Juno skims the cloud tops of Jupiter
nasa.gov
nasa.gov
I wonder if you could build a mesh network of satellites/probes out farther into the solar system to get better connectivity for projects like this.
A mesh network sounds fun, though you'd have to have a fair few probes, as their orbits wouldn't be in sync. Also that far from the sun, solar panela don't cut it and you need nuclear thermal generators, which have a finite lifespan.
From wikipedia:
Power: 14 kW at Earth,435 W at Jupiter
Incidentally, the relative speed you can napkin math estimate - an object in orbit flying that close to the planet is going to have escape-velocity-ish speed. It's around 60km/sec for Jupiter.
> We would come back about 20 ns older compared to her [the wife who stayed behind].
≥ Or, the other way to look at it (since this is relativity after all), is that she would become 20 ns younger than us upon our return. Note to husbands: this could be a useful gift idea for your wife.
https://en.wikipedia.org/wiki/Pound%E2%80%93Rebka_experiment
Scientific notation is also fine, but "210 megameter" is in my opinion easier to read than "2.1 * 10^8 meters", especially for the casual reader.
So while I respectfully make note of your feedback, I strongly disagree and stand by my choice of units. :)
Not that I don't agree (I fully do!), the ease of using multiples of 10 is way easier. But it is very difficult to introduce change to the masses, no matter how sensible it is.
The US is one of the only countries on the planet that still fully stick to the old system. And they're also one of the only countries that spell 'meter' instead of 'metre.' For everyone else in the world, 'meter' is a measuring gauge or tool, and so is everything that rhymes with 'thermometer' except for the American pronunciation of 'kilometre' that too many have adopted up here.
Likewise, adult Canadians still use pounds at the gym and their body weight, and feet/inches for their height. Young people are far more reasonable about measurements these days.
Change is hard, and seems to get really messy when everyone goes in different directions from the start.
... But as we speak about metric measurements I doubt that the US insistence on weird units apply. The average US citizen would presumably be confronted with "mega" and "giga" in their day-to-day lives, and millimeter, micrometer and nanometer are commonly used. Even femtosecond is a common, practical unit that anyone receiving refractive surgery will hear.
Picometer is unpopular because it only makes sense for sub-atomic lengths giving it few practical uses at the current time, not because "pico" is hard to grasp.
Also note that German, Dutch, Danish (my native tongue), Swedish, Norwegian, even Hindi and presumably many others also refer to the unit as "meter", so that particular disagreement is not "the US against the rest of the world".
(All languages have quirks - in Danish, we call a folding ruler in meters an "inch stick", and say the number "53" as "3 and half three's twenties" (skipping the "twenties" part in modern speech). Learn to enjoy the differences rather than hate on them.)
LISA is practically always described as a gigametre-scale observatory.
One example: "LISA, a gigameter-scale space-based gravitational wave observatory, will explore the gravitational wave universe in the band from below 0.1 mHz to above 0.1 Hz." <https://about.cern/news/announcement/physics/cern-colloquium...>, and a trawl through arxiv will show a common association of Gm and LISA.
Assuming LISA is successfully deployed, gigametre may be seen more commonly.
The only other place I've seen Gm scales in common use is in galactic physics, particularly with respect to turbulence and star and planetary nebula formation (stars have ~ Gm diameters; very large stars like VY Canis Majoris have ~ Tm diameters; star systems like ours have gravitationally bound rocky and icy objects at ~ Tm diameters).
1 petameter ~ 0.1 lightyear; 30 petameter ~ 1 parsec, so those are obvious cutoffs for the SI unit of length in astronomy and astrophysics.
Gigaparsecs and (less frequently) gigalightyears are commonly used in physical cosmology (e.g. <https://duckduckgo.com/?q=gigaparsec+site%3Aarxiv.org&ia=web>).
Penultimately, truly long lengths are typically measured in cosmological redshift z, which is unitless (being a ratio \frac{\delta\lambda}{\lambda}, or 1+z = \frac{a_{now}}{a_{then}} where a is the scale factor), leading to such things as a comoving volume (1 + z)^3. For z > 0.2 one would be using Gpc lengths, or in SI units Ym; or when working in these sorts of comological volumes in 2023's Britain, trevigintillions of acre-feet.
Finally, cf. the excellent printable table at <https://arxiv.org/abs/1303.5961>, the leftmost column (redshift) and the r_comov column (megaparsecs) being the most directly relevant.
Oops, megameters per hour.
210 Mm/s is a very* big deal, with the speed of light being around 299 Mm/s.
"Parker Solar Probe passing extremely close to the Sun; what relativistic effects will it experience and how large will they be?": https://physics.stackexchange.com/questions/348854/parker-so...
Wolfram Alpha could be helpful.
> 210,000 kilometers per hour.
I am so glad we live in an age where this is possible, and that it is celebrated and respected.
Fantastic.
I've never checked it.
However, if there was a box to say "Give NASA $20", I'd check it every time.
I agree, but to nitpick IMHO it's a foundation stone. Others are freedom and human rights (including for basic science: speech, to publish your controversial results uninhibited, religion, when your theory is heretical, etc.), rule of law (to protect your investment in your research from powerful people who want to stop or sieze it), and other basics.
Edit: Two hours of real-time Jupiter: https://www.youtube.com/watch?v=GPMK_6-QrIg
99.99997 percent is below 100km, but the exosphere is considered to go as far as 10k, and maybe further:
> A February 2019 study using data from the NASA/European Space Agency Solar and Heliospheric Observatory (SOHO) spacecraft suggests, however, that the farthest reaches of Earth’s atmosphere — a cloud of hydrogen atoms called the geocorona — may actually extend nearly 391,000 miles (629,300 kilometers) into space, far beyond the orbit of the Moon.