“Our knowledge of stars and interstellar matter must be based primarily on the electromagnetic radiation which reaches us. Nature has thoughtfully provided us with a universe in which radiant energy of almost all wave lengths travels in straight lines over enormous distances with usually rather negligible absorption.” -Lyman Spitzer, Jr.
There's nothing quite like looking at a galaxy, all aglow with the light from billions upon billions of stars shining at once. Some reaches our eyes, some is obscured by light-blocking dust, and all of it comes together to give a spectacular sight.
Yet many of the secrets of a galaxy like this are unable to be seen in visible light alone. If we want to know where new stars have formed, where the hottest ones are, where new ones will be forming and what lies behind the dust, we have to look in wavelengths beyond what our eyes can see. Yet our greatest space observatories can do exactly this, at both longer and shorter wavelengths, revealing a whole galaxy's worth of secrets!
Come peer behind the curtain of Andromeda at the highest resolution ultraviolet and infrared images ever assembled on today's Mostly Mute Monday.
Look at the galactic bulge on that one.
Just saw this, Stephen Hawking is doing an AMA (Ask Me Anything) over on reddit for anyone interested:
Brilliant, as ever ..... thanks, Ethan.
Great images, thanks.
But have you considered publishing on anything else but medium? It really is not good. Those images are 90 degrees rotated. Logical top and bottom of the "composite" image are one bellow another. They are split into many pieces, one can't even save them and view them properly.
RSS does not work there and more.
Long story short. That post is good only to click on the link to nasa and get annoyed in the middle.
Otherwise I love all of your posts. I'm reading about half of them. Can you please publish them in full on your blog not just synopsis?
There's nothing like looking at galaxies (and photos of them) for inspiring the kind of contemplation that reaches to the heart of some of our deepest questions of existence, and comes to abide with the necessarily long-term gratification of scientific discoveries.
Now contemplate this:
Over time we expect to find other life in our galaxy. The burning question is, "will it resemble us in meaningful ways?", by which is meant (in astrobiology) such things as whether it is carbon-based, uses water as its liquid transport medium, and uses nucleic acid chains for reproduction.
In all probability we will find a very small number of different "types" of life per criteria such as those, and numerous variations within those types. For example (variation within the scope of carbon-based, water-using, nucleic-acid-using life) we think of a brain as a discrete organ, but consider an animal whose information-processing capacity is distributed through several discrete "nodes" in its body. If it uses carbon, water, and nucleic acids as we do, then it's "similar to us" in terms of fundamentals.
In 1/2 billion years, the Sun will boil Earth's oceans, so by that time our distant descendants will need to have spread into an interstellar civilization, or Earth-originated life will be another tragic footnote in a distant civilization's galactic history logs. As we spread across the galaxy, we will discover numerous forms of life in other star systems, and reached some viable conclusions about the types of life that are possible in our galaxy.
But that will not answer the question of whether biology is convergent across galaxies. The only way to get that answer is to go to another galaxy.
Fortunately another galaxy is coming to us, that being Andromeda, in about 4 - 5 billion years if I recall correctly. (Coincidentally, about the same timeframe as the Sun exploding and wiping out the inner planets.) When the Milky Way intersects with Andromeda, we will gain the only opportunity in all of cosmic history (future as well as past, absent some kind of "new physics" that enables circumventing c) for answering this question.
We will be able to study native Andromedan star systems and study their own life forms. We will find out if Andromedan life uses the same mechanisms as Milky Way life (is there a good adjectival form of "Milky Way"?;-) or if there are other mechanisms in play there.
Now imagine being alive at the time when those answers start to come in.
We can give this to our distant descendants. All we have to do is support sustainability, science, and space exploration, in our times, as our early steps on the road to that future.
Carl Sagan in Cosmos goes into this.
Admitting, as many other theorists on the subject before, that there may be life out there so unimaginable to anything we have seen that we would never be able to guess at their attributes. Then saying that basically, what we KNOW is that these conditions are great for life to develop, so it's likely that we will find life in them.
In Carl's case, H2O is extremely common. And Silicon is not as common as Carbon, even if they have the same ability to assemble into complex life-capable chemistry, and can use so many fewer solvents to modify itself that it is unlikely to be a big player in life.
And that technology requires manipulation of the matter of this reality, therefore some form of manipulative digit not required for locomotion is very much a requirement for *technological* life.
When the Milky Way intersects with Andromeda,
However, this is no more an intersection than a score of people in Wembley Stadium walking from one side of the pitch to the other intersects.
There will be light years of distance between every star, even when merging.
Keep rein on the imagination when you use loaded words like intersection, it can lead you astray.
Nicely put, W. :)
Cool, thanks W.
I'm using "intersection" in preference to "collision" which IMHO is overdramatized. Thinking of "the intersection of sets" in math.
But in any case we're on the same page about that. My hope is that a galactic civilization with decent interstellar capabilities could mount long-term robotic and crewed missions to Andromedan star systems. A civilization that plans on interstellar time frames would be capable of doing that.
For example a many-generational ark ship heads out on a mission where they will be parking themselves in orbit of an Andromedan star with planets identified in advance as harboring some kind of life. They study the planets for some additional number of generations. Then they continue, either back where they came from, or off to establish themselves on a planet just as their distant predecessors did.
Identifying life-bearing planets in advance creates a bias toward finding life that is similar to what's already known, e.g. "type 1" (life as we know it, carbon, water, nucleic acids), or my hypothetical "types 2 through N" (different fundamentals). But where one type is found, others may also be found nearby. That would get us a potential for discovering radically different forms of life.
But all of life has to work in a manner that is scientifically understandable, and the core fundamentals of all of life are syntropy (conversion of ambient energy & materials into biological mass and functioning), metabolism (utilization of consumed matter in conjunction with ambient and stored energy), reproduction, and information storage & transmission. We should be able to spot those characteristics when we observe them, even if what we observe appears to be a bunch of rocks on a rocky surface.
Speaking of imagination...
Yes, technological life requires ability to manipulate matter, which requires opposable means of gripping objects. Though one could write interesting "devil's advocate" fiction about a species that requires cooperation of two or more members, each with non-opposable means of gripping, to grip any object and manipulate it.
This would be one heck of a difficult story to write because it would require envisioning the entities' anatomy and entire backstory of how they came to learn to cooperate in finely-coordinated manipulation of objects, and how they can communicate well enough to perform coordinated activity and so on. Then, every detail of culture that we take for granted because we have thumbs. And enough of their recent history to be plausible.
The closest I've ever come to that was to envision a culture in which the type of disability caused by thalidomide was the genetic norm: a culture in which all persons were incapable of feeding themselves without technological aid, but could feed each other as their bodies were naturally built. This would lead to "eating relationships" being the primary relationships of spouses and families, rather than sexual relationships or something else.
Any sort of technological life also requires to be terrestrial, since all known means of processing raw minerals into technologically usable form require heat in quantities that entail controlled use of fire to begin with. Thus no matter how intelligent an aquatic civilization may be, it's a dead end in terms of cosmic selection: it can't build the tech to get off its home planet and avoid solar incineration.
That would also make for interesting fiction: Earth-lineage life explores watery planets, finds a way to communicate with their advanced-intelligent but nontechnological native species, and seeks to convince them to accept help to move to other star systems to avoid extinction when their Sun eventually goes nova.
Fair enough, G "Collide" is commonly used and intersect isn't anywhere near as bad.
I'd probably use "pass through". AFAIK we're still not sure if our galaxy will merge with Andromeda or not, but likelihood is that most of the mass will remain in a new galaxy and much will pass on in another, whilst a large amount will be thrown hither and yon.
As to other types of life, I don't know that they'd be different enough, even if based on a different chemistry, to be other than "Type 1". I'd posit any type 2 to be based not on chemistry but on some other physical process.
Another planet's life could be based on carbon like ours and be no more compatible with our chemistry than the silicate bodies of dead coral.
As for non recognisable chemistry, we really have to just wait to see what happens. It's definitely something to keep in mind before declaring a planet lifeless. Though if the planet didn't form carbon chemistry based life, it's unlikely to manage to produce NON carbon chemistry based life if it were to be anything like compatible with our own.
A cautionary take against terraforming.
See EE Smith's Masters of the Vortex for an example of how presuming lifeless planets based on what you think life means and then making it suitable for life could appear like.
NOTE: It's entirely fiction. Just in case...