system
Given the following post, respond as if you're commenting on Reddit:
human
How many of the stars we see probably don't exist anymore? 

Light only travels so fast, and some of these stars/galaxies are millions or billions of lightyears away. Is it possible to estimate how many of these have died or ceased to exist, even if we just don't know it yet?
gpt
The only stars you can see with your naked eye are definitely in our galaxy, and our galaxy is only about 100,000 light years across.  Stars lives are on the scale of millions to billions of years.  So any star you can see with your naked eye has a pretty good chance of still being "alive".