observantTrapezium

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Cake day: June 30th, 2023

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  • Not sure this statement is true if “more closely related” is understood as shorter combined time between the two species from their most recent common ancestor. Hummingbirds and brachiosaurs had a more recent common ancestor than brachiosaurs and triceratopses (albeit probably still quite close to the dawn of dinosaurs in the Late Triassic ), but the latter pair lived closer in time to the common ancestor of all dinosaurs (while hummingbirds are from the Oligocene).



  • observantTrapezium@lemmy.catoScience Memes@mander.xyzSeconds
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    2 months ago

    That may be relativists (they would actually measure anything in units of mass, with everything else defined through G = c = 1). Astrophysicists commonly measure mass in solar masses, long distances in parsec (or kiloparsec, megaparsec), short distances in solar radii or AU, and time in whatever is relevant to their problem (could be seconds or gigayears)


  • I’m sitting on an Aeron at work, it’s good, but I can’t in good conscience pay that much for a chair. I was recently on the market for a new office chair and extensively researched it. It really looks like it’s a hit or miss with every chair in every price range, and I was very seriously considering replacing my Hyken with another Hyken. I decided to go with the IKEA Markus and have been sitting on it for about a month. I’m only moderately happy with it, may even return it before the year is up although I’d hate doing it.





  • EM and gravitational waves are seen as analogous because as I wrote, they are produced by acceleration of charges and masses, respectively. The physics behind them is very different (described by Maxwell’s equations for EM and Einstein field equations for GW), but all systems that have waves in them (including sound in the air, waves on the surface of water etc.) can be approximated as linear for small perturbations, which means that they satisfy the wave equation at that regime.


  • They are quite similar to electromagnetic waves, but also quite different. They are produced by masses accelerating (just like EM waves are produced by charges accelerating), and indeed cause orbital decay. But this orbital decay is only important in relativistic systems (so the Earth, which is orbiting the sun at 0.0001 the speed of light, is not going to fall into the sun because of gravitational waves).


  • See my response below to Captain Aggravated about how dilute those large stars are.

    It’s an interesting question whether anybody would actually feel spaghettification 😁 I actually don’t know. You can use physics to calculate the proper time derivative of the tidal forces, but you need biology to define the start (and end…) of the process. My intuition says that it probably happens too fast, so once the tidal forces are strong enough to be perceptible, they grow strong enough to rip you apart before you realize (again, just a hunch).


  • Yes, but red supergiants differ from the sun in that their photospheres are extremely dilute and don’t have a sharp transition to the corona. I don’t know the details of this particular star but take Betelgeuse as an example (it’s probably not particularly large for this catrgory), it’s radius is ~640 the sun’s per Wikipedia, which gives a volume of ~260 million that of the sun. But it is only x15 times as massive as the sun, so on average ~20 million times less dense.



  • observantTrapezium@lemmy.catoScience Memes@mander.xyzperspective
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    3 months ago

    In the case you are unlucky enough to encounter the black hole “heads on” and fall into it radially, the proper time timescale to spaghettification is the size of the event horizon divided by the speed of light. The most supermassive black holes will have a horizon of around one light day, so that’s what we’re working with, a matter of days. If you come in on the most tangential orbit possible though, I guess you’re buying some time but I’ve never heard that it’s supposed to take many years of proper time (I doubt that claim a little bit, but haven’t calculated myself).


  • Astrophysicist here. Yes, space is crazy, but interesting things to keep in mind:

    1. The size of a star is determined by something called the photosphere. With those extremely massive stars, you can be hundreds of millions of kilometres “inside” and not yet know it.
    2. Similar story with supermassive black holes, from the perspective of an astronaut falling in, they wouldn’t really be able to tell when they cross the horizon because the tidal forces there are very small (they will inevitably fall towards the centre and get spaghettified at some point)



  • I think younger people in Canada only know °F if their thermostat is set to it and they can’t or don’t bother to change. My stupid fridge is in Fahrenheit and that can’t be changed (even though the handbook shows the display in Celsius! A variation of the model is probably sold abroad).

    I think Canada properly adopted Celsius, kilometres, litres and millilitres (at least here in Toronto), but all other metric units are the underdog. Even CBC, that is probably the only media outlet that tries to stick to metric will specify people’s height in feet and inches. Shameful.