Bonus panel:
Then there’s the theory of gravity, this is our attempt to explain why gravity exists and why it does the things it does.
Not just the why, but also the what. We didn’t observe gravitational waves until 2015. People have proposed the existence of dark matter and dark energy because observed gravity doesn’t behave as our models would predict at certain cosmological scales.
I like to think of it in this way: What we call dark matter isn’t the cause/source, but the discrepancies we’ve seen in our observations/data. So anybody who says dark matter doesn’t exist is plain wrong, the discrepancies are there plain as day. And it isn’t a single thing, it’s many discrepancies in a lot of data. Now the name is probably not as good, as it isn’t clear it’s actually matter and it isn’t dark but simply doesn’t interact with EM radiation. So we can’t “see” it directly, only indirectly. The name is so poor, it leads to a lot of miscommunications. But the fact is, the data doesn’t match up. So there has to be something there. And that’s data going back almost 100 years.
Just like I said about gravity. There’s dark matter, the real thing that exists and we can “see”. And then there’s the theory of dark matter, the how and why, the thing we haven’t figured out yet.
So anybody who says dark matter doesn’t exist is plain wrong, the discrepancies are there plain as day.
There’s dark matter, the real thing that exists and we can “see”.
No, we have observations that are consistent with the existence of matter that does interact gravitationally with regular matter, but does not appear to interact with light or electromagnetic forces. It’s not like any matter we know about, other than the fact that it seems to have gravity.
General relativity works really well to explain matter in the solar system. Bigger than that, you have to use something else. The general consensus is that dark matter exists, but it’s not strictly proven, as there are alternative theories.
Then, even bigger than that, dark matter alone isn’t enough, you need dark energy to explain some observations, if you assume that cosmological constants are constant. If it turns out that they’re not truly universally constant, we might need to modify some theories (including the proposed existence of dark matter and dark energy).
