Oct 2014: This is an excerpt of a many-years old email I sent to friends which I wrote during my transition from a particle physicist to a cosmologist, trying to wrap my head around just how incomprehensibly and crazily large the Universe really is, to me at least.
It stops fairly abruptly partway through (we were about to land in Columbus, Ohio, coming from a conference/'summer school' in Puerto Vallarta, Mexico), but gives some sense of my thinking and feeling on these matters at that time.
Sun, 19 Nov 2006.
Hi there all:
So I'm on my way back on de plane (boss) to C-bus and I'll take this time to write my second, and final, report on the conference (conf) and school.
Now the rest of the conf went well and finely too, though as I'd said earlier, because I'd sort of been fulltime at all the talks at the school and put so much energy into it, I had to sit back more during the conf also, much of it was on topics I don't have a burning interest in at the moment. Though I certainly consider myself still a particle physicist, I just am not keen on the details of every number that continues to confirm the "Standard Model" (our current best picture of particle physics) to umpteen more digits - let's turn on the LHC (the Large Hadron Collider) and watch them sparks fly! Be they Higgs, or sparticles, or extra-dimensional gravitinos, let's see 'em!! And that's pretty much the feeling I'm gonna have from now until the LHC really turns on for bidness sometime in 2008 [hah, in 2010 or so, actually, -M].
The neutrino stuff is pretty cool though, and it seems that we'll be learning lots even from the long, steady experiments of the next few years: in Japan: Kamland, SuperK and in a few years T2K, Double Chooz fairly soon in France, and then at FNAL: Miniboone, Minos, Numi, Sciboone and potentially Minerva and Nova.
Then of course there are the big underground experiments all over: IceCube, Antares, SNOlab, and other future potential ones, but these are more about watching for supernovae, and/or other galactic/extragalactic sources, vs. being able to disentangle the neutrino mass hierarchy itself, of which theta_13, the Majorana/Dirac nature, the normal/inverted scenario, and eventually CP violation in the neutrino sector are the pressing issues in the mid-term future.
In any case - cosmology is where I got the most excited, by far, at this thing. It's just because it's moving *fast* and there's so much to be done and learned. And yes, the high energy physics (HEP, generally roughly synonymous with "particle physics") folk have a newfound respect for what cosmology can tell us, in neutrino masses, in info on dark matter constraints and such things. And more than anything, for the precision. Yeah, fine, they're not going to get 12 digit precision in anything, anytime soon, because there are so many open questions about the inflation scenario, primordial abundances etc. - but man, think on it - this is the *whole Universe* we're talking about! It's a big place!! And as I keep saying to people "infinity is a big 'number' " ! I really don't think humans can exactly grasp it. Infinity really is *that* -- it goes on for flippin *ever*. There is *nobody* who said that we get any final theory.
I personally don't sit around and think grand great design thoughts about the Ultimate Theory and all that - I don't have time for that. I, very much like Feynman, would like to apply myself to those problems I can *solve* or at least make some headway on in this life. Because science is so terribly staggeringly beautiful, just what all we know already, and can describe, in squiggly lines on paper. We, on this tiny little blue planet, what we can know about this really indescribably humongous Universe?
I guess it started hitting me sometime late in our conf just how different our world is than say that of Galileo and people around his time. Part of it is incremental, as we realized the other planets were
indeed separate bodies like the Earth, and then started getting a handle on their (at that time) staggeringly enormous distances compared to those on the surface of the Earth, and then figured out that the stars were other Suns, like our own, then figured out the structure of our Galaxy, then that there were *other* Galaxies -- which is, it seems, where it ends. For now. There are plenty of *theories* about what may be beyond that, a multiverse etc., but the Universe to me is mind-boggling enough.
And I will honestly confess that working now on cosmology as I do and thinking about these other systems so glibly on a daily basis - 100 million, a billion, 10 billion light years away, we throw the terms around like dominoes, easily, fluidly - I am staggered by it, at times. Truly.
Maybe it took me a while to feel it in my bones, but it's this: we have an Earth, even the ancients knew it was round, and we humans can go pretty much *anywhere* on it, by this point, or even send probes to those parts where we can't, in the deepest oceans.
Ok, fine, then come planets, which were initially quite a big shock, what are they there for??? But as we now know, we relate, we've even exchanged some gas and dust here and there during birth (yes, rather womblike) and later too. A bit weird, but not so far, relatively.
Then - stars. This is kind of weird, yes, no doubt. A lot of stars, throughout the Milky Way galaxy (about 300-400 billion, it seems). Can't say anyone feels at "ease" with this.
But then - the other galaxies. Just freaking *billions* of them. We don't even really know how to count them (because they get dim way back close to the Big Bang, 13.8 billion years ago). And since we haven't fully stopped reeling from the realization of how many *stars* there are in our one local home galaxy, how do we even make sense of so many others?
How do we make *SENSE* of them?
I don't know.
I really don't know. And if it seems like the first and most naïve question that a child would ask upon learning of this, let me not act like I know any better at all about it, whatsoever. But then, none amongst us does, so I can't feel very ignorant, in this regard.
I mean, once you start learning science, taking things apart and understanding them bit by bit, you eventually, either rapidly or more slowly, get to this question, in some guise or another. You start asking how the Earth formed, how old it is, how life evolved, how atoms work - any of it, and you're led to this: but why is any of it here? And there *is no answer to this question*. That is, we really don't even know if there is any *in principle* answer to this. Or if the question has any real meaning, as we humans understand meaning. But somehow, on the small scale of the Earth, when I generally thought on a daily basis about little atoms and leptons and quarks (and even about intermediate vector bosons) right in the present moment, it never kind of overwhelmed me as much.
But -- now. Now: as I look up at the big black night sky, or look across to my monitor showing plots of various galaxies scattered throughout, or sit and listen to a prosaic everyday discussion amongst astronomers of the redshift-supernova distance calibration relation out to a few hundred megaparsecs (a megaparsec = 3.3 million light years) - I'm left just kind of feeling a bit mixed up inside. I don't know how to describe it exactly, maybe because I don't know my exact feelings, because maybe it's a mix of so many things. Awe, wonder, minuteness, confusion, happiness to be alive. And others. But definitely this weird sense of: what are all those galaxies *for*? Why are they there? How did this happen?
Et cetera -- you get the idea. It's just strange to me.
But you know - I have a job to do. The government doesn't pay me to sit around and gibber like a child at how weird my job is, and that of all cosmologists. No, they're paying me *to* do it, to get that little bit of data that extends our knowledge that little bit, shines a light on one more piece of the puzzle, so more of its beauty can be unveiled. Yes, I suppose that really is as good an analogy as any: we are each of us scientists shining lights on different pieces of a vast, 3 dimensional puzzle. We all stumbled upon it, and we're each given lights of varying intensities with a highly focused beam that doesn't go too far, and it's also a climbing puzzle so you have to understand and know where the steps are below, which have now had floodlights set on them by your previous antecedents to show the way. But you just keep climbing, because it's a thing of beauty this puzzle, every little speck of it, each bit that's been uncovered and the every single bit that is further uncovered as well. And that's all we're here to do, is shine that light onto some further bit, while we can, as we can.
And, very importantly - we don't know if there's a top or edge in any direction. We don't know if there's an end at ALL.
I suppose I could work on this analogy more, as it does help me to think about what we're doing a little better, and I heard that somewhere, that the only way we really understand things is by analogies. I don't know what it means.. But it seems the case, at times.
I'm not sure where all this came from, it's not like I'm having a mid-life crisis about what I do. In fact, I still feel darn lucky and blessed and amazed that I'm paid to do what I can do. I guess it was just coming for a while, after looking at all these danged breathtakingly beautiful galaxy images all the time. I probably would *not* have gotten to this level of internal "weirdness" had I not turned to cosmology, with its assumed premise of understanding the *entire Universe*, on a "cosmic scale" (i.e. the biggest scales we know of). I mean, the fundamental questions of HEP, as it is currently construed in our time (which obviously may be very different from what it may be many centuries hence, if anyone is reading these words then!) are not really to me any different: they're about the basics of what our Universe is made of and why, and these two are not really separable questions, as both these camps have come to realize more and more in recent years - but: HEP seems kind of more mentally "manageable" on a daily basis, containable, normally. You're dealing with some big huge detector usually that is taking data from some particles you're smashing together, or watching come in from space, in which case you don't usually know the source. So you do these things, and you have some beautiful equations that through a lot of painstaking work by physicists over many decades (and centuries, really) have been written down and they just *check* with the data, and check damn well. You predict something, you go measure it. Boom, it's right on, excellent, build a bigger machine to hit things harder together and see what you get. That's really the essentials of what HEP folk have been doing since oh.. the late 19th century I guess, really. You don't necessarily think too much about the past history of the Universe, how it came to be and all that.
But cosmology? Now that's different - way different. You're sitting around with a big ole telescope, looking way way up into the night sky, at these galaxies that can be several *billion* light years away. If you step away from your pressing data analysis for just a few *minutes* and start thinking about it, man - you may want to have some Tylenol handy.
Because this stuff can *blow your mind* man.
Like in all the ways I've described above.
But -- we press onwards!
-M
(November 2006)
