Newness have been submitted recently and have a very short staying time. Often replaced with more current videos. There are many variables that go into how newness works. Maybe @lucky760 could give you a better understanding of how things work. I'm guessing its been discussed in a sift talk somewhere just not sure where.

Thanks for the info !

Now I see the main Sift page defaults to Hotness.
So weird, never noticed before really...
Newness is way better. Hotness seems to gets old after page 1...

Newness is just in the order they sifted, hotness has the videosift special sauce to show you the ones trending right now (or that had quality cast on them).

I usually browse front page in hotness mode, but always view unsifted in oldest first order (hide viewed).

Hotness is for new videos gaining in popularity. At the time of your writing, those videos were already around for a while and waning.

weird, because one just got into the top 15 despite being invisible o the main page.
There are plenty of dead videos in the Hotness pages going nowhere, yet my two videos with plenty of comments and votes are buried.
Weird.

I agree. I like the newness is better on home page. Also, it ias easier to catch up on the 10+ voted videos.

Not actually weird because the twain are irrelated.

Hotness is for newly-submitted videos forecast to be something many people will want to see. Top 15 is for videos that achieve lots of votes during their first 3 days of being published, regardless of how long ago they were initially submitted.