Hi scientists of lemmy, I'm a computer scientist with basic college level physics and an interest in physics.

I was reading Cosmos by Carl Sagan yesterday and he mentions that if you use a Geiger counter next to an uranium ingot you will detect the uranium's spontaneous decay as a stream of helium nucleei.

Does helium nucleei mean 2 protons and some number of neutrons? What happened to the respective electrons? Does this mean that each uranium atom, with 92 protons, entirely splits into 46 helium nucleei or does it release some number of helium nucleei leaving another element behind? How does the concept of half life play into this? Does it mean that in a uranium half life, half of my ingot would've become helium? Finally, how is this stream of helium nucleei so dangerous to living beings?

Thanks for your attention

Wolfram alpha has a sunburn calculator:

https://www.wolframalpha.com/input?i=time+to+sunburn

I'm out in the sun much longer then the calculator suggests, but I dont get burned.

How do scientists predict the future climate? Do they just calculate the current trends of temperature growth and take the causes of it into account? Or is there some other way. Is it basically some model y = a1*x1 + a2*x2 + ... or something more complex?

You can look at certain structures in one animal and show how they're made from repurposed parts of an earlier animal (like fish gills becoming human ears). Can that be done with humans and those animals with Xenomorph double-mouths? Can you say "in humans, this particular piece of tendon in the neck is what eels reused for an additional mouth" or something along those lines?

Thanks for your time!

If the answer is YES, a related follow-up question: if each visible color of the spectrum were to measure a centimeter in width, how far would I have to move the sensor from the red to detect the change from infrared to microwave, then to radio?

In the knowledge that Sir William Herschel discovered infrared by repeating Newton's experiment, but with a thermometer to measure the temperature of each component of the spectrum, and after placing the thermometer a bit to the side of the red light, in darkness, noticed quite by accident that the device would still register heat, therefore an invisible yet very real component of light was there, warming the thermometer.

Energy in physics feels analogous to money in economics. Is a manmade medium of exchange used for convenience. It is the exchange medium between measureable physical states/things.

Is energy is real in the same way money is? An incredibly useful accounting trick that is used so frequently it feels fundamental, but really it's just a mathmatical convenience?

Small aside: From this perspective 'conservatipn of energy' is a redundant statement. Of course energy must be conserved or else the equations are wrong. The definition of energy is it's conservation.

Now I'm just being the curious layman here, but a Google/YouTube search proved fruitless.

I keep seeing commercials for Gross Pointe Garden Society it made me wonder.

Cells divide and make new cells, is all life on Earth rooted in one super ancestor cell? Or are there parallel paths to cell creation?

Since I haven't found a sub for sociology I decided to post this question here looking for a scientific answer. I'm looking for a more empirical answer rather than opinion based since I think this is critical in understanding such a complex and nuanced topic.

So I noticed that in the USA people are often strongly divided based on whether they identify as being "black" or "white". Basically many people there make this a big part about their identity and separate communities based on it to the point where they developed different cultures and even different ways of talking and behavior solely based on whether they identify as "black" or "white".

As far as I understand it's based on the brightness of their skin color because of slavery but it's not quite clear to me who is considered "black" or "white" since I've seen many people who for example have very bright skin and seem to have almost no African ethnicity but they still identify and talk/behave as "being black".

I wonder why they still have this culture and separation since segregation ended in 1964.

Because in other regions like South America such as Brazil for example this culture doesn't seem to exist that much and people just identify as people and they talk, behave and connect the exact same way no matter the skin brightness. People such in South America seem way more mixed and seem to not have this type of separation like in the USA based on external features like skin, hair or eye color.

To me it kind of feels like this is a political and economic reason in the US that they purposefully want to divide people for their gains. Because the extent to which this seems to have been normalized in Americas every day conversation both in private and in public/commercial spaces feels like brainwashing. And I wonder if this will ever improve since it seems to go as far as people being proud about these racist stereotypes and think this is completely normal. But considering the broader global context and America's historical background it doesn't seem normal. Especially with America's context of slavery you would expect there to be strong efforts of fighting these stereotypes and having a political leadership that doesn't see "color" and only judges based on an individual's personality.

So, AI can do a lot of things. But it needs input data. So I was thinking, do we currently have any technology that could generate metrics that an AI might be able to train on such that it could estimate calories gotten from a meal. Not what was in the food, but what the body actually absorbed.

Obviously it could be used to make a killer diet tracking app. Cause tracking what you eat is the worst part.

And collecting the metric doesn't have to be "practical" today. This is just more of a thought experiment. So if currently it would require multiple blood tests per day or something, that would still be interesting to me.

Any recommendations on good introduction books for kids? Any science or engineering book would be good!

Basically, my question is the title. If a black hole crosses the Roche limit of another black hole, what happens?

For a hypothetical example, let's say you have a two black holes: one at 5 solar masses and one at 300 solar masses. If the smaller black hole crosses the Roche limit of the larger what happens? Does they simply merge? Would the event horizon of one or both black hole's be geometrically distorted in some way or retain their spherical shape?

L-methylfolate for example.

Are you supposed to pronounce it as dextro/levo or as a letter?

Context: I am not a fridgy, I work with electronics. I would love to answer my question by tearing open a dozen different aircon units, but I'm sorely lacking in that department.

Question: Are there some optional components or fancier materials that are simply too expensive to use in the lower end aircons; but are used in the higher efficiency expensive units? The range of COP/EER I see advertised is wild, from 2 to 6 or so.

I already vaguely understand that these things help efficiency:

• Bigger indoor & outdoor coils with more metal in them (working fluids get returned hotter/colder gives better carnot efficiency)
• Operating compressor at its optimal power level (I believe they have an efficiency vs power curve with a single peak, so it's better to use a bigger compressor if you need more power output)
• Inverter control instead of on/off control (most situations, but technically some use cases will have them on par)
• Choice of refrigerant (but that seems to be controlled in my market, I have not seen many options)

Is there anything else they change? Or is that most of the difference?