1.042 to 1.024 in less then 24 hours possible?

I did a batch yesterday and started with 1.042, I left a sample in my hydrometer jar overnight and today had a reading of 1.024. This is without yeast being added. How is that possible?

As a bonus I am adding a picture illustration with 2 tips for newbies:



When I poured from pot to bucket I topped off with 3 gallons of water that I had in gallon jugs. I aerated it a lot and generated a lot of bubbles:



It almost looks like krausen

Either you haven't mixed thoroughly enough, or you have a wild yeast infection (so to speak...).

Umm in the hydrometer jar or in my bucket? Bucket's bubbles are from me pouring 3 gallons of water, I splashed it around of my 9 gallon bucket.

I'd say you had some wild or residual yeast in the sample. Once you start brewing there will be yeast everywhere. That's how companies that do open fermentation with 'wild' yeast get consistent results.

Ok no problem, sample will be disposed. This is my 5th batch and first time using Wyest Activator pack. My next batch which I will do in 2 weeks will be using White Labs yeast.