This is a continuing journal to try to understand the rudiments of cosmology. I'm not organized, so ti may be jumpy: no apologies, this blog is my scratchpad! (Maybe I should use google docs for this instead.)

Anyway.

1/Ho =13e9yr, they say.

Cephid variable stars pulse in proportion to their luminosity (so the latter is easily known). These luminosities then can be used to calculate range. Velocity of course is known from redshift, and thus we can correlate one to the other. Range x Ho = V. A good (terse and childish) explanation of the universe's age is here, at the WMAP satellite site. WMAP calls the universe 13.7b yrs old.

Nucleosynthesis in the early universe considers the relative expected proportions of elements as a function of how hot it was. ("Hot" being the relative proportion of energy to mass in the early universe.) This plot, from about 3 minutes? shows the ratio of He to other elements eg Li, we find now, & thus calibrates the early energy density. They believe all the heavy elements were formed in stars or supernovae.

The Inflaton Field Theory supposes something more violently expanding happened right at first, as an answer to the problem of relics (where are the magnetic monopoles a hot cosmic soup would have created?) and the problem of flatness (some stars look older than 1/Ho)

Just some numbers...

• Critical density is 5 protons / m^3, and we are nowhere near that: where is it all? This is the motivation for the search for dark (unseen) matter & energy.
• Planck density = 10^93gm/cm^3
• Age of universe 13.7b yr
• Age of transparency 350,000 yr. (? ...from memory)
• Black hole density= (1.8x10¹⁶ g/cm³) x (M_sun / M)² ,usually M is 10x solar masses.
• Schwarzchild radius= (3x10⁵ cm) x (M / M_sun), this, from here.

THE horizon.

This is going to be a cosmology post. It will take a while to get up.
First some credit to Ned Wright, prof of Cosmology at UCLA. I'm mostly just trying to understand and interpret his excellent tutorial web site.

Ok, here we go. Beginning with a picture from the tutorial...

What we see above is a pitcure of the universe! Time is the up-down dimension and distance is the right left dimension. Each of the (almost) straight black lines is for a different observer, at a different place in the universe. Each of the different observers is moving away at a different speed, harking back to the big bang at the bottom when they were all colocated.

"Moving away from where?" you can ask, and the answer is "From me!" ...or from anyone. All viewpoints in the regularly expanding universe are equivalent. He shows that by skewing the frame of reference in this picture. The observer at "A" feels he is unmoving, so his line of position over time is straight, whereas the line showing "us" has relative motion.

There's a lot more to say by way of explaining this diagram, and I will try to get to it soon, but want to get my questions down first.

1) If it's the same for all observers, then everyone should see the same thing, right? That means both we and A should see the same CMB radiation, though we have dramatically different velocity. It is tempting here to say different absolute velocity but is there such a thing? If there's absolute velocity vs CMB, then there's a center: a preferred location in the universe and the point of this diagram is that that's not so. But (here's the question at last) if there is no preferred center, then there is no absolute velocity, and then seemingly none should be measured, by anyone, vs the CMB. Yet there is a dipole! Why? I think this has to be due to a recent velocity, an acceleration that has us moving relative to our local chunk of space. If it were secular (for all time) then we'd be in a different chunk of space (and seeing uniform CMB).

2) The picture shows "light cones" as little triangles along everyone's timeline. That's how fast a signal would travel if you emitted it. You could imagine adjacent societies communicating by radio, with delays for their successive messages (light cones) to reach each other. This elegant picture shows how the light from the big bang can reach us, after a long journey and an uphill race against the expanding universe wherein it actually loses ground before finally approaching us. That's the red pear shape. This explanation makes perfect sense to me if I think of it as an explosion in air. Everywhere, sound moves at the speed of sound, but the air through which it travels moves at different velocities depending on which part of the explosion each pocket of air is located in. As such the sound speeds up or slows down (in a coordinate frame fixed to the location of the original explosion). This all works perfectly for air, but air is the aether through which sound moves. Is there then aether for light? What if there is nobody there to measure the light as it travels from its source to us, through the intervening universe? Is it still doppler shifted along the way, or is it meaningless to talk about a doppler without an observer? Does it arrive along the same trajectory, covering the same distance in the same time?

I think the answers are: the light behaves the same whether there's someone there to see it or not, there is no way to define redshift without an observer to be shifted "relative to" and so, yes, it covers the same trajectory. This is clearly about relativity, wherein the photons, and their speed, are invariant. The doppler changes depending on who (at what velocity vs the emitter) is observing at any given time. Again I'll mention the sound analogy works well (for me at least), so long as you assume that each timeline on the picture represents a different hunk of air.

Another way to learn something from the sound metaphor is to picture the interaction from the transmitter's perspective. We can speak (continuously!) to a nearby observer who, at the bang, suddenly begins travelling away at a huge speed. Thereafter, they and we hear each other with a huge redshift. We would both be speaking in ordinary time at ordinary rates but not just pitch but (consequently!) the time of arrival of words and sentences would be greatly stretched out. To each observer, the other appears to have slowed down. We can know this 'cause we can observe everyone's lips move at the speed of light. However in space, when the redshift is itself that of light, there is no meaning to the idea of the 3rd party observer in absolute or unmoving space. Also, I can be moving far faster than the speed of sound vs the transmitter, but the sound waves speed up as they refract through intervening blocks of atmosphere, each of which is successively travelling faster, with it's local bits of embedded shrapnel & flotsam. From the listener's perspective (measuring the sound pulse approaching via some kind of laser rangefinder) the sound is speeding up: you may think of the doppler as being applied incrementally and it IS, by the incremental delta velocities by all the air pockets. In space we don't know anything about the intervening observers (they may not be there!), but we "see" the light's redshift (as we would hear the doppler shift of sound) and so time at the observer seems to have been slowed down.

Ok, I love this song. "Furr" by Blitzen Trapper

Everybody seen this show on NOVA? Surpassing Newton & Einstein with 11 dimensions, gravity radio between alternate universal branes (excellent, we can TALK to them by shaking an apple!) and the long struggle to squeeze the universe into one set of equations. I'm a little uncomfortable about how badly we seem to want the un...iverse to unify itself "just" to fit OUR need for order. The freaky-cool thing is that bits of pond scum can actually begin to understand the heartbeat of the big implacable pond. Gives me chills. Gotta look past the glossy popularization though: it takes a LOT of "dumbing down" to render these ideas for TV, and boy do they ever.

track, and bike crash

Well, I'm really enjoying track right now. Once a week for sure, maybe a bit more, and working on about a 1:15 pace (for 400m). This is a speed I can maintain for 6 or8 laps on long rest intervals, like 3 minutes. I can string together 1:30s and will shoot for a 6 minute mile soon. Long term goal is to get more comfortable at 1:15, where I'm very badly out of air, right now.

But, I realized after starting this, now it the right time to write something about the bike crash, so I can remember it later.

It was three weeks ago today, the CU Buffalo Bicycle Classic, a 100 mile ride to Ft. Collins & back. Steve and I were going to do it. I couldn't believe he could just pick up cycling and do 100 mile days, and I was a little apprehensive! Then Steve's knee got worse, or an order not to make it worse maybe, and I was gonna do this race alone. I almost didn't go, just out of boredom, but it is a great course and I thought it looked like good weather so I went. I cruised out of town in the chilly morning, gradually picking up speed as I warmed up. It's all uphill out of Boulder along Hwy 36 until you get to St Vrain road which is a downhill tear all the way to Hygiene. By now I was going pretty fast and had caught up with a pack made up of about 3 really strong guys and a bunch of hangers-on. I took a couple of pulls sort of to show I was able to keep up, and generally settled in towards the front of this group. The pack kept breaking up when someone would fall off the front few guys so I would have to pull back up which was no problem, just explaining that it wasn't a pace line so much as a few of us taking turns and a bunch of people barely sucking along. I remember thinking I'd have to be careful because these guys were not all that experienced, and getting tired. It would be a very different group after another hour, I thought. How true. We were approaching Hygiene.

The ambulance had a guy in it, sitting at my left, asking me impossible questions like what day was it, and where was I going and so forth. I don't remember much more than thinking it was hard and I wasn't answering his questions very well, and that it didn't hurt much.

Next is the hospital, same drill, except it's a couple of ladies asking the questions and Sue and the kids are there and I got two CAT scans and some very fluffy bandages on my knees. Then I was done, we drove to CU to get my bike and I rode it down to McGuckin's, loaded the car and drove home.

I told it that way because that's how I experienced it: in a couple of flashes with a ton of missing time. On the phone a week later, some dean from CU (who's responsible for the race, perhaps) offered condolences and a free entry next year and said he saw me laid out on the side of the road. I should've hit him up for a couple of jerseys! Steve & I didn't even get t-shirts out of it. So anyway, I learned I was unconscious for a while. It's interesting how the memories are gone, even from BEFORE the crash. Near as I can guess, there was from 5 sec to a half minute before the crash where I have no memories. Can't visualize the rear wheel that (I imagine) swiped across my front tire and wiped me out, or the tumble, or the asphalt, or laying there. Nothing.

The next remarkable thing was all the gyro failures. I couldn't call it dizziness, but that's the nearest thing I guess. Sometimes I'd turn my head, and the world would turn but then Just Keep Turning, never stopping. ...as though I'd gotten off a merry-go-round. So I guess that is dizziness. Anyway that kept up for weeks. It became a morning phenomenon. Monday, 15 days after, was the first time I woke up and could walk without lights on or holding on to something. Then yesterday (20 days after) the last of the saucer sized scabs on my knees peeled off. Those hurt a lot & still do. My knees continue to weep blood and pus and I can't wear long pants because of it. That's irrelevant though. My wrist feels sprained, or lower part of my arm maybe, so there are some things like dips and pullups and pushups I can't do yet, but that'll all heal soon enough I suppose. It is good to have it over with. I haven't gone back to "full" workouts yet, mostly because I'm daunted about starting up swimming again: even a 3 day layoff makes swimming hard again. As far as the bike? Well, I haven't had the urge.