That is a very good point! Gravity is just such an ingrained intuition that people tend to be ok with saying things go into the spacetime wells, but it is a little tautological.
My understanding is that a more correct intuition is thinking of straight paths on the curved sheet. Say it's like a loosely woven tablecloth - objects in free fall will go along the threads of the weave, so if you stretch the fabric by placing a heavy object on it, the paths of smaller objects on the fabric will be stretched towards the heavy thing.
This metaphor falls apart for orbits though, as it requires "stretching" the fabric so much that the threads now somehow go in a circle around the mass heh. But the underlying principle is the same - an object in orbit is in free fall along a straight path in curved spacetime.
In my explanation, if the particles trajectory can change, you can see how gravity affects distortion of space. Its not really that the space is some sort of entity that is being distorted, its the concept of measuring what you define as distance gets influenced by how these particles fly about.
This was an invaluable resource 5 years ago when I was working on a summer research project making a ray tracing-based optical levitation simulator - initially it felt a bit insane to try to deeply understand this obscure bit of maths to implement rotations, but once it clicked it clicked. Quaternions ended up being a super neat formalism for writing and computing rotational equations of motion.
The material is very cool, but I'm almost more interested in the progress in 3D nanofabrication this shows - "printing" material in 3D by selective solidification tends to be pretty slow, as you need to move around like a 3D printer head instead of one-shotting an entire layer like in 2D lithography.
The fact that they have made a millimeter scale version of their design instead of a small demo that looks cool under an electron microscope is very impressive! The method is pretty clever too - 2 photon absorption works only where the light is focused (and therefore high intensity). They use a lens array to create 49 focus points, allowing them to parallelize the printing of the repeating grid!
Scalable 3D fab could have fun implications for materials like this, and for chip-scale photonics.
Very glad to hear the Pebble dream lives on! I only switched away from my Pebble Time two years ago when I started to need heart rate monitoring for health reasons. The Pixel Watch is good, but in many ways I still consider the Time the optimal smartwatch design in many departments!
The UX especially is something l look back fondly on, especially the timeline interface was such a natural way to use a timepiece for me.
I have been reading HN for a while and never commented, but the translation thing is very close to my heart, what with learning Physics both in Polish and English at different stages of my life.
It uses Wikipedia's APIs to "click the language links" for you. It also displays short summaries of both languages' articles, so the translation can be verified. I know I'm a small sample, but I end up using it reasonably often.
My understanding is that a more correct intuition is thinking of straight paths on the curved sheet. Say it's like a loosely woven tablecloth - objects in free fall will go along the threads of the weave, so if you stretch the fabric by placing a heavy object on it, the paths of smaller objects on the fabric will be stretched towards the heavy thing.
This metaphor falls apart for orbits though, as it requires "stretching" the fabric so much that the threads now somehow go in a circle around the mass heh. But the underlying principle is the same - an object in orbit is in free fall along a straight path in curved spacetime.
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