the Meteor Swarm spell specifically lists Fireball as an origin point. if you are not familar with the spell. it creates four 40-ft radius balls of fire. which deal 6d6 points of damage each. that is a total of 24 dice of damage for a 9th level spell (so you can cast it at 17th level, or 18th if you cast spontaneously), and that's not even counting the bludgeoning damage if you hit an opponent with the meteors. this is an actual core spell, so it was built to be balanced. this is the same spell except: replaced the 40-ft radius spreads with 240 ft lines (40-ft is twice the radius of the Fireball spell, and 240 ft is twice the length of the Lightning Bolt spell, two spells which are the same level and therefore about equal. replaced the bludgeoning damage if the meteors hit with peircing damage if the, I don't know, spears of lightning hit. Meteor Swarm is a core spell, found on page 253 of the Players Handbook. it is also the signature spell of Xykon, who uses it regurarly, so I don't think it's unbalanced. I mean, come on, you can blast whole armies with this thing! Maybe I will allow the Lightning to blast from other bolts though.
Also, @Seharvepernfan: yes I could have just changed the fire damage to lightning damage, but the spell actually has mechanics for rocks on fire built in (if you hit with ranged touch attack, enemy suffers bludgeoning damage from the rock, and can't make a reflex save against the attack) and falling rocks that deal lightning damage just doesn't seem that thematically interesting. the idea of spears of lightning (that image is really starting to stick in my mind) is more interesting thematically, and since Lightning Bolt is about equal to Fireball (both are 3rd level Sor/Wiz spells), I decided to replace one with the other as the origin of this spell and see where it went. it's a nice idea and creates a more interesting spell than "Meteor Swarm that deals Electricity damage" which would be boring. I like things to be interesting and thematically tied. (also, about the lines being too long, the range of Meteor Swarm is 400-ft+40 ft per level so maybe the lines are actually too short, but again, this is replacing Fireball with Lightning Bolt (the radius of the Fireball spell was doubled for the Meteor Swarm spell, so maybe I should quadruple the length of the line (if you are familar with geometry, you don't need an explanation), but anyway, no, it's not to long)