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WikiCards · Card list · Science cards · Compact space
Uncommon card · Science
Compact space, an Uncommon card
In mathematics, especially general topology and mathematical analysis, compactness is a property of a space that makes it behave in many ways like a finite set.
- Rarity
- Uncommon
- Domain
- Science
- ATK
- 75
- DEF
- 49
- Power
- 124
- Wikipedia reads a year
- 110,000
Power 124 (ATK + DEF): stronger than 60 % of WikiCards cards.
Compact space quiz: 3 questions
Three questions on the Compact space card, the way WikiCards duels ask them. Pick an answer, the facts are just below.
Find the missing word
For instance, on a finite set every infinite sequence must take some value infinitely often, by the ______ principle.
Answer
pigeonhole. For instance, on a finite set every infinite sequence must take some value infinitely often, by the pigeonhole principle. From the Compact space article on Wikipedia.
Which of these Wikipedia articles is read the most in a year?
Answer
Bile. Bile 160,000 · Compact space 110,000 · Aspartic acid 63,000 · Artificial life 49,000 Wikipedia reads over a year.
In a duel, each round asks a question like these about the opposing card, with 15 seconds to answer.
The facts on the card
The card carries these facts from its Wikipedia article.
- For instance, on a finite set every infinite sequence must take some value infinitely often, by the pigeonhole principle.
- For subsets of Euclidean space, the analogous statement is sequential compactness: a set is compact if and only if every infinite sequence in the set has a subsequence that converges to a point of the set.
- Likewise, whereas every real-valued function on a finite set is bounded and attains its maximum and minimum, every continuous real-valued function on a compact space has these properties.
Why it is Uncommon
Rarity in WikiCards follows a year of Wikipedia page views: the most read articles become Epic and Legendary cards. The Compact space article was read about 110,000 times in a year. ATK comes from the length of the article and DEF from its quality, so this card hits with 75 and blocks with 49: each hit it takes is cut by 20 %.
How to get Compact space
Open packs. Each pack holds five cards drawn from real Wikipedia articles, the rarest last, and the fifth card is always Rare or better. The odds are shown in the game. A free pack arrives every hour and two can wait, and the Coins you win in duels buy more packs.
More Science cards
Cards close in power
The cards just above and just below Compact space in the power ranking, all domains together.
- Igor PaixãoUncommon · Society · ATK 68 DEF 56
- BulldozerUncommon · Science · ATK 67 DEF 57
- CanyonUncommon · Nature · ATK 66 DEF 58
- DiglossiaUncommon · Society · ATK 73 DEF 51
- Cessna Citation XUncommon · Society · ATK 64 DEF 60
- ScaffoldingUncommon · Science · ATK 69 DEF 55
Card lists
- Wikipedia quizNew questions every day
- All cards from A to ZEvery card, by name
- Science cards
- Legendary cards
- Tier listS and A tiers by power (ATK + DEF)
Credits
Text : Wikipedia, Compact space (revision), CC BY-SA 4.0. Photo : Brirush, CC BY-SA 3.0, Wikimedia Commons.
