Sijme-Jan Paardekooper
@sijme-jan.bsky.social
Computational astrophysicist at Delft University of Technology. Studying the formation of planets.
Reposted by Sijme-Jan Paardekooper
It's paper day 🎉🔭
arxiv.org/abs/2507.10719
Together with @sijme-jan.bsky.social we continue to look at dust instabilities in planet forming discs when considering many dust sizes (polydisperse). This time we probe the Dust Settling Instability (DSI) via hydro simulations in a local box
1/14
arxiv.org/abs/2507.10719
Together with @sijme-jan.bsky.social we continue to look at dust instabilities in planet forming discs when considering many dust sizes (polydisperse). This time we probe the Dust Settling Instability (DSI) via hydro simulations in a local box
1/14
Nonlinear Evolution of the Unstratified Polydisperse Dust Settling Instability
Context. The Dust Settling Instabilty (DSI) is a member of the Resonant Drag Instabilities (RDI) family, and is thus related to the Streaming Instability (SI). Linear calculations found that the unstr...
arxiv.org
July 16, 2025 at 10:08 AM
It's paper day 🎉🔭
arxiv.org/abs/2507.10719
Together with @sijme-jan.bsky.social we continue to look at dust instabilities in planet forming discs when considering many dust sizes (polydisperse). This time we probe the Dust Settling Instability (DSI) via hydro simulations in a local box
1/14
arxiv.org/abs/2507.10719
Together with @sijme-jan.bsky.social we continue to look at dust instabilities in planet forming discs when considering many dust sizes (polydisperse). This time we probe the Dust Settling Instability (DSI) via hydro simulations in a local box
1/14
"we must not fall into the trap of mistaking the outputs of writing (which are increasingly substitutable through technology) from the value of the cognitive process of writing (which hones mental development and cannot be substituted by a machine)."
After the latest round of grading papers, I wrote about AI, ChatGPT, the death of the student essay, and what it means for the future of human cognition.
The Death of the Student Essay—and the Future of Cognition
One professor's reflections on the end of an era, as AI tools such as ChatGPT have murdered the student essay (RIP). Here's why that threatens the future of human cognition—and how to save ourselves.
www.forkingpaths.co
June 20, 2025 at 6:48 AM
"we must not fall into the trap of mistaking the outputs of writing (which are increasingly substitutable through technology) from the value of the cognitive process of writing (which hones mental development and cannot be substituted by a machine)."
Reposted by Sijme-Jan Paardekooper
Our gift to the world.
"Recent Eurobarometer data confirm the shift: 74% of Europeans now view EU membership as a positive thing – the highest level of support ever recorded." - www.theguardian.com/commentisfre...
Europe should be standing up to Trump and Putin – instead it is mirroring them | Alberto Alemanno
Public opinion is clamouring for closer EU cooperation. The last thing we need is Ursula von der Leyen pandering to the far right, says Alberto Alemanno, Jean Monnet professor of EU law at HEC Paris
www.theguardian.com
June 16, 2025 at 1:42 PM
Our gift to the world.
Reposted by Sijme-Jan Paardekooper
It's not the biggest problem education is facing but at some point the preference of parents and students for coursework and fewer exams is going to collide with the fact that AI probably necessitates a big return to in-person exams
June 16, 2025 at 9:24 AM
It's not the biggest problem education is facing but at some point the preference of parents and students for coursework and fewer exams is going to collide with the fact that AI probably necessitates a big return to in-person exams
Reposted by Sijme-Jan Paardekooper
We are all in the gutter, but some of us are looking at our phones
June 9, 2025 at 11:27 AM
We are all in the gutter, but some of us are looking at our phones
Reposted by Sijme-Jan Paardekooper
I don’t know. I love this Joseph Fasano poem and have it pinned on my office door but I don’t know what to actually do about any of this.
June 4, 2025 at 9:08 AM
I don’t know. I love this Joseph Fasano poem and have it pinned on my office door but I don’t know what to actually do about any of this.
Prediction was a few months off, but good riddance
Prediction: forming a government will take longer than the resulting government will govern. #dutchelections
June 3, 2025 at 9:40 PM
Prediction was a few months off, but good riddance
Reposted by Sijme-Jan Paardekooper
The abstract submission for Rocky Worlds 4 is now open! groningen2026.rockyworlds.org/registration... 🌋🔭🧬😱
ROCKY WORLDS 4 - Abstract Submission
Abstract submission & conference registration
Abstract submission and conference registration are done in two steps. First, the abstract submission below (including requests for financial support) run...
groningen2026.rockyworlds.org
June 2, 2025 at 10:59 AM
The abstract submission for Rocky Worlds 4 is now open! groningen2026.rockyworlds.org/registration... 🌋🔭🧬😱
Reposted by Sijme-Jan Paardekooper
What the fuck, people. Do not do this.
We are seeing multiple instances of reviewers doing manuscript reviews via use of AI/LLM.
If you don't want to do a review the old-fashioned way, better to decline the request.
Giving someone else's manuscript to AI is a violation of intellectual property rights/laws; the manuscript isn't yours...
If you don't want to do a review the old-fashioned way, better to decline the request.
Giving someone else's manuscript to AI is a violation of intellectual property rights/laws; the manuscript isn't yours...
May 11, 2025 at 2:46 PM
What the fuck, people. Do not do this.
Reposted by Sijme-Jan Paardekooper
A core feature of the Trump regime is its embrace of "authoritarian democracy", as a battering ram with which to demolish any obstacle to its power.
The very notion of "authoritarian democracy" can sound contradictory.
But it's an old & dangerous idea, that needs to be better understood. [THREAD]
The very notion of "authoritarian democracy" can sound contradictory.
But it's an old & dangerous idea, that needs to be better understood. [THREAD]
Stephen Miller on the court order to release Tufts student Rümeysa Öztürk: "There's a judicial coup in this country....This judicial coup by a handful of Marxist judges...can only be understood as an attack on democracy."
May 11, 2025 at 5:43 PM
A core feature of the Trump regime is its embrace of "authoritarian democracy", as a battering ram with which to demolish any obstacle to its power.
The very notion of "authoritarian democracy" can sound contradictory.
But it's an old & dangerous idea, that needs to be better understood. [THREAD]
The very notion of "authoritarian democracy" can sound contradictory.
But it's an old & dangerous idea, that needs to be better understood. [THREAD]
Reposted by Sijme-Jan Paardekooper
It's final paper season.
May 5, 2025 at 9:55 PM
It's final paper season.
Reposted by Sijme-Jan Paardekooper
A new, thorough reanalysis of the data that led to claims of biosignatures on K2-18b from @luiswel.bsky.social & friends - a nicely written lesson on why this stuff is hard. They find no significant evidence for DMS, the gas the Cambridge team claimed to have found. arxiv.org/abs/2504.21788
The Challenges of Detecting Gases in Exoplanet Atmospheres
Claims of detections of gases in exoplanet atmospheres often rely on comparisons between models including and excluding specific chemical species. However, the space of molecular combinations availabl...
arxiv.org
May 1, 2025 at 3:01 AM
A new, thorough reanalysis of the data that led to claims of biosignatures on K2-18b from @luiswel.bsky.social & friends - a nicely written lesson on why this stuff is hard. They find no significant evidence for DMS, the gas the Cambridge team claimed to have found. arxiv.org/abs/2504.21788
Reposted by Sijme-Jan Paardekooper
Blimey! Prof Madhusudhan’s response to my friendly discussion of the many unknowns was that I’m a ‘commentator not a practitioner’.
April 17, 2025 at 7:46 AM
Blimey! Prof Madhusudhan’s response to my friendly discussion of the many unknowns was that I’m a ‘commentator not a practitioner’.
Reposted by Sijme-Jan Paardekooper
𝗡𝗼, 𝗮 𝗯𝗶𝗼𝘀𝗶𝗴𝗻𝗮𝘁𝘂𝗿𝗲 𝘄𝗮𝘀 𝗻𝗼𝘁 𝗷𝘂𝘀𝘁 𝗱𝗲𝘁𝗲𝗰𝘁𝗲𝗱 𝗶𝗻 𝗞𝟮-𝟭𝟴𝗯'𝘀 𝗮𝘁𝗺𝗼𝘀𝗽𝗵𝗲𝗿𝗲.
K2-18b is back in the news, now with a bold claim that biosignature molecules (DMS and/or DMDS) have been 'detected at 3σ'.
Most exoplanet astronomers are extremely sceptical about these claims, let's see why (1/n).
🔭🧪🪐 #exoplanet
K2-18b is back in the news, now with a bold claim that biosignature molecules (DMS and/or DMDS) have been 'detected at 3σ'.
Most exoplanet astronomers are extremely sceptical about these claims, let's see why (1/n).
🔭🧪🪐 #exoplanet
April 17, 2025 at 4:08 PM
𝗡𝗼, 𝗮 𝗯𝗶𝗼𝘀𝗶𝗴𝗻𝗮𝘁𝘂𝗿𝗲 𝘄𝗮𝘀 𝗻𝗼𝘁 𝗷𝘂𝘀𝘁 𝗱𝗲𝘁𝗲𝗰𝘁𝗲𝗱 𝗶𝗻 𝗞𝟮-𝟭𝟴𝗯'𝘀 𝗮𝘁𝗺𝗼𝘀𝗽𝗵𝗲𝗿𝗲.
K2-18b is back in the news, now with a bold claim that biosignature molecules (DMS and/or DMDS) have been 'detected at 3σ'.
Most exoplanet astronomers are extremely sceptical about these claims, let's see why (1/n).
🔭🧪🪐 #exoplanet
K2-18b is back in the news, now with a bold claim that biosignature molecules (DMS and/or DMDS) have been 'detected at 3σ'.
Most exoplanet astronomers are extremely sceptical about these claims, let's see why (1/n).
🔭🧪🪐 #exoplanet
Reposted by Sijme-Jan Paardekooper
An astonishing headline reporting on new observations from a team led to Nikku Madhusudhan claims they’ve found ‘hints of life’ on a planet orbiting a dwarf star some 124 light years away. What’s going on? (1/n) www.bbc.co.uk/news/article... 🔭 🧪
Promising hints of life found on distant planet K2-18b
Scientists find new but tentative evidence that a faraway world orbiting another star may be home to life.
www.bbc.co.uk
April 17, 2025 at 3:24 AM
An astonishing headline reporting on new observations from a team led to Nikku Madhusudhan claims they’ve found ‘hints of life’ on a planet orbiting a dwarf star some 124 light years away. What’s going on? (1/n) www.bbc.co.uk/news/article... 🔭 🧪
Reposted by Sijme-Jan Paardekooper
There are great conferences and science in the US, but with the way things are right now, it’s too risky to attend.
Australian academics refuse to attend US conferences for fear of being detained
‘When academics fear travelling or partnering with US institutions, the impacts ripple through the entire global knowledge ecosystem,’ one says
www.theguardian.com
April 13, 2025 at 11:00 PM
There are great conferences and science in the US, but with the way things are right now, it’s too risky to attend.
Reposted by Sijme-Jan Paardekooper
First the rumour was a 20% budget cut. Then, 50%. Now the president's NASA budget is out and it's a 68% cut to astrophysics ($1.5B to $487M).
Even if this gets reversed in four years, we will *never* recover the missions, partners, people who will be gone.
www.washingtonpost.com/science/2025...
Even if this gets reversed in four years, we will *never* recover the missions, partners, people who will be gone.
www.washingtonpost.com/science/2025...
Massive cuts to NASA science proposed in early White House budget plan
The preliminary version of President Donald Trump’s budget proposal to Congress, known as a “passback,” would cut the agency’s science budget funding nearly in half.
www.washingtonpost.com
April 11, 2025 at 2:54 PM
First the rumour was a 20% budget cut. Then, 50%. Now the president's NASA budget is out and it's a 68% cut to astrophysics ($1.5B to $487M).
Even if this gets reversed in four years, we will *never* recover the missions, partners, people who will be gone.
www.washingtonpost.com/science/2025...
Even if this gets reversed in four years, we will *never* recover the missions, partners, people who will be gone.
www.washingtonpost.com/science/2025...
Reposted by Sijme-Jan Paardekooper
Reposted by Sijme-Jan Paardekooper
A tricky thing about modern society is that no one has any idea when they don’t die.
Like, the number of lives saved by controlling air pollution in America is probably over 200,000 per year, but the number of people who think their life was saved by controlling air pollution is zero.
Like, the number of lives saved by controlling air pollution in America is probably over 200,000 per year, but the number of people who think their life was saved by controlling air pollution is zero.
April 7, 2025 at 4:13 AM
A tricky thing about modern society is that no one has any idea when they don’t die.
Like, the number of lives saved by controlling air pollution in America is probably over 200,000 per year, but the number of people who think their life was saved by controlling air pollution is zero.
Like, the number of lives saved by controlling air pollution in America is probably over 200,000 per year, but the number of people who think their life was saved by controlling air pollution is zero.
Reposted by Sijme-Jan Paardekooper
Here we go paper II is out today 🔭
arxiv.org/abs/2503.09265
Here @sijme-jan.bsky.social and I continue looking at the linear theory of RDIs when you have dust with size distributions, but this time we focus on the streaming and settling instabilities, which are important for planet formation
1/14
arxiv.org/abs/2503.09265
Here @sijme-jan.bsky.social and I continue looking at the linear theory of RDIs when you have dust with size distributions, but this time we focus on the streaming and settling instabilities, which are important for planet formation
1/14
March 13, 2025 at 3:10 PM
Here we go paper II is out today 🔭
arxiv.org/abs/2503.09265
Here @sijme-jan.bsky.social and I continue looking at the linear theory of RDIs when you have dust with size distributions, but this time we focus on the streaming and settling instabilities, which are important for planet formation
1/14
arxiv.org/abs/2503.09265
Here @sijme-jan.bsky.social and I continue looking at the linear theory of RDIs when you have dust with size distributions, but this time we focus on the streaming and settling instabilities, which are important for planet formation
1/14
Reposted by Sijme-Jan Paardekooper
A lot of people confuse writing with typing.
Writing isn’t typing.
It’s the entire process and yes that includes going for a walk or rearranging things in your office.
Writing isn’t typing.
It’s the entire process and yes that includes going for a walk or rearranging things in your office.
Sometimes you sit down to write and instead you think or cut or rewrite or unwrite. That’s okay. That’s a productive day because all of those are part of the process. Keep going.
February 27, 2025 at 3:10 AM
A lot of people confuse writing with typing.
Writing isn’t typing.
It’s the entire process and yes that includes going for a walk or rearranging things in your office.
Writing isn’t typing.
It’s the entire process and yes that includes going for a walk or rearranging things in your office.
Reposted by Sijme-Jan Paardekooper
It's paper day! 🔭
arxiv.org/abs/2503.05359
This is a 1st of a series where @sijme-jan.bsky.social and I look at how dust instabilities change when you start treating dust as a continuum of species with different sizes, i.e; "Polydisperse", instead of a single size species
1/9
arxiv.org/abs/2503.05359
This is a 1st of a series where @sijme-jan.bsky.social and I look at how dust instabilities change when you start treating dust as a continuum of species with different sizes, i.e; "Polydisperse", instead of a single size species
1/9
Resonant Drag Instabilities for Polydisperse Dust, I. The Acoustic Resonant Drag Instability
Dust grains embedded in gas flow give rise to a class of hydrodynamic instabilities that can occur whenever there exists a relative velocity between gas and dust. These instabilities have predominantl...
arxiv.org
March 10, 2025 at 12:53 PM
It's paper day! 🔭
arxiv.org/abs/2503.05359
This is a 1st of a series where @sijme-jan.bsky.social and I look at how dust instabilities change when you start treating dust as a continuum of species with different sizes, i.e; "Polydisperse", instead of a single size species
1/9
arxiv.org/abs/2503.05359
This is a 1st of a series where @sijme-jan.bsky.social and I look at how dust instabilities change when you start treating dust as a continuum of species with different sizes, i.e; "Polydisperse", instead of a single size species
1/9
Reposted by Sijme-Jan Paardekooper
No. Never.
I review 20+ of papers a year—it's my job as a scientist. The public pays my salary and trust me to use my time wisely to advance science. Through peer review, I do exactly that. I spend two or three weeks a year reviewing, but I’ve never wasted a day reviewing a paper, and never will.
I review 20+ of papers a year—it's my job as a scientist. The public pays my salary and trust me to use my time wisely to advance science. Through peer review, I do exactly that. I spend two or three weeks a year reviewing, but I’ve never wasted a day reviewing a paper, and never will.
March 6, 2025 at 5:36 AM
No. Never.
I review 20+ of papers a year—it's my job as a scientist. The public pays my salary and trust me to use my time wisely to advance science. Through peer review, I do exactly that. I spend two or three weeks a year reviewing, but I’ve never wasted a day reviewing a paper, and never will.
I review 20+ of papers a year—it's my job as a scientist. The public pays my salary and trust me to use my time wisely to advance science. Through peer review, I do exactly that. I spend two or three weeks a year reviewing, but I’ve never wasted a day reviewing a paper, and never will.
Reposted by Sijme-Jan Paardekooper
The average American voter thinks that the government is too big but that it should spend more money on everything it does. This explains a decent share of the political chaos of this country.
March 2, 2025 at 7:48 PM
The average American voter thinks that the government is too big but that it should spend more money on everything it does. This explains a decent share of the political chaos of this country.
Reposted by Sijme-Jan Paardekooper
Good luck today to the fellows of the Royal Society who are gathering in London to discuss “public pronouncements and behaviours of other fellows.” I trust there will be a candid and informed exchange of views. 1/4
March 3, 2025 at 9:54 AM
Good luck today to the fellows of the Royal Society who are gathering in London to discuss “public pronouncements and behaviours of other fellows.” I trust there will be a candid and informed exchange of views. 1/4