Thank you all for the comments and showing the weaknesses in the model and visualisation. I'll try to understand the issues and fix them soon.
Show HN: Gravity – Interactive solar-system simulator, from Newton to Einstein
21–30 of 63 posts
Re: Show HN: Gravity – Interactive solar-system simulator, from Newton to Einstein
#22>The Sun’s gravity (red arrow) pulls the Earth straight toward it the whole time — so why no collision? Because the Earth is also moving sideways (green arrow) at 29.8 km/s. Each moment it does fall toward the Sun, but its sideways speed carries it past — it keeps missing. The dashed line shows where inertia alone would send it; gravity bends that straight path into a closed loop. An orbit is simply falling, continuously, and always missing.
Reading stuff like this always makes me think "well that is fortunate." Of course there is survivorship bias so its not exactly surprising. But it also makes me wonder what could change the status quo.
I guess these are the things that could change it:
- suns becomes lighter (earth shoots into space)
- earth accelerates (earth shoots into space)
- sun becomes heavier (earth falls into sun)
- earth decelerates (earth falls into sun)
I guess in theory some large interstellar object could pass to close too earth and fling us off into space or into the sun.
Re: Show HN: Gravity – Interactive solar-system simulator, from Newton to Einstein
#23For something more rigorous, I would like to take this opportunity to share rebound[1], something we use for n-body simulations in our field (planet formation). Perhaps few people here are already familiar with it. It has a Python interface but the C interface is very easy to use as well and has plethora of pre-set examples which can be visualized using GLFW. It's very very cool!
Re: Show HN: Gravity – Interactive solar-system simulator, from Newton to Einstein
#24>The Sun’s gravity (red arrow) pulls the Earth straight toward it the whole time — so why no collision? Because the Earth is also moving sideways (green arrow) at 29.8 km/s. Each moment it does fall toward the Sun, but its sideways speed carries it past — it keeps missing. The dashed line shows where inertia alone would send it; gravity bends that straight path into a closed loop. An orbit is simply falling, continuo…
> well that is fortunate
I think that was one of the arguments of the Anthropic principle [1], that there doesn't appear to be any reason why there are 3 spatial dimensions and 1 time dimension, or why the fundamental constants are what they are - but if they weren't then there wouldn't be anyone to exist to say "well that is fortunate".
[1] https://en.wikipedia.org/wiki/Anthropic_principle#Dimensions...
Re: Show HN: Gravity – Interactive solar-system simulator, from Newton to Einstein
#25>The Sun’s gravity (red arrow) pulls the Earth straight toward it the whole time — so why no collision? Because the Earth is also moving sideways (green arrow) at 29.8 km/s. Each moment it does fall toward the Sun, but its sideways speed carries it past — it keeps missing. The dashed line shows where inertia alone would send it; gravity bends that straight path into a closed loop. An orbit is simply falling, continuo…
> well that is fortunate I think that was one of the arguments of the Anthropic principle [1], that there doesn't appear to be any reason why there are 3 spatial dimensions and 1 time dimension, or why the fundamental constants are what they are - but if they weren't then there wouldn't be anyone to exist to say "well that is fortunate". [1] https://en.wikipedia.org/wiki/Anthropic_principle#Dimensions...
yes, exactly. It didn't have to be this way, but it had to be this way to observe it. Survivorship bias.
Re: Show HN: Gravity – Interactive solar-system simulator, from Newton to Einstein
#26[dead]
Re: Show HN: Gravity – Interactive solar-system simulator, from Newton to Einstein
#27[flagged]
Re: Show HN: Gravity – Interactive solar-system simulator, from Newton to Einstein
#28The "focus" on planets doesn't work quite correctly. I love that you included true size, but it would be great if the focus worked, and one could zoom between the planets (until the planet shows up).
I also think Saturn's rings don't wobble that fast.
Re: Show HN: Gravity – Interactive solar-system simulator, from Newton to Einstein
#29This is neat! I love that your Step 15 shows an accurate version of the 3d helix, rather than the highly-viral "vortex" animation from a few years back[0]
It'd be awesome to scale this up to the Milk Way, and beyond, watching everything move in relation to larger time scales.
[0]https://astrorhysy.blogspot.com/2015/03/and-yet-it-moves-qui...
Re: Show HN: Gravity – Interactive solar-system simulator, from Newton to Einstein
#30I really liked your animations, but isn't step 14 incorrect? Earth's axis processes, but on a very long timescale. In the span of a day, the axis should be effectively stationary. That's why its the rotation 'axis' - it's the fixed line it rotates about. That's why Polaris is the north star: the axis of rotation points effectively directly at it at all times no matter the season. During summer in the northern hemisph…
This is exactly right; the phenomenon is known as axial parallelism.