\sqrt{r^2 + (vt)^2} = r \sqrt{1 + (vt/r)^2} = r + (1/2) (vt)^2 / r + o(t^2), так что вторая производная равна
v^2/r = (vr)^2 / r^3.
Числитель — (vr)^2 — это квадрат углового момента. Так что он вдоль орбиты всегда один и тот же! А знаменатель r^3 — как раз и соответствует закону всемирного тяготения: куб, как и раньше. Так что, если взять константу l = (vr)^2/ (GM), то для разницы (r-l) будет (r-l)’’ = r’’ = hr + (vr)^2 / r^3 = - GM r / r^3 + (vr)^2 / r^3 = - GM / r^3 * (r- l) = h (r-l).
Так что трёхмерный вектор R = (x,y,r-l) подчиняется центральному закону R’’ = h R, h = -GM/r^3.
\sqrt{r^2 + (vt)^2} = r \sqrt{1 + (vt/r)^2} = r + (1/2) (vt)^2 / r + o(t^2), так что вторая производная равна
v^2/r = (vr)^2 / r^3.
Числитель — (vr)^2 — это квадрат углового момента. Так что он вдоль орбиты всегда один и тот же! А знаменатель r^3 — как раз и соответствует закону всемирного тяготения: куб, как и раньше. Так что, если взять константу l = (vr)^2/ (GM), то для разницы (r-l) будет (r-l)’’ = r’’ = hr + (vr)^2 / r^3 = - GM r / r^3 + (vr)^2 / r^3 = - GM / r^3 * (r- l) = h (r-l).
Так что трёхмерный вектор R = (x,y,r-l) подчиняется центральному закону R’’ = h R, h = -GM/r^3.
Ура — теорема доказана!
BY Математические байки
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The next bit isn’t clear, but Durov reportedly claimed that his resignation, dated March 21st, was an April Fools’ prank. TechCrunch implies that it was a matter of principle, but it’s hard to be clear on the wheres, whos and whys. Similarly, on April 17th, the Moscow Times quoted Durov as saying that he quit the company after being pressured to reveal account details about Ukrainians protesting the then-president Viktor Yanukovych. In the past, it was noticed that through bulk SMSes, investors were induced to invest in or purchase the stocks of certain listed companies. Apparently upbeat developments in Russia's discussions with Ukraine helped at least temporarily send investors back into risk assets. Russian President Vladimir Putin said during a meeting with his Belarusian counterpart Alexander Lukashenko that there were "certain positive developments" occurring in the talks with Ukraine, according to a transcript of their meeting. Putin added that discussions were happening "almost on a daily basis." Russians and Ukrainians are both prolific users of Telegram. They rely on the app for channels that act as newsfeeds, group chats (both public and private), and one-to-one communication. Since the Russian invasion of Ukraine, Telegram has remained an important lifeline for both Russians and Ukrainians, as a way of staying aware of the latest news and keeping in touch with loved ones. If you initiate a Secret Chat, however, then these communications are end-to-end encrypted and are tied to the device you are using. That means it’s less convenient to access them across multiple platforms, but you are at far less risk of snooping. Back in the day, Secret Chats received some praise from the EFF, but the fact that its standard system isn’t as secure earned it some criticism. If you’re looking for something that is considered more reliable by privacy advocates, then Signal is the EFF’s preferred platform, although that too is not without some caveats.
from jp
