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.

Unknown008

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

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

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

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' ie, 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

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

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

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 aswell 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 doesnt.

asking

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

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

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 to 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

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...