[AFJ Editor David Woods calls our attention to the following from the Apollo 15 Preliminary Science Report: "During the final minutes of the third extravehicular activity, a short demonstration experiment was conducted. A heavy object (a 1.32-kg aluminum geological hammer) and a light object (a 0.03-kg falcon feather) were released simultaneously from approximately the same height (approximately 1.6 m) and were allowed to fall to the surface. Within the accuracy of the simultaneous release, the objects were observed to undergo the same acceleration and strike the lunar surface simultaneously, which was a result predicted by well-established theory, but a result nonetheless reassuring considering both the number of viewers that witnessed the experiment and the fact that the homeward journey was based critically on the validity of the particular theory being tested."]
.............................................................................
[Two of the numbers given in this experiment description have been called into question.]
[Journal Contributor Andrea Sondag notes that the given weight (0.03 kg = 30 g) for the feather is much too large. She contacted an ornithology club in Bayern, Germany, who introduced her to Hermann Rank, the owner of an extensive collection of falcon feathers. "He choose a primary flight feather (H7) of a female gyrfalcon (Falco rusticolus) which fits the Apollo 15 feather best, and measured it for us: length, 31.5 cm; weight, 1.19 g."]
[Journal Contributor Joonas Helminen notes that the stated height - 1.6 meters - from which the hammer and feather were dropped is in error. Although the important part of the experiment is the fact that these two objects of very different weight experienced the same motion, for completeness we offer the following. If we concentrate on the hammer, Helminen has stepped through the mpeg clip and finds that the time between Dave's release of the hammer and its impact is 36 frames. The framing rate is 30 frames per second, giving a fall time of 1.2 seconds. We have three separate estimates of the height. Helminen estimates the height as 120 cm and writes, "My estimation was simply from thinking how far you would bend forward with the PLSS on your back and from noticing how Dave did not hold his arms straight out parallel to the ground. I am just below 180cm tall and, when put myself in the same posture, 120 cm was a close estimate of the height of the bottom of the hammer head." An independent estimate is provided by the known length of the hammer, which is 39 cm. By noting the point on the ground where the hammer hits, a measurement can be made on the image of the initial height of 2.9 hammer lengths or 113 cm. A final estimate can be calculated knowing that the distance a dropped object falls is 0.5*acceleration multiplied by the square of the time in free fall. Gravity at the lunar surface is 163 cm/sec/sec. After falling for 1.2 seconds, a dropped object will have travelled 117 cm.]
JohnD wrote: ↑Wed Aug 25, 2021 5:50 pm
Aren't some web searchers weird? To check quickly, I entered "moon feather hammer", not into my usual (couldn't be &rs%d to get that out) and the first entry was "Love Honey Fetish Selection. See Our Latest Fetish Wear." !?!?!?
Web searchs use algorithms optimized to the users search history.
JohnD wrote: ↑Wed Aug 25, 2021 5:50 pm
ta152h20,
No, it was David Scott.
Aren't some web searchers weird? To check quickly, I entered "moon feather hammer", not into my usual (couldn't be &rs%d to get that out) and the first entry was "Love Honey Fetish Selection. See Our Latest Fetish Wear." !?!?!?
John
Hmm. When I put that search into Google I got the expected Apollo video at the top of the list. Google structures its search results based on what it thinks your interests are. So the question is... what else have you been searching for lately?
Why would I want to do that, when I have this lady at home?
JohnD wrote: ↑Wed Aug 25, 2021 5:50 pm
ta152h20,
No, it was David Scott.
Aren't some web searchers weird? To check quickly, I entered "moon feather hammer", not into my usual (couldn't be &rs%d to get that out) and the first entry was "Love Honey Fetish Selection. See Our Latest Fetish Wear." !?!?!?
John
Hmm. When I put that search into Google I got the expected Apollo video at the top of the list. Google structures its search results based on what it thinks your interests are. So the question is... what else have you been searching for lately?
Why would I want to do that, when I have this lady at home?
6_CATERS_WORLDS_SEXIEST_GORILLA_7-768x1150.jpg
Hmm. When I put that search into Google I got the expected Apollo video at the top of the list. Google structures its search results based on what it thinks your interests are. So the question is... what else have you been searching for lately?
Why would I want to do that, when I have this lady at home?
6_CATERS_WORLDS_SEXIEST_GORILLA_7-768x1150.jpg
neufer wrote: ↑Wed Aug 25, 2021 6:10 pm
"E Fish" read "a description once that a marshmallow would
hit the surface of a neutron star with the "force" [sic] an H-bomb".
Presumably, that involved a marshmallow with escape velocity.
The current discussion only involves dropping things from a height of 1 km
(such that it will not approach escape velocity at impact).
In any event, the marshmallow will have a maximum energy release of no more
than a 200 kt "A" bomb (; nevertheless, one should avoid the extra calories if possible).
Sorry, but this didn't help me. Now we have three numbers: 60 kilotons (impacting), 5 kilotons (dropping 1 km) and 200 kilotons (e=mc2), the first two resulting from a 7 gram marshmallow doing something in the vicinity of a neutron star.
If there is no impact, there is no energy release. Just a transfer of gravitational potential energy to kinetic energy, fully contained within the body.
I have more stuff to read no doubt, but in conclusion, when a 7 gm marshmallow falls from a height of 1 km and hits the surface of a neutron star, what is the energy released due to? Is it solely due to the kinetic energy of impact, or also the difference in gravitational potential energy? And since we're talking about a neutron star, I guess there might be relativistic effects as well?
Finally, in general, can a mass hitting something ever release more energy than you'd get by converting the mass to energy via e=mc2? What if it hits at a large fraction of the speed of light? I would think so, since the effective mass would be greater (relativistic effect), so the energy release would also have to be greater.
Re: APOD: Solar System Ball Drop (2021 Aug 25)
Posted: Thu Aug 26, 2021 4:22 pm
by neufer
johnnydeep wrote: ↑Thu Aug 26, 2021 12:46 pm
In conclusion, when a 7 gm marshmallow falls from a height of 1 km and hits the surface of a neutron star, what is the energy released due to? Is it solely due to the kinetic energy of impact, or also the difference in gravitational potential energy? And since we're talking about a neutron star, I guess there might be relativistic effects as well?
Finally, in general, can a mass hitting something ever release more energy than you'd get by converting the mass to energy via e=mc2? What if it hits at a large fraction of the speed of light? I would think so, since the effective mass would be greater (relativistic effect), so the energy release would also have to be greater.
I was doing a back of the envelope calculation based on the kinetic energy of impact = escape velocity energy based on the difference in gravitational potential energy. This formed the basis of my best guess as to the local impact effect at the surface.
Known (non gravitational) external energy releases of supernovas (e.g., collapse of a white dwarf to a black hole) or of kilonovas (e.g., merger of two neutron stars) amount to less than 0.1% of mc2.
[Note: Since gravitational quadrupole radiation scales as the square of the quadrupole moment small incoming objects (e.g., marshmallows) radiate a negligible percentage of their rest mass in gravitational radiation (... possibly not a single graviton).]
https://en.wikipedia.org/wiki/Foe_(unit) wrote:
<<A foe is a unit of energy equal to 1044 joules or 1051 ergs, used to express the large amount of energy released by a supernova. An acronym for "[ten to the power of] fifty-one ergs".
This unit of measure is convenient because a supernova typically releases about one foe of observable energy in a very short period (which can be measured in seconds). In comparison, if the Sun had its current luminosity throughout its entire lifetime, it would release ~1.2 foe.
One solar mass has a rest mass energy of 1787 foe.>>
<<A kilonova (also called a macronova or r-process supernova) is a transient astronomical event that occurs in a compact binary system when two neutron stars or a neutron star and a black hole merge into each other. Kilonovae are thought to emit short gamma-ray bursts and strong electromagnetic radiation due to the radioactive decay of heavy r-process nuclei that are produced and ejected fairly isotropically during the merger process.
The term kilonova was introduced by Metzger et al. in 2010 to characterize the peak brightness, which they showed reaches 1000 times that of a classical nova. They are 1⁄10 to 1⁄100 the brightness of a typical supernova, the self-detonation of a massive star. The first kilonova to be found was detected as a short gamma-ray burst, SGRB 130603B, by instruments on board the Swift Gamma-Ray Burst Explorer and KONUS/WIND spacecraft and then observed using the Hubble Space Telescope 9 and 30 days after burst.
In October 2018, astronomers reported that GRB 150101B, a gamma-ray burst event detected in 2015, may be analogous to the historic GW170817, a gravitational wave event detected in 2017, and associated with the merger of two neutron stars. The similarities between the two events, in terms of gamma ray, optical and x-ray emissions, as well as to the nature of the associated host galaxies, are considered "striking", and this remarkable resemblance suggests the two separate and independent events may both be the result of the merger of neutron stars, and both may be a hitherto-unknown class of kilonova transients. Kilonova events, therefore, may be more diverse and common in the universe than previously understood, according to the researchers.>>
Re: APOD: Solar System Ball Drop (2021 Aug 25)
Posted: Thu Aug 26, 2021 4:35 pm
by Chris Peterson
johnnydeep wrote: ↑Thu Aug 26, 2021 12:46 pm
I have more stuff to read no doubt, but in conclusion, when a 7 gm marshmallow falls from a height of 1 km and hits the surface of a neutron star, what is the energy released due to? Is it solely due to the kinetic energy of impact, or also the difference in gravitational potential energy?
They are essentially the same thing. The energy released is a product of the body's kinetic energy. Its kinetic energy is produced by a difference in gravitational potential energy. The latter is converted to the former.
johnnydeep wrote: ↑Thu Aug 26, 2021 12:46 pm
I have more stuff to read no doubt, but in conclusion, when a 7 gm marshmallow falls from a height of 1 km and hits the surface of a neutron star, what is the energy released due to? Is it solely due to the kinetic energy of impact, or also the difference in gravitational potential energy?
They are essentially the same thing. The energy released is a product of the body's kinetic energy. It's kinetic energy is produced by a difference in gravitational potential energy. The latter is converted to the former.
Thanks, Chris. (And "ten foe" neufer). I have more learning to do...
JohnD wrote: ↑Wed Aug 25, 2021 5:34 pm
Aren't some web searchers weird? To check quickly, I entered "moon feather hammer", not into my usual (couldn't be &rs%d to get that out) and the first entry was "Love Honey Fetish Selection. See Our Latest Fetish Wear." !?!?!?
Web searchs use algorithms optimized to the users search history.
<<Apollo 11 made the A7L the most iconic suit of the program. It proved to be the primary pressure suit worn by NASA astronauts for Project Apollo. Starting in 1969, the A7L suits were designed and produced by ILC Dover (a division of Playtex at the time). The A7L is an evolution of ILC's initial A5L, which won a 1965 pressure suit competition, and A6L, which introduced the integrated thermal and micrometeroid cover layer. After the deadly Apollo 1 fire, the suit was upgraded to be fire-resistant and designated A7L.
The Playtex brand began in 1947 when International Latex Corporation (ILC) created a division named Playtex to produce and sell latex products. Playtex was the first to advertise undergarments on national television in 1955, written by Howard Shavelson at Olgilvie and Mather, and the first to show a woman wearing only a bra from the waist-up in a commercial in 1977.>>
Re: APOD: Solar System Ball Drop (2021 Aug 25)
Posted: Fri Aug 27, 2021 3:03 pm
by Fred the Cat
1 Arg = the exact amount of anything at the precise moment it becomes totally incomprehensible per given person. I think I happily expend about 3 Arg's on average per APOD.
Re: APOD: Solar System Ball Drop (2021 Aug 25)
Posted: Fri Aug 27, 2021 3:25 pm
by johnnydeep
Fred the Cat wrote: ↑Fri Aug 27, 2021 3:03 pm
1 Arg = the exact amount of anything at the precise moment it becomes totally incomprehensible per given person. I think I happily expend about 3 Arg's on average per APOD.
I like it! But hopefully the size of your ARG increases over time to reflect your ever growing knowledge. At least that's what I strive to make happen in my particular case.
E Fish wrote: ↑Wed Aug 25, 2021 1:24 pm
Now, they need to make another one with balls dropping to other types of objects like onto a neutron star or something. I read a description once that a marshmallow would hit the surface of a neutron star with the force an H-bomb.
An A-bomb not an H-bomb.
1 regular marshmallow weighs 7 grams or an energy
of mc2 = 630 terajoule (TJ) = 200,000 tons of TNT
A marshmallow landing on a neutron star might release ~250 TJ
= 60,000 tons of TNT => a large fission ("atomic") bomb (s'more or less).
[A marshmallow dropping one kilometer might release 5,000 tons of TNT.]
The amount of energy released by fission bombs can range
from just under a ton to upwards of 500,000 tons of TNT
A thermonuclear [H-bomb] weapon weighing little more than 2,400 pounds
can release energy equal to more than 5,000 TJ (1.2 Megatons of TNT).
https://en.wikipedia.org/wiki/Joule#Terajoule wrote:
<<The terajoule (TJ) is equal to one trillion (1012) joules; or about 0.278 GWh. About 63 TJ of energy was released by Little Boy. The International Space Station, with a mass of approximately 450 megagrams and orbital velocity of 7700 m/s, has a kinetic energy of roughly 13 TJ. In 2017, Hurricane Irma was estimated to have a peak wind energy of 112 TJ. 90 TJ is about the amount of energy equivalent to 1 gram of mass.>>
That might be one of the best things I've read this last week. Way better than NASA just saying it. I love seeing the actual numbers. Thank you.
JohnD wrote: ↑Wed Aug 25, 2021 5:34 pm
Aren't some web searchers weird? To check quickly, I entered "moon feather hammer", not into my usual (couldn't be &rs%d to get that out) and the first entry was "Love Honey Fetish Selection. See Our Latest Fetish Wear." !?!?!?
Web searchs use algorithms optimized to the users search history.
<<Apollo 11 made the A7L the most iconic suit of the program. It proved to be the primary pressure suit worn by NASA astronauts for Project Apollo. Starting in 1969, the A7L suits were designed and produced by ILC Dover (a division of Playtex at the time). The A7L is an evolution of ILC's initial A5L, which won a 1965 pressure suit competition, and A6L, which introduced the integrated thermal and micrometeroid cover layer. After the deadly Apollo 1 fire, the suit was upgraded to be fire-resistant and designated A7L.
The Playtex brand began in 1947 when International Latex Corporation (ILC) created a division named Playtex to produce and sell latex products. Playtex was the first to advertise undergarments on national television in 1955, written by Howard Shavelson at Olgilvie and Mather, and the first to show a woman wearing only a bra from the waist-up in a commercial in 1977.>>
How you know that, Neufer, I could not possibly guess at!
John
I read a description once that a marshmallow would hit the surface of a neutron star with the force an H-bomb.