Physicist Reacts to Why We Might Be Alone in the Universe 

Almost any star can support life under some circumstances. Even with your estimate of 15-20 billion systems the chance we are the only ones with life is so low and thats per galaxy. You start your argument with that universe isn't teaming up with life and end with not in favour of intelligence which one are you trying to prove because according to your maths it is very probable that we are not the only life in the galaxy let alone the universe and if it intelligent life happened once who can say it can't happen again in our massive universe. Life is probably rare but in this vast universe its almost certainly happened again.

@BlazeGamer No, almost any star can't support life. That was the entire point of the SETI paper I mentioned. Using "life" as shorthand for "intelligent life" is a common, if confusing, practice. My argument did not change. There have been some ten billion species over Earth's history. Only one has evolved intelligence. That strongly implies that the odds of intelligence evolving are on the order of billions to one against. Which means that if there are only 20 billion suitable stars, and only a portion of those stars have a suitable planet, the odds of us being alone in the galaxy are very good. This is exactly why I say people who believe intelligent life is common are bad at math. If there are just six criteria that need to be met for intelligence to evolve and the odds of each of those criteria being met is 100:1, then the odds of intelligence evolving around any given suitable star is 100^6, or one trillion, to one. With 20 billion suitable stars in our galaxy, we'd expect to find one civilization in every five similar galaxies. There's no doubt more than six criteria required for intelligence. And I'm confident the odds of each are worse than 100:1. So even one civilization per every five similar galaxies is optimistic. Some galaxies are guaranteed to be sterile. The nearby Triangulum galaxy has low metalicity. It doesn't have the necessary building blocks to produce even simple life. So even if we scale our search up to the observable universe, we aren't going to find abundant life.

​@@johnterpack3940 Almost all stars have planets even if they are only gas giants, gas giants have moons. You also have to keep mind that everything is moving and the universe is old and still going so if an x star is not suitable currently it could be later and it could have been in the past. Also the 21 billion stars is based on the most conservative estimate of only stars like our sun, same temp, age, brightness, size, etc, so this number could be alot bigger than that. I'm familiar with the six criteria argument but its all built on a lot of assumptions that we just don't know for sure. I do agree that intelligent life is probably rare but not to the point that we are the only intelligent life in the galaxy, on the other hand I tend to believe that life itself could be common.

@@BlazeGamer The paper I mentioned does not limit stars to only ones like our sun. There is a range of traits they deemed suitable. Which is logical. We know our sun can sustain civilization. The further you get from those conditions, the less confidence we can have in finding intelligence since we don't know how different a star can be. But we can make some educated guesses. We can say for certain we aren't going to find civilization around a star that has very low metallicity. Without iron, copper, zinc, etc. you aren't going to have life at all most likely. There certainly won't be space-fairing neighbors for us to chat with. Similarly, unstable stars, like red dwarfs, aren't going to sustain evolution long enough for a civilization to arise. We know more than people want to admit. We know there have to be criteria to meet. Whatever those criteria might be, they have to exist. If biology could simply happen anywhere then we would have found it by now. And if criteria exist then there are odds for those criteria to happen. This isn't radical thinking, just basic logic. And if only six criteria are enough to make intelligence rare, what if there are dozens of criteria?

I think when it comes to intelligence it's important to distinguish between intelligent species and space capable intelligent species, because the 2nd is what is the most difficult and most rare compared to any other kind of life. There are too many factors that has to go exactly right for that to happen. There are other intelligent species on this planet like Dolphins, but they are not capable of creating such civilisation. Even when having the capability (like using limbs to create stuff) and looking at us as whole, we exist for roughly 200k years, but for about 185k years we lived pretty much the same way and if the agrarian revolution didn't happen we would still be living the same way and wouldn't have this sophisticated civilization. We may have gone extinct at some point without reaching civilization level just like the Neanderthals, Homo Heidelbergensis etc. (which have the bad rap of being stupid but they weren't stupid at all). So even if a species has the mental capability and the right means to be able to create tools doesn't necessarily mean it would reach level of civilization. This is what makes me more skeptical about other civilizations in our galaxy are there. The other thing is, if we don't find other intelligent species capable of reaching civilization in our own Galaxy does it really matter if there are in anither galaxy? The universe is expanding faster and faster, 94 % is already out of reach and lost to us which means we will never be able to go there. Andromeda is 4 billions of years from collision so for now that's also out of reach. By that time we would be either extinct or if we became an interstellar civilization, we would've already technically created different species when colonizers start adapting and evolving to the new planet conditions so we would be aliens to ourselves and the galaxy can be populated with different species who came from us.

Who’s gonna tell him andromeda is 6 times the size of the moon

@@Top-Code I mean, it appeared to be twice as large but in reality it’s still millions of light years away…did u ever have a otherworldly dream like mine?

@@Sarvesh_C well no I’m saying that the andromeda Galaxy that you can see with your eyes in non light polluted areas, is 6 times larger in the sky than the moon.

That's really weird and you read too many scifi books lmao

@Nepomniachtchi_Austin I don't mean a farmland in the War of Worlds fashion. I mean more like a museum / farmland of information for them that probably is laws restricted to alter or even touch for them too. But every now and again, there's always one law breaker.😆

That implies that other all other advanced species have the same moral/ethical outlook as humans. If a more advanced civilisation exists, It could have developed faster than us due to a supreme generosity and empathy of spirit. Just imagine how much more advanced the world would be if war and colonisation never happened and the human race worked in unity towards a greater future.

Never mind you correct yourself seconds later but then again end with emotions.

So original

@@mutdd3954 Hi Timmy why aren’t you sleeping yet don’t you have school tomorrow ?

@@ramseybolton1258 wow 😂 Mad disrespect to ppl named Timmy btw

If I had a dime for everytime I saw this comment under an astronomy related video I'd be richer than Bill Gates.

@@mutdd3954 First time I've heard of it.