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How do we know the universe outside our solar system truly exists?

This is something that has been bothering me for a while as I’m diving through space articles, documentaries etc. All seem to take our observations for granted, which are based on the data of the entire observable universe (light, waves, radiation…) we receive at our, in comparison, tiny speck. How do we know we are interpreting all this correctly with just the research we’ve done in our own solar system and we’re not completely wrong about everything outside of it?

This never seems to be addressed so maybe I’m having a fundamental flaw in my thought process.

Krudler , (edited )

How do you know the bird in the tree over there is real?

Well you can see it, photons have been emitted from the bird, which are captured by your eyes.

This is fundamentally identical to how we detect objects in deep space, we capture the photons, the neutrinos, the gamma rays, gravitational waves, whatever energetic emission is coming from them, and that’s how we know they exist.

E

skillissuer ,
@skillissuer@discuss.tchncs.de avatar

In some fundamental way we don’t really know, all you can do is to make a model and then test it as extensively as we can. Then, try to break it and improve it, making it more precise, more general etc. However several things makes that guessing easier

One thing is cosmological principle, ie assumption that laws of physics are basically the same everywhere. One argument that makes this assuption hold better is Noether’s theorem en.m.wikipedia.org/wiki/Noether's_theorem which means that at least some conservation laws are pretty fundamental. We don’t really know if laws of physics were the same in distant past, if they were then maybe there are some other, as of yet not discovered more fundamental laws of physics that hold in both conditions and simplify to what we know today in current conditions

cabron_offsets ,

Bruh. We can see it. We can also “see” wavelengths not visible to the human eye with radiotelescopes n shit.

You can see Andromeda, a whole-ass different galaxy, with your naked eye.

Kolanaki ,
@Kolanaki@yiffit.net avatar

Other than the fact we can see stuff and measure it? In which case: How do you know the solar system itself is real? That you exist? Everything could be a simulation or a dream.

tigerjerusalem ,

Just passing by to say that I love those kind of questions, because it’s so basic and elementary, yet really mind fucking when you stop to think about it. The answers here are really great.

lea OP ,

I absolutely love the answers.

ada , (edited )
@ada@lemmy.blahaj.zone avatar

The answer is predictability. We see things. We don’t know what they are or what they mean. We come up with theories about what they are and how they work. Those theories in turn let us make predictions about other things or behaviours we should see from similar things in the future.

If our predictions are correct, then we know our theories are good at describing what we see, and we thus have improved our understanding of how the universe works. Even if our predictions aren’t correct, we have learnt something.

Rinse and repeat over generations of scientists.

db2 ,

rationalwiki.org/wiki/Last_Thursdayism

blazera ,
@blazera@kbin.social avatar

Whats different in our understanding within the solar system compared to outside? It's telescopes looking at light from far away.

lea OP ,

In ours we can send probes to confirm our observations, but the closest other star is so far away we’ll never even get 1% closer in our lifetime.

I’ve already gotten good answers to why this shouldn’t matter though.

ShepherdPie ,

You could make the same argument about our own solar system during the hundreds of years before space flight or probes existed. We knew the planets were there based on observation alone. There were many theories previously like the Heliocentric model that had our sun as the center of the universe but these were proven wrong without ever leaving the planet itself. The fact that probes now confirm that the other planets exists lends credence to the theory that other galaxies and solar systems exist too.

Krudler ,

There’s lots to learn about and lots of perspective shifts that (counterintuitively) can be found when you start to learn about particle physics.

I started to get into it about 2 years ago, and at first I was totally baffled. I kind of saw that as a fun thing though because it gave me cause to keep exploring backwards until I understood some fundamentals better.

Every time I started to think I grasped something, it just made more questions bubble up.

In the end, for as much as I think I understand about particle physics, I really don’t, but I sure as hell know about all kinds of scientific measurement processes, theories, and underlying concepts of how the universe works (which is fundamentally different than what we assume and what we have been taught).

Candelestine ,

No fundamental flaw in your thoughts at all. Holding reasonable doubts is a core tenet of the scientific method, if we did not do so, that would prevent us from improving and refining our methods over time. We’d still be using things like Newtonian gravity.

This is, frankly, a very good question.

It’s only when people try to hold unreasonable doubts about very high certainty things here on Earth that people start getting a little irritated. Like, is the thing flat? No, no it is not.

Your doubt is about things that we cannot easily verify though, so is more reasonable.

One other thing to keep in mind, is that scientists communicate with us in narrative form, and say things like “such-and-such galaxy is x far away”, but amongst themselves, generally do not. They’re just treating us like children, and smoothing over the details to make things easy for us. Amongst themselves they just refer to the specific data that has been collected, like, “such-and-such light has x redshift”. No narrative translation. They do not think the way they talk to us.

ricecake ,

en.wikipedia.org/wiki/Cosmological_principle

We don’t, but it’s the simplest explanation that’s consistent with our observations.

If it’s not, then we can’t actually know anything about anything in a very real sense.

A related question is “how do you know that the universe outside your mind is real?”.
You don’t. You can’t disprove solipsism, but the existence of external reality is as consistent and significantly more actionable, so most people choose to follow that belief.

dumples ,
@dumples@kbin.social avatar

There are a few assumptions in scientific pursuits and the Cosmological Principle is a big one

IchNichtenLichten ,
@IchNichtenLichten@lemmy.world avatar

Voyager 1 has left the solar system and is in interstellar space, it hasn’t reported anything anomalous so far.

AngryCommieKender ,

Hasn’t hit the wall yet, lol

moody ,

Or it has, and the data we’re getting has been tampered with.

Ing0R ,

Well, with that assumption, the tree behind the window might not be real. OP might live in The Matrix and nothing was real.

HeyThisIsntTheYMCA ,
@HeyThisIsntTheYMCA@lemmy.world avatar

Has it looped around to the other side of the map yet?

AngryCommieKender ,

Oh, shit! That’s a possibility!

peto ,

We don’t, fundamentally. All we can do is construct models and see if they match our observations. How do we know the world exists beyond our sensation of it? That could be an illusion too.

The base assumption that we work on is that the universe is the same here as it is there. Same rules, same interactions. We work out what we should be able to see and then go looking for it, so far that has worked.

As an example, we can look at some hydrogen in a lab and see what kinds of light it absorbs, we can then look at the sun and see if it is absorbing the same light, we can then look at another star and see that it two is absorbing the same light. So we can be confident that the hydrogen in our lab is like the hydrogen in the sun, and that the distant star is made of the same stuff as our sun. We can do wlthis with each element. We can look at the motion of planets around the sun, and we can look at the motion of stars around the center of the galaxy and see that they follow the same patterns.

It’s like trying to work out what is going on in the next room by listening, you can get a good idea, but it could be an empty room with a radio.

kersploosh ,
@kersploosh@sh.itjust.works avatar

It’s the same way you know the things outside your window are real. You look at the light coming to you from that object and make inferences as best you can. As long as new observations and inferences line up with old observations and inferences, then you can be reasonably confident that your growing model of the outside world is accurate. When something doesn’t add up then you revise your model and keep iterating with new observations.

There’s no difference whether the object appears to be within our solar system or far outside it. We see something and we interpret what we can from the available observations. Occasionally, if something is close enough and interesting enough, we send a robot to orbit the thing or maybe land on it and gather better observations, like how Rosetta/Philae visited a passing comet.

CodexArcanum ,

We kind of don’t?

One of the basic axioms (that is, assumptions) of cosmology and physics is that the rules are the same everywhere. We see a big ball of burning gas in the center of our system. We have observations of other bright lights that appear to also be balls of hot gas. Our continued observations fit with predictions we can make, predictions based on our observations and codification of the rules of physics and chemistry and so on. We assume that all these big balls of gas operate on the same principles.

There’s also a general assumption that the rules don’t change over time. That axiom doesn’t fit with what we can observe about the earliest universe, so there are many theories on why physics seemed to work differently in the very first moments of the universe. Likewise, other observations that don’t quite fit those assumptions have led to ideas like dark energy and various theories of quantum gravity.

If those assumptions were extremely wrong, say the universe outside our solar bubble actually obeys totally different laws, and our observations have been misinterpreted, then we’d have no way to know. We need some observation that contradicts our previous observations in order to formulate new theories on why. It’s similar to a simulation argument: maybe god aliens or time beings or super AI or Satan have engineered a fake universe to trick us, but without some true observation that grounds our theories in the repeatable, it’s pointless to speculate because almost anything could be true. We have to build theories on what is repeatedly observed.

cosmicrose ,
@cosmicrose@lemmy.world avatar

There’s no way of knowing if anything we’ve determined via science is “correct,” we’ve just developed a model that is consistent with our observations. There are still plenty of unanswered questions in astronomy.

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