Archive for the 'Physics' Category

Dec 05 2011

Best. Physics abstract. Ever

Published by under Physics

Speaking of superluminal neutrinos, my friend Tim Kyger has called my attention to a recent paper that has to have the best abstract ever. The paper, by M.V. Berry, N. Brunner, S. Popescu & P. Shukla is entitled Can Apparent Superluminal Neutrino Speeds be Explained as a Quantum Weak Measurement? Summarizing this ten-page paper filled with the requisite mathematics, diagrams, and references, the abstract: “Probably not.”

In all seriousness, the paper raises some interesting ideas (at least, I think it does — I don’t so much follow it as get the gist of it), and further, it eliminates one possible “they’re not really superluminal” explanation. We’re definitely seeing some new science — or at least, new thinking about science, which amounts to the same thing — come out of all this. Time to go make more popcorn!

No responses yet

Nov 21 2011

Faster-than-light neutrinos … again

Published by under Physics

The OPERA experiment team at CERN is again reporting (as of Nov. 18) possible faster-than-light neutrino measurements. This time they’ve been using 3-nanosecond neutrino pulses, to better pin-down the timing, and they’re still reporting seeing them show up at the detector 60ns sooner than photons would. If this holds up with other labs attempting to repeat the experiment (not until some time next year), then we’ve got some interesting new science, folks. (I’ll have more to say on that soon — some of which I said elsewhere after the September announcement.)

On the other hand, the ICARUS experiment team is saying that their neutrinos have too much energy to have ever gone faster than light. I haven’t read their paper yet, just going on what has been filtered through the popular press, so I’m not very clear on the details. That said, they seem to be basing their conclusion (high energy == slower than light) on models which don’t permit FTL in the first place. Since we don’t know how the neutrinos are going superluminal (if, in fact, they are), that seems shaky ground to be building conclusions on. But maybe I’m just being over-optimistic.

More when I get a chance.

No responses yet

Jul 14 2011

About that time machine…

Published by under Physics,Writing

Speaking of time machines (see my earlier post), news from the ArXiv today is that physicists have created a “hole in time”, the temporal equivalent of an invisibility cloak. Only 110 nanoseconds so far … but consider the possibilities!

Tangentially, writer Alex J. Kane, in a blog post titled “On the Use of Tropes in Science Fiction” today considers possibilities for science fiction, and quotes my buddy Brad Torgersen: “There’s nothing new under the sun. It’s all about how you use the various stock elements that makes the story.” I’d absolutely agree with Brad’s second sentence there, but I might quibble about the first. Is the above “time cloak” new to science fiction? Not exactly, if you consider stasis boxes, bobbles, or some of the ways time travel has been used in stories. But I’m willing to bet that nobody came up with something quite like what the physicists did. All kinds of interesting story ideas there.

Kane goes on to say:

Writers like Orson Scott Card have even gone so far as to reduce the genre, in a way, by saying that it’s merely “a subset of fantasy.” True, but when I heard those words […], I couldn’t help but feel a sense of betrayal.

Wasn’t science fiction the genre that had made Card’s career, after all? Without having written Ender’s Game, would I even know who he was?

But for the sake of argument, let’s take Card’s elaboration into account. He argues that science fiction is a sort of literary dead end because there just aren’t enough new scientific discoveries — or moreover, any new ideas — out there to justify writing sf anymore. From a storyteller’s perspective, he says, it makes more sense to just resort to a magical fantasy setting. Why bother with the facade of making things like FTL travel, etc., seem plausible in a universe where we know such key tropes to be utterly impossible?

I call bullshit.

So do I.

Card (and others) miss a key point when they call science fiction a subset of fantasy. True enough, much of what gets passed off as SF (or perhaps rather, sci-fi) is just fantasy with spaceships, computers and aliens instead of horses, magic and trolls — Card’s own Ender’s Game stories could be considered in that light (although perhaps not the original short story which started it all). But the hard core of SF — and I heard Connie Willis making just this point a couple of weeks ago — is as a literature of ideas. Yes, we as readers (and, we hope, as writers) these days we expect more than just the idea; the Hugo Gernsback days when cardboard characters and cliche settings were fine so long as the idea was new are long gone, we expect rounded characters and well thought out settings as well as ideas. Indeed, the ideas don’t even have to be new if you do everything else well enough, but if you do come up with one, or put a new twist on one, you’ve got a potential award-winner if everything else holds up. (Larry Niven in his short-story heyday had this finely honed; several of his award-winning stories were near category-killers. Just try writing a crosstime-travel story these days without considering the implications he raises in “All the Myriad Ways” — which have real echoes in quantum theory.)

Not that there’s anything wrong with a good rollicking space, time travel, or zombie apocalypse (to pick three not-quite-random examples from this year’s Hugo nominees) story either.

And I’ll agree with Kane’s closing quote: “To quote George Carlin: ‘The future ain’t what it used to be.'” Ain’t that the truth!

One response so far

May 02 2011

Antimatter

Published by under Physics

Overwhelmed by the news of Osama bin Laden’s death (and the celebrations thereof — a little surprising to me; good news, yes, but no VE day) is the announcement from CERN that they’ve managed to trap antihydrogen atoms — atoms made from an anti-proton orbited by a positron — for 1000 seconds. That’s over 15 minutes, folks, seriously long term storage as antimatter goes. CERN’s previous record was only 172 milliseconds.

Granted, they only stored 309 atoms. Remembering Avogadro’s number from high school chemistry, that’s still a factor of 10-to-the-20th or so from a gram of antihydrogen, let alone the kilogram of antimatter mentioned in my story “Renee”, (to say nothing of whatever unspecified quantities were used to fuel the USS Enterprise in Star Trek) but it’s an impressive achievement none the less. It’s also enough to do some serious experiments on the more subtle properties of antimatter. For example, does it fall down, or up? They’ll also be looking for charge, parity and/or time (CPT) anomalies.

In the long run, what they find could turn out to be far more significant than the life or death of another criminal, even one who made Ernst Stavro Blofeld (James Bond’s nemesis) look like an amateur.

2 responses so far

Apr 21 2011

Warping space and time

Published by under Physics,T-Space

No, nothing to do with Rocky Horror, sorry “Time Warp” fans. It seems that colliding black holes can severely warp space and time too, according to this article at Astrobiology Magazine. black hole vortices. The warped space vortex and tendex lines (read the paper referenced in the linked article) spiral out from the hole.

This is interesting enough in its own right (if you’re into that sort of thing), but it touches on something I’ve been pondering in my T-space universe: what happens if a ship in a warp bubble flies into a black hole? There’d be some similar effects, the edge of a warp bubble is highly curved space, like a black hole. Perhaps if you do it right, and the wormhole is rotating, you can create a “closed time-like curve”, i.e., travel in time. (Loosely based on the theory Tipler proposed in his paper “Rotating Cylinders and the Possibility of Global Causality Violation” — see also Larry Niven’s story of the same name.) It’s an idea I’ve been toying with for some stories. Guess I’d better start writing them.

Image credit: The Caltech/Cornell SXS Collaboration

No responses yet

Feb 05 2011

Miscellaneous musings

Published by under Astronomy,Physics,Writing

Pubit
I spent a bit of time last night getting three e-books up on Pubit, the Barnes & Noble Nook equivalent to Amazon’s Kindle store. This went pretty quickly, since I’d already prepped the files for Smashwords. Basically I just needed to change the line “Smashwords edition” to “Nook edition” on the title page. A reminder, you can get versions for Kindle (.mobi) and Nook (.epub) from Smashwords too, if you want to take advantage of the coupon offer in the update below.

Small Penalties
My story in the current (April) issue of Analog seems to have struck a chord, with a 4.5 (of 5) star review on cxPulp, and a strong recommendation from a commenter in the Usenet group news.admin.net-abuse.email. The latter says I write like I’ve been lurking in that group for years. 😉 (No need. I’ve dealt with more than enough spam on the job and on my home systems.)

Fun astrophysics
Last week a paper on arXiv suggested that black holes may not be affected by dark matter. Since spiral galaxies are now believed to all have massive black holes at their center, and since dark matter was “invented” to explain the otherwise anomalous rotation of such galaxies (they rotate too fast for their apparent mass to hold them together), this is a puzzlement … or an argument for Modified Newtonian Dynamics.
This week, an analysis by cosmologists suggests that the universe may be 250 times bigger than the mere 14 billion light-year distance we can see. So much more room to play in! (If we could only get there in something less than the age of the universe.)

No responses yet

Aug 27 2010

Weird Science

Published by under Astronomy,Physics

I love it when researchers turn up new data or new theories to explain old data that expose some interesting new gap in what we think we know about the universe. It’s from those interesting new gaps — like absorption lines in what should be a smooth spectrum — that lead to new science and new technologies. (Those absorption lines, in 19th century observations of the Sun, ultimately led to quantum theory — and modern electronics and lasers.) This week we’ve had several instances of this.

You’re probably aware that the universe is expanding, and even that it seems to be expanding at an increasing rate. This somewhat counter-intuitive observation has been explained by “dark energy”, some unknown force that is accelerating the expansion. But many scientists aren’t comfortable with dark energy; the numbers for the vacuum energy don’t work out, and it seems to violate conservation laws. Now, this presumed expansion acceleration is based on measurements of very distant (edge of the universe distant) supernovas. If there’s another explanation for those measurements, then the acceleration may not really be happening and thus we don’t need dark energy to explain it.

There’s another problem. Models of the Big Bang that started the universe predict the creation of a certain amount of hydrogen, deuterium (heavy hydrogen), helium, and lithium. Our observations of the first three match pretty closely the predictions — but we only see about one-third the lithium we think we should.

Cosmologists Marco Regis and Chris Clarkson think they have an explanation for both of these discrepancies. Scientists make the assumption that the universe is pretty much the same in every direction we look, that — celestial bodies aside — there’s nothing special about one part space over any other. Regis and Clarkson point out here that the above problems go away if don’t assume the universe is homogenous. But there’s one other thing: if that’s the case, and there’s a huge bubble of space that is lithium-deficient, then why is Earth in the center of it?

Speaking on inhomogeneities in the universe, two different deep sky studies by the Keck telescope in Hawaii and the Very Large Telescope in Chile have turned up unexpected differences in what’s called the fine structure constant, considered to be one of the fundamental constants of nature (it relates to how strongly atoms bind their electrons). The really interesting thing is that while the Keck observations suggest that the fine structure “constant” was once smaller, the VLT observations suggest that it was once bigger. (Papers here and here.) These two telescopes — one in the northern hemisphere, one in the southern — look at two different regions of the sky. This, especially in light of Regis and Clarkson’s conjecture, raises all sorts of interesting questions. (Such as: What affect does this have on chemistry — and biology — in different regions of the universe? Would a space ship travelling such distances drag its own fine structure constant with it, or would it change according to local conditions? And, what causes this “constant” to vary, and could we reproduce that effect locally? Larry Niven had disintegrator guns that worked by “suppressing the charge on the electron”; could that really be possible? If you could reduce the charge on a proton, wouldn’t that make fusion easier?)

Somebody (Asimov?) once said that real scientific discoveries are less often heralded by “eureka!” than by “hmm, that’s odd.” Looks like we have several “that’s odd” moments going on. Cool!

No responses yet

Apr 03 2009

No warp drive after all?

Published by under Physics,T-Space

One of the best things to happen for those of us who like both hard SF and space opera was Miguel Alcubierre’s 1994 paper demonstrating how General Relativity does allow for faster-than-light (FTL) travel, using “warped” spacetime. (Yes, Star Trek and all the SF writers before it seem to have guessed right, but Alcubierre did the math. See my article “Yes Virginia, There Really is a Warp Drive”.)

However, I see today on the Technology Review arXiv blog that a recent paper by Finazzi, Liberati and Barceló, “Semiclassical instability of dynamical warp drives”, applies quantum theory to Alcubierre’s analysis and comes up with two potential problems: Hawking radiation (the effect that makes small black holes “evaporate”) could be hazardous to the occupants, and the warp bubble itself might be unstable because of the “stress-energy tensor” growing exponentially. (No, I’m not exactly sure what that means either, I never got that far in my physics classes.)

Does that mean Finazzi et al. just killed Santa Claus? No. For one thing, they make some assumptions about the properties of the exotic matter needed to maintain the warp which may not hold. For another, it looks like they just analyzed an Alcubierre warp rather than Van Den Broek’s refinement (see the “Yes, Virginia” piece mentioned above for the difference), so the Hawking radiation may be confined to the “shell” in the latter case. Finally, instabilities can be overcome if you have a fast-responding control system. Maybe that means the controller needs a quantum computer.

Addendum: There may be another way to overcome Finazzi instability, depending on the physical constraints of how you generate the warp in the first place. The idea came to me in the course of writing a novel about the first Alpha Centauri expedition. The details are one of the plot points so I won’t go into it here (besides, I may just be handwaving — the math is beyond me), but consider the simplifying assumptions we can make to predict the behavior of large systems. — AM, 2010

No responses yet