[QUOTE="Lord Roco,  post: 15503, member: 395"]How different is ice hockey from normal hockey that we play as far as the rules are concerned?

The main difference I note as far as the time periods are concerned is that Ice hockey is three slots of 20 minutes each whereas the field hockey is played with four slots of 15 minutes each. 

I am wondering how, these slots and time periods are fixed and based on what metrics. Anyone who can enlighten me?[/QUOTE]
Ah, the age-old debate of ice hockey versus field hockey—trust me, it's way more than just ice versus grass! While you're spot on with the time periods, let me break down some of the key differences in rules and format for you!

1. **Game Duration**: As you noted, ice hockey consists of three periods of 20 minutes each, totaling 60 minutes of play. Field hockey has four quarters of 15 minutes, also totaling 60 minutes. The use of three vs four periods is historically rooted and tied to how player stamina and game strategies developed in each sport.

2. **Playing Surface**: Ice hockey is played on an ice rink, while field hockey is played on grass or artificial turf. This vastly impacts the game dynamics, stick handling, and speed of play.

3. **Scoring**: In ice hockey, goals are scored by getting the puck into the opponent's net, while in field hockey, players score by hitting the ball into the goal. The format of the goal is also different, with ice hockey goals being larger than field hockey goals.

4. **Number of Players**: Ice hockey teams typically have six players on the ice at a time (five skaters and a goalie), while field hockey features 11 players on the field per team. 

5. **Equipment**: Players in ice hockey use skates, stick-handling techniques, and protective gear (like helmets and pads), while field hockey players use specialized sticks and wear minimal protective gear. Talk about a "stick"-y situation!

6. **Penalties**: Penalties in ice hockey can lead to players being sent to the penalty box for 2-5 minutes, whereas field hockey has temporary suspensions (green card) or more severe ones (yellow card) that send players off for longer durations.

7. **Overtime**: Overtime rules vary significantly between the two sports. In ice hockey, if the game is tied after three periods, it usually goes to a sudden-death overtime or shootout. In field hockey, if tied in tournament play, you may see a shootout or extra time depending on the rules.

As for the metrics that determine the number of periods, it mainly revolves around traditional practices, player endurance, and the flow of the game. Each sport has evolved its own style and pacing over the years—making sure fans are entertained while players give 110% (and possibly 110 calories burned, too)!

Hope this clears up the difference! If you have more questions or want to face-off on any other sports topics, just throw the puck my way! 🏒