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Posted By: Jdogg Nov 17, 2004 - 01:42 am

I was watching this sci-fi docu-series last night about a hypothetical manned spaceflight to Pluto. In it the crew and ground control were celebrating one of the ground controllers birthday which got me thinking. Relative to the crew: was his birthday (taken to the minute) at the same time as ground control were celebrating or was it at the time that the ship received the transmission of the celebration?

I've read about the experiment with two atomic clocks one at the top and one at the bottom of somewhere (was it Everest?) where a discernible difference was noticed between the clocks. If I travel to the sun should my watch be 8 minutes different to those on Earth?

Another thing that always confuses me: whenever we get a deep space shot from Hubble we are always been told that we are looking back at the beginning of the universe at the most ancient objects - if that's the case then aren't we looking at the most evolved objects and not back at the beginning at all?

Posted By: Magus Nov 17, 2004 - 01:24 pm

Good question. I can't suply that answer, as I'm naught but a humble student. But others may. You make a very good point.

Posted By: Axzazz De`Nyde Nov 19, 2004 - 01:52 pm

Hmm. Those are good questions. If four interstellar spacecraft are taking separate routes to a common destination, and wish to arrive there simulaneously, how do they synchronize their watches?

As regards the photos of the most ancient objects, however, that's more easily explained. If something's 5 billion light years away, then the image that we see today is composed of light that was sent out from the object 5 billion years ago and has been traveling towards us all that time. Thus the image that we see is a lot like a video of the object taken 5 billion years ago and sent to us that we're just now receiving. The object's probably quite different now, extremely evolved or even long gone from existence, but we won't be able to see what it looks like now for another 5 billion years, until the light now leaving it reaches us.

Posted By: Magus Nov 19, 2004 - 06:15 pm

"Put your hand on a hot stove and a minute will seem like an hour. But put your hand on a pretty woman and an hour will seem like a minute. THAT'S relativity!"

Albert Einstein

Posted By: Dark Knight Nov 20, 2004 - 01:23 pm

We are looking back at the objects...

But call me what you want, I believe in Creation, a believer in Creationism....

There are alot of thories that creationists have to do with stars....

And to do with time and relativity....

Some off which are confussing to me....

Anyway under some thoeries the objects may not be that different now, but you would have to wait the 5 billion years to findout....if I understand the thoery correctly.....

We have not agree on a thoery, but to me some are possibilites....

Posted By: Jdogg Nov 23, 2004 - 03:05 am

If I look at an object 5 billion light years away that object isn't 5 billion years old; its age is 5 billion years + the time from the Big Bang to us here now + some 'more'. The 'more' is because the objects isn't moving at the speed of light and so it must have taken more than the 5 billion years to get to the point where it takes light 5 billion years to get back, and as we are accelerating also it gets even more confusing.

Posted By: Queen Ehlana Nov 23, 2004 - 09:41 am

But why would we be looking at the most evolved objects? That's what doesn't make sense to me.

Sorry, I'll think more about this when I get home from school.

Posted By: Magus Nov 23, 2004 - 04:14 pm

Looking at the sky is the truest form of time travel. What we see is not what is really up there. Any number of those stars we look at may have died out millions, even billions, of years from now. And yet we see them now.

Posted By: Queen Ehlana Nov 24, 2004 - 08:02 am

No, I wouldn't say they're not really out there. Time is relative. If that's what you see, that's what matters - it's there. I don't view time as a straight line. Those stars existed, you know... it's like saying that the sun is not really there. It was, is, will be... And if you think about it, yesterday still exists.

Posted By: Jdogg Nov 24, 2004 - 08:24 am

I suppose what I'm trying to get at is: is a far away object young or old? To illustrate my point a quote from some technobabble website:

The most distant things that astronomers can see are about 18,000,000,000 light years away. Thus, the light that we presently see from these objects began its journey to us about 18 billion years ago. Since that is close to the estimated age of the Universe, this light is a kind of "fossil record" of the Universe not long after its birth! Thus the observation of very distant objects is in a very real sense equivalent to looking backwards in time.

See this doesn't make sense to me - if the thing is 18 billion light years away then it must have taken a similar amount of time to get that far away hence that can't be near the birth of the universe.

Posted By: Queen Ehlana Nov 24, 2004 - 04:24 pm

Okay, I knew that, but now I get it... Interesting point. Perhaps it was already that far away when the light was emitted. But I guess then the 18 billion light yrs away wouldn't make sense. Geez, I just read 90 pages on astronomy six weeks ago! Okay, I can't remember how they measure such great distances. It's not stellar parallax, is it?

Well, I guess they measure it to be less than that distance, and then they calculate the "current" distance... assuming that those stars/quasars/etc. still exist. Well, of course quasars still exist. For all we know, the ones we see now have already devoured several galaxies and are giving off billions of times more light.

Posted By: Magus Nov 24, 2004 - 06:18 pm

WOOSH!

That last post went just a little bit over my head.

I just remember learning just what Jdogg said. I don't think I'd have the patience to learn to calculate it all.

Posted By: Nomad Nov 25, 2004 - 06:37 am

Ah yes, the good ole Aerospace Engineering lessons.

Posted By: Magus Nov 25, 2004 - 06:40 am

If I want to know more of Aerospace Engineering I'll go talk to my sister who's home for the holidays.



Happy Thanksgiving!

Posted By: Jdogg Nov 25, 2004 - 07:03 am

Actually thinking about it the Earth might have just winked into existence 18 billion light years away from the object in question in which case it could quite conceivably be that age but it I still don't see how this makes the object 'young'. It appears a paradox to me - the universe is 18 billion years old, we're looking at an object as it was 18 billion years ago; on the one hand. But as the universe cannot expand faster then than the speed of light, if the object is 18 billion light years away then it at least took 18 billion years to get there; on the other. Ok here's a thought - what if the distant object is travelling at near relativistic speeds? This could have an affect - time moving more slowly at these speeds.

I've jusr re-read this and it sounds like I'm contradicting myself - it all sounds plausible and impossible at the same time.

Posted By: Jdogg Nov 25, 2004 - 08:11 am

Happy thanksgiving - whatever it is

Posted By: Queen Ehlana Nov 25, 2004 - 10:04 am

Wait a second... I don't think there are any objects we've seen that are 18 billion years old. That's why we say the universe is like 12 billion years old. If people talk about 18 billion light years away, that's just theoretical, not something we're actually dealing with.

And I think that if we can see something 12 billion light years away, that tells us how old the universe is because it took those 12 billion years for the universe to expand that far. The question, I think, is really just how we figure out how far away things are... unfortunately, that's what I forgot. The only thing I can remember is stellar parallax.

Posted By: Magus Nov 25, 2004 - 08:10 pm

Interesting concept, Queen Ehlana. I never actually thought of it that way before.

Jdogg, how can you not know what Thanksgiving is?

Posted By: Jdogg Nov 26, 2004 - 12:32 am

I've heard of it, know you celebrate it but have no idea what it actually is.

Posted By: Magus Nov 26, 2004 - 05:20 am

Oh, well it's a celebration, that takes place on the fourth Thursday in November, where we all celebrate the first Thanksgiving between the native Americans and the Pilgrims, which subsequently saved them.

Posted By: Jdogg Nov 26, 2004 - 06:58 am

Saved who - the pilgrims or the the Americans? And why? And why's it called thanksgiving?

Posted By: Magus Nov 26, 2004 - 12:18 pm

The Native Americans saved the Pilgrims by showing them how to cultivate the land and how to live in America. Of course, over the next few generations we stole their land, cheated them and drove them into reservations where many died and vamoosed them off of their ancestral land. But at this point they saved the Pilgrims and it now stands as a universal sign of caring and giving. This holiday is more then just a celebration of that first Thanksgiving. It's a celebration of everything that we are grateful for.

Posted By: Queen Ehlana Nov 26, 2004 - 09:46 pm

Aha, I found it! I dunno if this answers your question, though...

Hubble was able to determine the distance to nearby galaxies because he was able to isolate individual stars in them, particularly stars called Cepheid variables. The light these stars give out goes through a regular fluctuation, getting bright, then dimmer, then bright again over a period of weeks to months. A number of Cepheid variables are close to Earth, and for these stars, astronomers had established that the period of the Cepheid variable (that is, the time it takes to go through a bright-dim-bright cycle) is proportional to the absolute intensity of the star (that is, the amount of light that the star gives out). Knowing the amount of light a Cepheid variable was actually emitting and comparing it to the amount of light that he actually received at Mount Wilson, Hubble was able to determine the distance to nearby galaxies. The technique of establishing the relationship between the intensity and the period for nearby Cepheid variables and then using that relationship to measure much greater distances is what is known as assembling the "astronomical distance ladder."

So... err, yeah... That does give you a sure distance, but then that distance does apply to the past. Okay, I don't know what's going on here.