Or maybe the universe is so competitive that anyone who announces their presence eats the bad end of a relativistic weapon...
But why? That's the question you need to answer. Why would any civilization advanced enough for true interstellar travel even be slightly interested in smashing the Earth with a relativistic weapon, or any other kind of weapon?
Because the only motives we can ascribe to alien species are our own.
R is the one I understand the least so you could be right. In my view star formation on its own is not enough as it doesn't take the star lifecycle into account. In all there are 10 types of star, of which it might be reasonable to assume F/G/K can support planets with life, in which case it would be (R * 0.227 or R=1.589). (22.7% of main-sequence stars are F/G/K type)
F stars are comparatively short lived on the order of 100 million years or so... K stars are so dim that the theoretical "life belt" is so close that the solar winds would overwhelm the magnetosphere and blow away the planet's atmosphere.
You are ignoring the fact that it seems like one highly intelligent and technology-developing species could probably not evolve in coexistence with another one on the same planet, at some point one would win and kill off the other one.
I'm sure it's been proposed/discussed many times before, but I don't know if this concept has an "official" name or not.
it does... It's called natural selection. A niche can only be occupied by one species at a time. If there is competition, the species that outbreeds the other will drive the loser to extinction.
Also, while you're taking the past into account you're not taking the future. In 4.6 billion years whether you want to say 1 to 12 species evolved depending on how you want to frame it. The Earth has an estimated 5 billion years remaining... so lets say in the next 100 years, even a million years, there's an extinction event and primates all die. That's 4.9 billion years for another intelligent species to develop.
Actually the window for Earth closes a lot earlier than that. In about one billion years, the Sun's steadily increasing luminosity will grow to the point that no amount of Gaian adjustment can compensate for, and Earth will join Venus in the Runaway Greenhouse club.
Lastly, and more of a concern than the two previous is that a majority of police training today is geared toward attacking the public. There have been ample leaks from DHS training materials showing this to be true. Military and Law Enforcement agencies are using material claiming that "Patriots" and "Tea Party" type groups are potential terrorists.
This is not an unfounded concern. America has had periods where every now and then it became fashionable for whackos to gather in para-military groups put together frequently in reaction to progressive strides the country had made. In the post Civil War period it was the Klu Klux Klan drawn originally from Ex-Confederate troops. In more modern times there were Fascist and Nazi-Sympathizer BUNDS that would form for pretty much the same motivation only with anti-Semitism and anti-Catholicism spiced with a good deal of anti-immigrant hatred. When you put this together that the largest recent surge in gun ownership was not driven by a reasonable fear of crime, but the unreasoned fear by the election of a Black President, lots of things tend to add up. These studies aren't targeting the Tea Party, they are a recognition that the Tea Party DOES draw in a lot of the extreme whacko type among it's members. Gun ownership and crime are harder things to track, but what we are seeing in a new wave of shootings is a rise of impulse shootings, which have no real clear end to them... not even the survival of the shooters. So when it comes to trying to correlate trends in gun ownership, the real question to be asked is who's now buying guns in greater quantities than before. If the rise is that of the impulse, especially fear or angst-driven buyer than the decrease in crime is DESPITE the increase in gun ownership, not because of it.
2) Surface expedition. Landing at, and taking off from, Mars' surface. Mars' gravity is much stronger than the Moon's - the expeditionary module needs a really big rocket to return to Mars' orbit, which means it needs to be really big.
Don't forget there's also the atmosphere to contend with. Not thick enough to breathe or shield you against anything space throws at the surface, but enough to contend with when it comes to landing AND liftoff.
Setting up shop at a Lagrange point is a whole lot more interesting and likely profitable. Unless you really want little green men.
Profitable in what sense? What exactly is waiting to be mined at a Lagrange Point? It may be a good place to anchor a space telescope, but what beyond that?
Because we need resources, and we can get those resource from asteroids. Also, we need to expand for the survival of the species.
Ironically the tech to make what you speculate to happen will only come about as a spin off from space exploration. People in VR? we need to put them some place, we need them to be able to be still for large amounts of time, we need complete automated systems, and so on.
Technical spinoffs occur when you have any major effort in research and applied technology. There's a popular myth that the space program is the major, perhaps only source of "spinoffs". That's simply not true.
The Chinese. Right. Because they have rovers on Mars... uh... because they have orbiters around Saturn... uh... because they have probes in interstellar space... uh... because they have space telescopes... uh... because they have a mission to Pluto... uh...
Try again.
The US of 1960 had none of those, either. Yet in 1969 Neil Armstrong was standing in the Sea of Tranquility.
The Apollo Mission wasn't driven by the lure of exploration, but by the massive Cold War fear of the Soviet Union getting there first. As bad as Putin might be barking now, we're not nearly as afraid of them as we once were.
Last time I used Google Maps, it wanted me to sign in. I went back to Apple's app, even though it doesn't work as well. My personal paranoia, YMMV.
Google maps wants you to sign in so that you can access your personal lists of bookmarks and places. It's a very useful feature for quickly plotting travel times and routes to frequent places you want to go. I make heavy use of it for public transit. Your personal paranoia is barring your own access to a handy utility. Are they using this data to keep track of your shopping preferences, probably. Do I give a flipping damm? No.
you bought a highly outdated android phone. of course it will make you want to switch to the latest iphone.
The "highly outdated android phone" is running KitKat. The hardware spec difference between the 3 and the 5 and especially the 4 is hardly enough to qualify as "highly outdated", and the software is identical to that running on the 5.
Dynamically binding, you realize the magic. Statically binding, you see only the hierarchy.
