Are the stars really still there?

[Thunder]

The light from many of the stars in the sky, takes thousands if not millions of years to reach the Earth.

That said, how do we know that these stars and planets that we see from telescopes, even still exist??

Sure, the light reflected off them exists, but could it not be that many of these stars died out millions of years ago, and we are just looking at a long dead Universe?

If the sun suddenly was hit by a giant planet..and was blown away, we would not know for 8 minutes, cause it would take that amount of time for us to see the event.

Could it not be that if we invented a warp-drive, we would go to the Orion Belt and find that it no longer exists?

:confused::confused::confused:

[Uncayimmy]

Try this on for size: When you look between the stars, do you ever wonder if there used to be stars there?

But to answer your question, everything you see is as it was.

[Thunder]

Try this on for size: When you look between the stars, do you ever wonder if there used to be stars there?


well...the dark spots in the sky....might be where stars now exist today.

and a million years from now, someone on Earth will see those stars.

[wackyvorlon]

Certainly. I think very large scale change takes a long time, just by our own experience with the age of the earth and our sun. The further away we look, the further into the past we look. Amusingly, it kind of puts a maximum on how far away we can see. Far enough away, and the universe isn't old enough to have given the light time to reach us.

[jasonpatterson]

Is it possible that a given star is 'missing' now? Sure, there could have been some remarkable catastrophe that eliminated a star. The sun going missing suddenly isn't very likely, anything big enough to affect it would have been seen before it did so. However, we have solid theory describing the evolution of a star, so unless you're asking whether a star like Betelgeuse, which is near the end of its life, is no longer burning, the answer is almost certainly yes, the stars are still there.

This seems rather like asking about a tree falling in the woods. Yes, it makes a sound.

[Uncayimmy]

well...the dark spots in the sky....might be where stars now exist today.

and a million years from now, someone on Earth will see those stars.

But will there still be there? My desk will be in front of me before and I after I finish this post. From the vantage point of the sun, it will be somewhere else. From the vantage point of another star, our whole solar system will have moved.

[MG1962]

That said, how do we know that these stars and planets that we see from telescopes, even still exist??

Sure, the light reflected off them exists, but could it not be that many of these stars died out millions of years ago, and we are just looking at a long dead Universe?



By studying the light of a star, we can learn a lot about its life cycle and how long it can be expected to continue to shine. Knowing this and having a reasonable undertanding of the distance that star is from Earth will give us a reasonable certain answer to wether it is still out there or not.

Off all the naked eye stars in the sky today there are two that may not be there any more, and a further one that could be borderline. Using scopes and accessing more distant targets, the number of potential dead stars does climb, but so do the number that have been burning since the early universe and will be long after our sun passed away

[Bikewer]

Every once in a while we are privy to the death of a star, we see the brilliant expansion of a nova or supernova. These events will have occurred thousands or perhaps millions of years ago, of course.... The light of the event having just reached us.

We can gauge with some accuracy the life cycle of stars according to their mass and composition.

[Damien Evans]

Every once in a while we are privy to the death of a star, we see the brilliant expansion of a nova or supernova. These events will have occurred thousands or perhaps millions of years ago, of course.... The light of the event having just reached us.

We can gauge with some accuracy the life cycle of stars according to their mass and composition.

An example: Supernova 1987A, seen in the Large Magellanic Cloud in 1987 actually occurred 168,000 years ago, the light having taken that long to reach us.

[Zeuzzz]

An example: Supernova 1987A, seen in the Large Magellanic Cloud in 1987 actually occurred 168,000 years ago, the light having taken that long to reach us.


Yep, Supernova 1987A is a very well documented case, with numerous models proposed (http://ieeexplore.ieee.org/Xplore/login.jsp?url=http%3A%2F%2Fieeexplore.ieee.org%2Fi el5%2F27%2F4287017%2F04287093.pdf%3Farnumber%3D428 7093&authDecision=-203) to explain its enigmatic properties.

[Reality Check]

The light from many of the stars in the sky, takes thousands if not millions of years to reach the Earth.

That said, how do we know that these stars and planets that we see from telescopes, even still exist??

Sure, the light reflected off them exists, but could it not be that many of these stars died out millions of years ago, and we are just looking at a long dead Universe?

If the sun suddenly was hit by a giant planet..and was blown away, we would not know for 8 minutes, cause it would take that amount of time for us to see the event.

Could it not be that if we invented a warp-drive, we would go to the Orion Belt and find that it no longer exists?


Short answer: Yes

Longer answer:
We do not know that the stars are still there.
We do not know whether the Sun still exists.

We could "invent a warp drive" (but the scientific consensus is that seems impossible), travel anywhere and find that the star no longer exists. In fact if we chose the right star, e.g. a pre-supernova star, then we can guarantee that the star would no longer be there.

But...
We do know a lot about the how stars change with time. There will always be stars we could go to and find them still there, e.g. white dwarf stars have extremely long lifetimes and we could always visit black holes (essentially eternal).
We know that the Sun is likely to be around for billions of years.

[athon]

Although I might have this wrong, as I understand it it's meaningless to refer to another position in space by the time reference I have in my position. In other words, saying 'is that star still there now' might well mean something in terms of language, but not in physics.

Athon

[Reality Check]

What about GRB 080319B (http://en.wikipedia.org/wiki/GRB_080319B)?
About 7.5 billions light years away and visible to the naked eye (if you looked in the right direction at the right time) over a period of 30 seconds!

[wackyvorlon]

Gamma ray bursts are amazing. Imagine a celestial object that releases as much energy as our sun will in it's entire lifetime, in the space of about 30 seconds.

[Monketey Ghost]

I'd like to point out that something giant-planet-sized hitting the sun would merely (!) heat it up for a good length of time, and the earth would become inhospitably baked.

There are things out there which "no longer exist", in the time frame we call right now

, and whose light is still reaching us, showing us an image of a thing which once was. The same light shows us at all times differing stages in the life cycle of these objects... the right now in the existence of any of them is a span of time which is very hard to comprehend.

Most of the objects in question need a telescope to reveal them. The deepest space photographs, like the Hubble's Deep Field South mosaic, show galaxies in the early Universe that certainly no longer exist as we sit here, which have probably burned out by now. According to one perception anyways... considering the distances involved, does "now" have meaning, and how arbitrary a concept is "time"?

[Undesired Walrus]

The light from many of the stars in the sky, takes thousands if not millions of years to reach the Earth.

That said, how do we know that these stars and planets that we see from telescopes, even still exist??

Sure, the light reflected off them exists, but could it not be that many of these stars died out millions of years ago, and we are just looking at a long dead Universe?

If the sun suddenly was hit by a giant planet..and was blown away, we would not know for 8 minutes, cause it would take that amount of time for us to see the event.

Could it not be that if we invented a warp-drive, we would go to the Orion Belt and find that it no longer exists?

:confused::confused::confused:

Eh now? I don't understand how this differs from your thread three months ago? It's identical.
http://forums.randi.org/showthread.php?p=4498567

[Cuddles]

Eh now? I don't understand how this differs from your thread three months ago? It's identical.
http://forums.randi.org/showthread.php?p=4498567

Indeed it is. How odd.

In any case, the simple answer is that not only do we not know they still exist, but we're fairly certain that an awful lot of them do not. The universe is getting on for 14 billion years (although looking surprisingly good for its age). We can see objects as far away as 12 billion years. A fairly boring, regular star like the Sun can be expected to survive as a main sequence star for something like 10-11 billion years, and the more massive the star the shorter its life.

The obvious conclusion is that even were we seeing the very first light emitted as the stars began their life, an awful lot of them would have died by now anyway. Taking the more sensible assumption that most stars have been visible from the Earth for quite a long time, it seems unavoidable that a large proportion are no longer there, at least as main sequence stars (obviously there will be something still there, if only a dispersed planetary nebula with a fading white dwarf in the middle).

Of course, Athon has a good point that the whole concept of "now" doesn't really apply in situations like this. Within the framework of relativity there is simply no such thing as absolute simultaneity - two things that seem to happen at the same time from one reference frame do not necessarily happen at the same time in another. However, for this kind of discussion I think it's fair enough to look at the problem from a classical point of view, assuming that arbitrarily high velocity travel is possible without any relativistic effects on spacetime.

[cgordon]

The mind-staggeringly vast scale of time is really hard for the human mind to get wrapped around. Therein lies, I think, a big part of the problem with those who succumb to young-earth/young-universe theories.

And, on a somewhat less vast, but still staggeringly huge, scale, the same thing here on planet Earth. We get a snapshot of the planet/system/galaxy/universe in our lifetimes, and expect that it always has been and always will be just like that.

Deep time is an incredible concept, and the idea that just because we see the light of a star today, that it might not be there in the same space-time position millions of years later (whenthe light actually arrives here) is pretty wicked cool.

The stars, yes, the stars are still there. Some stars? Nope. Gone. All have moved, some have changed, some get eaten by galactic events, some are dimmer, some are brighter. We won't know all the details until their light reaches us, however.

But as previous poster mentioned, we can make some fairly educated guesses based on observation, analysis and some very complex maths.

[Z]

Imagine this:

We develop some manner of faster-than-light transport. Maybe we finally find one of those fictional, travel-ready wormholes everyone wants to write about. Maybe we develop the warp engine... I don't know. But we take an FTL trip out to the other side of our galaxy, look back with a super-dooper advanced telescope...

And see Earth thousands or even millions and billions of years ago.

That would be one heck of a way to find out whether the stories of Katherine the Great of Russia are true or not! :p

[Soapy Sam]

Imagine this.
A flashbulb.

[INRM]

Well, most stars I would assume would still be there as they have substantial lifespans unless they were like billions of light years away.

Red giants, and such might have gone supernova or collapsed already. Betelgeuse for example is under the process of collapsing, we may see a supernova some time in our lives, though I'm not sure. But regardless it could have gone supernova already

[Towlie]

According to Einstein's Relativity of Simultaneity, your question makes no sense. You can't discuss anything related to "now" in reference to a distant star.

[GlennB]

I'm surprised nobody has commented on the "reflected off them " aspect of the o/p :confused:

[Monketey Ghost]

Imagine this.
A flashbulb.

That's pretty much it, innit? Given enough time, it's all flashbulbs.

Since they were initially created, red dwarf stars have not had enough time to burn out, at the very low rate of fuel they consume... but eventually these dim stars too will fade out and become black dead objects.

[Sir Robin Goodfellow]

This thread is messing with my mind, but in a good way.

[Jimbo07]

It depends a little on how much you believe in the power of induction.

For example, I don't know that the sun hasn't gone extinct. However, I can make a prediction (right now, my time) that the sun has not, and wait 8 minutes (9, because I like to be safe ;)). I record this several times over a multi-hour period. Then, I am safe, inductively, to assume that if the sun is burning for any time, n it is also burning at time, n + 1.

Over a longer period you could do the same with Alpha Centauri, although a single trial of your experiment would take more than 4 years.

Regardless, these things have been going on long enough, that nobody bothers to do an experiment this ridiculous. The closest stars show behaviour within a single human lifetime, and so far, we have been successful in extrapolating from there.

[Cuddles]

Well, most stars I would assume would still be there as they have substantial lifespans unless they were like billions of light years away.

As I noted in my previous post, most stars are billions of light years away.

Regardless, these things have been going on long enough, that nobody bothers to do an experiment this ridiculous. The closest stars show behaviour within a single human lifetime, and so far, we have been successful in extrapolating from there.

Well, we've certainly been successful in extrapolating, but not so much in confirming those extrapolations. Unfortunately, that's really where your explanation falls down, and is one of the big problems in cosmology. The trouble is, most of the things we're looking at are far enough away that we simply cannot test our predictions in the way you describe.

We can look at the Sun, see that it's still there 8 minutes later and deduce that it's probably still there now. We can look at Alpha Centauri, see that it's still there 4 years later and deduce that it's probably still there now. We can just about look at Aldebaran, see that it's still there 65 years later and deduce that it's probably still there now, but you can't do any repeat experiments within a single person's lifetime. You absolutely can't look at WOH G64 and check that it's still there later, because humans haven't existed for long enough.

It's not because the experiment is ridiculous that no-one does it, it's just not actually possible to do so. As I say, this is quite a problem in cosmology, because it means that while we assume that things are still there, and that things behave in pretty much the same way elsewhere as they do here, we can't actually test those assumptions. It also makes it difficult to test many theories. For example, theories on stellar evolution seem to work fairly well, but we've never actually followed a star through even a very small part of its life - all we can do is look for things that appear similar, or that were probably similar in the past. Unfortunately there doesn't seem to be any way around this.

[ponderingturtle]

Although I might have this wrong, as I understand it it's meaningless to refer to another position in space by the time reference I have in my position. In other words, saying 'is that star still there now' might well mean something in terms of language, but not in physics.

Athon

Well the question is being asked in one reference frame, so you could privilige that frame when answering the question.

There are of course obsevers who will think that they got it wrong.