Here's a logic puzzle for you: Suppose I offer you a million dollars, in return for which you agree to answer a certain yes/no question. You can answer either truthfully or falsely as you desire. That's it. Should you accept that offer? Solution below the fold.
Those of you reading this who enjoy logic puzzles are probably familiar with Raymond Smullyan. I was pretty young, eight or nine I think, when I first discovered his writing. Somehow I noticed his book What is the Name of This Book? sitting in a bookstore, and I persuaded my parents to buy it for me. The book opened with some very elementary puzzles I was able to appreciate even as a young child. But pretty soon I came to one of his most famous creations, the island of knights and knaves.
On this island the knights always tell the truth and the knaves always lie. The inhabitants of this island are in the habit of gathering in small groups and making various statements, from which you are to determine who among them is a knight and who is a knave. Smullyan intended these puzzles as a device for teaching basic ideas in propositional logic, and I use them for that purpose in my discrete mathematics classes. Anyway, at some point little kid me came across the following problem:
Suppose you meet three people, who we shall call A, B and C. You ask A, “How many knights are among you?” A mumbles an answer, but you cannot understand what he said. So you ask B to tell you what A said. B says, “A said that there is one knight among us.” At this point C interrupts and says, “Don't listen to B! He's lying.” Can you determine anything about what type B and C are?Read the rest of this post... | Read the comments on this post...
The recent launch of the Curiosity Mars rover has quietly broken the record for oldest human-made object in space, and instantly pulled numismatics, the study of coinage, into the Space Age.
American geologists have long used copper Lincoln pennies as scale indicators in photographs. All the Mars rover missions are geology projects conducted at a distance. And so, as a homage to professional geology tradition, a 1909 one-cent coin is attached to Curiosity's camera calibration target.
Being over a hundred years old, the coin is from a time sufficiently far from the present that industrial and conflict archaeologists already routinely excavate and document its remains. As far as I know, this is the first time that an antique is launched into space (disregarding stuff astronauts have brought into orbit and then back home again).
Update 15 Feb: Long-time Aard regular Lassi Hippeläinen points out that in 1999, some cremated remains of planetary geologist Eugene Shoemaker were sent to the Moon, and he was born in 1928. In my opinion, burnt human bones do qualify as artefacts, but they were made at cremation, not when Shoemaker's original baby skeleton formed.Read the comments on this post...
"...the current situation calls for bold leadership and tough decisions and not merely the proverbial rearrangement of the chairs in the dining hall of the Costa Concordia as it approached the Isola del Giglio."14 Kulkarni (2011)Read the comments on this post...
We know that Darwin was a biologist, and in many ways he was the first prominent modern biologist. But many people do not realize that he was also a geologist. Really, he was mainly a geologist on the day he stepped foot on The Beagle for his famous five year tour. This is especially true if we count his work on coral reefs as a geological study, even though coral reefs are a biological phenomenon. After all, the standing model for coral reef formation at the time came from the field of Geology.
Here is a list of several of Darwin's first publications with their publication dates:
As I've said a bazillion times already this term, I'm teaching a class that is about research and writing, with a big final paper due at the end of the term. Because iterative feedback is key to learning to write, they also have to turn in a complete rough draft, which I will mark up and have them revise.
One of the many, many problems with teaching writing is that too many students regard the writing of drafts as pointless busy-work. Others have no real concept of what a rough draft is-- when I've collected drafts in the past, I often get things that would barely qualify as an outline, let alone a draft. Already this term, I've had to explain severl times that when I ask for a draft of the final paper, I want a draft of the whole thing.
I think this stems partly from a misconception about the nature of expertise when it comes to writing. That is, I think a lot of students believe that once you really know what you're doing, you don't have to write in stages. Expert writers, in this view, just sit down at the computer and crank out flawless articles, fully formed. There's some truth to this at the college level-- God knows I never did more than one draft of anything in college, before my senior honors thesis. But at the professional level, it's nonsense; indeed, between college and now, I've turned into an obsessive reviser. I do multiple drafts of blog posts.
Getting students to believe this is a hard sell, though, and I've struggled to get them to take the process seriously. I'm going to try something different this week, though: giving them a look inside the sausage factory of the writing process. I'm going to let them see my rough drafts.Read the rest of this post... | Read the comments on this post...
So, the big How to Teach Physics to Your Dog Photoshop contest concluded on Friday. We got five really good entries, and the judges (me and Kate) had a hard time reaching a decision. After long deliberation, though, we've come up with a solution.
But first, the entries:Read the rest of this post... | Read the comments on this post...
"What's in a name? That which we call a rose By any other name would smell as sweet." -William Shakespeare Up in the night sky, just a few degrees away from Orion, one of the most identifiable constellations in the winter sky, lies a cluster of newly formed stars.
5,000 light years away, this cluster of stars is loaded with the full gamut of stellar colors, from blue to white to red, and is easily visible through any astronomical tool from simple hand-held binoculars to pretty much any type of telescope. It's one of the brightest, most prominent star clusters in the entire night sky not to make it into the first astronomical catalog of interesting night sky objects.
(Image credit: Nigel Metcalfe.)
But young star clusters like this aren't all that rare, even within our own galaxy. But this one houses a surprise. With either extremely dark skies, a large, powerful, and low-magnification telescope, or a very long-exposure astrophotography project, you can see something extraordinary engulfing this star cluster.
This dim, red glow is actually evidence of incredibly hot temperatures, but not for the reasons you might think! Unlike lava, which glows a dim red because of its very high temperature of over a thousand degrees, this glow is produced by temperatures much, much higher than that. In fact, regions in the core of this star cluster reach a temperature of over 6 million Kelvin, and the red color that you can see comes from a very special property of the hydrogen gas surrounding the cluster.
(Image credit: Astronomy Know How.)
When this incredibly powerful radiation from the stars collides with a hydrogen atom, it kicks the atom's lone electron clear out of the nucleus, leaving just a proton behind. Eventually, another electron -- kicked off of some other hydrogen atom -- runs into our ionized nucleus, producing stable, neutral hydrogen and a cascade of infrared, visible, and ultraviolet light at well-defined frequencies.
The red color comes from the most powerful visible-light transition in hydrogen, and is the cause of this vast illumination of the interstellar medium. With temperatures this hot, you may wonder just how far this nebula extends, and the answer is a spectacular Valentine's Day treat.
Spanning an amazing 130 light years in diameter, the Rosette Nebula is one of the largest, most symmetric emission nebulae in the entire galaxy.
Looking at it, you may wonder how it got to be this way, and why it's the shape and size that it is. It turns out that our galaxy, in addition to the stars, planets, and dust that you know about, is also littered with huge, diffuse, cold and (often) fast-moving clouds of gas.
Most of the time, these clouds of gas are quite content to zip along without causing any sort of fracas, but every so often, something -- perhaps a nearby supernova, or a collision with another gas cloud -- starts this cold cloud on its way towards gravitational collapse. While this happens, the densest regions start accruing the most matter the fastest, and that's where new stars first form! We can learn about the newest stars by looking in the X-ray portion of the spectrum.
(Image credit: Chandra X-ray observatory, NASA / CXC / SAO / J. Wang et al.)
What we find is that not only is the core of this nebula the hottest, containing the youngest, most massive stars, but that's also the oldest part of the nebula, and the place where star formation, although ongoing, was triggered the earliest. In other words, even though stars are forming everywhere, while the hydrogen gas slowly condenses into stars in the densest locations and evaporates in the most diffuse, star formation started at the center and slowly, over hundreds of thousands to millions of years, worked its way outward!
If we look in the far infrared part of the spectrum, we can see this in action.
(Image credit: ESA / PACS & SPIRE Consortium / HOBYS Key Programme Consortia.)
This image of gas -- taken by the Herschel Space Telescope -- on the outskirts of the Rosette Nebula shows massive stars up to ten times the mass of our Sun forming in the brightest regions here, while stars only a fraction of our Sun's mass form in the central, smallest pockets of dust.
If we go back to a section of the original, visible light image, we can see where that dust is densest, from its light-blocking properties, as well as where its evaporating the fastest, right around the edges of those dusty regions.
This NOAO image, although impressively detailed, doesn't quite have either the highest resolution or the most information possible in there. Because it's confined to "true color," we can't really learn what elements are present in this nebula. But by looking in false color, where different colors correspond to different elements, we can see that there's actually a rich diversity of different types of elements here.
(Image credit: Ignacio de la Cueva Torregrosa.)
In this image, the color red corresponds to the element Sulfur, prominent in the atmospheres of all the bright, young, visible stars. The familiar Hydrogen is shown in green, while the bluish regions are dominated by Oxygen. As you can see, even though there's the red glow of hydrogen everywhere, many regions are dominated by a diversity of elements!
But what about resolution? Believe it or not, there was a survey designed to probe deep inside these regions! Known as the Isaac Newton Telescope Photometric Hα Survey of the Northern Galactic Plane, this very region of the Rosette Nebula was imaged at an unbelievably high resolution. (If you're only going to click and explore one image on this page, make it the one below!)
While massive stars continue to form and grow in these dusty, stellar nurseries, the winds from the ultra-hot central stars compete to blow the remaining dust away, stunting their growth and preventing them from reaching the sizes of the greatest central monstrosities, which can be many dozens of times the mass of our Sun, and have lifetimes of under a million years!
This image is at such high resolution that I can zoom in to this small of a region (can you find it, above) and still see this level of detail:
But what about zooming out, even farther than before, and viewing the entire cosmic rose in all of its glory? Here at Starts With A Bang, this is my Valentine's Day giift to all of you, in time to send it to your favorite person in the galaxy.
Happy Valentines Day, from the biggest Valentine in the galaxy!Read the comments on this post...
I've been falling down a little in the area of shameless self-promotion, but I will be at Boskone this coming weekend, where I'll be doing three program items:
Reading: Chad Orzel (Reading), Fri 19:30 - 20:00
This will be a section from the forthcoming book, probably involving Emmy and particle physics. Or possibly William Butler Yeats.
How to Wreck Your Career with Social Media (Special Interest Group)
(M), Sat 16:00 - 17:00
What are the new opportunities for public humiliation opened by the Internet? Join this entertaining discussion about authors getting into nasty public spats with reviewers and fans, going off on long unhinged political tirades, sharing a little too much of their unfiltered id, and so on.
I was originally thinking of this as a panel, but they suggested it as a group discussion instead. Lacking any experience with this format, I'm going to hope that somebody's doing one before 4pm on Saturday that sounds interesting, so I can see what exactly I'm supposed to do. Also, suggestions of really entertaining wreckage on social media (blogs, LiveJournal, Twitter, etc.) are welcome in comments.
What Every Dog Should Know About Quantum Physics (Solo Talk), Sun
14:00 - 15:00
Author of How to Teach Physics to Your Dog and How to Teach Relativity to Your Dog, Chad Orzel discusses the basics of quantum physics for two- and four-legged audiences.
This is my public-lecture talk on quantum physics. It's also the last program slot on the schedule, which makes me wonder how many people will still be around to hear it... If you're going to be there, please do stop by.Read the comments on this post...
Technology Review Magazine Poised to Return as Festival Sponsor! [USA Science and Engineering Festival: The Blog]
Known as "the authority on the future of technology " and the world's oldest technology magazine,Technology Review - published by the Massachusetts Institute of Technology (MIT) - is bringing its prestige and expertise back to the Festival as a Media Partner!
Technology Review, published by MIT since 1899, continues today to provide unparalleled insights into cutting edge technologies that are changing the world and the way science and engineering do business.
In returning as a Media Partner, the magazine joins a growing list of other top science media leaders who are also serving as Festival sponsors, including Popular Mechanics, Scientific American, Popular Science, Chemical & Engineering News, School Tube.com, ENGINEERING.com, EE Times, The Epoch Times, and PBS Kids.
"In many ways, the mission of the USA Science & Engineering Festival in educating tomorrow's innovators and the general public on the future of technology coincides with our publication's mission as well," says Kathleen Kennedy, Technology Review's Chief Strategy Officer. "Technology Review identifies emerging technologies and analyzes their impact for technology and business leaders-the senior executives, entrepreneurs, venture capitalists, engineers, developers, and researchers who create and fund the innovations that drive the global economy," she adds.
Technology Review is also an invaluable resource for early adopters, students, the media, those in government, and anyone who needs to understand trends in technology, including the hottest happenings in computing, the web and social media, communications, sci fi-inspired innovations, energy, materials, biomedicine and news from its thought-provoking blogs.
As a Media Partner in the Festival, Technology Review, like other key media sponsors for next year's event, will run advertisements pro bono via their respective media outlets. This will play a key role in not only giving the Festival heightened visibility on a national and international scale, but will also help the event recruit for new satellite venues and participation in the Expo, contests and other activities.
Owned by MIT as an independent media company,Technology Review boasts a worldwide readership of more than three million. The publication is published in five languages (including, Chinese, Spanish, Italian and an English edition for India) and is also available on a variety of digital and print platforms.
We thank Technology Review and our other Media Partners for their valued participation!
"The human world stands about midway between the infinitesimal and the immense. The size of our planet is near the geometric mean of the size of the known universe and the size of the atom. The mass of a human being is the geometric mean of the mass of the earth and the mass of a proton. A person contains about 1028 atoms, more atoms than there are stars in the universe. Such considerations yield perhaps only a relative location. Still, questions of place and proportion arise." -Holmes Rolston III One of the most difficult things to get a handle on, when it comes to astrophysics and particle physics, is just what, exactly, what these large and small scales actually mean. While you ponder this, have a listen to Edgar Meyer, Béla Fleck and Mike Marshall's expansive sound as the string trio takes on Fleck's catchy tune,
You might consider a whale "large" and a mouse "small," and perhaps they are when compared to you, but that's only an incredibly tiny fraction of the scales we're talking about when it comes to the Universe. A little over a year ago, I pointed you over to an interactive application showcasing the scale of the Universe. While it was very entertaining, I was also quick to point out that it was rife with errors, and not to be trusted about some matters.
But oh, has there ever been an upgrade, and you do not want to miss this!
First off, the images are much more detailed than before and some of them are even animated!
But there's much, much more, on every scale you could ask for.
As we go to larger scales, you can see there are a great many more objects placed in the application, to help you get a handle of relative scale. Where does our Moon fit in the scheme of the great moons of the Solar System? This scale comparison should help give you a great feel for it.
What about planets and stars? A vast array are not only presented here, you may notice a tremendous feature upgrade: each object is annotated, with a small tidbit of information about each specific object in question! Although some of them are silly, other than a few typos, the information is factually accurate!
What's also amazing is the difference between these scales. The Moon may be a million times larger than we are, the star, La Superba, above, may be another factor of a million larger than the Moon!
But if you want to pick up an entire galaxy, you need to go a factor of a billion larger than even those huge, supergiant stars! And finally, to encompass the entire observable Universe, you'd need to zoom out another factor of a million. (Which, remember, because space is three-dimensional, is a difference in volume of 1018, or 1,000,000,000,000,000,000!)
And this takes us to the edge of what we can ever see in the whole Universe! Unlike in the previous edition, they get the scale right in the new version, almost like they had read my criticisms exactly, and incorporated my recommended fixes!
But it gets even better, because you can zoom down to tiny scales, too. Going far inside a human, which is meter-scaled, you can go way, way down.
While the width of a strand of human DNA may be around a billion times smaller than a human, if you unravelled it and stretched the amount of DNA in any single cell, you'd find it's about ten feet long, or taller than any human being! (And all of that information is available in the annotation!)
But what about when we go to the smallest known particle scales? You actually get the information I wished they had included in the first version!
What do they tell you?
Lengths shorter than this are not confirmed
1 x 10-16 m
All the objects that are smaller than this are unmeasured. The sizes that they appear are only estimates. Some things, like quantum foam, are just parts of theories. They aren't fact. This is pretty close! For instance, if we go down to their particle, "High-energy neutrino," what are we told, and what's actually down there?
The numbers they're reporting are based on the interaction cross-section of these particles, which is what allows you to calculate the probability that they'll collide with another particle. The cross section, of course, is an area (a length-times-width), so you'll need to take the square root of that to get the approximate size, and that's how they get it!
This isn't the same as the actual, physical size, which we don't know how to measure. And that's why a low-energy neutrino -- like the ones left over from the Big Bang -- not only have a much smaller cross-section, they haven't even been detected yet!
And finally, if we go all the way down to the limit of what our best quantum theories can predict, to the Planck Scale, beyond which physics breaks down, this is where the most speculative of our theories live. Is there a quantum foam; are there strings and branes? What is the fundamental nature of spacetime at these scales; is it quantized and discrete or continuous? Is there a fundamental quantum theory of gravity or not? Although we don't know, this is where you'd look to find out, on scales 35 orders of magnitude smaller than we are.
And all of it, the whole Universe, spans some 63 orders of magnitude, from the smallest sensical quantum scale to the entire observable Universe (and beyond, for the particularly brave), is available for you to explore -- zooming in-and-out as you please -- in this one remarkable toy!
Say goodbye to a huge chunk of your weekend, and know that it will be time well spent!Read the comments on this post...
The 2012 Festival will be here in April and we thought it would be special to honor some of the people that make the Festival happen: our fans. The Festival would not be possible without the help of our partners, sponsors and exhibitors; however our fans play a huge impact in the success of the Festival.
Leading up to the Festival, we have decided to implement a "Featured Fan" segment. Our first Featured Fan is Dr. Jessica Carilli. Jessica shares her insight into her passion: science and her excitement for the Festival below. Enjoy!
Dr. Jessica Carilli happy at work
I'm a big fan of science outreach, and am always looking for ideas to improve my own outreach by seeing presentations and exhibits from other scientists. I also like to learn about totally different realms of science from what I study, so many of the Meet the Scientist talks would appeal to me. For those reasons I'd also enjoy seeing presentations such as the various science comedians, and the Eat a Bug and the Women in Science presentations. As a new parent and scientist, presentations such as Babies and Sound and Geek Dad also caught my eye.
In addition, I think it's important to spread ideas on what normal people can do to prevent global climate change, and for those reasons I'd really like to visit the exhibits relating to "Preventing Global Warming," "Making Agriculture More "Green"," and "Solar Energy."
Finally, I'm an aspiring science writer, working on a book about my experience earning a PhD in marine science. I'd love to meet some of the authors at the Festival, especially those who've written books about Stories in Science and Discovery in Science.
If you would like to be considered as a Featured Fan then please send an email to: email@example.com.
Read the rest of this post... | Read the comments on this post...
There are several signs o'doom for NASA bubbling up out there
In a book that I read recently (either The Cloud Roads or The Serpent Sea-- I finished the first and immediately started the second), as some characters are traveling from one place to another, there's a passing mention that they weren't able to hunt at night because the moon wasn't out and it was too dark. Which sort of bugged me, and I was reminded of it tonight when I took Emmy out for our post-dinner walk-- it's very clear tonight, and a lot of stars were visible, even here in the light-polluted suburbs, but the moon wasn't up yet.
And the thing is, while it's darker when the moon isn't out, it's not really too dark to see, because there are a whole lot of stars. This isn't that obvious if you live in a built-up area, but one time we went on a fishing trip up in the mountains in New Mexico, and it was really amazing just how bright the stars can be, if you're in a place with no clouds and no light pollution. A couple of times, I got up to go to the bathroom in the middle of the night (also, because the air mattress we were using had a leak, and would slowly deflate), and you really didn't need a flashlight-- just the stars provided plenty of light to see by.
Of course, if there's thick cloud cover and no moon, and you're out in the middle of nowhere, it really is alarmingly difficult to see anything. But that's a function of the overcast skies, not the absence of the moon per se.
I don't have a larger point to make here-- this is mostly to fill time while SteelyKid watches one more episode of Animaniacs before bedtime. But it's something that bugged me, and probably not all that many other people. This is the price of geekdom.Read the comments on this post...
"The phenomena of nature, especially those that fall under the inspection of the astronomer, are to be viewed, not only with the usual attention to facts as they occur, but with the eye of reason and experience." -William Herschel We live in the most plentiful of scientific times, where the full extent of both our experience and understanding has expanded tremendously since the time of Herschel. You must remember that to Herschel, living in the 18th century, there were but six known planets (including Earth) in the Solar System: Mercury through Saturn.
(Image credit: Daniel Dendy.)
While each of these classical, wandering objects can easily be seen with the naked eye under the right conditions, the seventh planet, Uranus, was not discovered until 1781, by William Herschel himself. Under the right dark sky conditions, Uranus is just barely visible to the naked eye, right at the limit of human vision. Unless you know where to look at any given time, it's very unlikely you'll see it.
But if you take a look at the sky just after sunset, tonight, you'll be in for a remarkable treat. Particularly if you live in the Americas.
(Image credit: Stellarium.)
As you may have noticed, looking towards the southwest portion of the sky just after sunset, there are two very bright objects hovering above the horizon. Venus, the brightest object (other than the Moon) in the night sky, follows the Sun into the west, while Jupiter (the second brightest) lags behind by a few hours.
Up at my latitude (about 45 degrees North), this is what clear skies will look like around 6:00 PM. But wait just a bit longer -- maybe a half-hour -- and darkness sets in, allowing the light from those distant orbs in the night sky to dominate.
To your naked eye, Venus will still shine more brightly than any other object. It will be a few hours before the Moon comes up and a few hours before Venus falls down below the horizon. But coming closer to Venus than any other time this year is the planet Uranus, and those of you in the Americas will get to see it near its closest approach, right around 7:00 PM Pacific time.
Have a pair of binoculars languishing somewhere at home? Break them out, and point it towards Venus. If you let your eyes get adapted to the dark, even if you have relatively urban skies, here's what you're likely to see.
In addition to the bright disk of Venus, you're likely to see a small point of light a small distance away from it. While it may appear to be a faint star or a small moon, it's neither. Venus has no moons of its own, and there are no stars anywhere near that magnitude in this region of the sky. What you're seeing, billions of miles away, is the planet Uranus!
(Image credit: Bob King, retrieved from Astro Bob.)
The bright, consistent disk of the planets make this a sight visible to many even in light-polluted regions. Unlike looking for a galaxy, nebula, or other extended object, everyone should give this a try. And for those of you with even a small telescope, you are in for a treat. Normally, Uranus is very difficult to find. But tonight, it will be separated from Venus by less than the angular size of the Full Moon! If you can find Venus in your telescope, you're not only likely to find Uranus, too, but to see that it is a disc, not just a point!
For a size comparison -- how big are these disks relative to the full Moon -- I give you this chart, modified from Peter Freiman's original.
The planet Uranus is a sight that most people never get to see in their lifetimes, but if you've got clear skies and you're in the Americas, don't miss your chance to hunt for it tonight!
And I should make this clear: this is one night only!!!
Venus moves somewhat rapidly across the sky, at least in astronomical terms. While tonight, it will be separated from Uranus by maybe half the size of the full Moon (around 0.3 degrees), by tomorrow at the same time, it will be more than two full Moons away!
(Venus and Uranus' separation, at 6:09 PM on February 10, 2012 from Portland, OR.)
This close dance of Venus and Uranus is a rare one, and it's rarer still that they occur when both planets are in prime viewing location in the early evening.
Tonight: one night only, it's Venus and Uranus, together in the sky. Don't miss it!
The Russian probe destine for the Mars system never made it out of Earth Orbit and recently crashed back into Planet Earth. Why did the rocket ship fail? There has apparently been a lot of obfuscation of what caused this disaster, but now there is some better information. It may have been caused by a computer programming error.
Though it may have been more complicated than that, and partly due to inadequate electronic parts in the computer, according The Planetary Society.Read the comments on this post...
"It took less than an hour to make the atoms, a few hundred million years to make the stars and planets, but five billion years to make man!" -George Gamow Let's pretend that, for all of our history on Earth, we had never once bothered to look up with any instruments beyond what our own eyes could offer. Imagine that all the technology we'd have would be the same -- telescopes, electronics, GPS, etc. -- as would our fundamental scientific knowledge -- Einstein's General Relativity, the Standard Model of Particle Physics, etc. -- but we had just never bothered to turn our attentions toward the Universe beyond our sphere of Earthly concern. (I know, I know, you can't even imagine. But imagine!)
What would we find, today, if we turned our attention upwards for the first time ever?
(Image credit: Mila Zinkova.)
Up in the night sky, we'd find some different classes of objects. Some wouldn't twinkle, ever, under any atmospheric conditions. These objects -- the Moon, satellites, and the planets -- we could easily see, with a telescope, had large angular sizes and big, identifiable parallaxes, allowing us to determine their actual size and their distance from us. These would be the objects within our own Solar System.
There would also be stars, in a variety of colors, temperatures, sizes, and distances. We would quickly discover the relationship between the distance to a star and its apparent brightness, and how that was related to its intrinsic brightness.
(Image credit: NASA / JPL - Caltech.)
We'd slowly start to -- with lots of observing targets and time -- learn the science of astronomy. We'd learn about different star types, including main-sequence stars, red giants, variable stars like Cepheids and RR Lyrae stars, and stars that went nova or even supernova!
Armed with the knowledge of what's in our Solar System and of the stars that lie beyond it, we'd have a strong base for peering beyond, into the rest of the Universe. So that finally, when we looked up at the third type of object in the night sky -- the extended nebulae -- we'd be ready to learn lots of interesting things about them.
(Image credit: NASA, ESA and Jesús Maíz Apellániz.)
How old are these young star clusters? With an understanding of stars, we can tell you. How far away are these nebulae and supernova remnants? By understanding individual stars and the distance/brightness relationship, we can tell you. And finally, what about these faint, fuzzy blobs and spirals in the sky? Just what are they?
(Image credit: ESA/Hubble, NASA and H. Ebeling.)
At this point in time, we can resolve individual stars inside many of them, and find that unlike the stars in our own galaxy -- which are hundreds, thousands, or even tens of thousands of light years away -- these objects are millions of light-years distant. In other words, they are island Universes, or galaxies entirely separate from our own!
This might seem like the most obvious thing in the world today, but consider that this was not known until less than a century ago. And while you were making these measurements of distances to these galaxies, you might have noticed something else.
(Image credit: retrieved from Western Kentucky University.)
These galaxies were not just very distant, but the light coming from them was also redshifted. When objects move towards or away from you, the frequency of the light gets shifted towards the blue or red end (respectively) of the spectrum, with the faster motions corresponding to a swifter velocity. According to general relativity, the expansion (or contraction) of spacetime could cause the same type of red (or blue) shift of the light.
What you'd find, when you looked out at all of the galaxies you could see, would've been something remarkable.
(Image credit: R. P. Kirshner, 2003.)
You'd find that the more distant a galaxy was from you, on average, the more redshifted its light was! You'd notice that this was virtually independent of direction on the sky, and that -- excepting the fact that there was a "scatter" of a few hundred to maybe a thousand km/s -- this was a Universal relation, extending for not just millions but billions of light years!
From this alone, you could draw a few different conclusions depending on how you interpreted your data, such as:
- the Universe was such that we were at the center, at rest, and that objects were moving away from us, with further objects moving away faster,
- light was getting tired, and that the further away a light-emitting object was, the more energy it lost, shifting further into the red end of the spectrum, or
- the Universe was expanding under the rules of General Relativity, and that the galaxies' light shifted deep into the red because of the Universe's expansion.
(Image credit: NASA / CXC / M. Weiss.)
We'd have a Universe that was expanding, that was smaller, denser, and (because of how wavelengths/frequencies work) hotter in the past. Which means we'd have a Universe that was expanding, diluting, and cooling today.
This "model" of the Universe is one you might recognize: this is the Big Bang picture of the Universe! If this were true, you'd ask yourself, what else would we expect to be the case?
(Image credit: 2dF Galaxy Redshift Survey.)
If we looked into the past, we'd expect that the Universe would have been more uniform, with fewer large galaxies and fewer giant clusters of galaxies. After all, if the Universe has been around for a finite amount of time, and gravity attracts things over time, the structure that existed billions and billions of years in the past should consist of smaller galaxies that are less clumped together than the ones that exist today.
In other words, the Universe should have been more homogeneous in the past. We also said that the Universe should have been hotter in the past! What does that mean?
(Image credit: retrieved from the Ministry of Science and Technology in Brazil.)
It means, at some point, the average temperature/energy of a photon in the Universe should have been so high that neutral atoms -- the stuff that makes up everything we know on Earth -- would not have been able to form! A hot, ionized plasma is all that should have been around, as every time an atomic nucleus tried to capture an electron, a photon should have come along and blasted it apart. So at some point, the Universe should have been filled with a hot, dense plasma. (Which we know -- by the way -- is opaque, or not transparent, to light! Remember this!!!)
But we can go back even further! Imagine a time that was even hotter and denser than when this plasma existed, to a time where it was so hot that even protons and neutrons -- the constituents of atomic nuclei -- would be blasted apart by the scorching hot radiation of the Universe!
(Image credit: me, modified from Lawrence Berkeley Labs.)
At some point, the lightest elements in the Universe would have been unable to form. These are some of the consequences of this Big Bang model of the Universe, and these are theoretical predictions that we can test!
Each of these events will leave observable signatures behind. If we start out in a hot, dense, roughly uniform state and come forward in time, we can predict what we should see today based on the Big Bang model of the Universe! Let's start at the beginning and come forward.
(Image credit: Ned Wright.)
The light elements: as the Universe expands and cools from an incredibly hot, dense state, eventually it will cool enough that the protons and neutrons, left over from an even hotter, denser state, will fuse together into the light elements deuterium, tritium, helium-3, helium-4, lithium-6, lithium-7, and beryllium-7. The only parameters that determine how much of these light elements get created are the ratio of photons to protons+neutrons. Because we know the particle physics behind it, we can know how much helium-4, helium-3, deuterium, lithium, etc., should be left over from the Big Bang, dependent only on that one, measurable parameter. If we can find some pristine gas from the early Universe, all of these elements should exist in those predicted abundances.
(Image credit: COBE / FIRAS, retrieved from Fermilab.)
The leftover radiation from the Big Bang: better known as the Cosmic Microwave Background! Because the hot plasma was opaque to light, we can't see all this radiation from the Big Bang until these neutral atoms form. But once these neutral atoms form, that leftover radiation from the Big Bang should not only stream directly to us, it should come to us practically uniformly in all directions, with a predictable, blackbody spectrum stretched by the expansion of the Universe. (Note that the other, above explanations for redshift -- including tired light -- do not give the proper spectrum!)
The discovery of this leftover radiation and the accurate measurement of its spectrum led, historically, to the acceptance of the Big Bang, as no other model of the Universe explains this observation, the abundance of the light elements, and the redshifts of the distant galaxies simultaneously. But there is one more great observation we can make.
(Image credit: V. Springel at Max-Planck-Institute at Garching.)
The Large-Scale Structure of the Universe: from the earliest stars and galaxies to modern times, from isolated dwarf galaxies to humongous clusters and superclusters, some of which have behemoth galaxies maybe 100 times the mass of the Milky Way inside of them, we should find larger, clumpier structure in the Universe today and more sparse, uniform structure in the past.
And we do! To all of it: WE DO!
And that's what the Big Bang is. That's how we'd figure it out today, and that's how we figured it out historically. And -- this is important, detractors and skeptics -- it isn't everything.
(Image credit: Composition of the Cosmos, retrieved from the LSST.)
It doesn't tell you exactly how much structure you have in the Universe and on what scales; you need a set of initial fluctuations for that, and that's what inflation gives you. It doesn't tell you exactly how the Universe has expanded over its history; you need to know how much total matter and dark energy are in the Universe for that, which is something the Big Bang doesn't predict for you. (You might assume that there isn't any dark energy, and that all the matter is normal -- protons, neutrons, and electrons -- but that would be awfully presumptive of you!) It doesn't tell you how the structure the Universe contains evolves over time; you need dark matter in addition to normal matter to get that right. And it doesn't tell you about the pattern of fluctuations you should see in the nearly-perfectly-uniform microwave background: you need inflation, dark matter, and dark energy for that. (Incidentally, the same amounts and types that the other measurements told you that you'd need, but that's a story for another time!)
But you mustn't deny the Big Bang because it couldn't predict those things. Those things went beyond the scope of the Big Bang. The Big Bang knows what to do with them if you put them in, but just like any theory, it can't do everything by itself. But that's what the Big Bang is, that's how it works, and that's how we know it's right.
Any questions?Read the comments on this post...
Rumors have been in the air for days, but we now think it confirmed that Russian Scientsts have penetrated the liquid part of Antarctica's Lake Vostok. The lake has been frozen over for something like 20 million years. Certainly there was life in it at the time. Is any of it still there? Has something new evolved? Just as interesting is question of paleoclimate data preserved, we hope, in the sediments at the bottom of the lake. The top section of the lake's bottom probably contains sediments that have formed over the last 20 million years, in the ice-bound southern lake, but below that will be sediments reflecting the regional and global biological conditions and climate for a long period of time before ice-over.
The upper sediment will come from erosion from the lake's sub-ice shoreline, mostly chemical in nature, settling of the finest of clays that would have been in the water at the time the ice covered the lake, but mostly, I suspect, a combination of re-settled light minerals moved by currents that may or may not have been operating there and biological materials from whatever may or may not have been living in the water.
BBC broke the news (more or less) with this:Read the rest of this post... | Read the comments on this post...
If all the water currently trapped in all the glaciers across the entire world melted, the sea level would rise far more than most people imagine. Almost everyone living anywhere in the world at an elevation of below about 500 feet with a direct drainage to the sea would be directly affected; The sea level rise itself might be a bit over 300 feet, but oceans tend to migrate horizontally when they rise onto previously uninnundated land surfaces. So if you lived at 500 feet above sea level in most of Maine, you'd have a much shorter walk to the rocky shoreline, but if you lived at 500 feet across much of the Gulf Coast it would only be a matter of time until the eroding sea cliff reached you incorporated you into the offshore sediments.
Having said that, Anthropogenic Global Warming has resulted in only modest sea level rise to date, and it is at this point probably true that warming of the ocean causing thermal expansion has been at the same level of magnitude (or greater) than seas rising because of the influx of melted glacial water.
The problem is, it is very difficult to measure either sea level rise or ice loss very accurately, for a number of reasons. But there is a saving grace. Or should I say, GRACE. GRACE is a NASA project; Twin satellites measure changes in the Earth's gravity field in such a way that it is possible to identify changes in the distribution of water. From the GRACE overview statement:
Through a weird quirk of scheduling, I haven't actually taught the intro modern physics course since I started writing pop-science books about modern physics. So, this week has been the first chance I've really had to use material I generated for the books to introduce topics in class.
In the approximately chronological ordering of the course, we're now up to the late 1800's, and the next book we're talking about is Einstein's Clocks, Poincar$eacute;'s Maps, which talks about how Einstein and Henri Poincaré were (arguably) influenced by developments in timekeeping as they looked for the theory that became Special Relativity.
This is a much more academic book than the previous readings, and as such has really long chapters and sections. To space things out a little bit (giving them more time to read), and to give them a better idea of what relativity is about (which I think is helpful when reading Galison's discussion), I've spent the last two classes talking about relativity. Monday's lecture introduced Special Relativity and spacetime, and today's lecture introduced the Equivalence Principle and general relativity. Those slides are a little short on words because I was largely copying figures from the book, and because I'm trying to generate less wordy PowerPoints as a general matter. They should give you the right basic idea, though, and if you want more explanation, well, you can pre-order How to Teach Relativity to Your Dog (or enter our Photoshop contest)...Read the rest of this post... | Read the comments on this post...