Where have we observed time directly?
Every time a thing happens immediately after another thing, that's time.
Where have we observed gravity directly?
I shouldn't have said "directly", but we certainly observe gravity's effects constantly.
Yes, I'm used to people using "assumption" to mean that what's being assumed is baseless, so I dislike the word. I still consider it only technically correct.
The human mind interprets lots of things uniquely.
How do we know? We seem to agree when a thing is "spicy" and react similarily. Salty, lemony, whatever. We have no reason to presume someone interprets a sensation in a
meaningfully different way. On the occasions we do, we can come up with a name for that difference, like when someone is color-blind and thus lack the ability to sense certain colors. There's no need to get into the whole, pointless, "Is your blue the same as my blue" bullcrap if we can agree that we can call that sensation "blue" and agree when we see it. Frankly, who
cares if your blue is a different sensation than my blue? I don't. We cannot ever know what the other senses as our blue, and it doesn't matter. It's not meaningful to discuss that "problem" (it's not a problem).
What makes "blue" so special? My impression of the USA or my hand or this forum or a poster on this forum is mine and is never the same (exactly) as yours, so what is that impression? It's real isn't it even though it is unique? So why can't blue be like that? Unique even if strange. A color blind person doesn't see blue even though the real phenomenon that causes me to see blue is really out there. What happened to blue for the color blind person?
They didn't sense it. It's pretty much that simple. Just like a person who doesn't feel pain, or fear. Exactly why they didn't sense it, I sure can't say, but
that they didn't sense it is... obvious.
Wait a minute! The rays of light at that particular wavelength may be real, but that doesn't make "blue" real. How do you know this "blue" is there for the color-blind person? How do you know it isn't only in your and my mind?
Because it's verified to exist with light sensing tools. We even know what the wavelengths for blue
are. We also know that color-blind people simply don't sense (at least) one of the three basic colors our eyes detect.
I would put it that blue is an emergent phenomenon and not there at all for the non-blue seeing.
The light exists whether it's detected or not.
One could say those are the same thing.
Yet who is savvy enough to say the heavy weight we feel when we try to jump high in the air is the same as a spaceship flying around the Earth?
The people who calculate and correct the ship's path? Your question is too unspecific, though, since the relative forces are not the same.
Colours do not come from, 'waves of [insert colour] light'...
Except they do, they're simply not one specific wavelength, but rather a combination of different wavelengths.
Study
basic chemistry. There really is an overarching pattern that you just don't understand some very basic parts of science.
There's an overarching pattern that people are using how a thing works to say it doesn't really exist. Also, yes color does come from wavelengths of light. Just because it's not only one wavelength doesn't make it not true. My being less than explicitly specific about the exact process doesn't make me wrong about that.
Just in case you somehow don't understand after reading that: objects contain colour because materials absorb different parts of the electromagnetic spectrum.
We only see what colors they reflect, yes, I said exactly that before in this thread, I'm pretty sure. If not this thread, I've said specifically that some other time on this forum, relatively recently.
It's like how lasers are not actually coloured light - it's light filtered through materials that absorb particular wavelengths while reflecting others.
... Thus they leave the non-absorbed wavelengths. So how is this relevant? What's the point?