Dark Matter
esiegel | January 18, 2013"The cosmos is all that is or ever was or ever will be. Our feeblest contemplations of the Cosmos stir us—there is a tingling in the spine, a catch in the voice, a faint sensation, as if a distant memory, or falling from a height. We know we are approaching the greatest of mysteries." -Carl Sagan
If you looked out at the planets in the Solar System orbiting our Sun, you'd expect that if you know where they are right now and how quickly they're moving, you can figure out exactly where they're going to be at any time-and-date arbitrarily far into the future. That's the great power that comes…
esiegel | January 11, 2013"Every man has a right to utter what he thinks truth, and every other man has a right to knock him down for it." - Samuel Johnson
I have a six-sided die. I'm going to roll it ten times, and record each roll. And when I'm done, I'm going to have an incredibly rare, bet-you-can't-reproduce-it result!
Image credit: random.org's dice roller.
Look at that! Ten rolls of a six-sided die, and I got: 3, 2, 3, 5, 5, 5, 4, 1, 4, and 3! What a glorious, odds-defying sequence of events!
In fact, if you took a fair six-sided die and rolled it ten times, you'd have less than a 1-in-60,000,000 chance of…
esiegel | December 14, 2012"And in the end
The love you take
Is equal to the love you make." -Paul McCartney
Every once in a while, I throw the chance out there (on facebook, twitter, or google+) to ask me whatever questions you want. Yesterday, for some insane reason, I invited people across all three platforms to ask me whatever they liked, with a dual promise that I'd not only answer them, but that the best ones would receive a free "The Year In Space" calendar for 2013, courtesy of the Planetary Society.
Image credit: The Planetary Society.
So I got a ton of questions, and now I'll do my best to answer them as…
esiegel | December 7, 2012"If you wish to make an apple pie from scratch, you must first invent the Universe." -Carl Sagan
The Universe is a lot like an extremely intricate cake. We view it today as a snapshot in time, now that it's complete.
Image credit: Blogger user Hilly of http://makesbakesfakes.blogspot.com/.
We can view the whole thing from one point of view, determined by where we happened to be located. But we can also look intricately inside certain sections of it, so long as we have the right tools.
Image credit: Blogger user Hilly of http://makesbakesfakes.blogspot.com/.
But if we truly want to…
esiegel | December 6, 2012"Forget it. I didn't have that thing inside me where I wanted to smash against somebody and watch them break. I was too sensitive for that and disliked being that sensitive." -Josh Brolin
How do you figure out what something is made of? You take it apart -- cracking it open if necessary -- and look inside. This is something we've been doing since... well, since before our ancestors were even human.
Images credit: Elisabetta Visalberghi.
For most things here on Earth, that's easy enough. If you wanted to go down to the smallest scales possible, however, it becomes harder and harder to "crack…
esiegel | November 16, 2012"Other than the laws of physics, rules have never really worked out for me." -Craig Ferguson
Earlier this week, evidence was presented measuring a very rare decay rate -- albeit not incredibly precisely -- which point towards the Standard Model being it as far as new particles accessible to colliders (such as the LHC) go. In other words, unless we get hit by a big physics surprise, the LHC will become renowned for having found the Higgs Boson and nothing else, meaning that there's no window into what lies beyond the Standard Model via traditional experimental particle physics.
Image credit:…
esiegel | October 31, 2012"A cosmic mystery of immense proportions, once seemingly on the verge of solution, has deepened and left astronomers and astrophysicists more baffled than ever. The crux ... is that the vast majority of the mass of the universe seems to be missing." -William J. Broad
Despite the wondrous, luminous sights of the night sky, we've learned that normal matter -- protons, neutrons, electrons and the like -- make up only 4% of the total energy in the Universe.
Image credit: Large Suite of Dark Matter Simulations (LasDamas) simulation; Vanderbilt.
The galaxies and clusters of galaxies lighting up…
catdynamics | August 16, 2012Continuing slow live blog of the “New Particle Physics at the LHC and Its Connection to Dark Matter” workshop at the Aspen Center for Physics.
Series of short talks this morning:
"A WIMPy Baryogenesis Miracle" by
Yanou Cui, Lisa Randall, Brian Shuve (arXiv:1112.2704) interesting and possibly useful speculation on how electroweak scale WIMPs could couple to normal matter in early universe and actually generate some or all of the normal matter, in particular in such a way as to generate the observed matter/anti-matter asymmetry.
Aside: Quantum Diaries has the down and dirty details of the Higgs…
esiegel | August 9, 2012"Who are we? We find that we live on an insignificant planet of a humdrum star lost in a galaxy tucked away in some forgotten corner of a universe in which there are far more galaxies than people." -Carl Sagan
Our night sky, quite literally, is our window to the Universe.
Image credit: Miloslav Druckmuller, Brno University of Technology.
Well, it's kind of a window to the Universe. I say only "kind of" because, with the exception of those two faint, fuzzy clouds in the lower right, everything else visible in the image above is part of our own Milky Way galaxy. In fact, practically…
esiegel | July 18, 2012"The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge." -Stephen Hawking
The Universe is a vast, seemingly unending marvel of existence. Over the past century, we've learned that the Universe stretches out beyond the billions of stars in our Milky Way, out across billions of light years, containing close to a trillion galaxies all told.
Image credit: NASA, ESA, S. Beckwith (STScI) and the HUDF Team.
And yet, that's just the observable Universe! There are good reasons to believe that the Universe continues on and on beyond the limits of what we can see; the…
esiegel | April 27, 2012"And what I wanted to do was, I wanted to explore problems and areas where we didn't have answers. In fact, where we didn't even know the right questions to ask." -Donald Johanson
You can learn an awful lot about the Universe by asking it different questions than you asked about it previously. If all you ever used were your own senses, there would be an awful lot to learn, but you would be severely limited.
Image credit: Kerri Rankin Thoreson.
Even from the highest mountaintops, for example, you'd never be able to distinguish whether the Earth was round like a sphere or flat as a pancake,…
esiegel | April 19, 2012"Science progresses best when observations force us to alter our preconceptions." -Vera Rubin
I want you to think about the Universe. The whole thing; about everything that physically exists, both visible and invisible, about the laws of nature that they obey, and about your place in it.
It's a daunting, terrifying, and simultaneously beautiful and wondrous thing, isn't it?
Image credit: NASA, ESA, S. Beckwith (STScI) and the HUDF Team.
After all, we spend our entire lives on one rocky world, that's just one of many planets orbiting our Sun, which is just one star among hundreds of billions…
esiegel | March 5, 2012"I soon became convinced... that all the theorizing would be empty brain exercise and therefore a waste of time unless one first ascertained what the population of the Universe really consists of." -Fritz Zwicky
You very likely know that there are four fundamental forces in the Universe: gravity, electromagnetism, and the weak and strong nuclear forces. While only some particles experience the nuclear and electromagnetic forces, anything with mass or energy -- which is everything we know of -- is subject to gravity.
Image credit: CountInfinity by Ananth.
The strong nuclear force binds all…
esiegel | January 11, 2012"I soon became convinced... that all the theorizing would be empty brain exercise and therefore a waste of time unless one first ascertained what the population of the Universe really consists of." -Fritz Zwicky
Making the entire Universe isn't easy. Even with 13.7 billion years of time, general relativity and all the known particles in the Universe, we still can't reproduce all the observations we see today.
Image credit: Canada-France-Hawaii Telescope LenS team.
What does it take to get galaxies to form and cluster together the way they do in the Universe?
The large-scale structure in the…
esiegel | October 21, 2011"By now you must know that your father can never be turned from the Dark Side. So will it be with you." -Emperor Palpatine, Return of the Jedi
You've heard about dark matter. It's the notion that the Universe is somehow very much different than the small corner of it that we're most familiar with.
Photo credit: International Astronomical Union, retrieved from bbc.co.uk.
When we look at our Solar System, we can add up all the rocky planets, the gas giants, the asteroids, moons, and comets, as well as the entire Kuiper belt, and find out just how much of our neighborhood is dark.
And we can…
esiegel | October 11, 2011"The best way to escape from a problem is to solve it." -Alan Saporta
One of the greatest puzzles in the Universe today is just why the Universe is structured the way it is.
Image credit: Robert Gendler / Hubble Legacy Archive.
For the individual galaxies that we see, the puzzle is why they rotate at the speeds they do. If the only matter in these galaxies were normal matter (made out of protons, neutrons, electrons, etc.), the outskirts of these galaxies would rotate around their centers much more slowly than they actually do.
Image credit: Victor Andersen, University of Alabama, KPNO,…
esiegel | September 22, 2011"A fact never went into partnership with a miracle. Truth scorns the assistance of wonders. A fact will fit every other fact in the universe, and that is how you can tell whether it is or is not a fact. A lie will not fit anything except another lie."
-Robert Green Ingersoll
One of the most amazing facts to comprehend about the Universe is that it actually is comprehensible! A few basic laws, properties and particles, given our current understanding, can take us from a hot, dense, nearly uniform Universe to the complexity of the billions of stars within the billions of galaxies we see today…
esiegel | September 2, 2011"When you make the finding yourself -- even if you're the last person on Earth to see the light -- you'll never forget it." -Carl Sagan
When we talk about dark matter and its alternatives, we are talking about no less a task than explaining the structure of every large object in the Universe. This means every one of the billions of galaxies, including the way they form, merge, and cluster together.
Image credit: Mark Subbarao, Dinoj Surendran, and Randy Landsberg for the SDSS team.
On the largest scales -- where each pixel in the map above represents an entire galaxy -- dark matter blows…
esiegel | August 25, 2011"Fortunately for serious minds, a bias recognized is a bias sterilized." -Benjamin Haydon
You might look up at the night sky, at the vast canopy of stars we can see, and ask, exactly, what we're seeing?
Image credit: Jim at Pictures Of My Universe.
Thousands upon thousands of stars, of course, even with just your naked eye. These stars come in all sorts of different sizes, temperatures, and distances, and what we see in the night sky is largely determined by a star's brightness and distance from us.
All the stars you can see with your naked eye belong to one of the seven color classes of…
esiegel | August 18, 2011"The only relevant test of the validity of a hypothesis is comparison of prediction with experience." -Milton Friedman
Dark matter is one of the most important components of the Universe today. And yet in the public's eye, almost no one accepts it the way, say, the Big Bang is accepted. But it should be, and I'll show you why.
Image credit: NASA / ESA / Marc Davis.
I've talked before about what it took to convince me that dark matter was the best theory out there (and gave a simpler version here), but -- with alternative theories making big headlines -- it's important to truly know why dark…