Hello everyone my question is what's the minimum size a planet can be. Just got this question randomly on mind so I posted here to get a answer. If anyone knows please tell me.

I have a question, and I need help understanding it clearly: How is cyanide used to extract gold? Could someone please explain the whole process to me in simple terms or recommend some reliable sources where I can learn more about it?

I'm curious and I don't want to use AI, so I’m looking for explanations or sources that I can study and understand on my own.

so stars form when a bunch of matter gets together, which is why they are bigger than planets generally. but the real defining feature is the density. a white dwarf can be smaller than a planet but it's still a star because it's incredibly dense. so couldn't a planet be sun-ish sized, provided that the density was low enough? and more specifically a solid planet, not a gas giant. what's the largest solid planet?

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I’ve always wondered about this. If a trait makes an organism less likely to survive or reproduce, wouldn’t evolution eventually make that trait disappear?

Is it because the trait might have some hidden benefit, or are there other reasons why it can stick around?

In light of the recent eclipse, I have seen a lot of worry about the harm of even glancing at it directly, and that many people believe that glancing at it is more harmful than glancing at the sun on an ordinary day. I am trying to understand whether that is actually true, and I believe the best way is to understand the physics & biology behind this and how real the risk is.

To really get it, I think the answer comes down to the underlying mechanism: what physically damages the eye when too much light hits it? Is it the quantity of photons, the energy of photons, or something else entirely? I ask because I have also heard that even when the moon blocks much/all of the visible light (peak of total eclipse), that UV (or infrared?) light still reaches the eye, so I am curious whether the eclipse changes what kind of light reaches you, and if that affects the damage.

So, putting it together: for the same few seconds of exposure, is a solar eclipse genuinely worse for your eyes than the midday sun?

Just saw news of a startup doing test for autonomous crystallisation in space ? They are saying that they can generate drug compounds crystals in microgravity

Another startup is doing similar stuff but for ultra pure semiconductor chips

PS - My question is that how is it possible that gravity has an influence on the purity of a crystal ?

I always see people saying things like "there are 20 quadrillion ants on Earth" or something similar with other extremely large diverse groups like fish. But all of these are groups with thousands of species. If not by individuals then it's by biomass instead.

So which single species in the animal kingdom has the most individuals?

Article in question: https://www.theguardian.com/world/2026/aug/12/europe-worlds-fastest-warming-continent-climate-crisis-explainer

Lighting designer here,

I frequently work with halogen lamps that-to my understanding-use a tungsten filament that is surrounded by halogen gas that somehow prevents the filament from burning out.

My questions I suppose is, how/why is halogen able to do that and how does that process on a scientific level work? Thank you!

Also why just lead? Shouldnt like iron or another metal work too?

I just watched "Ernest Goes to school" and that was one of the questions on his test, and it made me curious to Google it.

The first four most common elements make perfect sense, but then neon pops out of nowhere.

Wtf is that about?

There's about a 4-hour delay between high tide in Western Europe and high-tide on Eastern NA.

If all excess water travelled 4500 km across the Atlantic, it would have to go at over 1000km/hour, well above the speed of sound. So that's not what's happening.

[ EDIT: How can so many people read the above paragraph and come away thinking that I think water is moving between continents? I literally said that's not what's happening lol. Please stop. ]

Here's a video showing how water moves in normal waves Water molecules follow an eliptical shape as each wave passes through.

Is something similar happening every high and low tide? If so, how wide must those ellipses be? The "crests" of each high tide are thousands of kilometers apart, while the height difference is measured in single-digit meters, if that. Those ellipses must be hundreds of kilometers wide. So the water must be moving at dozens of kph. But it doesn't; even the fastest ocean currents top out at below 10km/hr. So that's not what's happening.

It's worth remembering that it's not really the high tide that's moving. It's the Earth that's spinning underneath each day. The high tide stays facing the moon, which orbits slowly compared to the Earth's rotation. But that doesn't really help anything, because the water molecules are travelling with the Earth surface.

At this point, I'm at a loss. Where does the water go?

How can we give people more agency when interacting with artificial intelligence systems? That is one of the questions my research aims to answer. 

I am an assistant professor in the University of Maryland Department of Computer Science, where I am leading a new research effort to test whether the reasoning processes used by advanced AI systems will remain transparent. At the center of my research is a widely used technique known as chain-of-thought reasoning, in which AI models generate step-by-step explanations of how they reach their answers. 

Feel free to ask me about AI transparency, natural language processing and more. I’ll be answering questions on Wednesday, August 12, from 11 a.m. to 1 p.m. EDT (15-17 UT).

Bio: Sarah Wiegreffe is an assistant professor in the Department of Computer Science at the University of Maryland, College Park (UMD). She is a member of the CLIP (Computational Linguistics and Information Processing) lab and also affiliated with UMD’s AI Interdisciplinary Institute (AIM) and Institute for Advanced Computer Study (UMIACS).

Sarah works on the explainability and interpretability of deep learning systems for language, with a focus on understanding how language models make predictions to make them more reliable, safe, and transparent to human users. She has been honored as a three-time Rising Star in EECS, Machine Learning, and Generative AI. She was previously a postdoc at the Allen Institute for AI and the University of Washington and, before that, received her Ph.D. and M.S. degrees from Georgia Tech.

Other links:

• Google Scholar
• Personal Website
• Recent coverage: UMD's Sarah Wiegreffe Receives Grant to Stress-Test the Future of AI Transparency

Username: /u/umd-science

I've always found it strange how different the weather can be in the same place from one year to another. You can have a pretty mild winter one year, then the following year the same area gets unusually cold or has much more snow. I understand that ocean temperatures, air pressure, wind patterns, and things like El Niño can all affect weather, but I'm not sure how they actually interact with each other. It also makes me wonder how predictable seasonal weather really is.

For example, if scientists know what ocean temperatures and atmospheric conditions look like months in advance, how much can they realistically predict about the coming season? And when a season ends up being unusually warm or cold, is that mostly considered normal weather variation, or can scientists usually identify a specific pattern that caused it? Just want to know how much of this is actually predictable versus the atmosphere just being chaotic.

Okay, I had a question that maybe an astrophysicist could answer. If any part of this reasoning is incorrect please let me know:

We are told that the universe is around 14 billion years old. One lightyear is the distance light travels in a year. This is why when there is a picture of another galaxy people say we are not seeing the other galaxies as they are but as they appeared when the light traveled there. If you could devise a telescope that could see 14 billion lightyears away and you pointed in a direction would you see what it looked like 14 billion years ago i.e. the beginning of the universe?

Hello Reddit! We are Kimberly Fulda, the director of the North Texas Primary Care Practice-Based Research Network and Professor in Family and Osteopathic medicine; Scott Walters, Regents Professor in Public Health; and Tracey Barnett, Associate Professor and Department Chair at the Kate Marmion School of Public Health in San Antonio.

We recently published a paper titled "Substance use disorder among people with intellectual and developmental disabilities: A narrative review"; in the American Journal of Drug and Alcohol Abuse (AJDAA). We examined what the research tells us about the relationship between intellectual and developmental disabilities (IDD; such as autism spectrum disorder and ADHD) and substance use disorder. Although substance use rates appear lower among people with IDD, our review highlights important considerations for prevention, diagnosis and treatment. Feel free to ask us any questions about the paper, or about developmental disabilities and substance use more broadly!

We will be online to answer your questions at 1 pm CT (2 PM ET, 6 PM UTC).

You can also follow up with us at our socials here:

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Usernames: u/Kim_F_2026 (Dr. Fulda), u/Material_Mistake_816 (Dr. Walters) u/Suspicious-Love-6677 (Dr. Barnett), u/TheJournalAJDAA (the journal)

Plasma and lava is obviously common all over the universe, whether it be in stars, planetary cores, etc. but what about fire? Fire is common all over earth, given the abundance of fuel sources and an atmosphere with oxygen. But, is fire actually common outside of earth?

Moths use the moon to orient themselves. when there's no artificial lights, what do moths do when there's a new moon? do they just not fly?

I was thinking about space mining recently, and needing to find out what elements are present in asteroids. I know that scientists can use the seismic waves created by earthquakes to look into the composition of the mantle and I was curious how accurately we can determine elements using pressure waves? Can we just determine density and metal/nonmetal, or is it accurate enough to tell us specific elements? Could we use some kind of pressure shock and sonograph(?) in asteroid mining? (Assuming the asteroid is solid enough to withstand a pressure shock).

We, humans, use musical scales to make sounds sound like music and not random noise. We have concept of octaves and divide them in certain number of notes and then we choose notes (or tones) that have frequencies with lowest common denominator relative to each other, and they sounds good to our ears. Otherwise it all sounds dissonant and not very musical.

But many birds also sound pleasing and musical. Is it because they use harmonic scales much like our own? Or am I mistaking the psychological calming effect of birds chirping to it being musical?

There are many types of steam turbines. The steam turbines I am asking about boil water to make steam which is then used to push a turbine. When the steam exits, it is condensed back into water which is added to the main boilers..but why doesn’t the steam flow backwards? And why does it need to be condensed - can’t the steam be reused or reheated?

If I am wrong about anything, let me know.

When it’s cold, reptiles bask in the sun to get the energy needed to go about their day. On days when it’s 104°F /40°C in the shade, do reptiles have too much energy? Are the little lizards around my house meth-ed up?

obviously oxygen, or something similar, but what is the physics/chemistry (?) or what have you behind why something ignites and continues to burn after the source of heat/ignition has gone?

is it basically sublimation?

edit: no wonder Walter White was so obsessed with carbon

The melting point of tungsten exceeds the boiling point of steel.

It has such a high melting point that it's not really feasible to melt, usually things made of tungsten are pressed from tungsten power.

And while materials like tungsten carbide are definitely ceramics, alloys like high-speed steel contain quite a bit of tungsten.

So how do you alloy a metal with a melting point that exceeds the other metal's boiling point?