# Are there any dead stars in the sky? **URL:** \ **Category:** Factual Questions\ **Created:** [March 30, 2016, 10:52am UTC](https://boards.straightdope.com/t/are-there-any-dead-stars-in-the-sky/750621 "2016-03-30T10:52:55Z")\ **Posts on this page:** 7\ **Page:** 3
**Author:** ![Mijin](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mijin/32/9369_2.png) [@Mijin](https://boards.straightdope.com/u/Mijin)\ **Post date:** [April 1, 2016, 3:30am UTC](https://boards.straightdope.com/t/are-there-any-dead-stars-in-the-sky/750621/41 "2016-04-01T03:30:37Z")
> [@Chronos](#): > > “Why are you telling me the timing in that cosmic ray’s reference frame? That’s not useful to me. All of my clocks and calendars are sitting in my lab, not riding that cosmic ray.” Sure, but is the star dead from your view in the lab? Let me put it another way, because I think there’s a degree of talking past each other going on: The classic relativity example, the one where most of us hear of multiple reference frames for the first time, is the one with two astronauts, Anne and Bob, moving apart. Anne looks out of her telescope (which is so powerful it can see Bob’s clock), and she sees Bob’s clock appears to both be behind her clock, and also ticking more slowly than hers (IIRC). Now, in this scenario, we don’t try to work out what time it “really” is as there is no “really”. Likewise we don’t try to extrapolate backwards and say how long the light beam spent travelling because even that is problematic (how long the light beam spent travelling _according to whom_)? We just simply say, in Anne’s reference frame, Bob’s clock says X. Then we come to the example with the supernova, and ISTM we’re doing something quite different. We’re saying that from the POV of year 2000 astronomer, it only _looked like_ the far away star’s clock was reading X. We can extrapolate backwards and apparently say that _really_ the star’s clock was at time Y where Y is past the point it went nova. This different treatment is what is making me uncomfortable. I can see why in a practical sense we might choose to interpret events this way…in cosmology of course we are broadly looking “back in time” by looking further out, even if there is no universal “now”. But that seems different to me than making a specific claim about reality of a specific event in the earth’s reference frame. ---
**Author:** ![Peter\_Morris](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/peter_morris/32/359_2.png) [@Peter\_Morris](https://boards.straightdope.com/u/Peter_Morris)\ **Post date:** [April 1, 2016, 4:24am UTC](https://boards.straightdope.com/t/are-there-any-dead-stars-in-the-sky/750621/42 "2016-04-01T04:24:20Z")
Sigh. Look, just for the sake of argument, lets assume that God exists. Now, consider the question from God’s frame of reference. He can see, by power of omniscience, that a star went supernova centuries ago, AND that light from the star continues to shine on Earth. ---
**Author:** ![Mijin](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mijin/32/9369_2.png) [@Mijin](https://boards.straightdope.com/u/Mijin)\ **Post date:** [April 1, 2016, 4:53am UTC](https://boards.straightdope.com/t/are-there-any-dead-stars-in-the-sky/750621/43 "2016-04-01T04:53:19Z")
I’m not trying to fight the hypothetical. I’m trying to…hijack it…a little, I guess, but anyway the original question has been answered. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [April 1, 2016, 2:06pm UTC](https://boards.straightdope.com/t/are-there-any-dead-stars-in-the-sky/750621/44 "2016-04-01T14:06:13Z")
> [@](#): > > Quoth **Mijin** : > > Sure, but is the star dead from your view in the lab? We’re not talking about my view here, but about my reference frame. They are not the same thing. In the reference frame of my lab, yes, the star is indeed dead, even though I don’t know it yet, and won’t know it for many years. This is a very common source of confusion about relativity. ---
**Author:** ![D18](https://avatars.discourse-cdn.com/v4/letter/d/c57346/32.png) [@D18](https://boards.straightdope.com/u/D18)\ **Post date:** [April 1, 2016, 2:29pm UTC](https://boards.straightdope.com/t/are-there-any-dead-stars-in-the-sky/750621/45 "2016-04-01T14:29:10Z")
> [@JKellyMap](#): > > Oh, thanks. So even this doesn’t fit the OP. > > So, to sum, is it fair to say that there it’s very likely that all the stars we can see with the naked eye or a low-powered telescope – let’s say binoculars – are are really still there (although a few of them have varied in magnitude, something we’ll observe in the future)? I’m sorry if I missed it, but could one of you guys in the SDMB fizzicks consortium confirm that this summary statement is true? I’d like to pass it along to my kids if so. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [April 1, 2016, 3:04pm UTC](https://boards.straightdope.com/t/are-there-any-dead-stars-in-the-sky/750621/46 "2016-04-01T15:04:37Z")
Almost all of them are almost certainly still there. There are a small number for which there is some doubt, enough that we shouldn’t be surprised if the dead number is, say, one or two. But there’s enough we don’t know about stellar evolution that we really can’t say for sure. ---
**Author:** ![D18](https://avatars.discourse-cdn.com/v4/letter/d/c57346/32.png) [@D18](https://boards.straightdope.com/u/D18)\ **Post date:** [April 1, 2016, 3:40pm UTC](https://boards.straightdope.com/t/are-there-any-dead-stars-in-the-sky/750621/47 "2016-04-01T15:40:51Z")
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