4 ms·

If they are close enough to each other and far enough from everything else, then why not. The smallest objects for which we measured their gravitational intera

If they are close enough to each other and far enough from everything else, then why not. The smallest objects for which we measured their gravitational interaction weighed just 90 mg (https://arstechnica.com/science/2021/03/researchers-measure-the-gravity-exerted-by-a-90-milligram-object/ https://arstechnica.com/science/2021/03/researchers-measure-...). The biggest object put in quantum superposition weighed around 1 mcg (https://physics.aps.org/articles/v16/s45 https://physics.aps.org/articles/v16/s45).

feoren 3y ago
So 90,000 times smaller. At first glance you made it look 90x smaller because I couldn't tell if "mcg" was a typo for "mg" or not (without clicking the link). I've never seen anyone use "mcg" to mean "microgram" before and I feel like it's misleading. Use "ug", or "μg" if you're feeling fancy.
- twic 3y ago
  Use of "mcg" for micrograms is common practice in medicine. I always assumed it was because it's easier to type than μg, but it seems a medical body recommends it because μg is too easily mistaken for mg: https://www.ismp.org/sites/default/files/attachments/2017-11/Error%20Prone%20Abbreviations%202015.pdf https://www.ismp.org/sites/default/files/attachments/2017-11...
  - marcosdumay 3y ago
    > μg is too easily mistaken for mg Is that some joke about medical writing? Anyway, I just noticed that table doesn't have rules for nanogram. There is also no mega-anything. (On a serious parenthesis, I think I actually understand their rationale; but changing the abbreviation of only one of them is still confusing.)
    - tlb 3y ago
      Before Unicode, 'μ' was typically entered as an 'm' in a Greek font. This can go wrong in several ways, like if you converted the document to plain text, or if your laser printer didn't have the font and it substituted a regular font, you're suddenly off by a factor of 1000. 'mc' is ugly but safe.
      - marcosdumay 3y ago
        Interesting. There's that too. I assumed it was because of the phonetic similarity.
      - danbruc 3y ago
        What time period, system and region are we talking about? For some characters using a specific font was certainly necessary but for µ? It is in the original IBM PC character set from 1981 and could easily be put into plain text files. I would guess that most extended ASCII character sets contain it but I don't know for sure. Every [German] keyboard I ever used had it on the M key.
        tlb 3y ago
        I remember having to get a µ that way using FrameMaker on SunOS 4 in the mid-90s. Mac had a µ from the beginning. And some PC code pages did. But PCs in Canada (where I'm from) used code page 850, which had an Á (for French) where µ would be. Just the sort of thing that would hose you if you tried printing a Mac document on a school printer. Here's a howto article that suggests using an 'm' in the Symbol font in Word: https://www.officetooltips.com/word_2016/tips/how_to_insert_micro_sign_or_mu_symbol_in_word.html https://www.officetooltips.com/word_2016/tips/how_to_insert_...
- eterevsky 3y ago
  Yes, I meant micrograms. 90'000 times sounds a lot, but just a few decades ago the biggest objects in superposition were individual particles and atoms, and the crystal from the new study is 10^16 times bigger than that.
- jojobas 3y ago
  That's not it. The mass difference of entangled states should be over the 90mg, suggesting much, MUCH heavier entangled object.
_a_a_a_ 3y ago
90 mg... that is beyond gobsmacking
- lamontcg 3y ago
  I honestly can't tell if you're impressed we've measured the gravitational interaction of something that small, or staggered by our inability to measure a feature of things so large that you can easily hold them in your hand.
  - _a_a_a_ 3y ago
    "The current best estimate for the mass of Earth is M⊕ = 5.9722 × 10^24 kg" (wiki) so ~6 × 10^27 grammes, so 90mg ~ 28 orders of magnitude smaller. So very, very much the former.
audunw 3y ago
I think the comparison you're giving here is quite misleading. You're implying that we "only" need to scale up the objects we put in quantum superposition by tens of thousands of times. But that's not all there is to it. You'd have to put it in a kind of superposition that affects its mass enough to be measured. For instance, having the whole object be in superposition of one position, or another position several centimeters away. Or being in an extremely high energy state vs extremely low energy state, with an energy difference on the order of 90mg. Given E=mc2 that's an insane amount of energy. Seems to me that such an experiment is borderline unthinkable with present day technology.
- eterevsky 3y ago
  I do understand that there's more to it than just closing the gap of 90'000x. That said, the fact that these numbers are on roughly the same order of magnitude makes me cautiously optimistic. If anything, to me both measuring the gravity of 90 mg weight and putting a crystal that you could see with your naked eye into quantum superposition already seem borderline unthinkable.

feoren 3y ago

So 90,000 times smaller. At first glance you made it look 90x smaller because I couldn't tell if "mcg" was a typo for "mg" or not (without clicking the link). I've never seen anyone use "mcg" to mean "microgram" before and I feel like it's misleading. Use "ug", or "μg" if you're feeling fancy.

twic 3y ago
Use of "mcg" for micrograms is common practice in medicine. I always assumed it was because it's easier to type than μg, but it seems a medical body recommends it because μg is too easily mistaken for mg: https://www.ismp.org/sites/default/files/attachments/2017-11/Error%20Prone%20Abbreviations%202015.pdf https://www.ismp.org/sites/default/files/attachments/2017-11...
- marcosdumay 3y ago
  > μg is too easily mistaken for mg Is that some joke about medical writing? Anyway, I just noticed that table doesn't have rules for nanogram. There is also no mega-anything. (On a serious parenthesis, I think I actually understand their rationale; but changing the abbreviation of only one of them is still confusing.)
  - tlb 3y ago
    Before Unicode, 'μ' was typically entered as an 'm' in a Greek font. This can go wrong in several ways, like if you converted the document to plain text, or if your laser printer didn't have the font and it substituted a regular font, you're suddenly off by a factor of 1000. 'mc' is ugly but safe.
    - marcosdumay 3y ago
      Interesting. There's that too. I assumed it was because of the phonetic similarity.
    - danbruc 3y ago
      What time period, system and region are we talking about? For some characters using a specific font was certainly necessary but for µ? It is in the original IBM PC character set from 1981 and could easily be put into plain text files. I would guess that most extended ASCII character sets contain it but I don't know for sure. Every [German] keyboard I ever used had it on the M key.
      - tlb 3y ago
        I remember having to get a µ that way using FrameMaker on SunOS 4 in the mid-90s. Mac had a µ from the beginning. And some PC code pages did. But PCs in Canada (where I'm from) used code page 850, which had an Á (for French) where µ would be. Just the sort of thing that would hose you if you tried printing a Mac document on a school printer. Here's a howto article that suggests using an 'm' in the Symbol font in Word: https://www.officetooltips.com/word_2016/tips/how_to_insert_micro_sign_or_mu_symbol_in_word.html https://www.officetooltips.com/word_2016/tips/how_to_insert_...
eterevsky 3y ago
Yes, I meant micrograms. 90'000 times sounds a lot, but just a few decades ago the biggest objects in superposition were individual particles and atoms, and the crystal from the new study is 10^16 times bigger than that.
jojobas 3y ago
That's not it. The mass difference of entangled states should be over the 90mg, suggesting much, MUCH heavier entangled object.

_a_a_a_ 3y ago

90 mg... that is beyond gobsmacking

lamontcg 3y ago
I honestly can't tell if you're impressed we've measured the gravitational interaction of something that small, or staggered by our inability to measure a feature of things so large that you can easily hold them in your hand.
- _a_a_a_ 3y ago
  "The current best estimate for the mass of Earth is M⊕ = 5.9722 × 10^24 kg" (wiki) so ~6 × 10^27 grammes, so 90mg ~ 28 orders of magnitude smaller. So very, very much the former.

audunw 3y ago

I think the comparison you're giving here is quite misleading. You're implying that we "only" need to scale up the objects we put in quantum superposition by tens of thousands of times. But that's not all there is to it. You'd have to put it in a kind of superposition that affects its mass enough to be measured. For instance, having the whole object be in superposition of one position, or another position several centimeters away. Or being in an extremely high energy state vs extremely low energy state, with an energy difference on the order of 90mg. Given E=mc2 that's an insane amount of energy. Seems to me that such an experiment is borderline unthinkable with present day technology.

eterevsky 3y ago
I do understand that there's more to it than just closing the gap of 90'000x. That said, the fact that these numbers are on roughly the same order of magnitude makes me cautiously optimistic. If anything, to me both measuring the gravity of 90 mg weight and putting a crystal that you could see with your naked eye into quantum superposition already seem borderline unthinkable.