I blame history/discovery channel for these sorts of misconceptions. In their astrology and cosmology type documentaries they often talk of "seeing into the past" when looking at distant stars, since indeed what we are seeing is something that occurred ages ago, and it is easy to get caught up in the magic of it all, seeing something from so long ago and far away, and convince ourselves that we are actually "seeing into the past."
It's not that the phrase is inaccurate, but that it's not a scientific statement at all, rather a metaphorical or poetic statement about what we are looking at.
But it's merely that
a star throws a photon at you and it takes awhile for your eye to catch it. This is no more time travel than, as Zapper said, receiving a letter that was sent which takes you awhile to receive.
When you watch a video on youtube, are you "seeing into the past?"
When you read a novel by Charles Dickens are you "seeing into the past?"
In our imagination it can feel like it. But what we are witnessing is simply the current effect of an even that happened in the past. It's just that this fact is exaggerated by the immense distance of the stars and the immense time that has passed. I think this mystique is not even lost on physicists and astronomers who know very well what is actually happening.
Without this exaggeration the fact that we're not seeing into the past becomes more obvious. If you look at the sun (don't) you're seeing light from 8 minutes ago. This is still pretty remarkable, but perhaps not so much as billions year old light. If you're gazing at the moon you are seeing light from about 1.3 seconds old. If you are looking at a light on a street, a light in your room, your computer monitor or anything at all, you are looking at light that was emitted at some time in the past.
To me the most amazing thing is that we can't see anything BUT old light. Perhaps this is what leads to misconceptions about time travel. But again -
it's just that a thing throws a photon at you and it takes some time for your eye to catch it. That's all.
The second mistaken idea was " I mean if we were to create a "machine" to take us instantaneously right at the stars as we perceive them, we would go to a place back in time"
It was answered by Pengwuino:
No. If you receive the starlight, then that is what the star was doing X million years ago or what have you. If you were able to instantly go to that star, you would see what the star would be doing after having lived for another X million years.
And Flexgunship:
Negative, friend. If you could travel to them instantaneously, you would be close to the source of the light. The light you see at that point would no longer be delayed by the extreme distance. Instead of seeing old light, you would simply see "current" light.
Which say the same thing, though the first explanation took me a few reads to get what he was saying, as it seemed to imply the future "another X million years." But of course he was referring to the present ("current") light. Sometimes I just read too fast.
I think I've managed to grasp the OPs line of thinking here. "If when we look at stars, we're looking at the past, then by going instantly to the star we will instantly go back to the past."
But I think this should be clear now. "Looking at the past" just means it took your eyes awhile to catch the light that was sent at a later time. Over at the actual star, there is nothing extraordinary happening time-wise. It's just throwing more photons all over the place including in our direction.
By going instantly to the star you'd basically be getting a head start on what we earth-people would see some billion years later. If I send Zapper fan-mail once per day, it takes him 3 days to receive it and he receives one letter per day. If he travels instantly to my location, he may catch me in the midst of writing another letter. Before he can tell me to stop this creepy behavior I have already dropped the letter into a mailbox which zapper cannot get into. After throwing up his arms in frustration, he goes home, and three days later he receives that same letter. At no point did he travel into the past, but it did take him awhile to receive the letter.
Similarly if I travel instantly to a star I will see photons that are being thrown my way, and when I instantly go back home I will see those same photons a few billion years later (when I'm in the ultra-old folks home).
-DaveKA
