Danijel Gorupec

Did they actually test this? My understanding was that all test hits were performed on non-functional satellites that had predictable trajectories - and if the weapon is designed to target evasion-capable satellite, then they tested shit. Are you saying that the weapon has a local sensing system that locks it on the satellite? I was under impression that all guidance is made from Earth. (Because if the weapon does not have any local sensing, then you can still play the game with an 'imagined evasion-capable satellite'.) EDIT: just occurred to me that even if local sensing is employed, they could still easily reprogram the software to miss 'five yards to the left'... and confirm the expected result using the all-mighty earth-based tracking systems.

Maybe, but such agreements generally do not hold in case of war. Just brainstorming: maybe we can calculate the critical satellite density that can cause the destructive chain-reaction, then make an agreement to keep the density lower.

Why does someone need to actually hit a satellite to test an anti-satelite weapon? You simply imagine a point in space and make your weapon fly through that point at certain exact time - this is a hit. Hitting an actual satellite seems more like an exhibition to me.

I would say it is naive to think that only one thing happens when two civilizations make a contact. All possible things happen instead. There are various fractions and interest groups, 'freedom fighters', smugglers, opposition groups, shady business persons etc. I guess, at least some of them would try to make a contact with us... It is difficult to me to imagine a monolithic civilization (if I imagine aliens as a product of evolution). So, I would say, lack of contact is not due to their rational decision, but must be due to 'technical' difficulties. For the 'technical' difficulties... obviously, distances and limited light speed do not help. But there must also be something else - there must be one more prohibitive rule that I cannot figure out.

Yet, some people cannot live without insulin shots - and it would unfair to ban them from sports (as you know, sadly, many top athletes today are registered as diabetic - is this fair or not?)

This is also my opinion (the existence the 'unlimited' class), but I see drawbacks. For example, drug assisted vs drug non-assisted sports (should there be several 'unlimited' classes depending on the amount of drugs allowed, or should drug usage, like insulin, be completely banned?). Further, soon there will be cyborg kids around - what about them (we already had complains about runners with prostheses).

All powerful. I want to know the theoretical distance that I can still 'touch' by any means possible. I was playing with this number a little, and if my back-of-envelope calculations are any good, then my light ray will not be able to reach an object that is currently farther than cca 5.3 billion light years (and the ray will reach an object at this limiting distance in about 14 billion years). If my calculations are correct, then this 'controllable' universe is much smaller than the observable universe.

what then is the approximate size of this 'controllable' universe? (That is, the part of the universe that we can affect in any way... I don't know if this universe is already named somehow; borrowed the term 'controllable' from the control theory).

If I choose a galaxy near the edge of the observable universe, and I send a ray of light toward this galaxy, will the light ever reach the galaxy?

I did not understand if they added water to the soil or not? (btw, I would be more interested about an experiment to check if lithoautotrops can live there - but I guess it could take a long time to check it)

I see. So it seems the effect is especially pronounced for 'overexposed' stars. So I guess they can have certain control by using proper exposition time. But, since we know how the effect is caused, shouldn't we be able to simply remove the effect from the image numerically? If this can be done, I guess they didn't do it just because the image looks more interesting to general population with all those rays sparkling around.

Recently I saw comparison between an image taken by Spitzer and an image taken by James Webb space telescope (here, for example: https://www.planetary.org/space-images/spitzer-vs-jwst-in-infrared ). Why there are those rays of light visible around bright starts on the James Webb image (but not on the Spitzer image)? BTW, Is there a specific English term for this effect? Also, does anybody know what could be the exposition time needed to make these pictures (both, Spitzer and James Webb)?

I actually wanted to know if there is any domestic animal, or any animal at all, that can synthesize lysine. There is a chapter on the Wikipedia about biosynthesis of lysine, which I cannot understand. It seems that the biosynthesis differs somewhat with (life) kingdom. I cannot conclude anything about the animal kingdom. May there be any truth to the claim that lysine production actually limits how small land area we need for our sustenance?

Once upon, on this internet thingy, I read an article that examined how much we can decrease our land usage if we stop farming animals and start obtaining all our food only from plant farming. They claimed that the needed lysine (an essential amino acid) production is the limiting factor on how low land area we must use (because high-yield crops, grains specifically, are lysine limited). So I am wondering about the most basic question - is there any domesticated animal that can actually synthesize lysine? I see pigs and chickens are given lysine supplementation for better growth, so obviously pigs and chicken can not. Can any animal at all synthesize lysine or is this ability only reserved for plants, bacteria, fungi? Also, I see lysine is massively produced by bacterial fermentation from sugar. This seems good enough, but I was wondering if the molecule can be synthesized in an industrial process without any biological agent (well, the molecule does not seem that complex to me)?

I never heard even a good definition of consciousness, and so I don't expect there can be a test. But the philosopher in me speculate... If you can communicate with the subject, maybe simple questions like 'what do you think' or 'what do you feel' would suffice. This might show if the subject is aware of its own thinking process, and maybe even if it possesses a model of its own mind... I really have no idea, but I always felt that having a model of your own mind has something to do with your own consciousness (well, it sounds recursive - a mind with a model of itself)

I am not sure what do you mean by this, but I suppose you speak about yet unknown species or branches of life. Unfortunately, up until now we didn't find any 'alien' here - all life we met were our relatives. For me, this is worrying and is a hint that life might be a rare event. If we could find anything completely separate here on Earth, that would be a big deal. Fortunately, there is another way to think - it seems to me the life on Earth started very quickly after the last sterilization event (like the Theia impact, but I would guess there might be few smaller ones that followed).... hinting that that life arises readily. True, but I think it is more likely that if life ever existed on Mars, it must still be there - possibly underground. I just don't see how a very slow change, even into extreme, can eradicate life... My understating is that we only recently discovered the life deep below earth surface, so I guess there is still some hope for Mars too. Still, for me finding it anywhere, anytime would be a major thing - completely changing my mindset. Maybe I would even start writing SF again Yes, I sign that belief too.

Yes, that was also my thinking.... I was afraid that they plan to kill the shark; which would make no sense unless sharks can quickly habituate to new food. Fortunately, Beecee explained that they are only planning to move it somewhere else. Easily possible. Still I would imagine that there are actually too few shark attacks worldwide that science would have some reliable statistics about wet suit color and shark attack probability? [Which leads me to a funny idea ... let's paint seals into various colors and patterns and check if some can survive for longer... and then paint our wet suits accordingly.]

I don't understand two things: - what are they doing while beaches are closed - do they look for the shark? - what will they do if they find the shark? It only makes sense to me if sharks can learn the new food source (like tigers, perhaps) - do they?

I first heard about 'von Neumann' machines when I was a kid. Since then, I occasionally think about it. As Ken Fabian, I also think that it is easier to build an ecosystem of machines (or, better, a 'super-organism' of machines) than a single self-replicating machine. I also think that it could be easier to accomplish this in nanotechnology. For the difference, I don't think it is impossible. In fact, I think it is inevitable (if we manage not to destroy ourselves sooner). Once our artificial intelligence machines become sufficiently advanced and self-motivated, it seem logical that they will start experimenting with self replication. Or, humans themselves might start experimenting with from-scratch designed bio-organisms using already-proven self replicating 'technology'. Maybe it is possible to intelligently design organisms that have properties completely out of reach to the good old evolution. Although, I must admit, if it is that easy... where are they?

Yes, indeed.

Do we keep discovering life or life forms? I am not a native English speaker, so I am not sure if 'discovering life' is to mean discovering new separate life or new forms within the same single life (as you can see, I don't know how to even ask this question properly)? Ah, but you must be aware that this is a limiting definition - If you strictly use it, you might not detect extra-terrestrial life even if it slaps you in the face. I don't know how to define life, but always felt the best way would have something to do with actively maintaining complexity within less complex environment (that is, in spite of statistical mechanics that works against life).

Yes, the possibility that we bio-colonize a non-sterile world is the real ethical problem. And I don't think we are ready to try this experiment yet, not even on (in) the Moon... But after decades of honest and concentrated effort to find life at some world, I guess we should be able to take the reasonable risk. And it seems to me, if the alien life is so much different that we aren't even able to sense its existence after extended efforts, then I guess it is a good chance the clash between life will be delayed - we might have hundred more years between the two start to interfere. So not everything is lost in one single moment of the first colonization... It would be a major scandal, though. On the other hand, I don't feel any ethical problem with colonizing sterile worlds - I am surprised that other people in this thread expressed concerns even with that. And I am only considering colonization within solar system. Near-blind colonization of extra-solar places, that seems to be the focus of this thread, is not exciting to me and indeed might be pointless at this moment of our development. Hmm... can our chemolithoauthotrophs 'infest' Moon or Ceres - an exciting question. Even if they are too slow to show much result in my lifetime. Of course, finding native chemolithoautotrophs there would be even more exciting. Hmm... just thinking... if life ever existed on Mars, then it had to produce chemolithoautotrophs too.... and they must be still alive. For me it is difficult to find reasons not to be so.

I also think that a point is missing - one that a theory should not be more complex than necessary.

My thinking was more down to solar system. Possible targets don't have to be Earth-like. Perhaps: - Mars sub-surface - clouds on Venus - oceans of Europa, Ganymede, Enceladus I guess, a simplest type of experiment would be just seed those places with collection of unicellular organisms and observe how things will develop. (Imo, it would be harder than we think).

I am supporting the idea (once we are damn sure the target world is sterile). Much to learn about life. The problem is: who decides what to do and how to proceed. There is no 'world-level scientific government' or similar. So, it seems thugs will just happen. I understand, we had already some experience with unintentional life spreading on ISS. But ISS is a nice place. So, I still wonder if all this sterilization of Mars rovers is necessary - maybe we wouldn't be able to spread life there even if we try hard. Thinking to extremes: what if we never ever encounter any sign of life anywhere in the Universe - would we then be morally obligated to spread it out, or should we keep it confined here on one fragile planet?