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Comment by speedplane | Hacker News Reader

Given that most cosmology relies on a huge percentage of dark matter, which cannot be detected, and a huge amount of dark energy, with enormous conflicting calculations, I think it's fair to say that astronomers are wrong about a lot of things.

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You seem to be having a weird definition of 'detect'. The only reason the concepts dark matter and dark energy are on the table in the first place is that we seem to be detecting a lot of both. You might not like that scientists can't really explain what it is that's being detected, but for sure it's being detected. There's pretty good summaries of how dark energy and dark matter are being detected on Wikipedia [1][2].

[1]: https://en.wikipedia.org/wiki/Dark_energy#Evidence_of_existe... [2]: https://en.wikipedia.org/wiki/Dark_matter#Observational_evid...

People really seem to be having trouble with the fact that dark matter and dark energy are 'placeholder terms' to account for stuff we're actually seeing. With future discoveries in science the terms will be replaced, superseded or perhaps disappear. But observation or 'detection' of both dark matter and dark energy is in fact there.

Not "stuff we're actually seeing" technically, more effects we can't explain using our current theories.

Placeholder is the correct term but people tend to leap from "matter" and "energy" to "stuff" (I'm assuming you didn't intend the implication) without understanding those terms (dark matter and dark energy) are preliminary - if well informed - guesses.

Ok, but at the risk of being pedantic...

They are "placeholders" because our models are wrong. Which is fine: all models are wrong, but some models are useful.

And astronomy is particularly vulnerable to this - its models are being applied to make predications at extremes of both time and scale.

But I PROMISE you, we're wrong. We know we're wrong, and we don't know why (and recently there's even been some fair criticism of our models that we use to gauge distance, so no, I'd argue we have not reasonably "detected" anything other than that our models are wrong - STILL USEFUL but wrong)

Of course dark matter can be detected. If its gravitational attraction on visible matter weren't so easy to detect, there wouldn't have been a reason to come up with explanations for it. That explanation may be wrong, but that's a different issue.

This playlist seems to make sense of dark matter and dark energy: https://www.youtube.com/playlist?list=PLsPUh22kYmNA6WUmOsEEi...

Just because you cannot detect something does not make you wrong nor does it mean it doesn't exist. What a ridiculous statement.

> Just because you cannot detect something does not make you wrong nor does it mean it doesn't exist. What a ridiculous statement.

If you cannot detect something, it's can be equally ridiculous to say it exists.

Many discoveries in physics have quite large timespans between being theorised to exist, and being actually detected.

Was it ridiculous to say those might exist?

Well, most of the other theories back then would seem ridiculous and obviously wrong nowadays. That's the nature of theorizing when you have little information.

Obviously we mostly remember those theories that turned out to be right.

And how do you find out if they turn out to be right, if you dismiss them immediately as "ridiculous"?

That is not how science works. There are other ways of judging if a theory is worth exploring than just a "it must be testable right now".

https://en.m.wikipedia.org/wiki/Russell's_teapot

Not at all relevant, as we can see the effects of dark matter in many places, very clearly.

So you can detect it after all?

We're not sure it's matter, but let's just say 'dark matter' is a useful abstract label (like 'teapot'). We know that SOMETHING is perturbing our models that are useful (to simplify the analogy, let's just posit that newtonian orbits are casually affected, for example) by measurement. As much as an orbiting 'teapot' is ridiculous, it's also provable that something is unaccounted for, 'teapot' or 'dark matter', whatever the label.

This does not mean that it's matter specifically (just a label), but is a phenomena.

Indirectly, yes. Directly, not yet.

Define "directly". The definition of dark matter is that it's electromagnetically non-interacting, therefore observing it's gravitational effect is as direct as it gets.

Since we do not know what exactly it is, defining "directly" is not really something you can do.

But, for instance, electroweak interaction is being looked at, I gather?

It's hard to do experiments.

It's a limitation of all purely observational sciences.

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