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jinxprotocol · Aug 12, 2009, 05:54 PM

I recently watched a program on the Science network about the history of the universe, and a representative from Hubble said that pointing the Hubble Telescope into deep space represented looking back in time. What does this mean, exactly? It's not a literal statement, is it? Does it relate to how long light takes to reach us? I'm just getting into learning about the cosmos, so please help me! Thanks.

HelpinHere · Aug 12, 2009, 06:00 PM

Yes, it does relate to the speed of light. And, yes, it is literal. However, it doesn't mean we are seeing what happened on earth back in time.

To put simply. Something 10 light years away, a star. When we see the light from that star, we are seeing the light it made 10 years ago. It may look like a white dwarf now, but between the time it took for the light to reach our eyes, that star could have died.
Does that make sense?

JimGunther · Aug 12, 2009, 07:06 PM

I took a lot of astronomy in college and I can guanrantee you that when you look up in the sky, you are not seeing the stars or other distant objects as they are now, but what they looked light when the light that is hitting your eyes now was generated from their surface, this could be billions of years ago.

When you look at the Sun (don't make it a habit), you are seeing it as it was about 8 minutes ago.

Capuchin · Aug 21, 2009, 07:20 AM

I would argue that it is be meaningless to say that how we see the stars is not how they actually are. It doesn't really confer any actual information.

This might be a little too philosophical though :)

HelpinHere · Aug 21, 2009, 01:09 PM

Originally Posted by Capuchin

i would argue that it is be meaningless to say that how we see the stars is not how they actually are. It doesn't really confer any actual information.

This might be a little too philosophical though :)

Hmm... I see your point... I think... correct me if I'm wrong.

Since we can't travel at the speed of light, then how we see them, is how they exist from our point of reference. Because the information we receive is however old we think it is, and if we sent a deep space radio telemetry satelight to send us back information, that would take even longer, then how we observe anything through a telescope might as well be exactly how it is, because that light is the closest to a present reality we could ever experience here on Earth.

Or, at least, that's what I think you are saying.

But, because of the speed of light, from the stars' point of reference, we are behind, but it really doesn't make any difference for us. (except a lot of headaches)

JimGunther · Aug 21, 2009, 08:45 PM

The knowledge that the image of a star is something that reflects past, not current reality is an important bit of knowledge to the science of astronomy. In determing how long it takes for the "image" of a star to get here, and how that image presents itself, we can draw scientific conclusions about the universe. In other words, we can learn things about the universe by knowing that what we are seeing is not present reality, but reality as it was sometime in the past. For example, by looking at the spectrum of the light from a distant star, we can learn something about its composition and its direction of travel.

We can also make some judgements about the size of our universe, because we find that images of stars are never are older than a certain age, and this might mean that the universe is no older than the oldest inages we see, or that there are objects out there that are much older but whose light has not got to us yet.

The more we know about what goes on in the universe, the closer we are to knowing about the true nature of its, and our own, existence. And we are just beginning in our quest.

HelpinHere · Aug 22, 2009, 05:22 PM

Originally Posted by JimGunther

We can also make some judgements about the size of our universe, because we find that images of stars are never are older than a certain age, and this might mean that the universe is no older than the oldest inages we see, or that there are objects out there that are much older but whose light has not got to us yet.

Or, that light cannot travel a certain distance, or plenty of other theories.
When it comes right down to it, by simply staying on Earth, we have no way of proving anything, and theories is all we can come up with.

I think it's a waste of time. We are investing so much money and time and effort on something that can't possibly help us right now. Why not cure cancer, for all you know, someone that has cancer could discover faster-than-light travel if he were to live 10 years longer. I mean, it was a farmer boy who invented the television by looking at rows of corn, so why can't we see that anyone could discover the next thing to further us, and work on saving people instead of making pointless theories?

Sorry, I am rambling... :o

JimGunther · Aug 22, 2009, 06:17 PM

Its amazing to me that there are actually arguments in favor of the notion that the study of astronomy is pointless. We cannot live on this plant forever, it is doomed by forces in the universe that will eventually destroy it. If we don't advance far enough in our study of the universe before these catastrophic events occur, all human life could be lost. What could be more important?

jinxprotocol · Sep 2, 2009, 10:04 AM

Okay, I think I'm getting a better understanding of it now. But what about when we use a telescope? How does that effect what "time" we are seeing? When we look through a telescope at something 1,000 light years away, are we still seeing the light from 1,000 years ago, or does the magnification affect it somehow?

jinxprotocol · Sep 2, 2009, 10:14 AM

Originally Posted by HelpinHere

I think it's a waste of time. We are investing so much money and time and effort on something that can't possibly help us right now. Why not cure cancer, for all you know, someone that has cancer could discover faster-than-light travel if he were to live 10 years longer. I mean, it was a farmer boy who invented the television by looking at rows of corn, so why can't we see that anyone could discover the next thing to further us, and work on saving people instead of making pointless theories?

This is a complete non-sequitur. Many of our breakthroughs in medical science have a direct correlation with breaththroughs in the technologies of our other sciences. Cures for cancer won't come from research in a scientific vacuum. Think of the way that discovering X-Rays - not a medical discovery, by the way - helped us with, well, obviously X-Rays. How many people's lives have been saved due to that? :)

Truth is, all of these things work in connection with one another, and we should encourage the advancement of most all sciences, since they end up helping humanity in most circumstances. It isn't just people looking into space for the sake of it (i.e. a waste of time). That is a quite monstrous assertion, and it is unenlightened dogma.

Unknown008 · Sep 7, 2009, 10:49 AM

Originally Posted by jinxprotocol

Okay, I think I'm getting a better understanding of it now. But what about when we use a telescope? How does that effect what "time" we are seeing? When we look through a telescope at something 1,000 light years away, are we still seeing the light from 1,000 years ago, or does the magnification affect it somehow?

Magnification can only affect the colours that you see. I don't think that it would affect in any way the 'age' of the light that we see. Better telescopes makes use of mirrors instead of lenses to focus on a distant star.

TUT317 · Sep 7, 2009, 03:48 PM

I was interested in Capuchin's comment earlier. It sounds a bit Newtonian. If the sun were to suddenly disappear then all of the planets of the solar system would immediately experience (at the same time) zero gravitational attraction.

Could you expand a little more on your earlier statement?

Unknown008 · Sep 8, 2009, 09:01 AM

Well, I don't think that the planets in the solar system will experience exactly zero gravitational attraction. So long two bodies are close, there is gravity. I'm not sure, but Jupiter being the most massive planet in the system may very well attract the other planets... of course, the attraction will be reciprocal with the other planets.

I wonder thought if they could crash into one another because of that 'inter-planetar' attraction...

TUT317 · Sep 8, 2009, 03:06 PM

You are probably right Unknown008. The sun will not suddenly disappear, it was just a thought experiment to see what would happen if we took Newton's Laws of Motion to its logical conclusion. It seemed to me that Newton's laws violate the principle of Locality on a macro scale( information being instantly transmitted from one location to another).
It all seems a bit silly now, but it was suggested there was a element of philosophical realism attached to the idea of 'looking back in time' i.e. what we see when looking back in time at a distant object is somehow not accurate. The 'actual' reality is somehow lost when light travels all that distance.

Unknown008 · Sep 9, 2009, 07:36 AM

Yes, I know that the sun would swell into a giant red star, engulfing the nearby planets, then shrink, burning its last 'drops' of fuel and then 'switch off'. You asked an interesting question, that pushed me thinking, and I loved it! :)

Originally Posted by TUT317

The 'actual' reality is somehow lost when light travels all that distance.

Well, I don't know if that's a fact, but in my opinion, that can be true. With all the cosmic gases and other things that is in between the light source and the viewer, I think that some of the light gets 'lost' (absorbed by other matter).

Capuchin · Sep 9, 2009, 08:22 AM

Originally Posted by TUT317

I was interested in Capuchin's comment earlier. It sounds a bit Newtonian. If the sun were to suddenly disappear then all of the planets of the solar system would immediately experience (at the same time) zero gravitational attraction.

Could you expand a little more on your earlier statement?

Apologies, I've tried a few times to expand what I was trying to say, without much success. Perhaps that's a sign that I'm talking absolute drivel.

I think I was trying to highlight the fact that saying that that's how the star used to be 2 billion years ago or whatever is pretty pointless, because that's all we can see of the star, you might as well say that it's how the star is now, because nothing you do is going to be able to reveal the true present state of the star.

Essentially I'm trying to make a distinction between the photons arriving from the star, and the actual star. You're detecting how the photons that left the star x billion years ago are now. It's not really looking back in time, because it's the only way you can experience that star from our perspective.

Does that make sense? I fear that it doesn't.

asking · Sep 9, 2009, 11:21 PM

As for the discussion between HelpinHere and JimGunther, I think it's unlikely that we will make it out of the solar system before it ends. In fact, I think we will likely go extinct like all other organisms have before us long before the Earth is cooked by the overheating sun. 99.9% of species that have ever lived are gone... There's no reason to think we'll be different --except denial, I guess.

So, if you accept that, then EVERYTHING is "pointless." You can make the same argument about an individual life. Why sweep the floor; it will just get dirty again? Why educate yourself, if you are going to lose all that knowledge when you die? Why improve your house or your city if you won't be around to see the improvement? Why raise children if eventually your lineage will come to an end?

Fortunately, not everyone feels that way. The joy is in the doing and the living. Life is ephemeral.

Why do you sweep the floor? Knowing that tomorrow it will be dirty again...
Why build a house, knowing someday it will rot and blow away?
Why raise a child, knowing it will grow old and die one day?

asking · Sep 10, 2009, 11:31 AM

Hi Unknown,

It's possible that we will cause our own extinction, but that's not what I as saying.

The dinosaurs didn't cause their own extinction, nor did the giant ground sloths, pleistocene camels, or saber toothed cats. The trilobites, which dominated the seas for milenia, are gone. And so shall we be someday. I'm saying that virtually every organism that has ever lived has gone extinct. It is hubris to think we are different and either won't go extinct at all or will go extinct only by our own hand. I don't think our species is immortal.

Unknown008 · Sep 10, 2009, 11:39 AM

The big difference is that we have got technology... I know, nature has its ways, and can be devastating at times. Already, there is climate change, due too much human activity. My point is, human will perhaps be able to find a way to escape the Earth, and establish on Mars for example.

Wait... I've heard somewhere that the first organism that probably was on Earth just after it was formed was some bacteria that could photosynthesise. Perhaps that bacteria is still here... Correct me if I'm wrong (not my field here), but I've heard also that the simplest organism have better chances to survive, even after drastic changes. Once I also heard that cockroaches were one of these simple organisms that were here since very long ago...

I'm not saying the opposite of what you are saying, just trying to clear some matters.

asking · Sep 10, 2009, 01:14 PM

It's true that a few organisms have survived with only small changes for millions of years. But (1) we really only know that they LOOK similar--cockroaches and horseshoe crabs are two popular examples. The modern versions might be different in ways that are not obvious--differences in physiology or behavior, although we just don't know. (2) These organisms are the exceptions. Most organisms disappear over time, either going extinct with no descendants, or leaving descendants that have evolved into different forms.

It's not so much that "simpler" organisms are more likely to survive a big change in environment as that less specialized organisms are more likely to survive. So, for example, an insect that can only eat one kind of plant will go extinct immediately if that plant disappears. Whereas an insect that eats almost any plant can move to a different climate or eat pretty much whatever is available.

Bacteria are extremely diverse physiologically, so it's likely that some of them would survive a drastic change in climate. Some bacteria can live in hot springs, highly salty pools, at low temperatures, and so on. So, yes, at least a few of them are more likely to survive, but it's because they are diverse more than because they are simple.

And some specializations just turn out to be lucky, depending on circumstances. Others unlucky. There are little shrimplike animals that live in the antarctic that freeze solid when the tide goes out and thaw out when the tide comes in. They live like this every day and are fine. These guys would do great in a new ice age, while Gulf shrimp, which prefer warm waters, would likely go extinct. On the other hand, if the world heats up, the gulf shrimp may spread to new habitats while the Antarctic krill go extinct.

The technology that would allow us to make Mars hospitable would more easily allow us to make Earth habitable--if it had become uninhabitable. And if not, why leave? (Maybe I'm missing something... ) In the case of the sun becoming a red giant and overheating the Earth, Mars would be no safer. So we'd have to go further if you are thinking red giant...