dark energy
esiegel | October 17, 2014“I must choose between despair and Energy —— I choose the latter.” -John Keats
Yes, we know that the fabric of the Universe is not made up of space and time but rather a unified spacetime; that the spacetime isn't static but rather expands as the Universe goes on; and that the expansion isn't slowing down but is rather accelerating as we continue. The term we give to this phenomenon is dark energy, and we arrive at it via multiple, independent lines of evidence.
Image credit: Supernova Cosmology Project / Amanullah et al., Ap.J. (2010).
But with all of that, just what exactly is dark…
esiegel | October 2, 2014“The mind, once expanded to the dimensions of larger ideas, never returns to its original size.” -Oliver Wendell Holmes
But it isn't just your mind that expands as time goes on and you increase your knowledge, but the entire Universe as well. General Relativity, as it turns out, doesn't leave us with much of a choice. If you start with a Universe full of matter and radiation, it's got to expand, otherwise it will collapse in on itself!
Image credit: James N. Imamura of U. of Oregon.
But this expansion has consequences of its own, including the surprising fact that there's not only a finite…
esiegel | September 5, 2014“Why do people have to be this lonely? What’s the point of it all? Millions of people in this world, all of them yearning, looking to others to satisfy them, yet isolating themselves. Why? Was the earth put here just to nourish human loneliness?” -Haruki Murakami
Of all the ways our Universe can end -- recollapsing into a firey singularity, freezing out into a cold, icy void -- perhaps the scariest conceivable fate is one where galaxies are ripped apart, stripped of their stars, where planets come undone, molecules and atoms are torn away from one another and, at last, spacetime itself is…
esiegel | August 29, 2014“After all the ‘Universe’ is a hypothesis, like the atom, & must be allowed the freedom to have properties & to do things which would be contradictory & impossible for a finite material structure.” -Willem de Sitter
Dark energy was one of the biggest surprises to come along in the past generation, from a scientific standpoint. It's only intuitive to think that the Universe -- with gravity fighting the initial expansion ever since the Big Bang -- and all the galaxies in it would continue to slow down over time. But with a significant positive amount of energy inherent to space…
esiegel | July 11, 2014“It is always wise to look ahead, but difficult to look further than you can see.” -Winston Churchill
There's plenty to learn about, to see and to discover when we look out at the Universe today. From the leftover glow from the Big Bang in the microwave to the hundreds of billions of galaxies and the tremendous variety of stars in our galaxy and others, there's no shortage of mysteries to solve and curiosities to uncover.
Image credit: NASA, ESA, the GOODS team and M. Giavalisco (STScI).
But what if we, instead, came about in this Universe 100 billion years from now? How would we perceive…
esiegel | June 3, 2014“I realise now that I wanted to disappear. To get so lost that nobody ever found me. To go so far away that I’d never be able to make my way home again. But I have no idea why.” -Jessica Warman
When you think about the galaxies up there in the night sky, only visible with the most powerful telescopes in the world, it also behooves us to think about how incredibly rapidly they're moving.
Image credit: Tony Hallas of Astrophoto.com, via http://apod.nasa.gov/apod/ap070719.html.
As the Universe expands, the space between us and them expands as well, causing an incredibly fast apparent…
esiegel | February 21, 2014“If you put yourself in a position where you have to stretch outside your comfort zone, then you are forced to expand your consciousness.” -Les Brown
On the one hand, you've got gravitation, the most powerful force in the Universe, trying to attract all the matter in it together. If it had its way, not only would everything eventually merge together, but the Universe itself would recollapse!
Image credit: Eugenio Bianchi, Carlo Rovelli & Rocky Kolb, modifications by me.
But on the other hand, the Universe is not only expanding, but that expansion is accelerating, thanks to the presence…
esiegel | February 14, 2014"For the wise man looks into space and he knows there is no limited dimensions." -Lao Tzu
You know the deal: it's the end of the week, so it's time for another Ask Ethan! You've continued to send in your questions-and-suggestions, much to my delight, and I'm pleased to tell you that this week's question comes from Peter Tibbles. Peter asks about obtaining information from beyond where Einstein's theory of relativity allows us to see:
Because of the expansion of the universe there is an event horizon beyond which we can know nothing. There’s been one instance of intelligent life evolved (us);…
esiegel | December 5, 2013"Some say the world will end in fire,
Some say in ice.
From what I've tasted of desire
I hold with those who favor fire.
But if it had to perish twice,
I think I know enough of hate
To say that for destruction ice
Is also great
And would suffice." -Robert Frost
Depending on where you are in the world right now, you might really be feeling the effects of the emerging winter, as cold snaps, freezes and snowstorms take hold across the northern hemisphere.
Image credit: NASA's Scientific Visualization Studio, Goddard Space Flight Center.
But we can all be pretty sure that this is temporary,…
esiegel | September 5, 2013"One sees qualities at a distance and defects at close range." -Victor Hugo
A couple of weeks ago we took a look at the most distant galaxy (so far) in the known Universe, a galaxy so far away that it takes exclusively infrared observations from our most power space telescopes (Hubble and Spitzer) in order to detect it. What's perhaps even more remarkable is that the light we do detect from it -- the light we detected in the infrared -- was actually emitted in the Ultraviolet part of the spectrum!
Image credit: NASA, ESA, Garth Illingworth (University of California, Santa Cruz) and Rychard…
catdynamics | July 18, 2013Simon White Director of Max Planck Institut für Astrophysik giving today's Physics Colloquium at ACP on the Planck Results
Likely to be interesting, hence the semi-liveblog.
Starts with description of the collaboration and historical perspective; Penzias and Wilson, COBE and WMAP
Cute ESA video showing Planck science
Even better ESA video explaining stuff
Very good description of baryon acoustic oscillations and polarization.
Quick glimpse of stacked and normalized Planck measurements of tangential/radial polarization of cold/hot spots at ~ 1 degree scales.
Nice animation blinking weak…
esiegel | May 23, 2013“Because dark energy makes up about 70 percent of the content of the universe, it dominates over the matter content. That means dark energy will govern expansion and, ultimately, determine the fate of the universe.” -Eric Linder
It's been a while since we've spoken about dark energy, and we were just talking about Einstein's greatest blunder, so let's just dive right in.
Image credit: S. Beckwith & the HUDF Working Group (STScI), HST, ESA, NASA.
This is our observable Universe, as unveiled by the Hubble Space Telescope. With hundreds of billions of galaxies stretched out some 41…
esiegel | May 17, 2013"Anyone who has never made a mistake has never tried anything new." -Albert Einstein
Back when Einstein first proposed his theory of General Relativity, his revolutionary picture of the Universe was met with a mix of curiosity, awe, and intense skepticism. It isn't every day that your most cherished of all physical theories -- the theory of Newtonian Gravity that had ruled the cosmos for nearly two-and-a-half centuries -- gets challenged by a newcomer.
Image credit: Brooks/Cole - Thomson publishing, 2005.
And yet, that's exactly what Einstein did when he proposed General Relativity at the…
esiegel | May 8, 2013"No valid plans for the future can be made by those who have no capacity for living now." -Alan Watts
"They do not see what lies ahead, when Sun has faded and Moon is dead." -J.R.R. Tolkien
One of the most amazing facts about the Universe is that, despite only having spent a few hundred years studying the fundamental constituents and forces of what makes us up, humanity has been able to accurately figure out just what all this actually is.
Image credit: ESO / S. Brunier.
The laws of nature are almost completely understood in a few, very important senses. We know that our Universe is about…
esiegel | April 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
One of the greatest things we can do -- when we study and learn the story of the Universe -- is simply to tell that story, as best as modern science allows us to. Earlier this week, I had a chance to do this in front of a small, intimate audience at the Hand-Eye Supply Curiosity Club here in Portland…
esiegel | April 12, 2013"Orbiting Earth in spaceship, I saw how beautiful our planet is. People, let us preserve and increase beauty, not destroy it!" -Yuri Gagarin
Fifty-two years ago today, the first human being left Earth, and we began our journey into outer space. But back in 1961, we didn't really know how far outer space stretched, or where all the matter and energy in the Universe came from.
Image credit: NASA, 1962.
That all changed with the discovery of the Cosmic Microwave Background (by Penzias and Wilson, with the Horn Antenna, above), and subsequent measurements that led us to the Big Bang picture of…
esiegel | April 10, 2013"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
Three classic observations -- the Hubble expansion of the Universe, the leftover cosmic microwave background radiation, and the observed abundance of the light elements -- lead us inevitably to modeling our Universe as having begun in a hot, dense state from which it expanded and cooled. There is no other explanation that agrees…
esiegel | March 27, 2013"The radiation left over from the Big Bang is the same as that in your microwave oven but very much less powerful. It would heat your pizza only to -271.3°C, not much good for defrosting the pizza, let alone cooking it." -Stephen Hawking
One of the most powerful predictions of the Big Bang -- the fact that our cold, star-and-galaxy-rich, slowly-expanding Universe came from a hot, dense, much more homogeneous state -- was the existence of a bath of leftover radiation that should be detectable, even today.
Image credit: Pearson / Addison Wesley, retrieved from Jill Bechtold.
Back when the…
esiegel | March 21, 2013"Much later, when I discussed the problem with Einstein, he remarked that the introduction of the cosmological term was the biggest blunder he ever made in his life. But this “blunder,” rejected by Einstein, is still sometimes used by cosmologists even today, and the cosmological constant denoted by the Greek letter Λ rears its ugly head again and again and again." -George Gamow, the father of the Big Bang model
The Big Bang -- the prediction that the Universe started from a hot, dense, rapidly expanding state -- tells us where our cold, star-and-galaxy-rich, slowly expanding Universe full of…
esiegel | March 20, 2013"Scientific discovery and scientific knowledge have been achieved only by those who have gone in pursuit of it without any practical purpose whatsoever in view." -Max Planck
Tomorrow morning, at 8 AM my time, the press conference that cosmologists have spent the past decade waiting for will finally happen, and the Planck satellite -- the most powerful satellite ever to measure the leftover radiation from the Big Bang -- will finally unveil its results about the origin and composition of the Universe.
Image credit: ESA / LFI and HFI Consortia.
They've figured out how to subtract the…