by johnnydeep » Tue Feb 21, 2023 2:44 pm
Chris Peterson wrote: ↑Tue Feb 21, 2023 5:49 am
I think it's a bit marginal to say that a body in an open (hyperbolic) orbit that is moving faster than the Solar System escape velocity and will never return is really falling toward the Sun... in either direction.
Yeah. Plus, though "intuitively", a body in a closed elliptical orbit around the Sun is only falling toward it prior to perihelion, such an object is in reality falling toward the sun at all times! And even a rock thrown upward from the Earth's surface is falling even when it is rising!
So, does "falling" just mean the direction that gravity is acting regardless of the direction of motion of the object?
[quote="Chris Peterson" post_id=329352 time=1676958575 user_id=117706]
[quote="APOD Robot" post_id=329349 time=1676955994 user_id=128559]
[url=https://apod.nasa.gov/apod/ap230221.html] [img]https://apod.nasa.gov/apod/calendar/S_230221.jpg[/img] [size=150]Comet ZTF over Yosemite Falls[/size][/url]
[b] Explanation: [/b] They are both falling. The water in [url=https://youtu.be/2x80TEw45Gs]Yosemite Falls[/url], [url=https://en.wikipedia.org/wiki/California]California[/url], [url=https://en.wikipedia.org/wiki/United_States]USA[/url], is falling toward the Earth. [url=https://www.facebook.com/media/set/?set=a.172146088847310&type=3]Comet ZTF[/url] is falling toward the [url=https://solarsystem.nasa.gov/solar-system/sun/in-depth/]Sun[/url]. This double cosmic cascade was captured late last month as fading [url=https://en.wikipedia.org/wiki/C/2022_E3_(ZTF)]Comet C/2022 E3 (ZTF)[/url] had just passed its closest to planet Earth. The orange star just over the falls is [url=https://en.wikipedia.org/wiki/Beta_Ursae_Minoris]Kochab[/url]. With the exception of a brief encounter with a [url=https://bear.org/how-dangerous-are-black-bears/]black bear[/url], the [url=https://www.flickr.com/photos/84642732@N02/52685564588/]featured image[/url] was a [url=https://d1hfln2sfez66z.cloudfront.net/11-18-2021/t_9bb7158ef7834e80b0793c26fdf6b8d5_name_DogPhone_could_offer_dogs_the_ability_to_619676d229f511256af6ffc3_1_Nov_18_2021_16_25_58_poster.jpg]well-planned[/url] composite of a moonlit-foreground and long-duration background exposures - all designed to reconstruct a deep version of an actual single sight. Although [url=https://www.newsweek.com/how-see-green-comet-ztf-leaving-solar-system-1778426]Comet ZTF[/url] is [url=https://in-the-sky.org/ephemeris.php?objtxt=CK22E030]now fading[/url] as it glides back to the outer [url=https://apod.nasa.gov/apod/ap220911.html]Solar System[/url], its path is [url=https://apod.nasa.gov/apod/ap220619.html]determined by gravity[/url] and so it can be considered to still be falling toward the Sun -- but backwards.
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[/quote]
I think it's a bit marginal to say that a body in an open (hyperbolic) orbit that is moving faster than the Solar System escape velocity and will never return is really falling toward the Sun... in either direction.
[/quote]
Yeah. Plus, though "intuitively", a body in a closed elliptical orbit around the Sun is only falling toward it prior to perihelion, such an object is in reality falling toward the sun at all times! And even a rock thrown upward from the Earth's surface is falling even when it is rising!
So, does "falling" just mean the direction that gravity is acting regardless of the direction of motion of the object?