I can see that several of you guys mentions the minefield in Deep Space 9, but don't forget that the Romulans also had a minefield in Star Trek Enterprise, where one of those mines severely damaged the Enterprise.
These mines where cloaked though.

I guess an invisible minefield would be even better (and closer to mines on the ground) but it still is a good defensive measure that keeps ships from entering a certain space.
A gentleman will not insult me, and no man not a gentleman can insult me.

Knowing it's there is half the point.
Prof. Farnsworth: Oh. A lesson in not changing history from Mr. I'm-My-Own-Grandpa!

Space mines are a big deal in sci-fi, mostly for dramatic reasons. Galaxy Quest is playing fun at it.
http://tvtropes.org/pmwiki/pmwiki.php/Main/SpaceMines

Last movie watched:
The Wall
(6/10)

It makes as much sense in space as it does on earth.
Mines ain't used on the open sea, they're used in narrows, esp harbour entrances. The idea is to deny the enemy passage through a fairly small area, forcing them to use monitored routes. In other words, in order advance, the enemy has to pass under the guns (or whatever other defences are in place).
Landmines are used in a similar manner.
In context to the movie, the minefield might be the remnant of a barrier to restrict access to the wormhole, given it's proximity. To achieve that, there doesn't need to be a huge field that covers the whole circumference. All that needs to be done is to force the enemy through a narrow channel, where a large force has to pass through in line, thereby negating the large firepower.
I did not save the boy, God did. I only CARRIED him.

Yes, I think it definitely works. It adds to the whole "eye opening" saga of humans on Earth being let in on the universe at large. Eloquently stated by Justin Longs character, I knew it. Humanity may not have experienced any of this larger history of the universe, but mines in the middle of space, left over from an ancient war, certainly plays into the revelation and possibility that a homeless band of aliens could rebuild their civilization based on Earthly historical documents.

in context of Galaxy Quest im not sure if it makes sense as we dont have enough information ,but minefields in SF are very common usually their used to mine gateways/wormholes that are used for interstellar travel or places where an attacker has no other option to go ..on tv DS9 used one very effectively surprisingly Babylon5 didn't but it is what it is i supposein books Alastair Reynolds David Weber and Jack Campbell use minefields a lot especially Campbell

The minefield was a leftover of an interstellar war between 2 powers, both long since gone. Mines are nasty things, people are dying daily from forgotten mines in various places of the world.
In Stargate SG-1 there was a minefield episode too, space mines are always good plot devices.

It only worked in Deep Space Nine because it was placed around a natural chokepointthe wormhole entrance, which isn't that large. But otherwise, a minefield in space is pretty stupid,

a minefield in space would defend something within it, not beyond it

astrolupine: even with makeup, you can't make an actor's face look like a chair

Maybe by "leaving early" he really meant "escaping".

WOW!!!"Chick" magnet that you are, how do you get them in there in the first place? A tractor beam? Just askin'.

This message has been deleted.

The Thermians touched on this when they were talking in the Limousine. Apparently there was a HUGE war a few thousand earth years ago and it was a leftover.
Space is huge, but if you are trying to defend a small territory in space, a magnetic minefield could be feasible. The purpose of a minefield is not to destroy an enemy but to divert him through a particular portion of territory that is not advantageous to him strategically.

Well there were the chompy-crushy things, now that was pointless, but hey it was in the original show!
Give the Thermians credit for accuracy.

This message has been deleted.

Seeing the mine field didn't necessarily make it pointless. Most electrified fences will usually have a warning on it that touching it will electrocute you. The message essentially comes down to- stay out.

Worked in Deep Space 9!
Well they worked on DS9 because they were used correctly, They were self replicating mines that were invisable and placed at the entrance of the worm hole, no ships could enter or exit or fly around so its a big difference in comparing the use of mines to this film that were just floating in space

given the fact that a ship can fly in muliple directions (you can't just place one wall otherwise they can just fly above or below it)
Every time there was a blockade-in-space of some sort in a Star Trek episode, I had that thought.

Didn't they try to plug this hole by making them magnetic mines?
Really? Well, then why did I do it? Huh? 'Cause I did it! Riddle me that!

Exactly!

Yeah I know, but I wouldn't be a nerd if I wouldn't take it completely serious.

That was what made the movie funny. The real universe was full of the same plotholes that the show was.
The best diplomat I know is a fully activated phaser bank.

Given the fact that those spaceships fly a thousands of miles per hour and should ussually pass it in a few seconds and given the fact that a ship can fly in muliple directions (you can't just place one wall otherwise they can just fly above or below it) means you you need a gazillion amount mines to cover a fully fuctional minefield.
Also the universe is an enormously or infinite place, the odds that somebody will actually fly past the spot you just happend to put a minefield is like 1 to a 10000000000000000000000000000000000000000 (well you get the picture).