dark energy
esiegel | October 6, 2011"Deep into that darkness peering, long I stood there, wondering, fearing, doubting, dreaming dreams no mortal ever dared to dream before." -Edgar Allen Poe
Earlier this week, the Nobel Prize in Physics was announced for the discovery that the Universe is not only expanding,
but that this expansion is accelerating!
What does an accelerated expansion physically mean?
If all you had in the Universe was some initial expansion and the mutual gravitational attraction of everything in it, you'd expect that as an object got farther and farther away from you, over time, its apparent motion away from…
esiegel | October 4, 2011Some 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
Ever since the discovery of the radiation glow left over from the initial hot, dense state of the Universe -- the cosmic microwave background -- the Big Bang has proven to be the best description of the early Universe.
Image credit: Stephen van Vuuren.
This hot and dense initial state has, for the past 14 billion years, been expanding…
esiegel | July 29, 2011"It has been rightly said that nothing is unimportant, nothing powerless in the universe; a single atom can dissolve everything, and save everything! What terror! There lies the eternal distinction between good and evil." -Gerard De Nerval
(For Rich C. and Sili, for their questions on this post.)
The humble hydrogen atom -- one proton and one electron, bound together -- is the most common form of normal matter in the entire Universe. When you look out at all the galaxies in the Universe, what you're seeing is predominantly light coming from those simple hydrogen atoms fusing together at the…
esiegel | May 20, 2011"We all need to look into the dark side of our nature - that's where the energy is, the passion. People are afraid of that because it holds pieces of us we're busy denying." -Sue Grafton
No, not the dark side of our nature, just the dark side of nature! Because if all our Universe were made out of were atoms and photons, we wouldn't get a Universe that looks like ours.
What do I mean? Let's take a look.
Image credit: MPA Garching and Volker Springel.
The Universe starts off as a very smooth place, where regions that are denser or less dense than average are only something like 0.003% away…
esiegel | May 16, 2011Some 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
Sure, if all we're talking about is the Earth, that one's a no-brainer. It's fire.
Our Sun, very slowly, is burning up its Hydrogen fuel into Helium, through the process of nuclear fusion. But over the course of billions of years, it starts to burn its remaining fuel at an ever increasing rate. Over the next billion or two years, the…
esiegel | April 14, 2011"All of nature begins to whisper its secrets to us through its sounds. Sounds that were previously incomprehensible to our soul now become the meaningful language of nature." -Rudolf Steiner
For millenia, humans have looked to the heavens for answers about the cosmos.
Image credit: ESO/S. Guisard.
And one of the main reasons I write what I do for all of you is to help give you -- as I've said many times -- is an awareness and an appreciation for what we've learned, what we think we know, and how we think we know it.
Which is why I was a little bit confused when I read this article from…
catdynamics | January 13, 2011So all good things must come to an end, and the 3000 or so astronomers disperse from SEA-TAC to destinations worldwide.
It was a good meeting, though light on major announcements.
I have a backlog of press releases that I may or may not get round to picking over.
Some nice pretty pics in there.
Think I did ok for myself, we'll see how it goes.
As we were wrapping up and heading for the last couple of exoplanet sessions, John (no not that John, the other John) pointed out a couple of poignant remnants
Wery Silli
The large astrophysics missions were doing Silli Band swag:
a LISA constellation…
esiegel | December 30, 2010"There is only one corner of the universe you can be certain of improving, and that's your own self." -Aldous Huxley
Earlier this week, I told you the story of how we went from a Universe that was -- at one time -- almost perfectly smooth, full of tiny, random fluctuations in density,
to the Universe we have today, full of stars, galaxies, and clusters of galaxies all clumped together in a beautiful cosmic web of structure.
But there was one picture I showed that generated a lot of questions. I put up an image showing what the Universe was made out of today (when we have this great cosmic…
esiegel | November 19, 2010"I came at exactly the right time... I was 26 years old, and all the monks and priests down here were ready to retire. So I overlapped enough that I got to know them all." -Allan Sandage
As many of you have heard, Allan Sandage passed away last Saturday. Let me tell you a little bit about this man, why he stands as such a towering figure in modern cosmology, and why he should be held in even higher esteem than he normally is.
Allan Sandage was a coworker of Edwin Hubble's, and he took up one of the most pressing questions of the day after Hubble's death in 1953: What is the Age of the…
esiegel | August 30, 2010"The whole fabric of the space-time continuum is not merely curved, it is in fact totally bent." -Douglas Adams
As many of you know, if you take a whole bunch of mass, and you've got nothing going on except gravity, it's going to gravitationally collapse. And if atoms, nuclei, pressure, and nuclear reactions don't (or can't) prevent that gravitational collapse from running away, you're going to wind up with a black hole.
But last week, I told you that if you took all the matter in the Universe and shaped it into a cylinder, you'd actually wind up with a huge cylinder of solid matter, as big…
drorzel | July 14, 2010With the rumors of a Higgs Boson detected at Fermilab now getting the sort of official denial that in politics would mean the rumors were about to be confirmed in spectacular fashion, it's looking like we'll have to wait a little while longer before the next "Holy Grail" of physics gets discovered.
Strictly speaking, the only thing I recall being officially dubbed a "Holy Grail" that's been discovered was Bose-Einstein Condensation (BEC), first produced by eventual Nobelists Carl Wieman and Eric Cornell in 1995. Somebody, I think it was Keith Burnett of Oxford, was quoted in the media calling…
esiegel | June 28, 2010The task is not so much to see what no one yet has seen, but to think what no body yet has thought about that which everyone sees. -Arthur Schopenhauer
Most of you who've been reading Starts With A Bang for a while have seen this picture come up many, many times.
Why do I keep putting it up, and why is it so important?
Let's go back to the 1960s for a little bit. Back then, there were two major rival theories about the origin of the Universe: the Big Bang theory and the Steady-State model of the Universe. The Big Bang contended that the Universe was hotter and denser in the past, and thus of…
esiegel | April 9, 2010"Cosmologists are often in error, but never in doubt." -Lev Landau
I've been telling you about the Big Bang, the greatest story ever told, and the entire natural history of the Universe. Let's remind you -- historically -- of how our conception of the Universe changed as we learned more about our surroundings.
Maybe the first astronomical observation ever made was that the Sun rises in the East, passes overhead, and sets in the West. And it does this day after day, every day. It's no wonder that our first "cosmological model" of the Universe was that the Earth is stationary, and the Sun…
esiegel | February 22, 2010Free energy will promulgate a forward leap in human progress akin to the discovery of fire. It will bring the dawn of an entirely new civilization -- one based on freedom and abundance. -Sterling Allan
Of course, when Sterling Allan talks about free energy, he's talking about natural energy from sources like wind and solar, not the violating-the-laws-of-thermodynamics type of energy.
There is, of course, no such thing as truly free energy, or energy that we can take out of nothing and use for something, which is why perpetual motion machines not only don't work, but are physically impossible…
esiegel | January 15, 2010This is what science is all about; getting thrown a curveball by Nature and plunging in to find out what's going on. -Andy Albrecht
Imagine waking up in the morning and heading out into the sand dunes. They never look exactly the same from day to day. But each day that you go out, they'll look somewhat like this.
You consider yourself smart and well-informed, and you have a sense of adventure. So each morning, you venture out a little farther into the dunes. You find a variety of different features, but everything pretty much just looks like, well, sand dunes. One day, however, all of that…
esiegel | November 30, 2009Follow humbly wherever and to whatever abyss Nature leads, or you shall learn nothing. -T.H. Huxley
We've spent a little bit of time talking about dark energy, including what we think of it, how we first discovered it, and how we knew that there wasn't just something out there blocking the light. It seems to be the latest abyss that Nature is leading us, so we needed to look beyond the type Ia supernova data and see what else the Universe was telling us.
Image credit: Don Dixon.
So what do we do? First off, we can try to measure how much matter is in the Universe independent of anything…
esiegel | November 11, 2009Though the Sun is gone, I have a light. -Kurt Cobain
Last time we visited dark energy, we discussed its initial discovery. This came about from the fact that supernovae observed with a certain redshift (i.e., moving away from us) appear to be systematically fainter than we were able to explain.
But we weren't satisfied with simply saying that there must be dark energy. We asked a lot of critical questions about why these supernovae might appear so faint.
First off, we asked the question, "Could these supernovae from far away be different than the type Ia supernovae we have today?"…
esiegel | November 5, 2009Last time, we talked about the discovery of dark energy. How did it happen? Well, there are certain kinds of Supernovae, type Ia supernovae, that are practically identical to one another all across the Universe. In fact, we had one happen in our own galaxy in 1572; it outshone everything besides the Moon in the night sky for weeks.
How do type Ia supernovae work? Many solar systems out there are like our own, with one star dominating the system. Others, however, have two or more stars present in the system. Stars up to about four times the mass of our Sun, when they finish burning their…
esiegel | November 4, 2009Once you can accept the Universe as being something expanding into an infinite nothing which is something, wearing stripes with plaid is easy. -A. Einstein
But accepting the expansion of the Universe is easy compared to accepting the existence of dark energy. Why -- and how -- is there some mysterious property inherent to space that prevents the expansion rate from dropping to zero? Why is the expansion rate as large as it is today? Why, of the four options we can reasonably conceive of, is the Universe obeying this "accelerating" picture below?
The why and how are questions that we do not…
esiegel | August 5, 2009Last week, we began talking about understanding the size of the Universe, and we continued this week with some information on distances and motion in the Universe. This brings us to my favorite application, which leads to the Hubble expansion:
Redshift. You see, whenever an atom or molecule emits light, it gives off that light at a very few particular wavelengths. For instance, if you have hydrogen, you'll always get light at wavelengths of 656 nanometers (red), 486 nm (cyan), 434 nm (indigo), 410 nm (violet), and 397 nm (on the border of violet/ultraviolet):
Now there are three things --…