No you don't. As a matter of fact when it comes to discounts you actually have to be there in person with your ID and whatever method you're using as a discount in hand. It's just if you order your tickets at normal price online, you ensure that you're able to get in and it's not overcrowded. As I've seen though the mosh hasn't been crowded and my husband and my four-year-old and myself thoroughly enjoy going!
Hello! Oliver here, one of MOSH's Guest Relations representatives. No, you don't have to purchase general admission tickets online, but we strongly encourage it to help speed up your admission process and get you set on your journey through the museum. However, all planetarium/animal encounter (at $5 per person) or Extreme Science Show (free, but with limited seating) tickets do have to be purchased at the front desk or the gift shop before the show.
Not sure about general admission, but i saw a show in the planetarium last week and paid at the desk. I hope this helps
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