does the constitution specify the number of justices
Article III of the United States Constitution does not specify the number of justices. The Judiciary Act of 1789 called for the appointment of six ``judges''. Although an 1801 act would have reduced the size of the court to five members upon its next vacancy, an 1802 act promptly negated the 1801 act, legally restoring the court's size to six members before any such vacancy occurred. As the nation's boundaries grew, Congress added justices to correspond with the growing number of judicial circuits: seven in 1807, nine in 1837, and ten in 1863.
Supreme Court of the United States