i ve doubts with light years?

Question

for eg alpha centuri is 4light years away.so in night if i look at alpha centuri the light i will be seeing has left alpha centuri 4 yrs ago but does that mean at the present time the actual position alpha centuri will be diff in sky?

i hope ive been able to ask in a clear way?

thanks to all u guys

Answer 1

Alpha Centauri is 4.3 light-years from earth, and your theory is true.

Answer 2

What an idiot that guy above is. It does not take a second for the sense of touch to reach my brain. Try 1/10000000th of a second.
Yes something that is 4 light years away does mean the light from it took 4 year to get to you. Therefore the light itself is 4 years old. Alpha Centuri could have suffered some type of devistating problem and no longer exist. We would not know until four years after the fact.

Answer 3

Yes that is true.Since it is 4 light years away, it takes light 4 years to get to Earth.And yes, since Alpha Centauri moves like everything else, you are not seeing the present Alpha Centauri.

Answer 4

Yes, that is exactly what it means. Today you see it where it was 4 years ago and 4 years ago you saw it where it was 8 years ago. And so on. It does not make any difference at all in how fast you would see the star moving, you just see its position in the past. Like watching a movie the day after your friend saw it. You see all the same movement in the movie, just a day later than your friend. So the fact that we don't see the stars where they are right now isn't really important. Also, compared to their distance, the stars move very slowly, so it takes thousands of years before they shift position enough to notice. That is how we are able to see the same constellations that Plato or Galileo saw.

Answer 5

Yes. When you look at Alpha Centauri, you're looking at what it was doing 4 years ago. And that's the closest star. Others are millions of light years away. Alpha Centauri could have gone supernova and exploded, and we wouldn't know about it for 4 years.

Answer 6

Yep, that is absolutely correct. We are seeing Alpha Centauri as it was 4.3 years ago.

Remarkably, at this very moment, the Alpha Centauris are seeing us as we were 4.3 years ago.

So which one of those is "now"? Whose perspective can be described as "now"?

Space and time are not linked together in relativistic physics! Kinda wild to consider, isn't it.

Answer 7

Yes. in other words, the current position of Alpha Centauri will be visible to us only in another 4.3 years' time.

Answer 8

Hi. Alpha Centauri will have moved but not by an amount visible from Earth. Look up "Barnard's Star" for info on a star that is moving (from our point of view) faster than any other.

Answer 9

of course. you're seeing alpha centauri as it was 4 years ago, and where it was 4 years ago.

mind you, when you're looking at the sun, you see it as it was about 8 min 15 sec ago. And when you're looking at the moon, you're looking at it as it was about 1.3 seconds ago. And when you're looking at a friend during conversation, you see him as he was about one 300 millionth of a second ago. And when you take someone's hand and feel that touch, well the signal takes maybe 1 second to reach your brain so you're also behind the times.

And when you hear the sound of thunder, the lightning will have stopped many seconds ago.

So yes, it is a bit frustrating to think that all the stars we're looking at could have disappeared years, or for some million of years, ago, and we wouldn't notice.

But when you think about it, the same holds true for our daily lives.

Answer 10

yes, the current actual position of Alpha Centuri is not where it appears to us to be