Field of Science

Hubble Ultra Deep Field Part II

The Hubble Ultra Deep field realized in 3D:
and the scientific image:
The Hubble Ultra Deep field is a 3 dimensional snapshot of our Universe, like a deep ice core taken from Antarctica, it has secrets which are frozen in time by the finite travel speed of light. Each galaxy is literally a frame of the time when the photons from that galaxy began their journey to our detectors on the Hubble Space telescope. The most distant galaxies visible in the image are the small red galaxies which existed when the Universe was just some 400 to 800 million years old; the larger bluer spiral shaped galaxies are snapshots when the Universe was some 13 billion years old. I should point out that the 'interesting' objects in the HUDF are galaxies; the few objects which are point like (and diffracted) are foreground stars in the Milky Way (the patch of sky selected for the HUDF is towards the constellation Fornax and was selected precisely because it was so devoid of stars). These stars are extremely close compared to the galaxies, they are like smudges on an airplane window as you gaze upon the landscape below.

I am now going to attempt to describe the canonical history of a galaxy seen in the Hubble Ultra Deep field. I will discuss the cosmic epochs, describe how the galaxies in the the HUDF formed, and what they tell us about the Universe. The image below displays graphically the cosmic epochs.
This illustration shows the cosmic epochs of our Universe from the Big Bang to the Present. The position of galaxy A1689-zD1 is shown as an example of a particularly early forming and distant galaxy. Image credt NASA, ESA, and A. Feild (STScI).

I. Big Bang
It began with nothing (or did it... see video below). No time. No space. No concepts and no questions to ask. Then approximately 13.7 billion years ago the Universe began; time and space were created. During the process known as inflation the Universe expanded exponentially and random quantum mechanical fluctuations in space time seeded the Universe with over dense regions which would later be the starting point for the formation of galaxy clusters. The flood of free energy in the Universe led to the spontaneous creation of particles via Einsteins famous equation.
From pure energy we obtained the fundamental particles and the forces of nature. The Universe cooled and from a fundamental particle soup formed electrons, protons, neutrons, and other familiar particles. These particles fused together in the process of Big Bang nucleosynthesis to form mostly Hydrogen and Helium. This all happened within the first 3 minutes or so of the Universe. This video below briefly describes the Big Bang and other possibilities.

At this time the Universe was in the radiation epoch. Photons were constantly interacting with particles (the Hydrogen was ionized, that is electrons and protons) through Thomson scattering, but as the Universe cooled these interactions became less likely to occur. When the Universe was approximately 370,000 years old we can say in a statistical sense that the photons scattered for the last time. In a cosmological phase transition known as recombination protons captured electrons to form neutral hydrogen. Photons began to travel freely through space and these photons constitute what we now call the cosmic microwave background radiation.

II. Dark Ages
The Universe was suddenly a lonely place. There were no stars or galaxies at this time and nothing was emitting any light, only the glow of of the cosmic background radiation was present. There was lots of matter in the form of neutral hydrogen, but mostly there was dark matter which was gravitating. The dark matter formed clumps at the same sites where quantum mechanical fluctuations had occurred during inflation. The Hydrogen and other normal matter followed the Dark Matter closely. As more matter began to aggregate at certain locations in space it attracted even more matter to that location in a runaway process such that massive clumps of matter began to dominate. Some regions of space became very under dense and formed voids. Other regions became very over dense. The dark ages lasted for about 400 million years, and then the conditions were right for there to be light again.

III. First Stars and Galaxies
The dark ages may have been dark, but the first stars in the Universe were spawned from the over dense regions that were forming during the dark ages. That is what was happening during the dark ages ignited the first stars. As matter gravitationally bound itself together tighter and denser it heated up to the point at which it could sustain nuclear fusion. These first stars, known as Population III stars, were hundreds of times more massive than our sun and they burned up extremely quickly. In their brief life time they created (they started shinning using only the abundant fuels available after big bang nucleosynthesis: hydrogen and helium, but as they exhausted these fuels they 'burned' successively heavier and heavier elements in their cores) many of the elements found in the periodic table up to iron and then these stars extinguished themselves as supernovae. These stellar explosions seeded the surrounding medium with heavy elements and the cycle repeated forming later generations of stars. The first star ionized the neutral hydrogen in their vicinity; hydrogen was blasted apart into free electrons and protons as it had been before recombination. Each star formed an ionizing bubble around it that grew and merged with other ionizing bubbles to form galaxies composed of a single monolithic bubble of ionized Hydrogen. Hierarchically the ionized bubbles of galaxies merged with other galaxies in their local cluster and ultimately the ionized bubbles around each cluster merged to form an ionized intergalactic medium around super clusters and eventually the entire Universe was ionized. In the simulation video below we begin by seeing a cube of t the Universe in a completely unionized state and we witness the bright ionizing bubbles expanding and merging.

A numerical simulation of cosmic reionization in a box 100/h Mpc, beginning at redshift z=20 and ending at z=8. Produced by Marcelo Alvarez, Ralf Kaehler, and Tom Abel, Kavli Institute for Particle Astrophysics and Cosmology, Stanford University.

This process of reionization was a gradually process that heralded the epoch of the first galaxies. At the center of the ionizing bubbles were generations of stars in groups of billions forming the young galaxies in the HUDF. The galaxies that appear to be interacting in the image are likely the very young galaxies before much order and structure and time to form. Galaxies evolved and formed relatively quickly in the Universe such that most of the important formation had occurred within a billion years of the big bang.

IV. Galaxy Evolution to Present
Galaxies continued to mature, merge, and collide in the next 12 billion years, but the major formation of entirely new galaxies was largely complete. It is hard to trace the evolution of a single galaxy for the next 12 billion years up to the point at which it was imaged in the HUDF, but the story I have told holds true for every galaxy seen in the HUDF. And remember from the the 3D HUDF video that some galaxies are distant and are seen as they were when they were very young and so the whole story has been told for these galaxies. The HUDF shows us what galaxies have looked like during each stage of their evolution. I have discussed up to this point the evolution of the Universe as a whole; I should also point out that some where along the way, towards the end of this timeline, there was the evolution of man, the scientific revolution, and the construction of the Hubble Space Telescope. Then people began to ask where did we come from? Why are we here? And where are we going?

V. The Distant Distant Future
Nobody knows what the future holds, but if Dark Energy continues its domination of space time the Universe may end in either in Heat Death, the Big Rip, both, or something entirely unexpected. What would we see or perhaps aliens see in the distant future if they created a new HUDF? If the Universe continues its Dark Energy driven accelerating expansion then eventually galaxies will be beyond our visible horizon and the image would be incredibly stark. This may be reason to enjoy our image all the more.

Semi-analytical or semi-numerical

Some people think that asking whether the glass is half full or half empty is a deep and telling question; these people may also think that banal is a country. Scientists also play this little game sometimes when describing their work. Some science is numerical (of or pertaining to numbers; of the nature of a number). Some science is analytical (pertaining to or proceeding by analysis). Many scientists claim that their work is semi-analytical or semi-numerical. The prefix semi may be defined as precisely half (as per its original etymology), but here it must be used meaning partially or quasi. These definitions are useless because in the context of the 'hard' sciences, every shred of research is based on numbers (so it must be numerical) and every number is scrutinized and extrapolated (so it must be analytical) to relevant cases with theory. In conclusion all work is numerical and analytical, but it can't be 100% either so all work is semi-analytical and semi-numerical. Thus the actual labeling of research under one category or the other is useless.

In colloquial scientific usage numerical seems to apply when the research has reached some arbitrary threshold where the number of lines of code is much greater than the number of equations used. So maybe numerical means

Except, this definition seems necessary but not sufficient because if your doing observations then you probably also meet this criteria doing the data reduction. So really, numerical means that the result you derive cannot be proven with a single succinct analytical equation (though the correlations found may be analytical the proof of such correlations cannot be proven analytically). For example the four color theorem has only been proven using a computer-assisted proof. Some mathematicians fundamentally object to putting their trust in computers over the logical deductions of humans, and yet the four color theorem stands proven only by computers.
And so colloquially most scientists would be content to say that the four-color theorem or simulations (thought the comparison of these kinds of research together is dubious) done in the physical sciences are numerical. Scientists seem to think their research leans one direction or another on the analytical/numerical spectrum (also, I have no idea if this is standard or just my interpretation, but as I have seen it research is normally described as being semi with respect to the lesser used approach; that is research that is primarily analytic and only uses a tiny bit of numerical work is described as semi-numerical), but the distinction seems delicate given accepted modern scientific approaches . Upon cursory examination it is all semi-numerical or semi-analytical and the difference well the difference makes no difference all, but that isn't true is it?


Mark Devlin recently appeared on the Colbert Report. Devlin's project the Balloon-borne Large Aperture Submillimeter Telescope, BLAST, was the subject of the well received documentary Blast! It is still screening at select theatres across the world. Catch the trailer below.

Hubble Ultra Deep Field Part 1

The Hubble Ultra Deep Field (HUDF) was a major inspiration in my decision to study astronomy. The image is simply breathtaking. The video above presents a broad overview of the science of the HUDF very well, but in my next post I will attempt to take a closer look at the subtleties of what is going on here.

Perseid Meteor Shower

Perseids Meteor Over the North Cascades. Image by Fort Photo
The Perseid meteor shower occurs annually as the earth crosses the debris wake of comet Swift-Tuttle. Look towards the constellation Perseus this week and you may spot shooting stars spewing forth towards you (if you are in the northern hemisphere). The shower peaks August 12th and 13th, but because of city lights and the (waning) gibbous moon it may be hard to get a good view. The Moon may down any chance of seeing shooting stars when you look up, so one trick is to look before the moon is up. The moon will rise an hour or so after dark, so early in the evening you may actually have the best chance to view spectacular and bright earth grazers; earth grazers are meteors that skim along the top of the earth's atmosphere resulting in horizontally traveling overhead meteors (as opposed to downward traveling for most meteors in the shower). The moon will continue to wane this week and because the peak of the shower is extended over several nights there may continue to be frequency meteor viewing even Thursday or Friday evening. Each night the shower has peak activity hours which are 11 p.m. to dawn so you may hear contradictory advice to look after 11 p.m. or to look early; what you should do is simply look often. To see the meteors simply find a dark open view of the sky and look towards Perseus in the northeast as indicated in the star chart below and be patient. I have seen hundreds of shooting stars in my time, but most of them were not during a famous meteor shower event. Simply look up and observe on any night and good things will come.

Update: Un artículo excelente en español, Perseidas: un regalo caído del cielo.

Marx is claiming it was offside

Hegel is arguing that the reality is merely an a priori adjunct of non-naturalistic ethics, Kant via the categorical imperative is holding that ontologically it exists only in the imagination, and Marx is claiming it was offside.

McSweeney's Lists



She exposed me to excessive ultraviolet radiation, which gave me terrible cataracts.

She removed all traces of vitamin A from my diet.

She launched well-targeted projectiles at my eyes, causing severe trauma.

She poisoned me repeatedly with steroids, which over time caused the formation of a pituitary tumor that pressed against my optic chiasm severing my optic-nerve pathways.

She replaced my contact-lens solution with corrosive acid.

She unleashed upon me lab rats trained to preferentially eat eyes.

She, my ophthalmologist, botched my Lasik surgery.

She exacerbated my diabetes by replacing my insulin with Frappuccino, which led to retinal problems.

She put me under general anesthesia and surgically removed my eyes.

She altered my parents' germ-cell chromosomes before my conception so that I lack the proper genetic code to distinguish the colors red and green.

She calibrated a refraction experiment with her laser pointer that scorched my retinas.

Other great lists from McSweeney's to enjoy:


To Octavio Paz

It looks like the NASA STEREO mission is continuing to not only study our closest star, but also inspire artists. Some lines from The Broken Jar by Octavio Paz,
A world of spin and flame is born in the head of the dreamer, blue suns, green whirlwinds, bird beaks of light pecking open the pomegranate stars
In this next film scientists at UC Berkeley talk about their research and the secret lives of invisible magnetic fields are revealed as chaotic ever-changing geometries,
Photons take hundreds of thousands of years to random walk there way from the core [of the sun] all the way out to where we see them in the photosphere yet in a millionth of second a [magnetic field line] reconnection completely changes topology of the corona