c) An alien civilization can trivial visit Earth and has been for thousands of years.

You make a lot of assumptions how difficult it wouldv be to visit and even why they would be here.

I assume that interstellar travel is really difficult for any civilization. That assumption is based on my knowledge of physics (relativity in particular).

> That assumption is based on my knowledge of physics

based on your knowledge of known physics. We're still adding to the periodic table...

>We're still adding to the periodic table...

That doesn't violate known physics in any way.

Very true, but the point is it just shows there's a lot we don't know still that an advanced civilization might and likely have already discovered and learned to harness/control.

>based on your knowledge of known physics.

Right, and for exactly that reason, it enjoys the advantage over competing theories.

We're not still adding to the periodic table. https://en.wikipedia.org/wiki/Oganesson , 118, was synthesized in 2002, and confirmed in 2015 and I don't think anybody is actively working on making https://en.wikipedia.org/wiki/Ununennium or https://en.wikipedia.org/wiki/Unbinilium for lack of resources right now.

If somebody is aware of groups actively working to synthesize above 119 please let me know.

Why is it difficult? You just point and shoot. Will take a long time but you will get there in the end.

First you need an incredible amount of energy to get even a modest mass out of the earth's gravity well. Then you you need a truly fantastic amount of energy to get it up to a fraction of the speed of light. Then you need an equally fantastic amount of energy to slow it down again at it's destination. Then you run into time dilation effects, which diminish the usefulness to the sender of any information they are going to get back (due to the delay).

My point was that you don't need to go fast if you have plenty of time. You just need to get out of gravity which we can do.

Going slowly has it's own issues. If it takes you 100,000 years to cross the space between 2 stars, you are going to need a lot of energy/food to keep your crew/robots/computers going - because there isn't going to be much solar energy available. Also is any civilization going to invest the effort to create a probe/mission that they are not going to hear back from over that sort of time-scale?

I thought that way 3 or 4 years ago. PBS Spacetime has quite a few great videos about that. (Videos by actual physicists and astrologers.)

Extend that too: a) An alien civilization has overcome the massive problems of interstellar travel and is able to visit in a manner that doesn't create a second sun in the sky

Seriously people underestimate the ludicrous energies involved in near-c travel. Even with engines off at those speeds the interstellar dust undergoing nuclear fusion off your hull will give you away

But what if it's 0.5c travel?

That's a massive difference from 0.99c travel

Agree, visitors may have traveled for millions of years to get here. We should not project human timescales on aliens.

Humans as we know them today will never visit other galaxies, but our AI descendants almost certainly will.

If you have 20 million years and don't mind waiting, you can send probes to every system in the galaxy at sub-light speeds.

Idk what’s so special about the speed of light/causality, in an alien universe it may not even be relevant. When talking about alien intelligence and technology literally everything is on the table.

> literally everything is on the table

Right, they could have ridden dragon-unicorn hybrids through a magic portal made from the dust of black hole centers.

That's what you mean when you say "literally everything is on the table."

Or, start drawing lines for me if you disagree.

There is only one universe

I'm not sure we will ever know if this is the only universe. However it seems highly unlikely that aliens could travel from another universe and, even if they could, bring their own laws on physics with them.

with coldsleep technology, or a species evolved or self-engineered for ultralongterm hibernation, speed might not matter.

Having just finished Iain Banks excellent The Algebraist, this is immediately what came to mind: we have no idea what timescales aliens would operate on.

Machines would be more likely than anything biological in any case. Not implying this is what we have here, just a general observation. It's weird people believe space travel requires pilots.

> Machines would be more likely than anything biological in any case.

Counterpoint: biology is a machine in itself.

Our machines of metal and microchips are incredibly primitive compared to where they'll be in 100, 500, 1000, 10K+ years from now - and when a machine has the ability to to self-replicate, have autonomy, and to protect itself from microscopic threats, then it sure looks a lot like life-as-we-know it.

Extend that too: a) An alien civilization has overcome the massive problems of interstellar travel and is able to visit in a manner that doesn't create a second sun in the sky b) then crash

Why near c travel is assumed?

To be fair, COVID escaping from the one and only lab capable of doing that kind of research in the area seems the most likely too. However, the best evidence so far points elsewhere. Sometimes the unlikely circumstance turns out to be the real one.

Occam's razor.

Even at non-relativistic speeds self replicating robots could have visited every star system in the galaxy within a few tens of millions of years. We haven't seen any evidence.

Everyone has the most advanced cameras in history in their phones and there's exactly zero indisputable pictures of UFOs, ghosts, fairies, chupacabras, Nessie, Bigfoots, Yetis, and so on.

If aliens can travel even a light year, they almost certainly also have the technology to not crash.

There are zero indisputable photos of 99.9999999% of things that happen on earth. I mean, even if you have 10 separate people seeing the same thing and someone videoing, that's still disputable. You'd need a stadium of observers and several camera rigs before photo/video evidence would be the necessary level of "sure" to be considered indisputable when it comes to UFOs.

Agree with everything you’re saying except the cameras in phones. Cameras in phones are advanced but most do not have kind of optical zoom. Try to take a picture of a plane flying overhead with your iPhone or a bird. It’s hard to get a clear photo of something so far away.

But surely you can get a clear shot over your shoulder as you are being probed? ;0)

>Everyone has the most advanced cameras in history in their phones and there's exactly zero indisputable pictures of UFOs, ghosts, fairies, chupacabras, Nessie, Bigfoots, Yetis, and so on.

This is key in why I was much more optimistic of finding any of those paranormal items than I was 10 years ago. I hope I'm wrong.

there could be life in our solar system or at the bottom of our own oceans

Or c) we live in a simulation, and simulation admins break the 4th wall sometimes to leave us gifts... from Jeanne D'Arc to UFOs

and Shazaam!

Can't there be a c) of "Who the hell knows, but there's a lot of evidence piling up." I'm with you in that I don't believe that an alien civilization that has overcome challenges of FTL, etc. would come to Earth to apparently joy-ride. There's something else that's causing trustworthy individuals to make these claims. At this point I just call it "magic" until a better word comes along.

One theory is that these bogeys have been here as long as we have and are basically automated tests, sort-of like the monolith in 2001 A Space Odyssey. It's ridiculous, but less ridiculous than a). The more I think about it, flying octopuses from Europa is less ridiculous than a).

The spacefaring octopuses from Europa aren't going to be impressed with this: https://www.bbc.co.uk/news/science-environment-64814781

Who said anything about a joyride?

The whistleblower clearly is implying that we are being spied on.

Oooh I didn't catch that. I think that's funny. Given the limitations of FTL, etc., that'd be the equivalent of me canoeing across the Atlantic to spy on a nest of rather dull shrews. I should clearly read what he's saying.