deletions | additions       diff --git a/subsection_Age_vs_lots_of__.tex b/subsection_Age_vs_lots_of__.tex  index f59280c..1468c46 100644  --- a/subsection_Age_vs_lots_of__.tex  +++ b/subsection_Age_vs_lots_of__.tex 
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What we could learn: It should be obvious that mass will increase with age, but how quickly, and is this rate affected by any other factors (ie morphology, environment?) Would directly measuring the increase in mass over time match the current calculations of star formation rate over time?   \subsubsection{Age vs Spiral arms} arms and/or clumpiness}  How do spiral arms form in a disk - are they present from early formation or do spiral galaxies begin their lives as Lenticulars? Can the number of spiral arms change as the galaxy ages?   \citet{Elmegreen2014} found stuff \textbf{What's been done so far:}  \citet{Elmegreen2014}: Spiral structure develops around $1.4~z~1.8$; around the time the disk has cooled, rotational motion dominates over turbulent, and clumps become less frequent. Galaxies tend to go from a high-redshift clumpy phase to a low-redshift spiral (or elliptical) phase. Mel - what are the details of this transition? Are there clumpy spiral galaxies? Can we use GZH + GZH2 to confirm/narrow the redshift at which spiral structure develops?  \subsection{Morphological changes over time}  Current observations suggest that a large fraction of originally-disk galaxies can change morphology into elliptical shape. Does this transformation occur around the same time for all disks? Can disks spontaneously lose their disk structure over time, or does it have to undergo an interaction with another galaxy to transform? Is there a third option? Are there any very old disk galaxies, or do they all lose their disk structure at some point?