What Did Einstein Mean when He Said Space is Curved?

[Rhondazvous]

How does he define the word curved as he used it to describe space?

He meant well known geometric principles known since Euclidean to be true for angles and lines inscribed on a flat plane would not hold true with physical representations of these lines and angles created on sufficiently large scale in space near sufficiently massivee objects.  Instead these physical lines and angles would behave as if they were inscribed on a curved surface.

That makes sense. So are you saying is that what is actually curved is not empty space but objects of matter in space? Like Alex's example of parallel lines on a sphere.

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now make a triangle inside a saddle seat, and it will be off the other way

Yeah, I grasp it now, but until I started at uni, I was taught three things:  1) Don't pick your nose where people can see you, 2) always vote the straight SDLP ticket, and 3) the sum of the interior angles of a triangle is always 180 degrees.

I was so impressed with what the teaching assistant demonstrated that I asked her out on the spot, hoping she had some other mysteries to unlock for me.

Boru

I could understand this if I knew what's being added. When you say sum, I'm assuming that something is being added. I'm also assuming that , like circlces, a triagle is 360 degrees all around. And this is where I get lost trying to take 3 angles and get 180. I get really lost when I think of right angles, obtuse angles, acute angles. eeteecee. I fear that I'm doing something very wrong.