What do the round numbers on the tech tree mean, and why are some nodes greyed out

[Dave Kerbin]

The node at the bottom has a 6 on it, any idea what that means? I've got several marked 2 and one marked 8.

The two nodes on the right are greyed out, I can't even select them. Why?

These are the first nodes that behave that way. I've reached other nodes that had more then one path to them, but that didn't stop me from selecting or unlocking them.

Edited October 17, 2013 by Dave Kerbin

[UmbralRaptor]

The number is how many parts are on that node. Not sure about the grayed out ones.

[Keome]

Greyed out ones mean that you haven't unlocked the other prerequisite tech nodes.

[Rusty6899]

The prerequisites don't seem to make that much sense, some techs are available to me after only researching one of two prerequisites, for others they require all prerequisites.

[SRV Ron]

They may also be place holders for future updates where the parts are currently unavailable.

[Depth]

The prerequisites don't seem to make that much sense, some techs are available to me after only researching one of two prerequisites, for others they require all prerequisites.

That's the difference in two technologies that lead to the same advancement, and an advancement that requires the two previous technologies.

[lajoswinkler]

Gray stuff is the stuff you can unlock, and dim gray stuff is the stuff you'll be able to unlock when you unlock enough gray stuff.