (unit of luminosity, integrated luminosity to be precise) basically tells us how many events the Tevatron experiment produced. One “barn” is a whimsical name for a tiny unit of area, 10−24 square centimeters. A femtobarn is 10−15 barn. And when a particle physicist speaks of “inverse femtobarns”, what he really means is “events per femtobarn”. Ten inverse femtobarns of “integrated luminosity”, then, means a particle beam that, over time, produced ten events per every 10−39 square centimeters.
Now this makes sense intuitively if you think of a yet to be discovered particle or process as something that has a size. Suppose the cross-sectional size of what you are trying to discover is 10−36 square centimeters, or 1000 femtobarns. Now your accelerator just peppered each femtobarn with 10 events… that’s 10,000 events that fall onto your intended target, which means 10,000 opportunities to discover it. On the other hand, if your yet to be discovered object is 10−42 square centimeters in size, which is just one one thousandths of a femtobarn… ten events per femtobarn is really not enough, chances are your particle beam never hit the target and there is nothing to see.
The Tevatron operated for a long time, which allowed them to reach this very high level of integrated luminosity. But the cross-section, or apparent “size” of Higgs-related events also depends on the energy of the particles being accelerated. The Tevatron was only able to accelerate particles to 2 TeV. In contrast, the LHC is currently running at 8 TeV, and at such a high energy, some events are simply more likely to occur, which means that they are effectively “bigger” in cross section, more likely to be “illuminated” by the particle beam.
The Tevatron is not collecting any new data, but it seems they don’t want to be left out of the party. Hence, I guess, this annoucement, dated July 2, indicating a strong hint that the Higgs particle exists with a mass around 125 GeV/c2.
On the other hand, CERN already made it clear that their announcement will not be a definitive yes/no statement on the Higgs. Or so they say. Yet it has been said that Peter Higgs, after whom the Higgs boson is named, has been invited to be present when the announcement will be made. This is more than enough for the rumors to go rampant.
I really don’t know what to think. There are strong reasons to believe that the Higgs particle is real. There are equally strong reasons to doubt its existence. The observed events are important, but an unambiguous confirmation requires further analysis to exclude possibilities such as statistical flukes, events due to something else like a hadronic resonance, and who knows what else. And once again, I am also reminded of another historical announcement by CERN exactly 28 years prior to this upcoming one, on July 4, 1984, when they announced the discovery of the top quark at 40 GeV. Except that there is no top quark at 40 GeV… their announcement was wrong. Yet the top quark is real, later to be discovered having a mass of about 173 GeV.
Higgs or no Higgs? I suspect the jury will still be out on July 5.
My blog is supposed to be (mostly) about physics. So let me write something about physics for a change.
John Moffat, with whom I have been collaborating (mostly on his modified gravity theory, MOG) for the past six years or so, has many ideas. Recently, he was wondering: could the celebrated 125 GeV (125 gigaelectronvolts divided the speed of light squared, to be precise, which is about about 134 times the mass of a hydrogen atom) peak observed last year at the LHC (and if rumors are to be believed, perhaps to be confirmed next week) be a sign of something other than the Higgs particle?
All popular accounts emphasize the role of the Higgs particle in making particles massive. This is a bit misleading. For one thing, the Higgs mechanism is directly responsible for the masses of only some particles (the vector bosons); for another, even this part of the mechanism requires that, in addition to the Higgs particle, we also presume the existence of a potential field (the famous “Mexican hat” potential) that is responsible for spontaneous symmetry breaking.
Higgs mechanism aside though, the Standard Model of particle physics needs the Higgs particle. Without the Higgs, the Standard Model is not renormalizable; its predictions diverge into meaningless infinities.
The Higgs particle solves this problem by “eating up” the last misbehaving bits of the Standard Model that cannot be eliminated by other means. The theory is then complete: although it remains unreconciled with gravity, it successfully unites the other three forces and all known particles into a unified (albeit somewhat messy) whole. The theory’s predictions are fully in accordance with data that include laboratory experiments as well as astrophysical observations.
Well, almost. There is still this pesky business with neutrinos. Neutrinos in the Standard Model are massless. Since the 1980s, however, we had strong reasons to suspect that neutrinos have mass. The reason is the “solar neutrino problem”, a discrepancy between the predicted and observed number of neutrinos originating from the inner core of the Sun. This problem is resolved if different types of neutrinos can turn into one another, since the detectors in question could only “see” electron neutrinos. This “neutrino flavor mixing” or “neutrino oscillation” can occur if neutrinos have mass, represented by a mass matrix that is not completely diagonal.
What’s wrong with introducing such a matrix, one might ask? Two things. First, this matrix necessarily contains dimensionless quantities that are very small. While there is no a priori reason to reject them, dimensionless numbers in a theory that are orders of magnitude bigger or smaller than 1 are always suspect. But the second problem is perhaps the bigger one: massive neutrinos make the Standard Model non-renormalizable again. This can only be resolved by either exotic mechanisms or the introduction of new elementary particles.
This challenge to the Standard Model perhaps makes the finding of the Higgs particle less imperative. Far from turning a nearly flawless theory into a perfect one, it only addresses some problems in an otherwise still flawed, incomplete theory. Conversely, not finding the Higgs particle is less devastating: it does invalidate a theory that would have been perfect otherwise, it simply prompts us to look for solutions elsewhere.
In light of that, one may wish to take a second look at the observations reported at the LHC last fall. The Higgs particle, if it exists, can decay in several ways. We already know that the Higgs particle cannot be heavier than 130 GeV, and this excludes certain forms of decay. One of the decays that remains is the decay into a quark and its antiparticle that, in turn, decay into two photons. Photons are easy to observe, but there is a catch: when the LHC collides large numbers of protons with one another at high energies, a huge number of photons are created as a background. It is against this background that two-photon events with a signature specific to the Higgs particle must be observed.
Diphoton results from the Atlas detector at the LHC, late 2011.
And observed they have been, albeit not with a resounding statistical significance. There is a small excess of such two-photon events indicating a possible Higgs mass of 125 GeV. Many believe that this is because there is indeed a Higgs particle with this mass, and its discovery will be confirmed with the necessary statistical certainty once more data are collected.
Others remain skeptical. For one thing, that 125 GeV peak is not the only peak in the data. For another, it is a peak that is a tad more pronounced than what the Higgs particle would produce. Furthermore, there is no corresponding peak in other “channels” that would correspond to other forms of decay of the Higgs particle.
This is when Moffat’s idea comes in. John had in mind the many “hadronic resonances”, all sorts of combinations of quarks that appear at lower energies, some of which still befuddle particle physicists. What if, he asks, this 125 GeV peak is due to just another such resonance?
Easier said than done. At low energies, there are plenty of quarks to choose from and combine. But 125 GeV is not a very convenient energy from this perspective. The heaviest quark, the top quark has a mass of 173 GeV or so; far too heavy for this purpose. The next quark in terms of mass, the bottom quark, is much too light at around 4.5 Gev. There is no obvious way to combine a reasonably small number of quarks into a 125 GeV composite particle that sticks around long enough for it to be detected. Indeed, the top quark is so heavy that “toponium”, a hypothetical combination of a top quark and its antiparticle, is believed to be undetectable; it decays so rapidly, it really never has time to form in the first place.
But then, there is another possibility. Remember how neutrinos oscillate between different states? Well, composite particles can do that, too. And as to what these “eigenstates” are, that really depends on the measurement. One notorious example is the neutral kaon (also known as the neutral K meson). It has one eigenstate with respect to the strong interaction, but two quite different eigenstates with respect to the weak interaction.
So here is John’s perhaps not so outlandish proposal: what if there is a form of quarkonium whose eigenstates are toponium (not observed) and bottomonium with respect to some interactions, but two different mixed states with respect to whatever interaction is responsible for the 125 GeV resonance observed by the LHC?
Such an eigenstate requires a mixing angle, easily calculated as 20 degrees. This mixing also results in another eigenstate, at 330 GeV, which is likely so heavy that it is not stable enough to be observed. This proposal, if valid, would explain why the LHC sees a resonance at 125 GeV without a Higgs particle.
Indeed, this proposal can also explain a) why the peak is stronger than what one would predict for the Higgs particle, b) why no other Higgs-specific decay modes were observed, and perhaps most intriguingly, c) why there are additional peaks in the data!
That is because if there is a “ground state”, there are also excited states, the same way a hydrogen atom (to use a more commonplace example) has a ground state and excited states with its lone electron in higher energy orbits. These excited states would show up in the plots as additional resonances, usually closely bunched together, with decreasing magnitude.
Could John be right? I certainly like his proposal, though I am not exactly the unbiased observer, since I did contribute a little to its development through numerous discussions. In any case, we will know a little more next week. An announcement from the LHC is expected on July 4. It is going to be interesting.
Here is a wonderful solution to the problem of climate change: if you don’t like the science, outlaw it. At least this is what the state legislature of North Carolina is doing, in an attempt to address the escalating costs of protecting the state from rising sea levels.
I may have concerns about the quality of climate models and the validity of some of the more hysterical predictions, but politicians should be obligated to follow the best scientific advice available. Picking the science based on ideological preferences belongs to the Dark Ages, not the 21st century.
Our latest Pioneer paper, in which we discuss the results from the Pioneer thermal model and its incorporation into the orbital analysis (the conclusion being that no significant anomalous acceleration remains once thermal radiation is properly accounted for) made it to the cover of Physical Review Letters. I am very grateful that I was given the opportunity to participate in this research, and I am very proud of this work and our results.
Yesterday, Venus transited the Sun. It won’t happen again for more than a century.
I had paper “welder’s glasses” courtesy of Sky News. Looking through them, I did indeed see a tiny black speck on the disk of the Sun. However, it was nowhere as impressive as the pictures taken through professional telescopes.
These live pictures were streamed to us courtesy of NASA. One planned broadcast from Alice Springs, Australia, was briefly interrupted. At first, it was thought that a road worker cutting an optical cable was the culprit, but later it turned out to be a case of misconfigured hardware. Or could it be that they were trying to fix a problem with an “intellectual property address”, a wording that appeared on several Australian news sites today? (Note to editors: if you don’t understand the text, don’t be over-eager replacing acronyms with what you think they stand for.)
I also tried to take pictures myself, holding my set of paper welder’s glasses in front of my (decidedly non-professional) cameras. Surprisingly, it was with my cell phone that I was able to take the best picture, but it did not even come close in resolution to what would have been required to see Venus.
The lesson? I think I’ll leave astrophotography to the professionals. Or, at least, to expert amateurs. Unfortunately, I am neither.
That said, I remain utterly fascinated by the experience of staring at a sphere of gas, close to a million and a half kilometers wide, containing 2 nonillion (2,000,000,000,000,000,000,000,000,000,000) kilograms of mostly hydrogen gas, burning roughly 580 billion kilograms of it every second in the form of nuclear fusion deep in its core, releasing photons amounting to about 4.3 billion kilograms of energy… and most of these photons remain trapped for a very long time, producing extreme pressures (so that the interior of the Sun is dominated by this ultrarelativistic photon gas) that prevent the Sun from collapsing upon itself, which will indeed be its fate when it can no longer sustain hydrogen fusion in its core a few billion years from now. And then, this huge orb is briefly occulted by a tiny black speck, the shadow of a world as big as our own… just a tiny black dot, too small for my handheld cameras to see.
I sometimes try to use a human-scale analogy when trying to explain to friends just how mind-bogglingly big the solar system is. Imagine a beach ball that is a meter wide. Now suppose you stand about a hundred meters away from it, like the length of a large sports field. Okay… now imagine that that beach ball is so bleeping hot, even at this distance its heat is burning your face. That’s how hot the Sun is.
Now hold up a large pea, about a centimeter in size. That’s the Earth. Another pea, roughly halfway between you and the beach ball would be Venus.
A peppercorn, some thirty centimeters or so from your Earth pea… that’s the Moon. Incidentally, if you hold that peppercorn up, at about thirty centimeters from your eye it is just large enough to obscure the beach ball in the distance, producing a solar eclipse.
Now let’s go a little further. Some half a kilometer from the beach ball you see a large-ish orange… Jupiter. Twice as far, you see a smaller orange with a ribbon around it; that’s Saturn. Pluto would be another peppercorn, more than three kilometers away.
But your beach ball’s influence does not end there. There will be specks of dust in orbit around it as far out as several hundred kilometers, maybe more. So where would the next beach ball be, representing the nearest star? Well, here’s the problem… the surface of the Earth is just not large enough, because the next beach ball would be more than 20,000 kilometers away.
To represent other stars, not to mention the whole of the Milky Way, we would once again need astronomical distance scales. If a star like our Sun was a one meter wide beach ball, the Milky Way of beech balls would be larger than the orbit of the Earth around the Sun. And the nearest full-size galaxy, Andromeda, would need to be located in distant parts of the solar system, far beyond the orbits of planets.
The only way we could reduce galaxies and groups of galaxies to a scale that humans can comprehend is by making stars and planets microscopic. So whereas the size of the solar system can perhaps be grasped by my beach ball and pea analogy, it is simply impossible to imagine simultaneously just how large the Milky Way is, not to mention the entire visible universe.
Or, as Douglas Adams wrote in The Hitchhiker’s Guide to the Galaxy: “Space is big. You just won’t believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it’s a long way down the road to the chemist’s, but that’s just peanuts to space.”
The Dragon spacecraft of SpaceX corporation successfully splashed down after a successful overall mission of hauling cargo to and from the International Space Station.
It’s an incredible success for a commercial venture.
I also found the appearance of the SpaceX mission control facility revealing. Ordinary office desks, ordinary office chairs, ordinary flat screen monitors. Nothing special, no horrendously expensive custom hardware.
This reinforces my impression that the SpaceX venture actually brought the 21st century to NASA and the ISS. An impression that was created by the ISS crew’s reaction to the Dragon capsule’s “new car smell” and its space-age interior complete with smooth surfaces, blue LEDs and whatnot.
Congrats to SpaceX. Well done. Here is to the future.
A few days ago, a bright 16-year old German student of Indian descent, Shouryya Ray of Dresden, won second prize in a national science competition with an essay entitled “Analytische Lösung von zwei ungelösten fundamentalen Partikeldynamikproblemen” (Analytic solution of two unsolved fundamental particle dynamics problems).
This story should have ended there. And perhaps it would have, were it not for the words in the abstract that said, among other things: “Das zugrundeliegende Kraftgesetz wurde bereits von Newton (17. Jhd.) entdeckt. […] Diese Arbeit setzt sich also die analytische Lösung dieser bisher nur näherungsweise oder numerisch gelösten Probleme zum Ziele.” (The underlying power law was discovered by Newton (17th century). The goal of this work is then the analytic solution of these until now only approximately or numerically solved problems.)
This was more than enough for sensation-seeking science journalists. The story was picked up first by Die Welt with the title “Mit 16 ein Genie: Shouryya Ray löste ein jahrhundertealtes mathematisches Problem” (Genius at 16: Shouryya Ray solves centuries-old mathametical problem) and then translated into English and other languages, even appearing in the Ottawa Citizen. In short order, even a biographical entry on Wikipedia was created; now nominated for deletion, many are voting to keep it because in their view, the press coverage is sufficient to establish encyclopedic notability.
Cooler heads should have prevailed. What science journalists neglected to ask is why, if this is such a breakthrough, the youth only received second prize. And in any case, what on Earth did he actually do? His essay or details about it were not published. The only clue to go by was a press photo in which the student holds up a large sheet of paper containing an equation:
As I discussed this very topic on a page I placed on my Web site a few years back (reacting to some bad math and flawed physics reasoning in an episode of the Mythbusters) I felt compelled to find out more. I guessed (correctly, as it turns out) that \(u\) and \(v\) must be the horizontal and vertical (or vertical and horizontal?) components of the projectile’s velocity, \(g\) is the gravitational constant, and \(\alpha\) is the coefficient of air resistance. However, I am embarrassed to admit that although I spent some time trying, I was not able to find a way to separate the variables and integrate the relevant differential equations to obtain Ray’s formula. I was ready to give up actually when I came across a derivation on reddit (and I realized that I was on the right track all along, I was just stubbornly trying to do a slightly different trick, which didn’t work). The formula is correct, and it is certainly an impressive result for a 16-year old, worthy of a second prize.
But no more. This is not a breakthrough. As it turns out, similar implicit solutions were well known in the 19th century. A formulation that differs from Ray’s only in notational details appeared in a paper by Parker (Am. J. Phys, 45, 7, 606, July 1977). Alas, such an implicit form is of limited utility; one still requires numerical methods to actually solve the equation.
Much of this was probably known to the judges of the competition, which is probably why they awarded the student second prize.
Hopefully none of this will deter young Mr. Ray from pursuing a successful career as a physicist or mathematician.
According to astronauts on board the ISS, the interior of the SpaceX capsule has a “new car smell“. Seeing the world’s first commercial spacecraft dock with the ISS successfully is, well, awesome I think is an appropriate word here.
The Dragon capsule of SpaceX Corporation is on its way after a successful launch towards the International Space Station. If all goes well, it will dock with the ISS in two days’ time, making it the first commercial spacecraft to do so, and paving the way to eventual human flight to the ISS on board commercial vehicles. This really is the beginning of a new era.
And the end of an old one. The ashes of James Doohan, better known as Scotty to Star Trek fans, are reportedly on board the Dragon capsule, to fulfil the actor’s final wishes.
I just read (link in Hungarian) that a far right member of the Hungarian parliament found it necessary to use a genetic test to prove that he is free of Jewish and Roma blood.
Even if it were possible to do so, I have no inclination to use a genetic testing service to find out the ethnicity of my ancestors. But, I do hope that I have Roma, Jewish, Hungarian, Slav, Russian, German, or for that matter Chinese or Indian ancestors. That is because there is only one group of people that I wish to belong to: the group of human beings. I have zero desire to join any subgroup whose sole purpose is to revel in the idea that they are somehow superior by birth to other subgroups. And, well, if all this makes me a mongrel or a tyke in the eyes of some with a better defined ethnicity… you know what, I don’t really like your purebred attitude either.
I am really disappointed to learn this morning that the world will not come to an end December this year. According to a new discovery, the Mayan calendar may have had at least 17 baktuns, not 13 as previously believed, so we are good for something like another two millennia.
Just as I was getting ready to sell my house and all my earthly possessions…
Here is a photograph of the cockpit of the Space Shuttle Endeavour, powered up for the very last time ever:
It is an emotional moment. But we must not let those emotions get in the way of reason. The Shuttle program swallowed up huge amounts of money and these orbiters, however wonderful, didn’t really take humanity anywhere.
Just consider: the Shuttle flew a few hundred kilometers from the surface of planet Earth. That is one one-thousandths (!) of the distance to the Moon, visited by Apollo astronauts over 40 years ago. But no human has been beyond Low Earth Orbit (LEO) since Apollo 17 flew in late 1972. Now if all goes well, in a few short years one of the very first missions of NASA’s new spacecraft, the Orion capsule, may take humans beyond the Moon, to the L2 Lagrange point. At last, this is real exploration again… not just a routine (albeit dangerous) taxiing between the surface and LEO.
And the taxiing is not going to stop for Americans. The Dragon capsule of SpaceX corporation is set to fly to the International Space Station next week. It is still an unmanned flight but if all goes well, perhaps the next time they’ll ferry not just cargo but also people.
In 2004, NASA landed two rovers on Mars, Spirit and Opportunity. Both far surpassed expectations, operating much longer than their planned design lifetime of 6 months.
Spirit was ultimately lost in 2010, but Opportunity, having spent the last five months in hibernation during the Martian winter, is now driving again. It is amazing that this machine is still functioning. Imagine leaving a solar powered remote control toy in the sandy desert somewhere. How long would it survive and remain drivable?
It’s one setback after another, sometimes with tragic consequences.
Last year it was Phobos-Grunt, Russia’s attempt to return to deep space beyond Earth orbit after a 15-year hiatus. Alas, Phobos-Grunt never managed to go too far… it failed to reach escape orbit and eventually fell back to the Earth.
And now, it’s the Sukhoi Superjet’s turn. After more than two decades, Russia is again trying to capture a small segment of the passenger jet market. Their demonstration model was on an Asian tour, trying to impress new customers. Well, they certainly created an impression… just not the impression they were hoping for. More tragically, 48 souls perished.
I suppose that from a Canadian (or Brazilian) perspective, this should be considered “good news”, since the Sukhoi Superjet 100 is intended to compete in a market that is dominated by Canada’s Bombardier and Brazil’s Embraer. But I don’t find this comforting. In fact, for the sake of the future of Russia’s commercial jet industry, I hope that this tragic accident will turn out to be a case of pilot error. Controlled flight into terrain.
Astronomy is supposed to be a relatively safe profession. I suppose observational astronomers may occasionally injure themselves when working on a telescope, but it’s probably rare. For them to become murder victims is even more unlikely.
So why would a Japanese astronomer, working in Chile on the Atacama Large Millimeter Array, be murdered on the street just outside his apartment?
Everyone who saw the 1986 disaster of the space shuttle Challenger remembers the words from mission control: “Flight control is here looking very carefully at the situation, obviously a major malfunction.”
I was watching a newly surfaced home video of the explosion courtesy of The Huffington Post. (Well worth watching. In particular, notice just how cold it must have been that morning, as evidenced by the clothing people wore.) This led me to a link about Steve Nesbitt, the NASA communications officer who uttered those sad but memorable words.
By the time NASA was ready to fly shuttles again, Nesbitt was already promoted to a new position. But he asked his bosses to be the announcer for the next flight, because “the last one ended rather badly.” Thus he became the voice of NASA in September 1988, when Discovery flew.
Nesbitt retired last year and the shuttles are now heading to museums. But, I admit, the emotional impact of the failed launch of Challenger remains just as strong today as it was 26 years ago.
I was having a discussion with a lawyer friend of mine. I was trying to illustrate the difference between the advocating done by lawyers and the scientist’s unbiased (or at least, not intentionally biased) search for the truth. One is about cherry-picking facts and arguments to prove a preconceived notion; the other about trying to understand the world around us.
I told him that anything and the opposite of anything can be proven by cherry-picking facts. Then it occurred to me that it is true even in math. For instance, by cherry-picking facts, I can easily prove that \(2\times 2=5\). Let’s start with three variables, \(a\), \(b\) and \(c\), for which it is true that \(a=b+c\). Then, multiplying by 5 gives
$$5a=5b+5c.$$
Multiplying by 4 and switching the two sides gives
$$4b+4c=4a.$$
Adding these two equations together, we get
$$5a+4b+4c=4a+5b+5c.$$
Subtracting \(9a\) from both sides, we obtain
$$4b+4c-4a=5b+5c-5a,$$
or
$$4(b+c-a)=5(b+c-a).$$
Dividing both sides by \(b+c-a\) gives the final result:
$$4=5.$$
And no, I did not make some simple mistake in my derivation. In fact, I can use computer algebra to obtain the same result, and computers surely don’t lie. Here it is, with Maxima:
(%i1) eq1:5*a=5*b+5*c$ (%i2) eq2:4*b+4*c=4*a$ (%i3) eq3:eq1+eq2$ (%i4) eq4:eq3-9*a$ (%i5) eq5:factor(eq4)$ (%i6) eq6:eq5/(b+c-a); (%o6) 4 = 5
All I had to do to make this happen was to ignore an inconvenient little fact, which is precisely what lawyers (not to mention politicians) do all the time. Surely, if I can prove that \(2\times 2=5\), I can prove anything. So can lawyers and they know it.
April 23, 2012, and this is what I see through my window:
A month ago, I had to run my air conditioner. Grumble.
The Space Shuttle Discovery is on its way to its final resting place.
Many lament the end of the Shuttle program. They shouldn’t. Beautiful as these machines were, they really stifled the American space program. For decades, countless billions of dollars were spent… on going around, and around, and around, in low-Earth orbit, ultimately getting nowhere.
When Barack Obama opted for a variant of the Augustine Commission‘s “flexible path” approach, some pundits called it the end of America’s space dominance. I think the contrary is true. Instead of opting for an overly ambitious but ultimately unrealistic space program that would eventually die on the floors of Congress due to lack of funding, Obama chose a space program that places the emphasis on sustainable development: a long term vision of expanding human presence beyond Earth orbit in the solar system, not necessarily with spectacular landings on Mars (however desirable such a landing may be, it’s also insanely risky and expensive) but with building the infrastructure for a permanent human presence beyond the protective shield of the Earth’s radiation belts.