Wonder Wednesday - Wondering About Ice Skating

This week's #WonderWednesday inspiration comes from ice skating.  

Some wondering I had about ice skating this week:

• Is it harder to skate on indoor ice, or outdoor ice?
• How is indoor ice made?
• How much water is used to make an indoor ice rink?
• How have ice skates evolved over the years?

Related Wonders from Wonderopolis:

• #67 When Were Ice Skates Invented?
• #109 What Is a Zamboni?
• #494 Why Is Ice Slipper?