ScienceBlogs Channel : Physical Science

Another Week of GW News, January 29, 2012 [A Few Things Ill Considered]
Defending Physics Against Cracked.com [Starts With A Bang]
The Arxiv Is Not a Journal [Uncertain Principles]

Another Week of GW News, January 29, 2012 [A Few Things Ill Considered]

Posted: 30 Jan 2012 12:42 PM PST

Logging the Onset of The Bottleneck Years

This weekly posting is brought to you courtesy of H. E. Taylor. Happy reading, I hope you enjoy this week's Global Warming news roundup

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Defending Physics Against Cracked.com [Starts With A Bang]

Posted: 30 Jan 2012 08:07 AM PST

"In science, "fact" can only mean "confirmed to such a degree that it would be perverse to withhold provisional assent." I suppose that apples might start to rise tomorrow, but the possibility does not merit equal time in physics classrooms." -Stephen Jay Gould

Those of you who follow me on either google+, facebook or twitter know that I sometimes post interesting articles about science from around the world, including this very good article about myths about outer space, from the often-entertaining cracked.com. So, as you can imagine, I was (at first) very excited when I saw this article last week over there.

(Image credit: cracked.com.)

Imagine my disappointment when I read this, and realized that the "6 Scientific Discoveries that Laugh in the Face of Physics" turn out to all be things that physics understands and can explain! Looking at it today, you can see that well over 1,000,000 people have read this, so let's see if we can't get the correct information back out there to as many of them as possible. Without further ado, let's take a look at these six scientific discoveries, and do our best to get it right!

(Image credit: Miloslav Druckmuller / SWNS.)

6.) The Sun Can Make Stuff Hotter Than Itself.

Above is the Sun's Corona, visible only during a total solar eclipse, as shown above. And while the surface of the Sun is very hot, at something around 5800 K, the Corona comes in at temperatures over one million Kelvin. Mysterious, mind-boggling and inexplicable by the laws of physics, right?

Except that temperature is not the same thing as heat! The Sun's surface is much, much denser than the incredibly rarified corona, so that even though the Sun's photosphere is less than 1% of the corona's temperature, it emits energy at a rate that's over 40,000 times the amount required to heat the corona up to it's high temperature. We even think we know why: the wave heating theory, where energy can be transferred over long distances from the solar interior to the corona.

(Image credits: Robert Krampf; stills taken from MetaCafe.)

Remember what temperature is: a measure of the mean speed of the particles. Similar to how two balls -- a tiny one and a very massive one -- dropped one-atop-the-other will lead the tiny ball to rocket upwards at an incredible speed, the problem isn't getting a few particles to have a very large speed. The problem also isn't unique to the Sun; if we take a look at Earth's upper atmosphere, where it gets really rarified (above 80 km), we find that it does the same thing in terms of temperature!

(Image credit: Earth's Atmosphere, from kowoma.de.)

The problem is that we associate temperature with heat in our minds, but the "very high temperature" corona contains almost no heat! But if we look in terms of heat, the Sun's photosphere contains much more than the corona; the corona merely reaches higher temperatures.

5.) When You Look Closely, Gravity Stops Making Sense.

The article laments that gravity is so mind-numbingly weak. How dare you, gravity! And it's true; weaker by something like 38 orders of magnitude than the electromagnetic force, even your puny comb can outdo the gravitational pull of the entire Earth when it comes to lifting certain objects. But this isn't a mystery, it's an empirical fact of nature!

(Image credit: Joan Adler, Technion, Israel.)

The standard model of particles and interactions can do a whole lot, but one of the things it can't do is explain why the fundamental forces are the strength that they are. Neither can general relativity, our theory of gravity. As you can see, gravity is very, mind-numbingly weak, even compared to the weakest other force.

But whether you look close or far, at something as massive as a supermassive black hole or as tiny as a laboratory mass, general relativity still gives the correct answer to everything. The only argument that one could even make that "when you look very close, it stops making sense" would be to go down to the smallest scales we know of.

(Image credits: Ultra-Cold Matter Research at William & Mary.)

Only, with gravity, we can barely make it below the millimeter-scale before it becomes too difficult to measure. And we can measure the effects of gravitation down to these sub-millimeter scales: it obeys general relativity just fine, thank you. Perhaps someday, we'll reach down to quantum mechanical scales and find that our classical theory of gravity, general relativity, is insufficient. But in theory, general relativity is good all the way down to the quantum limit of the Universe, and we have yet to find an experiment or observation that contradicts it.

(Image credit: Pioneer 10 by Don Davis, for NASA.)

4.) Satellites Speed Up for No Reason.

So, get this. In the 1970s, we launched two probes -- Pioneer 10 and 11 -- into the outer Solar System. As we tracked their positions over many decades, we knew exactly what to expect. After all, we know the laws of gravity, we know the masses and positions of the Sun and all the planets, and we should be able to predict the spacecrafts' motions flawlessly. Except we saw a small -- but definitely non-negligible -- acceleration back towards the Sun!

Immediately, a number of spectacular explanations arose. Gravity is wrong! The solar system is full of dark matter! Spaghetti! Except among most astrophysicists (like me), another explanation arose: maybe the asymmetric spacecraft is being heated (and is radiating) asymmetrically.

(Image credit: NASA / Francisco et al., retrieved from Jennifer Ouellette.)

For decades, the debate raged, as much as anything where one side doesn't really give the other side much credibility can rage. And then last year, it was definitively measured that the "anomalous acceleration" is not constant, but decreasing, and hence in total agreement with the theory that it's due to the thermal effects that the astrophysicists pointed out. So yes, cracked, satellites speed up for no reason, but only if you ignore the actual reason.

(Image credit: retrieved from Phantastic Physics / Wikispaces.)

3.) The Law of Conservation of Energy? More of a Suggestion, Really.

Looking at black holes, there are only a few types of hair they can have: mass, angular momentum, and electric charge. (And, if you believe in it, magnetic charge.) All of that stuff is conserved. But what about information? That's something that needs to be conserved. If I throw the Count of Monte Cristo into a black hole, it contains a different amount of information than an equal-mass book of all work and no play makes Jack a dull boy. But if energy must truly be conserved, mass, charge, and angular momentum won't take care of it! This conundrum was known as the black hole information paradox.

(Image credit: retrieved from Phantastic Physics / Wikispaces.)

I said "was known" as that. Because the information isn't lost; we know exactly where it goes! When any object falls into a black hole, from its point of view, it simply passes through the event horizon and falls into the singularity, getting torn apart in spectacular fashion. But to an observer outside the event horizon? The object appears to get stretched out, fainter, and reddened, but you'll never see it cross over onto the inside. What we see, instead, is that information gets imprinted, forever and ever, onto the surface of that black hole's event horizon!

So even though you might have amazing difficulty reading it, that information from the Count of Monte Cristo is still there on the surface, even if its mass is the only thing you know from the black hole's insides.

(Image credit: Indira Gandhi Center for Atomic Research.)

2.) The Particle That Knows We're Watching.

Radioactive decay, the process that allows an unstable atomic nucleus to transmute into a different element, is one of the slowest physical processes known to man. Often taking billions of years, radioactivity is built on a foundation of quantum mechanics, where a metastable nucleus must quantum mechanically tunnel into a less energetic, more stable state.

(Image credit: retrieved from Aggeli K at BrightHub.com.)

It isn't easy, as you can imagine, because there's no good way to get up-and-over the proverbial hill; it isn't like those protons and neutrons just spontaneously align into that less energetic configuration! What you need to remember is that each of these particles that make up the nucleus are quantum mechanical in nature: they're not just particles, but they're waves, too. And waves spread out over time, where they can attempt to tunnel into that more stable (post-decay) state. Every once in a while, after enough time has passed, a nucleus will find its way into that state, and when that happens, you get a decay!

(Image credit: Chi LF collaboration, from John von Neumann Institut fur Computing.)

But it takes time to get there. If you're too impatient, and you can't wait, you might be tempted to look right away. Only, you know what happens in quantum mechanics when you make an observation: you collapse the wavefunction into one particular state! So if you can't help yourself from making observations, what you're basically doing is resetting the clock every time you look!

(Image credit: Peter Byrne / Scientific American.)

If you're cracked, you'll lament that this is like the watched teapot that never boils. While if you're a physicist, you know the teapot boils, but the nucleus won't decay unless you stop continually collapsing its wavefunction!

(Image credit: CERN neutrinos to Gran Sasso, retrieved from Universe Today.)

1.) Einstein's Theory: Relatively Full of Crap (Also? Time Travel!).

And finally, the faster-than-light neutrinos thing, again. For those of you who've been living under a rock, the OPERA experiment in a mine under Gran Sasso detected neutrinos sent from CERN, and they detected them 60 nanoseconds sooner than they would have had they moved "only" at the speed of light.

Like many others, I was skeptical, and believed we were fooling ourselves. I still am, and I still do. We have plenty of evidence indicating otherwise.

(Image credit: NASA, ESA, K. France, and P. Challis and R. Kirshner.)

For one, we had a supernova in 1987, which raced photons and neutrinos for over 100,000 light years; were the neutrinos moving at the speed OPERA indicated, they'd have arrived four years earlier; instead, they arrived within hours. There are actually a host of other experiments that have constrained the speed of neutrinos, and if you look at all of them -- across a wide variety of energies -- you find that the new experiment, OPERA, is the one outlier, in conflict with everything else.

(Image credit: Matt Strassler and me.)

The OPERA results are bizarre enough that experiments in the United States and Japan are being set up right now to either verify or refute them. When it comes to this story, I've been doing my best to inform the world, and I'll stay on top of it and keep reporting all the latest developments that come up, too. But for right now, it's going to take some extraordinary evidence before I'm ready to chuck special relativity, even for something as mundane as the neutrino.

And there you have it: six scientific discoveries that might appear to laugh in the face of physics, but only until you learn the physics behind it! Isn't information beautiful?

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The Arxiv Is Not a Journal [Uncertain Principles]

Posted: 30 Jan 2012 06:58 AM PST

There's been a lot written recently about academic publishing, in the kerfuffle over the "Research Works Act"-- John's roundup should keep you in reading material for a good while. This has led some people to decide to boycott Elsevier, including Aram Harrow of the Quantum Vatican. I'm generally in favor of this, but Aram says one thing that bugs me a bit:

Just like the walled gardens of Compuserve and AOL would never grow into the Internet, no commercial publisher will ever be able to match the scope and ease of access of arxiv.org. Nor can they match the price. In 2010, there were about 70,000 new papers added to arxiv.org and there were 30 million articles downloaded, while their annual budget was $420,000. This comes to $6 per article uploaded (or 1.4 cents per download). Publishers talk about how much their business costs and how even “open access” isn’t free, but thanks to arxiv.org, we know how low the costs can go.

This is very nice, but has one major problem: The arxiv is not a journal.

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