Today, Wednesday December 4th, at 8 pm Eastern/5 pm Pacific time, Sean Carroll and I will be interviewed again by Alan Boyle on “Virtually Speaking Science”. The link where you can listen in (in real time or at your leisure) is
What is “Virtually Speaking Science“? It is an online radio program that presents, according to its website:
Informal conversations hosted by science writers Alan Boyle, Tom Levenson and Jennifer Ouellette, who explore the explore the often-volatile landscape of science, politics and policy, the history and economics of science, science deniers and its relationship to democracy, and the role of women in the sciences.
Ah, the fast-paced life of a theoretical physicist! I just got done giving a one-hour talk in Rome, given at a workshop for experts on the ATLAS experiment, one of the two general purpose experiments at the Large Hadron Collider [LHC]. Tomorrow morning I’ll be talking with a colleague at the Rutherford Appleton Lab in the U.K., an expert from CMS (the other general purpose experiment at the LHC). Then it’s off to San Francisco, where tomorrow (Wednesday, 5 p.m. Pacific Time, 8 p.m. Eastern), at the Exploratorium, I’ll be joined by Caltech’s Sean Carroll, who is an expert on cosmology and particle physics and whose book on the Higgs boson discovery just won a nice prize, and we’ll be discussing science with science writer Alan Boyle, as we did back in February. [You can click here to listen in to Wednesday’s event.] Next, on Thursday I’ll be at a meeting hosted in Stony Brook, on Long Island in New York State, discussing a Higgs-particle-related scientific project with theoretical physics colleagues as far flung as Hong Kong. On Friday I shall rest.
“How does he do it?”, you ask. Hey, a private jet is a wonderful thing! Simple, convenient, no waiting at the gate; I highly recommend it! However — I don’t own one. All I have is Skype, and other Skype-like software. My words will cross the globe, but my body won’t be going anywhere this week.
We should not take this kind of communication for granted! If the speed of light were 186,000 miles (300,000 kilometers) per hour, instead of 186,000 miles (300,000 kilometers) per second, ordinary life wouldn’t obviously change that much, but we simply couldn’t communicate internationally the way we do. It’s 4100 miles (6500 kilometers) across the earth’s surface to Rome; light takes about 0.02 seconds to travel that distance, so that’s the fastest anything can travel to make the trip. But if light traveled 186,000 miles per hour, then it would take over a minute for my words to reach Rome, making conversation completely impossible. A back-and-forth conversation would be difficult even between New York and Boston — for any signal to travel the 200 miles (300 kilometers) would require four seconds, so you’d be waiting for 8 seconds to hear the other person answer your questions. We’d have similar problems — slightly less severe — if the earth were as large as the sun. And someday, as we populate the solar system, we’ll actually have this problem.
So think about that next time you call or Skype or otherwise contact a distant friend or colleague, and you have a conversation just as though you were next door, despite your being separated half-way round the planet. It’s a small world (and a fast one) after all.
Take a ball of loosely aggregated rock and ice, the nucleus of a comet, fresh from the distant reaches of the solar system. Throw it past the sun, really fast, but so close that the sun takes up a large fraction of the sky. What’s going to happen? The answer: nobody knows for sure. Yesterday we actually got to see this experiment carried out by nature. And what happened? After all the photographs and other data, nobody knows for sure. Comet ISON dimmed sharply and virtually disappeared, then, in part, reappeared [see the SOHO satellite’s latest photo below, showing a medium-bright comet-like smudge receding from the sun, which is blacked out to protect the camera.] What is its future, and how bright will it be in the sky when it starts to be potentially visible at dawn in a day or two? Nobody knows for sure.
[Note Added — Now we know: the comet did not survive, and the bright spot that appeared shortly after closest approach to the sun appears to have been all debris, without a cometary “core”, or nucleus, to produce the additional dust and gas to maintain the comet’s appearance. Farewell, ISON! Click here to see the video of the comet’s pass by the sun, its brief flare after passage, and the ensuing fade-out.]
I could not possibly express this better than was done last night in a terrific post by Karl Battams, who has been blogging for NASA’s Comet ISON Observing Campaign. He playfully calls ISON “Schroedinger’s Comet”, in honor of Schroedinger’s Cat, referring to a famous and conceptually puzzling thought-experiment of Erwin Schroedinger, in which a cat is (in a sense) put in a quantum state in which it is neither/both alive nor/and dead. Linking the comet and the cat is a matter of poetic metaphor, not scientific analogy, but the metaphor is a pretty one.
Battams’ post beautifully captures the slightly giddy mindset of a scientist in the midst of intellectual chaos, one whose ideas, expectations and understanding are currently strewn about the solar system. He brings to you the experience of being flooded with data and being humbled by it… a moment simultaneously exciting and frustrating, when scientists know they’re about to learn something important, but right now they haven’t the faintest idea what going on.
Comet ISON, a pristine chunk of rock and ice from the extreme edges of the solar system, is making its first visit to the vicinity of the Earth and the Sun. And what a trip!
Today, in a few hours, at 1:45 in the afternoon on the U.S. east coast, the comet will pass exceptionally close to the Sun — much, much closer to the Sun than the Earth or even the planet Mercury. At its closest, the distance from the comet to the Sun’s center will be only 2.5 times larger than the distance from the surface of the Sun to its center. To say it another way, the radius of the Sun is about 700,000 kilometers (430,000 miles) and the comet’s closest approach will be 1,200,000 kilometers (730,000 miles) above the Sun’s surface, or 1,900,000 kilometers (1,160,000 miles) from its center.
This will be a very fiery place for an icy object to find itself!! A comet may or may not survive such a close approach; its central core (or “nucleus”, an agglomeration of rock and ice, about the size of a big mountain on Earth) may fragment if the heat radiating from the sun sufficiently vaporizes and weakens the core. If it does survive, and perhaps even if it fragments, we may begin to see it in the sky in a couple of days, just before sunrise. And if we’re very lucky, it will be spectacular. [Note Added (updated): It appears we are unlucky this time. Indications are now strong that Comet ISON’s nucleus (mostly) did not survive its close approach to the sun, and began falling apart just before or shortly after this post went on-line. You can see evidence of this in a video from SOHO’s close-up camera.Whether the remnants of its dust tail might be visible for a few days isn’t clear to me (or probably to anyone) yet.We can now see that some fragment of the nucleus appears to remain, but the comet is a shadow of its former self. We’ll know soon how visible it will be. [Unfortunately it appears that was visible was all dust, and the comet is just debris now; it will not be visible at all.]]
Over the first few days of December, the comet will dim, but it will also move away from the sun and from the brightest light of dawn, and so it will also become easier to see. Try to look for it in the coming week! My current amateur’s guess (to be updated when I know) is that its remnant dust trail will spread out and dim very rapidly; you should not wait too long if you want to try to see it.
For the moment, you can’t see the comet by eye; it is way too close to the incredibly bright light of the sun. The only way to observe the comet right now is via satellites. The close approach is best watched through the camera of SOHO (the Solar and Heliospheric Observatory satellite). There’s a recent movie here from SOHO that shows the comet has brightened very rapidly in the last 24 hours. [The sun lies at the center of the image, drawn as a white circle, and is shaded from SOHO’s camera by a shield that forms a larger black dot in the center of the image.] The bright star Arcturus sits at the lower left of the image, and the comet is [was, this morning,] much brighter than that! Its maximum brightness may eventually approach that of the brighter planets, Jupiter and even perhaps Venus.Click here for the latest SOHO image, and here for the latest closeup image (which as of writing doesn’t show the comet yet.) A recent image is below.
Comet C/2012 S1 ISON from the NASA SOHO spacecraft on November 28th as it approached the sun. [Image credit: NRL/NASA]
For those who don’t know of him, Sean is a very fine scientist, an expert on the early and current universe, among other things, as well as a very skilled and engaging writer and speaker… and very importantly, he maintains very high standards for accuracy and clarity. I recommend him highly!
Sean and I were interviewed on a Virtually Speaking Science on-line radio show in February (you can listen to it here) and will be appearing again in early December. (By the way, I also appeared on this show when the hunt for the Higgs was still on…)
Today I’m looking for insights from readers on two issues that were nagging me over the weekend.
The first issue has to do with the Fukushima nuclear accident and subsequent radiation fears, which I first brought up on this blog last week. I’ve been thinking about how to write articles that explain radioactivity and radiation in rather plain language, and about what we know is dangerous and what we know is not. One of the challenges is to confront the extreme irrationality of people’s fear of radioactivity. I’d like to hear my readers’ opinions of where this fear really comes from. One explanation of this fear that you’ll commonly read is that “radioactivity is scary because you can’t see or smell or feel it”. But that makes no sense; you can’t see, smell, or feel viruses either, or low levels of chemicals, so why aren’t people equally afraid of those things? Especially since the average person is far more at risk of getting cancer or other potentially deadly diseases from viruses (such as papilloma) or from chemicals (asbestos, benzene, etc.) then from radioactivity, despite all the atmospheric nuclear tests in the 1950s and 1960s and the Chernobyl and Fukushima nuclear plant accidents. So I don’t think this explanation is correct; there are plenty of invisible scary things in the world, and people’s fears are totally out of proportion to the true risks. I have my own suspicions as to the real causes, but I am wondering what my readers think.
The second issue is more technical. Comet ISON, dubbed, as is typical of our sensationalist age, “comet of the century” before it has even become easily visible [and it might still be a dud, or it might be the best of the year or even the last twenty years; but of the century? check back in 2099!]) is approaching the sun. There is indeed the tentative possibility, if it survives its very close encounter with the sun on November 28th, that it will give us a spectacular early morning display in December. In preparation, I’m wanting to read more details about the properties of cometary tails, which are generated by the physics of particles and fields (photons, ions, magnetic fields, momentum conservation, etc.). [Here’s a nice video of ISON’s tail and its interaction with the solar wind, the stream of charged particles emanating from the sun; also visible to its upper right is Comet Encke, which by chance is also near the sun. By the way you can also see, watching Encke, that its tail is not a trail; it does not point along its direction of motion but instead points away from the sun.] But I’ve been unable to find anything online other than vague descriptions with no technical information, or references to books or review articles from several decades ago. Do any of my readers know of a roughly up-to-date technical introduction to the physics of comets’ tails?
