Radio Astronomy Unmasks Early Universe

Dave on Earth (5:15 PM): Hello Dr. Wolfe!
Dave Mosher with Discovery Space here. Where is "here" for you right now?

RadioAstro4Life (5:18 PM): Right now I'm sitting at my desk in my office at the University of California San Diego

Dave on Earth (5:18 PM): What's it like outside your window?

RadioAstro4Life (5:19 PM): The weather is great today, I even went for a swim in the University pool this morning.

Dave on Earth (5:20 PM): You were recently recognized for your ground-breaking work in astronomy with the 2008 Karl G. Jansky Lectureship.
So that means you're a great astronomer AND a great swimmer?

RadioAstro4Life (5:20 PM): I don't know about great. But I enjoy swimming and I enjoy astronomy, optical as well as radio.

Dave on Earth (5:21 PM): What's the difference?

RadioAstro4Life (5:22 PM): Both optical and radio astronomy depend on "seeing" electromagnetic waves.
The difference: Radio waves are much longer than optical waves, and optical wavelengths are only 1/10,000th of a centimeter long (which we see as light). The radio waves I work with are 30 to 50 cm in length.
And of course they can be far longer than that.

Dave on Earth (5:24 PM): Why 30cm to 50cm -- what does that niche help us see?

RadioAstro4Life (5:25 PM): One advantage is that they can be used to detect hydrogen in galaxies (neutral hydrogen, to be precise)
Radio waves travel easily through interstellar dust, whereas optical waves get absorbed.

Dave on Earth (5:25 PM): So radio waves about as long as my forearm penetrate all the grit between the Earth and distant objects, and allow us to see it?

RadioAstro4Life (5:27 PM): Yes, they do. This part of the radio wave spectrum helps us map hydrogen between stars in galaxies.
In my case I study very distant galaxies; i.e., galaxies 2 to 3 billion years old (whose current age is about 12.7 billion)

Dave on Earth (5:28 PM): Ah, because light can take billions of years to reach us from distant objects.
So these newborn (but now very old) galaxies... What story do they tell us about the universe?

RadioAstro4Life (5:29 PM): They're telling us that far back in time, most of the ordinary matter in galaxies was diffuse gas -- not stars.
I've been trying to figure out the processes by which that gas turns into stars.

Dave on Earth (5:29 PM): Any ideas?

RadioAstro4Life (5:30 PM): Well, early in time the Universe was exceedingly smooth -- the gas was spread out pretty evenly. The smoothness in the maps of the cosmic background radiation tell us this.
But little ripples in the temperature of this radiation tell us there were some irregularities in gas density
Ray Sachs (U. C. Berkeley) and I worked out how those variations translated into density in 1967.

Dave on Earth (5:31 PM): I hear you and Sachs have an effect named after you...

RadioAstro4Life (5:31PM): Yes, this is the Sachs-Wolfe effect.
As the universe expands, these little ripples eventually build up like cars piling up on a bridge, until the bridge collapses under its own weight. Galaxies, clusters of galaxies, super clusters of galaxies, and so on are formed from such events.

Dave on Earth (5:33 PM): How does one go about getting a universal effect named after them?

RadioAstro4Life (5:33 PM): I think the effect was first named by Jim Peebles (Princeton) the father of modern cosmology. Might want to ask him!

Dave on Earth (5:33 PM): Back to "how do we get stars from gas?"

RadioAstro4Life (5:34 PM): Right. Stars form out of cold gas in galaxies, in clouds that look something we see in the distant parts of the universe.
I need to say that I've been mainly studying them with optical techniques using the Keck 10-meter telescopes in Hawaii. But radio astronomy recently reeled me back in.
My colleagues and I -- for the first time -- showed some of this gas actually generates magnetic fields.

Dave on Earth (5:36 PM): Well that seems kind of odd...

RadioAstro4Life (5:37 PM): Yes, and it's not weak. It's very large, and we are trying to understand this puzzle.

Dave on Earth (5:37 PM): What does this mean for people back on Earth?