Thanks Bro,
It looks a little sorry for having been rained on, but it should do the trick of making clearer what a 7.5 hour sleep pattern should look like.
Your doctor would generally suggest you need about 8 hours of sleep, but in reality 7.5 hours is correct. When a sleep pattern is monitored on an EEG machine, surprisingly, an undisturbed sleep segment lasts 90 minutes -- give or take a few seconds either way.
7 hours of sleep leaves you groggy, likewise an 8 hours sleep, the last 1/2 hour being a virtual waste of time. However, 9 hours is good, too, being 6 segments of 90 minutes each.
The above drawing shows the main levels in which our brain operates -- Beta, Alpha, Theta and Delta.
In Beta one might actively "chase" a red sports car, or the pretty gal next door.
In Alpha sleep (one could say) only truth exists, and dreams come to the fore. In Theta a stocktake of body requirements and emotional requirements takes place, whilst in Delta the Thought Adjuster has an opportunity to do His or Her task of "adjustment" re the person's spiritual outlook.
That isn't a great deal of info, but it could be said that there is more un-known about sleep than what is known.
More than 50% of us have irregular sleep patterns, affecting much of our lives in all we do and think about.
The drawing above shows only a single line. In reality, Beta, Alpha, Theta, and Delta (and a big bunch of minor patterns) all function at the same time, but the single line represent the pattern that is (becomes)
predominant.
God bless......