If distant stars are light years away aren't we seeing them at that moment in time not in present condition.
117139
The answer to your question is yes.  What you are observing in the sky is what happened in the past, in your example 100,000 years ago.
92547
This is a very difficult question. We don't really know how many stars currently exist, so let's rephrase the question to "how many stars in the night sky visible to the naked eye still exist?" (An easier question would be "does star xyz still exist?") If all of these stars are classified into groups whose average lifespans are known, and if the current ages of these stars can be estimated, then using the estimated time that light takes to travel from a particular star to Earth, we can determine if the star has already gone supernova, or if it has darkened. Since most stars visible to the naked eye are relatively young (as compared with super-distant stars visible through huge telescopes), it is likely that a significant proportion of them do still exist. But, again, the question is extremely difficult, but makes for some good thinking.
376769
light years isn't a time, it is a distance \nso it would be 2 light years
1022362
Off course scienists investigate this. Our galaxy is pretty flat around where we are - only 3,000 light years wide. It gets thicker then that in the center -16,000 light years but that's still pretty thin compare to it's length - about 100,000 light years across. "above" and "below" us are other stars, possibly with other planets. Basically the same things that are "in front" and "behind" us across the length of the galactic disk. \nOn a very dark night you'll be able to see a bright band across the night sky - that's the Milky Way. You'll then be looking towards the galactic center. The pictures we recive from satelites and telescope come from different directions.\nAs for a 3D model of the universe there is such a project in progress but it deals with objects on a much larger scale - galaxy clusters, superclusters, walls and fillaments.
79768
yes. i don't think any pre-existing celestial body can be reflective like that, but if there somehow were one far enough away, then yes.  it would have to be very very far though. for example, if it were 2 light years away, then we would see events from four years ago, the light would have to travel 2 years there and 2 years back. but we would see the events being exactly played out, in real time, and always exactly four years ago, and it would follow the rotation of the earth, so it would only be certain parts at certain times.
524831
It takes millions of years for the light from a star to get here. If you look at the stars you are seeing the stars light from a million years ago so if you see a star in the sky it might have already gone out. For instance if a star was born 5 million years ago if you go outside and it is there for the first time you are seeing what it was like 5 million years ago. The star is 5 million years old
862196
From our perception here on earth, it would appear to end at where space and time begins.  Remember that because the speed of light is finite, you can look at a galaxy that's 10 billion light-years away and you'll actually see it AS IT WAS 10 billion years ago....so theoretically, you can look back to the beginning of time itself.  You can't see that far away and perceive anything as it is NOW.  So the CURRENT limits are quite unknown...if there are indeed any.
547876
If there is life on other planets (outside of our solar system), the odds of ever finding out that there is life there is infinitely, ridiculously small. The next-closest star to our solar system, Alpha Centauri, is just a shade under 4.3 light years away. Even if someone or something from a planet orbiting Alpha Centauri had the ability to travel the distance between our two solar systems and not die of starvation or, if they were able to achieve near-light speed, keep their molecular structures from becoming severely distorted, they would have to make an amazing pinpoint shot to hit Earth. Even if there is "intelligent" life out there, I think it's impossible for us to ever make any sort of meaningful contact with it. Anyone who has ever shot a rifle knows how just a fraction of a degree can determine a hit or miss on a distant target. The odds are that much more exponentially outlandish if we imagine interstellar travelers getting lucky enough to find our planet and solar system out of all the others out there, no matter how "close" we are.
914780
Well, we look at the light and determine "this light is about a million years old." :-) Not really, but that's the general idea.\n\nFor galaxies of very large distance, we can determine how fast the galaxy is receding from us. The easiest way is the Doppler shift - we can see the galaxy (obviously) and therefore astronomers can determine how big it is, what type of stars must be in them, and therefore what color light we should see. However, the light is slightly redder than what models predict (and what nearby galaxies have). We can measure this "red shift", plug it into Doppler's equation, and determine how fast the galaxy is moving. (This is similar to how when a police siren passes you, it drops its pitch - and how much it changes is proportional to how fast the police car is going.)\n\nThen there's a nice relationship called Hubble's Law, which states that the farther a galaxy is from us, the faster it's receding. This is a consequence of the Big Bang, and indeed the constant in this equation must be the reciprocal of the age of the universe. So we can then estimate (within a few thousand years or so) how far the galaxy must be from us.\n\nFor closer galaxies, there are some other techniques. There are certain types of variable stars (stars that, every few hours or days, increase and decrease their brightness) that in order to be stable must vary between two known brightnesses. Of course the brightness isn't exact, but the average among the thousands of variables in a galaxy is very close to exact. Now when we measure brightness (actually, apparent magnitude) from Earth, we see stars dimmer if they're farther from us. But because we know the absolute magnitude of these variables, and we can measure their apparent magnitude, we can calculate the distance we must be for them to become this much dimmer.\n\nThere are actually a lot of techniques, which work better for certain distance ranges. Look up the "distance ladder" if you're interested.
1022881
Hi Itsverystrange\n\nIt is actually true that distant galaxies can (and are) travelling away from us at apparently greater than the speed of light.  Any galaxies outside our Hubble volume (r = c/H) are apparently receding from us at greater than c - this is why they're outside our past light cone.  \n\nThere's no conflict with special relativity here because SRT is a strictly local theory.  The coordinate system itself is doing the expanding, the galaxies aren't moving with respect to their local coordinates.\n\nHope this helps!\nThe Chicken
10479
The answer is really quite simple:\n\nWhen we speak of the 'age of the universe' we are talking about how old all the rest of the mass of the universe would appear from within _our_ frame of reference.\n\nSo, to a cosmic radiation particle traveling at near the speed of light the whole universe would "appear" to be just seconds or minutes old. (As if such a particle could have perception, which it cannot).\n\nYet we, all living on the same planet and having less than a thousand mile-per-hour difference in our respective velocities, are unable to notice the effect of Relativity.
671170
Are you including the stars that are being created, as well as those that do not actually exist anymore but have died out/ supernova'd/ etc. that we are just still seeing since the light has to travel so far?  \n\nI would be interested in how you determined this number ^_^
1100163
The light from distant galaxies that we see now started on its journey through space long, long ago.... in a way its like looking back in time, trippy huh?
95460
Your thinking is correct! There's a phrase that's unfortunately left out when we read about the universe -- "observable universe." We see a galaxy 13-billion light years distant as it was 13-billion years ago. During the 13-billion years it took light from there to reach us, that galaxy has moved beyond the limits of the "observable universe." Remember, the farther away a distant galaxy is when we observe it, the faster it's rushing away.\n\nIn the case of the galaxy 13-billion light years away, it's recessional velocity is 3^11 km/sec. That's NOW. But in the 13-billion years it's taken light to get here, that same galaxy has moved another 1.2^16 light years farther away, and that puts it well beyond the limits of the "observable universe."
774125
if u r already looking at a star, then there is no point of the star not being there.......
1023696
No there are far older stars. \nThe sun wasn't born it condensed out of nebulous gas and dust.\nThe universe is so large it is possible to see back in time ( and space) to objects like quasars that have not existed for billions of years.\nGod doesn't exist hence never said anything
740634
To begin, it's unfortunate that many people cannot see beyond their everyday, boring. Job, home, sleep - repeat until you get old and die. Thinking about the Universe teaches us about ourselves. As Carl Sagan always said, "We are made of star stuff!". Every single thing on Earth is made of of atom and molecules that once burned inside stars. Every atom in our bodies come from stars. Like it or not, we are directly linked to the Universe.\n\nOn average, there are 100,000 stars in every galaxy. And galaxies hang out in groups of a few hundred. If you look at very foamy suds in your sink, that's how scientists see the Universe - there are empty spaces but the white foam around the bubbles would be where all the galaxies are.\n\nRight now, the best telescope that can see the farthest is the Hubble. A few years ago, scientists working with the Hubble pointed it at one of the darkest regions in the night sky. All other telescopes saw only the deepest black. But when Hubble's images returned they saw thousands of galaxies (see Hubble Heritage - Deep Field). Light travels at 160,000 miles per second. That's pretty fast but over great distances it still takes time for light to travel. The deeper you look into space, the farther back you're looking into time. Those faraway galaxies Hubble photographed were 24 billion light years away! So we're seeing 24 billion years into the past. The Universe is estimated to be 27 billion years old so we're close to seeing the Universe in its begining.\n\nIf you have the time, check out the Hubble Heritage site. A lot of people say that seeing its images is uplifting and inspirational. Maybe these images will ease your mind.