I've just downloaded the Arduino software onto an Apple MacBook Pro running 10.9.5. The computer is about 10 years old. The software downloads from the Arduino site just fine but when I open the program it immediately crashes. Any insights what might be causing this? Thank you for the help.
OP here.... found out what the problem is. Downloaded the previous version 1.8.7 and that solved the issue.
Thanks for taking the time to share your solution. For anyone else with the same problem who finds this thread, here is the explanation of the issue:
The bug has been fixed but there has not been a release of the Arduino IDE since that time. For now, it's best for people using versions of macOS older than 10.12 to use Arduino IDE 1.8.7 instead of Arduino IDE 1.8.8, but Arduino IDE 1.8.9 will not have the problem.