Gravity
Languages and libraries
educational simulator
SHOW HN2026
How HN took it
11 positive, 10 neutral or asking, 5 mixed, 8 critical, out of 34 comments about the project. Thread score +0.10.
Idea: 4 for, 1 againstExecution: 0 for, 4 againstDocs: 0 for, 2 againstDesign: 1 for, 1 against
The thread, comment by comment
Each row is a top-level comment and its replies, in HN's order. Select a cell to open that comment on HN.
positive neutral or mixed critical about another commenter or something else the maker
What HN said
What people liked
Fun and effective for teaching orbits and visualising 3D motion
From 3 comments
Really cool project! I always struggled to understand the motion of the planets looking at 2D images in textbooks. So I really enjoyed the ability to click and drag to explore…
simon145 on HNIt feels like touring space, and I like that it seems like a creative work. Regarding the part after the tour, my only regret is that I wish the camera had a bit more freedom.…
twosky on HNthe way the original mathematicians figured all this out absolutely melts my brain no computers, no calculators, barely working telescopes looking at the moons orbiting Jupiter…
ck2 on HN
Calming music and narration
From 2 comments
This is so cool and the music is so calming to listen to as well. I did turn off the AI voice :)
vj-vibing on HNReally cool project! I always struggled to understand the motion of the planets looking at 2D images in textbooks. So I really enjoyed the ability to click and drag to explore…
simon145 on HN
Objections
Axial tilt animation at step 14 misrepresents precession
From 2 comments
I 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…
jrflo on HNGreat job! 14 is misleading though - while the context is one day, the animation depicts axial precession which takes place over ~26,000 years
BigTuna on HN
Focus and camera controls on planets do not work well
From 2 comments
The "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…
xixixao on HNIt feels like touring space, and I like that it seems like a creative work. Regarding the part after the tour, my only regret is that I wish the camera had a bit more freedom.…
twosky on HN
Mobile layout overlaps the simulation
From 2 comments
Looks great but on mobile the popover covers a quarter of the screen, obscuring the sun
stevenalowe on HNIt works pretty well on iPhone, except the descriptive text fills most of the bottom half of the screen, overlapping the sim which is centered on the screen. If the sim were…
iainmerrick on HN
Some physics values and rendering are inaccurate (orbital speeds, Moon tidal locking, Saturn rings)
From 3 comments
Step 5 shows the earth going as slow as 21.5 km/sec at aphelion and as fast as 39km/sec at the perihelion. I believe that should be closer to 29.3 and 30.3 km/sec, respectively.
nerdsniper on HNVery nice! Nitpick: the Moon is tidally locked, so it should always face the Earth with the same side.
artemave on HNThe "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…
xixixao on HN
Requests
Model satellite launches and Artemis missions
From 1 comment
This is fun! It would be cool to get new updates that model ongoing/future satellite launches or Artemis missions.
Retirology on HN
Show black holes at galactic centres
From 1 comment
Neat. How about mentioning the massive black holes at the center of the galaxies?
Tepix on HN
Show Earth forming with rotation
From 1 comment
Really cool and I love educational apps like this. One suggestion is to show the rotation of the earth as the particles come together to form it rather than a static image.
scamdrill on HN
Questions
How are relativistic effects handled in the N-body simulation
From 1 comment
> Einstein How are you handling relativistic effects in the N-body simulation?
genpfault on HN
Performance on older devices and switch between physics modes
From 1 comment
I'm curious: does generating the planet textures slow down older devices, and how seamless is the switch between the two physics modes?
AmareshHebbar on HN
How the narration was made
From 1 comment
Really cool project! I always struggled to understand the motion of the planets looking at 2D images in textbooks. So I really enjoyed the ability to click and drag to explore…
simon145 on HN
Alternatives named
rebound N-body simulation library
From 1 comment
For 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…
kmaitreys on HN