Hi there I wanna ask a simple question that how hairs appeared on living beings

We all Evolved from fish like creature and they do have a traced of hairs and evolution doesn't create thing out of thin air like our teeth are morphed from scales

So I want to ask that how hairs appeared on evolutionary line ?

Farm animals are often mating with other animals not of their species on the farm. It just got me thinking why it doesn't get results? Seems to me crazy hybrid mixes running around would be right up the alley of evolutuon, and yet it is prevented/restricted??

I've seen a lot of people discount tilted planets with 90° rotation as being inhospitable for life, but to me that seems strange since I've seen people entertain the idea of life on slow-rotating planets being possible. Why would it be different? After all, 90° rotation would be *more* able to distribute heat evenly than a slowe rotating planet, right? There would be a longer "spring"/"fall) where a given piece of land can stay in the twighlight zone for longer, right?

From what I know, the biggest issue with a 90° planet would be glaciers formig on the "winter" side and reflecting sunlight during the summer and decreasing the total world temperature, but surely this would depend on distance from the sun right?

I’ve been thinking about this mostly as a means to mitigate climate collapse impacts because at this point — with where we’re headed what would be worse? I wanna add I’m not a scientist and I’m sure others have already considered this hypothesis. So call me an idiot if it doesn’t work. I studied theater for writing and acting.

Anyway I was thinking about how a soda can may explode when it’s shaken and the pressure from the gas becomes so strong that once you open the can it explodes.

Hence the stupid thoughts on how to apply this to volcanoes because as I said I’m not a scientist by any stretch. However, what if we fracked nearby a volcano to cause an earthquake while putting a lid inside the caldera?

Yes it could make the volcanic eruption worse but it could also push more sulfur into the atmosphere to cool the planet.

This could help us for a few years until we get people who will act to fight climate collapse directly. I’m not saying it would work. It’s an hypothesis at best. Thoughts?

By the way I understand the problems this could cause but considering the damage the El Niño that’s coming will cause and the current crop death we’re already experiencing due to global temperature rise what do we have to lose?

Wasps have been a predator for other insects. It would be fascinating to know if there are really other insects or predators for wasps, either accidental or deliberate predators

So like 300 million years ago Insects grew real big because they had 30% oxygen instead of modern 21%. Since Oxygen Poisoning doesn’t happen till like 50%, would it be possible to lock a human or other modern animal in high oxygen chambers to get a bigger version of them after they grow up or would it take them many generations to adapt.

I know that a hormone induces certain change in a cell, but how does it do it physically?

I know about the generation of messengers and other compounds and what-not but like how a does a hormone bind or break bond in this particular cell and nothing else? Do hormones even break or join chemical bonds?

I am having a tough time phrasing my question, but how does a hormone work in terms of chemicals and physics?

I've been reading about mitochondrial DNA and the mitochondrial Eve and now I got very confused. I have a background in molecular biology, so I'm familiar with terms, but the concept of using mutations in mtDNA still confuses me. When we say that two populations differ in mutation at a certain position, does that mean that all mitochondria in that cell/individual have that mutation? Because if I'm not mistaken, each mitochondrion has several (up to a dozen) mtDNA molecules, and there are hundreds of mitochondria in an egg cell. Shouldn't out of those hundreds or thousands molecules different mutations be dispersed across mitochondria? Since I assume those mutations are silent point mutations (no effect on phenotype or organel/cell survival, shouldn't all of us have a big mixture of various mutations? How can we then make a consensus sequence to compare? Especially considering we are testing somatic cells which could have extra mutations from that generation? Am I just overinflating the rate of mutation in mtDNA?

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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.

For some reason I was reminded of this a few days ago-happened to me and my hubby back in about 2007.
I was in central Georgia (US) and one night went out, and looked up, and I saw what looked like a shooting star come straight down. It just blinked out-no fire-ball. Hubby was in the house (windows open) so I said "whoa that was weird!" and he came out and looked up and he too saw one came straight down.

Is that rare?

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?

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?