Posts Tagged ‘matter’

More about Cosmology, Mass, and Dark Matter

January 13, 2013

I kept thinking about this. I don’t think astronomers pay enough attention to the time factor when they analyze the universe. I know that they’re aware of it; but do they truly analyze galaxies and other objects based on their assumed age?
Let me illustrate: from our point of view, everything out there is older. We think the universe is about 14 billion years. Our solar system is about 4.5 billion years old. It’s estimated that the sun is somewhere in the middle of its cycle of existence, so for argument consider that mid-level stars such as Sol last about 9 billion years.
Our closest neighbor star is Proxima Centauri, about 4.2 light years. So when we observe that star, a part of a binary system, we’re seeing it as it was 4.2 years ago.
We extrapolate to describe this star, based on what we know of stars in general. That’s what we do with all stars, including our own.
But not much happens in a year, so far as a star is concerned. So we can assume that we’re observing P. Centauri as it is now. By contrast, the most distant objects we’re seeing are protogalaxies and gamma-ray burst objects (structure not defined; just something that’s emitting a lot of energy) that are 13 000 to 13 370 million light years away. So we’re looking at those as they were back when the universe began.
Objects in between are intermediate in age.
Consider a mind experiment, if you will. Say I was to surround myself with people, organized in layers, from about 5 meters to perhaps 1 000 meters. In the first layer, I put teenagers. The second layer would be 20-somethings, and in the third layer there would be 30-somethings, right up to a final layer of centenarians.
I would then try to describe this thing called ‘human’ by looking at those people. Could I truly do so without considering the effects of age?
And yet, that’s what astronomers do. When they describe a galaxy, do they take approximate age into consideration?
Extrapolating from this, can they describe the universe without considering that each ‘layer’ contains objects that are young, middle-aged, and old?
To really describe the universe, I would think that we need to break down the universe according to ‘age’. And since stars age in billion-year time frames, perhaps we could use a hundred-million light-year ‘slice’ of the universe. So anything up to a hundred light years would be about the same age, from P Centauri to 100 light years out. Slice two would run from about 100 to 200 light years. These are only off-the-cuff ideas; perhaps slicing by 500 million years or even a billion years would work better in practice.
The next thing would be to attempt to extrapolate what would likely be happening in those older sections. If we’re observing them a billion years ago, what would they be like in half a billion years? Would they have collided with another galaxy, or most of their bigger stars gone nova/supernova and reformed into smaller stars? Would they have more or fewer star systems within the galaxy?
Do all that, and then we might get some idea of how much mass there really is in the universe.
Say there are X galaxies in that oldest slice, 1 000 mly or more. Say further that there are X+Y galaxies in the slice 900 to 1000 mly distant. Calculate that there are X+?Y galaxies in the 800 to 900 mly slice. Continue until done.
Then graph the numbers. We can decide whether the process of galactic formation is increasing, remaining the same, or decreasing over 100 my time segments.
That, in turn, should give us an idea of about how much normal matter there is in the universe.
I don’t think this has been done. If you’re aware of something along this line, feel free to correct me.