@CrystalMarker - oddly they discovered by mistake. the "propel" is due to wind, as it quite flat wind might beat from any direction and then over the ice, the stones glide.
@Penguin_Petey (long note sorry, but point you raised is very interesting, I had written about it in some thread, but at times too much text can feel - yawn-inducing)
So a bit of patience - please - and to the topic -
So Let me start with Drake, who over a lunch-debate about number "sentient" species came up with Drake's Equation on an approximate number of habitable planets in the universe.
So he took most pessimistic numbers in consideration, he looked at Rate of Star formation, a fraction of those stars with planets, average number of planets with potential for life, fraction of life to become intelligent, fraction of intelligent life to go to space, and lengths of time for them to send signals in outer space. (I am just giving a gist of the main thought). This number in the observable universe itself is humungous. This number might go into billions.
Drake formulated this in the 1960's and then later came Fermi with his Paradox. If Drake's number was so high why haven't we heard from anyone yet?
So two main school of thoughts are:
1)
There are Aliens but no one is interested: (why?)
a) They think of us as inferior, there is nothing they could get from us, so they don't care about us
b) All civilizations eventually go mechanical and thus start reaching a state of self-actualization where they wonder and ponder about existence and life rather than going about some space adventures
c) The universe is MASSIVE and our part of the universe is silent and relatively empty
d) Speed of light, it is how we see it. if Alpha Centauri is 4.5 Light years away, What we observe on AC today is how it was 4.5 LYs ago. So if there is someone looking at us they would not even see Dinosaurs as they would be looking back at maybe a molten Earth
e) Space travel is really really tricky, if you go to Jupiter at high speed and return. If you took 2 days, it might be over a week on Earth. Time behaves strangely.
2)
There are no aliens (at least no intelligent space-faring aliens) (why?)
So till the last decade, it was considered hubris to think of humanity as the only possible civilization in the universe. However, lately, some other things have come into Drake's equation which somewhere makes Earth actually an anomaly
a) Our star - Sun is a G Type Star. G Type are most rare in the universe. G Type is stable, they do not expand or contract or throw tons of radiation. That radiation itself would kill any life that might be close to the star. The constant change of the star's pulsation could strip off the atmosphere. So a planet, even with water, the inhabitable zone around any star that is Not a G Type, would have almost zero probability of sustaining or nurturing an intelligent life. This figure is so less than in 100 Light Year distance there are only 512 G Type stars. Out of these 512, only 28 have some form of planets. (just regular planets not habitable zone)
b) Meteors - Twice our planet has been cleansed so to speak. One happened when Earth was settling down and that Meteor most probably brought life to a sterile planet. Life to start needs that seeding that too at the right time. A planet can be habitable yet sterile. That life bloomed and reached almost to the Jurassic age. Then came the second Meteor, if that wouldnt have happened to wipe out the dinosaur, the apes would never get to be dominant species on the planet. So the timing of both the impacts is extraordinary.
c) Jupiter and Saturn - Most solar systems we observe from Earth, have interior planets as large planets with sizes going down as we go away from their star. The reason for this is simple, in earlier stages of the formation of any sun+planet system, all planets are debris and the Star attracts more of them towards it due to its massive gravity. Most debris gets together and forms planets over a period of time. Most planetary systems we observe have larger innermost planets. However, in our case we got Jupiter and Saturn, they have been like big overprotective brothers. Amount of comets, meteorites they attract towards them kept and keeps Earth Safe.
d) Galaxy Core - Galaxies have a core, we are not sure yet what their colour signifies, however, we have recently found that these cores have gone calmer in relatively recent times (recent in astronomical terms). So when the core is not calm it spews a lot of energy outwards, that energy is strong radiation and almost for sure life wiping across HUGE distances. This calmness actually signifies that "Life" in any form is a relatively recent phenomenon. As these Galaxy cores in newly formed Galaxies are violent and spew enough radiation to wipe out any things in its entire star systems.
e) Position in the Galaxy - So Milkway got it's spirally arms. We are on an outward arm, that too almost flat embedded in the disc. Due to this, we cannot even see the black hole that is there in the middle of our own galaxy. If we were little high or lower, the black hole would be visible but its radiation could again wipe out planets in an instant.
e) Moon - A tidally locked Moon, gives us currents, climates, and spin to our axis. More importantly in most of the observable systems, nowhere we have Planet vs Sattelite ratio as Earth vs Moon in sizes. Our Moon is super special.
f) Lastly the basics, a molten core to give us magnetic shield, presence in the habitable zone - the basic hygiene factors.
Thus it feels we are special, There is just one race Human race, and there is just this planet. Not being arrogant but makes me feel more humble to do good.
Phew
