Because we have no means of ever communicating with one’s that haven’t, so they might as well not exist to us.

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Issues, poppycock! Nothing wrong with spinning. Just attach the crew section to the engine section via tether and let it reel out so they're far enough apart that it's not disorienting as you spin them like a set of bolos. 80% of the time it works every time.

I mean, the adjacent line of thinking is "they didn't go down the same path and advanced faster than we have due to some other environmental influence or factor that we haven't encountered."

If your perhaps works, it works the other way, too.

No but the gains we have left won't be things that people assume are possible like faster than light travel, faster than light communication, easy space travel, etc. All this stuff will remain super hard to do or impossible.

We will likely get better computers, communication technology, telescopes, better power sources, better computer learning, maybe AIs, faster travel across earth, but that's about it.

Going out of our solar system or between galaxies is never likely to be a thing that people will do.

Elon seems to be more of a figurehead now. Walks around running his mouth and spending money. While his executives are the ones really running the business.

The success of the Falcon 9 launches is on the personnel actually doing the work, not musk.

Maybe caring about those questions is a human preoccupation. Space lichens might just enjoy the sunlight and the peace of the hard vacuum. Questions are a plague of the brained.

To give some idea of the amount of fuel needed. Say we wanted to JUST send a SpaceX raptor a 2 day burn(About the 1g time to Mars from u/trogon link) about 230,000,000 lbs of fuel and would start off at about 1/460th of a G acceleration. (Ignoring tanks, structural supports etc.) That gives an average acceleration over 2 days of 1/230th of a G.

So, you could never achieve it with combustion rocket engines.

Nuclear engines have much higher ISP, but only in the region of 2-3 times so they'd use roughly 1/3rd the fuel.

Accelerating at 1g for half of the trip and then decelerating at 1g for the remainder would certainly be a way to produce artificial gravity.

However, current (and future) propulsion methods either have high thrust or high specific impulse. This means you can only have 1g acceleration for a short period or much lower acceleration for an extended period of time.

Ships that can achieve continuous 1g acceleration are called torchships in sci-fi but unfortunately there are no predicted methods to produce them yet.

Sure, it would work. Where are you going to get the "unlimited power"? Not even nuclear power is unlimited. It could be used to produce heat, which would be used to kick something out of the rear of the spaceship.

You just need something 50 times the mass of the payload (including that nuclear heater). So 1 part living system & heater, and 50 parts reaction mass to kick out. Now, how heavy is a nuclear reactor that can heat water (or whatever you're using) to super hot plasma?

That would be very interesting, although how could we communicate with them? Would they even know we're here? Would we even know they're there?

Yes, if you have unlimited fuel and/or energy.

Unlimited energy solves a lot of problems.

Which comes back to colonialism and imperialism.

Do you think we're near the end of technological progress?

But then again, other human species had the potential and didn't take it, so why do we assume intelligent alien species would?

Yeah, you're totally right. Also, it doesn't require civilization or industrialization to become space fairing. Imagine this concept:

A type of life that isn't intelligent to our understanding. They're sort of like lichen, so a lot of symbiosis with other species to create one whole. Together, over millions of years, they build massive biological structures that contain entire ecosystems and platform up to the edge of their atmosphere. (perhaps they grow towards light)

In the ecosystems on the edge of their atmosphere, their life has evolved to survive in hard vacuum, high radiation environments.

Their planet gets hit by an asteroid, sending bits of the structure out into space. Space-faring life, no civilization. (this is like the panspermia argument, except it'd be an entire complex ecosystem drifting through space instead of a few micro-organisms)

You're missing a few key possibilities. Travel I'm space, why? Explore, conquer or survival due to lack of resources on home planet. Also if we did discover life on a other planet who knows what it will be. I'm sure there are planets with living microbes and bacteria, hell they survive near volcanoes here on earth. Possibly more advanced civilizations. If they're exploring I would imagine there's a possible unity among beings on their planet , some sort of peace to collectively use ideas and resources for the betterment of their species, existence.

There are documented UAPs (the tic tac videos) of things traveling at 50,000 mph and doing right angle turns. Diving into the sea and not making a splash. It's not the USA, Russia is using 50 year old tanks and 80 year old rifles. China just figured out how to make ball point pens. Maybe the Sentinelese?

It's wishful thinking. We think we will progress a lot further than we have and expect other races to have also.

To be fair most aliens come from places that are much worse off but that’s mainly due to poverty

You can not use quantum entanglement for communication.

If you have two entangled particles, and you measure spin of one of them, you'll randomly get a result 50% of the time that it is up, and 50% of the time that it is down. Depending on that measurement, you know that the other particle will have opposite spin 100% of time, once measured by distant observer.

But for the second far away observer, doing that second measurement on the other particle from the entangled pair, they'll also see particle with either up or down spin randomly 50% of the time. Because, and this is important bit, the 1st observer is not forcing the spin to be either up or down. The 1st observer is measuring it and getting random result, and thus the 2nd observer sees random results from their viewpoint too. The 1st observer knows what the 2nd observer will get even before the 2nd observer measures the other particle on their end. But that doesn't communicate any information to the 2nd observer.

What this means is that the two observers can not communicate (i.e. exchange information) using quantum entanglement.

EDIT:

Think of it this way. Let say we have a set of two "entangled" dice. When I roll my dice, you'll always get the number on the opposite side on your dice.

So, I roll my dice and get 3. This means when you roll your dice, you'll get 4. I roll my dice again, and get 5. You roll your dice and get 2.

For both of us, those are just meaningless sequences of random numbers. I can not set my dice to 3, to force your dice to roll 4. I can only roll my dice, and get some random number; when you roll your dice, you'll get the number on the opposite side. This is what entanglement is.

This means, I can not communicate anything to you using these entangled set of dice. I have no control over what number will appear on my dice when I roll it, and thus I also have no control over what number will appear on your dice when you roll it. From your point of view, the signal you get is simply random noise.

I know, this was a thought experiment.