Andy Hall
@testtubegames.com
Game Developer behind TestTubeGames.
Enjoy building, finding, and sharing cool science through games / toys / simulations.
My games: https://testtubegames.com
Other games I love: https://thescienceplayground.com/
he/him
Enjoy building, finding, and sharing cool science through games / toys / simulations.
My games: https://testtubegames.com
Other games I love: https://thescienceplayground.com/
he/him
A box of gas (blue) + dark matter (green), now with a smoother distribution at the start.
(gravity + pressure + viscosity, 16k particles, periodic 2d)
(gravity + pressure + viscosity, 16k particles, periodic 2d)
October 7, 2025 at 3:48 PM
A box of gas (blue) + dark matter (green), now with a smoother distribution at the start.
(gravity + pressure + viscosity, 16k particles, periodic 2d)
(gravity + pressure + viscosity, 16k particles, periodic 2d)
And here we are at about 380,000 years after the Big Bang.
The universe has cooled enough that neutral atoms are common, and loose charges are rarer. Photons can finally travel in mostly straight lines.
Some of them traveled in mostly straight lines for billions and billions of years, in fact!
The universe has cooled enough that neutral atoms are common, and loose charges are rarer. Photons can finally travel in mostly straight lines.
Some of them traveled in mostly straight lines for billions and billions of years, in fact!
October 3, 2025 at 3:07 PM
And here we are at about 380,000 years after the Big Bang.
The universe has cooled enough that neutral atoms are common, and loose charges are rarer. Photons can finally travel in mostly straight lines.
Some of them traveled in mostly straight lines for billions and billions of years, in fact!
The universe has cooled enough that neutral atoms are common, and loose charges are rarer. Photons can finally travel in mostly straight lines.
Some of them traveled in mostly straight lines for billions and billions of years, in fact!
As the universe expands, it cools. Some neutral atoms (grey) are able to form briefly -- and these don't scatter the photons as much. Still the photons get bounced around.
(This is at about ~360,000 years after the Big Bang.)
(This is at about ~360,000 years after the Big Bang.)
October 3, 2025 at 3:03 PM
As the universe expands, it cools. Some neutral atoms (grey) are able to form briefly -- and these don't scatter the photons as much. Still the photons get bounced around.
(This is at about ~360,000 years after the Big Bang.)
(This is at about ~360,000 years after the Big Bang.)
I love this simulation of the early universe, part of our new CMB project.
This is early on - (~300,000 years after the Big Bang). The universe is so hot, plasma is everywhere. Photons can't travel far, bouncing off electric charges.
This is early on - (~300,000 years after the Big Bang). The universe is so hot, plasma is everywhere. Photons can't travel far, bouncing off electric charges.
October 3, 2025 at 2:59 PM
I love this simulation of the early universe, part of our new CMB project.
This is early on - (~300,000 years after the Big Bang). The universe is so hot, plasma is everywhere. Photons can't travel far, bouncing off electric charges.
This is early on - (~300,000 years after the Big Bang). The universe is so hot, plasma is everywhere. Photons can't travel far, bouncing off electric charges.
Some more 'gas' particles - this time two clumps in orbit. Pretty dangerous tides, if you ask me.
(16k particles, gravity + pressure + viscosity)
(16k particles, gravity + pressure + viscosity)
October 3, 2025 at 2:39 PM
Some more 'gas' particles - this time two clumps in orbit. Pretty dangerous tides, if you ask me.
(16k particles, gravity + pressure + viscosity)
(16k particles, gravity + pressure + viscosity)
Oops, the gas simulation made a Saturn, I guess?
(8k particles, all feeling gravity + pressure + viscosity)
(8k particles, all feeling gravity + pressure + viscosity)
October 2, 2025 at 1:29 AM
Oops, the gas simulation made a Saturn, I guess?
(8k particles, all feeling gravity + pressure + viscosity)
(8k particles, all feeling gravity + pressure + viscosity)
Related physics puzzle - can you figure out this SPOOKY force law?
Bonus point: If this force law were to dress up for Halloween, what costume would it wear?
Bonus point: If this force law were to dress up for Halloween, what costume would it wear?
October 1, 2025 at 5:15 PM
Related physics puzzle - can you figure out this SPOOKY force law?
Bonus point: If this force law were to dress up for Halloween, what costume would it wear?
Bonus point: If this force law were to dress up for Halloween, what costume would it wear?
Tis a season.
Why does the ghost behave the way the ghost does? An eternal, and in this case, very specific, question.
(Single central pumpkin-y mass, gravity with a 1/r^2 force law.)
Why does the ghost behave the way the ghost does? An eternal, and in this case, very specific, question.
(Single central pumpkin-y mass, gravity with a 1/r^2 force law.)
October 1, 2025 at 3:31 PM
Tis a season.
Why does the ghost behave the way the ghost does? An eternal, and in this case, very specific, question.
(Single central pumpkin-y mass, gravity with a 1/r^2 force law.)
Why does the ghost behave the way the ghost does? An eternal, and in this case, very specific, question.
(Single central pumpkin-y mass, gravity with a 1/r^2 force law.)
The CMB pattern you see drawn is actually a map of different temperatures...
But the temperature differences are tiny. If you look at the blackbody curve... the 'hot' spots and 'cold' spots are nearly identical. Good luck telling the difference...
But the temperature differences are tiny. If you look at the blackbody curve... the 'hot' spots and 'cold' spots are nearly identical. Good luck telling the difference...
September 25, 2025 at 1:36 PM
The CMB pattern you see drawn is actually a map of different temperatures...
But the temperature differences are tiny. If you look at the blackbody curve... the 'hot' spots and 'cold' spots are nearly identical. Good luck telling the difference...
But the temperature differences are tiny. If you look at the blackbody curve... the 'hot' spots and 'cold' spots are nearly identical. Good luck telling the difference...
To understand the CMB map... you need to know a bit about Blackbody Spectrum.
So we've included a fully interactive spectrum. Slide the temperature to your heart's content!
testtubegames.com/cmbjourney.h...
So we've included a fully interactive spectrum. Slide the temperature to your heart's content!
testtubegames.com/cmbjourney.h...
September 25, 2025 at 1:31 PM
To understand the CMB map... you need to know a bit about Blackbody Spectrum.
So we've included a fully interactive spectrum. Slide the temperature to your heart's content!
testtubegames.com/cmbjourney.h...
So we've included a fully interactive spectrum. Slide the temperature to your heart's content!
testtubegames.com/cmbjourney.h...
Now, instead of 50/50 -- here's a cloud that's 80% dark matter, 20% normal matter. A bit closer to our universe (which sits around 85%).
(I turn the dark matter halos invisible occasionally so you can see the gas structures.)
(I turn the dark matter halos invisible occasionally so you can see the gas structures.)
September 24, 2025 at 4:23 PM
Now, instead of 50/50 -- here's a cloud that's 80% dark matter, 20% normal matter. A bit closer to our universe (which sits around 85%).
(I turn the dark matter halos invisible occasionally so you can see the gas structures.)
(I turn the dark matter halos invisible occasionally so you can see the gas structures.)
A mix of both Dark Matter (green) and Gas (blue).
What do you notice?
(16k particles, gravity, gas feels pressure + viscosity also, 3D with view slowly rotating to showcase structures.)
What do you notice?
(16k particles, gravity, gas feels pressure + viscosity also, 3D with view slowly rotating to showcase structures.)
September 24, 2025 at 3:51 PM
A mix of both Dark Matter (green) and Gas (blue).
What do you notice?
(16k particles, gravity, gas feels pressure + viscosity also, 3D with view slowly rotating to showcase structures.)
What do you notice?
(16k particles, gravity, gas feels pressure + viscosity also, 3D with view slowly rotating to showcase structures.)
Ooh, this time a spherical cloud of gas, initially spinning slowly.
No periodic boundary conditions now, just let it collapse.
...whoa.
(Gravity + Pressure + Viscosity, 16k particles.)
No periodic boundary conditions now, just let it collapse.
...whoa.
(Gravity + Pressure + Viscosity, 16k particles.)
September 24, 2025 at 3:00 PM
Ooh, this time a spherical cloud of gas, initially spinning slowly.
No periodic boundary conditions now, just let it collapse.
...whoa.
(Gravity + Pressure + Viscosity, 16k particles.)
No periodic boundary conditions now, just let it collapse.
...whoa.
(Gravity + Pressure + Viscosity, 16k particles.)
And to compare, here's the same setup without pressure or viscosity. So, imagine dark matter instead of a gas.
(Gravity, 16k particles, periodic boundary. Rotating to help make structures visible.)
(Gravity, 16k particles, periodic boundary. Rotating to help make structures visible.)
September 24, 2025 at 2:42 PM
And to compare, here's the same setup without pressure or viscosity. So, imagine dark matter instead of a gas.
(Gravity, 16k particles, periodic boundary. Rotating to help make structures visible.)
(Gravity, 16k particles, periodic boundary. Rotating to help make structures visible.)
This question got me interested...
So, here's the same sim in 3d, a true box of 'gas'.
(Gravity + Pressure + Viscosity, 16k particles. Rotating slowly to help make the structures visible.)
So, here's the same sim in 3d, a true box of 'gas'.
(Gravity + Pressure + Viscosity, 16k particles. Rotating slowly to help make the structures visible.)
September 24, 2025 at 2:19 PM
This question got me interested...
So, here's the same sim in 3d, a true box of 'gas'.
(Gravity + Pressure + Viscosity, 16k particles. Rotating slowly to help make the structures visible.)
So, here's the same sim in 3d, a true box of 'gas'.
(Gravity + Pressure + Viscosity, 16k particles. Rotating slowly to help make the structures visible.)
For comparison, here's a box of matter that just experiences gravity. No pressure or viscosity.
(Gravity only, 30k particles)
(Gravity only, 30k particles)
September 23, 2025 at 4:14 PM
For comparison, here's a box of matter that just experiences gravity. No pressure or viscosity.
(Gravity only, 30k particles)
(Gravity only, 30k particles)
Box of gas with periodic boundary conditions.
(Gravity + Pressure + Viscosity, 30k particles)
Modeled with SPH, so picture large regions, not individual molecules.
(Gravity + Pressure + Viscosity, 30k particles)
Modeled with SPH, so picture large regions, not individual molecules.
September 23, 2025 at 4:11 PM
Box of gas with periodic boundary conditions.
(Gravity + Pressure + Viscosity, 30k particles)
Modeled with SPH, so picture large regions, not individual molecules.
(Gravity + Pressure + Viscosity, 30k particles)
Modeled with SPH, so picture large regions, not individual molecules.
Let it go for long enough, and it forms something like a planet going around a star.
Wait! Enhance, enhance... that's no star... well, err, it's two stars and an accretion disk.
Wait! Enhance, enhance... that's no star... well, err, it's two stars and an accretion disk.
September 22, 2025 at 6:13 PM
Let it go for long enough, and it forms something like a planet going around a star.
Wait! Enhance, enhance... that's no star... well, err, it's two stars and an accretion disk.
Wait! Enhance, enhance... that's no star... well, err, it's two stars and an accretion disk.
Simulating a disk of gas.
(Gravity + Pressure + Viscosity, 16k particles)
(Gravity + Pressure + Viscosity, 16k particles)
September 22, 2025 at 5:59 PM
Simulating a disk of gas.
(Gravity + Pressure + Viscosity, 16k particles)
(Gravity + Pressure + Viscosity, 16k particles)
New project in the wild!
A CMB Photon's Journey. Learn what the Cosmic Microwave Background is and how it formed. My favorite bits are the interactive blackbody spectra (ch 2) and the simulation of the early universe (ch 3).
In Beta, so feedback welcome!
testtubegames.com/cmbjourney.h...
A CMB Photon's Journey. Learn what the Cosmic Microwave Background is and how it formed. My favorite bits are the interactive blackbody spectra (ch 2) and the simulation of the early universe (ch 3).
In Beta, so feedback welcome!
testtubegames.com/cmbjourney.h...
September 17, 2025 at 2:21 PM
New project in the wild!
A CMB Photon's Journey. Learn what the Cosmic Microwave Background is and how it formed. My favorite bits are the interactive blackbody spectra (ch 2) and the simulation of the early universe (ch 3).
In Beta, so feedback welcome!
testtubegames.com/cmbjourney.h...
A CMB Photon's Journey. Learn what the Cosmic Microwave Background is and how it formed. My favorite bits are the interactive blackbody spectra (ch 2) and the simulation of the early universe (ch 3).
In Beta, so feedback welcome!
testtubegames.com/cmbjourney.h...
Enhance again!
Well, that's a surprise. How did that get there?
I like to think my site was hacked by the sweetest hackers ever.
Well, that's a surprise. How did that get there?
I like to think my site was hacked by the sweetest hackers ever.
September 3, 2025 at 2:13 PM
Enhance again!
Well, that's a surprise. How did that get there?
I like to think my site was hacked by the sweetest hackers ever.
Well, that's a surprise. How did that get there?
I like to think my site was hacked by the sweetest hackers ever.
Looking for a Gravity Simulator to play around with?
Well, here's a list of interesting ones I pulled together.
thescienceplayground.com?tx_category=...
Well, here's a list of interesting ones I pulled together.
thescienceplayground.com?tx_category=...
September 3, 2025 at 2:08 PM
Looking for a Gravity Simulator to play around with?
Well, here's a list of interesting ones I pulled together.
thescienceplayground.com?tx_category=...
Well, here's a list of interesting ones I pulled together.
thescienceplayground.com?tx_category=...
It's book day! So proud of @kslivensky.bsky.social!
I, ROCK is an adorable origin story grounded in science.
-
A picture book that's not afraid to entomb the main character for millions of years.
-
The greatest combination of rock and paper since the invention of scissors.
Congratulations, Katie!!
I, ROCK is an adorable origin story grounded in science.
-
A picture book that's not afraid to entomb the main character for millions of years.
-
The greatest combination of rock and paper since the invention of scissors.
Congratulations, Katie!!
June 10, 2025 at 3:19 PM
It's book day! So proud of @kslivensky.bsky.social!
I, ROCK is an adorable origin story grounded in science.
-
A picture book that's not afraid to entomb the main character for millions of years.
-
The greatest combination of rock and paper since the invention of scissors.
Congratulations, Katie!!
I, ROCK is an adorable origin story grounded in science.
-
A picture book that's not afraid to entomb the main character for millions of years.
-
The greatest combination of rock and paper since the invention of scissors.
Congratulations, Katie!!
Working on a project (about photons from the CMB) - and got a chance to simulate a blackbody spectrum graph. Which is just super satisfying.
May 8, 2025 at 2:48 PM
Working on a project (about photons from the CMB) - and got a chance to simulate a blackbody spectrum graph. Which is just super satisfying.