Recent comments in /f/askscience

Pharmer3 t1_j6z6k04 wrote

Reply to A medical isotope made from nuclear weapons waste (Tc-99m) has a six-hour half-life. How do hospitals keep it in stock? by Gwaiian

Pharmacist who used to work in a nuclear pharmacy - they don’t keep it in stock! Doses are custom made for each patient every day at a (usually) offsite nuclear pharmacy, and then a van delivers them to the imaging center so they can be injected at precisely the right time to deliver the prescribed dose of radiation for the imaging! Logistically, it doesn’t make sense for most medical centers to have their own nuclear pharmacy, so one location will service large metropolitan areas. Happy to answer any addition questions!

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lankymjc t1_j6z63dc wrote

Reply to comment by Alfred_The_Sartan in extremely long stick additional questions? by Unnombrepls

I used to think that I had theoretically cracked FTL communication through the use of really long sticks (though the engineering would be its own impossible issue). Took me ages before finding out about compressing objects, which made me feel better because I was sure someone must have already thought of it and disproved it, I just couldn't find the answer until a few years ago!

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Max-Phallus OP t1_j6z45xi wrote

Reply to comment by mckulty in Do photons of different wavelengths combine to make complex wave forms? by Max-Phallus

Thanks for the answer. I think it highlights some holes in my understanding though.

While we do mostly think of AM and FM radio transmissions; we can pass any waveform into an antenna.

Is the output from that antenna a variable waveform photon, or is it multiple photons of different wavelengths being produced at once.

Or is it pretty much semantics? Where a variable waveform is just one waveform, but it can be described as multiple photons of different wavelengths, as per it's Fourier transform?

Apologies if I'm being dim.

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stu54 t1_j6z354n wrote

Reply to Suppose I have a container of water with a ball floating on top of it. I put it outside overnight and the water freezes. Since the water's volume increases as it freezes, the ball is raised. Where does the increased gravitational potential energy come from? by schematicboy

Latent heat. At higher pressures water freezes at lower temperatures. At higher pressures the latent heat of fusion increases.

As a material passes from liquid phase down to solid energy is released. Same as how steam releases a lot of heat as it condenses on your hand when you delid a boiling pot of water. This is called latent heat of fusion, and latent heat of vaporization.

Water is weird. It is most dense at 4°C then begins to expand toward 0°C as it forms transient nano scale clusters of molecules. At high pressures these nano clusters are less able to form.

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Environ_MENTAL_ist t1_j6z0tte wrote

Reply to Are plants growing from cuttings as healthy as those grown from seed? by [deleted]

One of the major differences between seed grown plants and cuttings are the development of their root system.

From seed, roots form generally from the top of the soil down to the bottom of the pot. But from cuttings, since the end of the cutting is under the soil, the roots tend to grow from wherever that cut end is sitting in the pot. If you’ve shoved your cuttings all the way down into their pots so that their cut ends are touching the bottom, you will likely get roots growing UPWARD rather than downward which can cause problems for the plants long term health. But, if you position them more towards the middle, or are using an aeroponic system to mist their new roots directly, there should be minimal differences between plants from cuttings and those grown from seed.

Pelargoniums can live for a long time compared to some other common house plants. I wouldn’t be concerned about their vigor. Any issues with flowering are more likely related to light/season/temp, water availability, or nutrient availability.

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