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Cake day: August 11th, 2023

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  • Out of interest I did some estimates and it seems that an asymmetry of three billionth of the total thermal radiation would be enough to rotate the probe once over a timescale of 10 years. So if the radioisotope generator has even just a tiny bit of a different infrared brightness on one side, it would turn voyager in a few years.

    notes on calculation

    Voyager weight: 815 kg
    Approximate Diameter: 1 m
    Assume mass and thermal radiation emitted with a center distance of this diameter. Then we can calculate as it would need to move 2π 2 m. It should be enough as coarse estimate and underestimate the acceleration. Distance to move: d = 6.3 m

    Assume constant acceleration due to thermal radiation
    RTG power at start: 3 * 2.4 kW = 7.2kW
    RTG power now: 7.2kW * 10^(48/88) = 4.9 kW
    Total of thermal radiation: 4.9kW / c = 16 uN
    distance moved: d = a t^2 / 2
    assuming 10 years accelerated movement movement:
    a = 63 mm/yr^2
    F = 52 fN
    3 * 10^-9 of thermal force



  • The thing is, now we have one 1-2 3.7 meter sized antenna on the voyager probes and a 100 meter sized antenna on earth with high transmission power. Signal decays with distance squared. To get the same signal power to the voyager probe assuming an relay in the middle, it would need an 25 meter antenna with the large transmitter/receiver currently on earth on space.

    In short it’s easier to build a 4 times better transmission system on earth than in an relay in space.

    One point where relays are used are mars rovers. There the orbiter has an large antenna and is close to the rover, so you don’t need to land the large antenna at the surface.

    Edit: fixed antenna diameter



  • lurker2718toLemmy Shitpost@lemmy.worldWinning
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    25 days ago

    I was always annoyed by this question for the same reasoning. However, as another person already said, you can sometimes feel it in some part of the body. When feeling bad, it feels like pressure in my stomach, there a a few other.such connections. Now I find it somewhat useful as part of mindfullness.

    I do still get annoyed when asked this question, partly because whenever he asks the question i do not feel it anywhere, also it seems irrelevant. But the main reason is probably defiance that this seemingly stupid question of him was sensible all along. So much I had to write this response.


  • To add what the others said, this image is most likely taken with a special filter for taking only one specific wavelength, so color. In this case H-alpha, so excited hydrogen atoms, which is deep red. With this and additional filters for safety you can see more or less this image yourself, except it’s red. I already had the opportunity to try this.

    Here is a site showing daily images of the sun taken with different filters. Red is H-alpha, also shown in OP. Only with this filter you can see the protuberances. White is white, so what you would see if you could look directly without burning your eyes, or what you see with eclipse goggles. Right is another special Line, Calcium K. All of this you can look at with the right filters and a telescope and it looks similar to the images here, except the two colors are even more saturated than shown here. However, changes are on the order of minutes, so it looks more like an still image.

    However, the sun and planets are pretty much the only object where images are similar to what you could see with telescope and filters. Colorful images of the moon are always heavily processed. For nebulas and galaxies its even more of a difference, they are just too dark to see more than a grey blob. For this a telescope does not help much, similar to a lens not helping to see in the dark. So nebulas and galaxies are shown at least hat they would look like, if they were brighter. But most of the time they are shown with a lot brighter colors than reality.


  • I think it’s possible to prove, under the right conditions. One assumption is, that Humans are not point like, so that depending on the exact position the person may be half on two sides. For simplicity, I assume a continuos finite population density everywhere, which can be a small peak where a person is and zero everywhere else.

    In this case, it is obvious that for any angle, we can draw a line splitting the population in half. Imagine just shifting the line until the population on both sides is the same. This means we can, for any angle, draw a cross with each line splitting the population in half. This can be written as the following condition, considering the colors above and R, G, Y, B as populations in the Red, Green, Yellow, and Blue quarters, respectively: R+G=B+Y and R+B=Y+G. So G=B and R=Y. What we still need to prove is that it is always possible to have G=R. Now we can do this continuously for each angle of the cross, so starting with an arbitrary cross, we rotate it slowly 1/4 turn counterclockwise. Now R is where G was before. Due to the conditions it can be exactly the same cross but with colors switched. So if R>G before, we now have R<B=G, so during this path, and everything being continuous, there must be an angle for which R=G holds and so all four quarters are at equal size.

    The real question is, does this hold on a globe with great circles is splitting lines?






  • This post and thread gives me (back) so much hope. I always hoped for something like described here. But I never came anywhere close and so I have lost the hope over time. I was thinking in the direction of “I just want someone to share my life with. It will work out to be ok somehow.” But some recent events and post like this give me back the hope to find a the person I really want to share time with. It also brings me the motivation to work on myself, so to be more like I would like to be. Thanks you all.


  • No, to orbit the earth at an height of let’s say 1000 km you would need a speed of around 7km/s. If you go faster, you don’t follow an circular orbit. Wirh around 11km/s you would be so fast to leave the gravity well of earth. The particles in those colliders are almost moving at the speed of light. To be exact, they move only 3.1m/s slower than the speed of light, so almost 300000km/s. They would fly almost straight and would be barely influenced by the gravity well.



  • lurker2718to196@lemmy.blahaj.zonerule
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    1 year ago

    The more self-sufficient you can be, the fewer societal resources you will take up, which could then go to someone else in greater need. That’s my perspective at least.

    But the more self-sufficient you are, the more resources of yourself you need to supply yourself. So you can provide less societal resources. If you do not need to provide clothes for yourself, you have more time caring for elderly, etc.

    As another view, the total resources need does not directly change by changing who does what. The advantages of helping each other are in the OP. At some point however, I would think, the overhead of organization grows so large that it may not be worth it anymore. Just think of the amount of work put into “useless” administration in many countries. But in a 30 person village, this is probably negligible.

    Edit: Thanks for helping other people on the feet!


  • lurker2718tomemes@lemmy.worldnuanceposting
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    1 year ago

    I think your post is exactly what is criticized by OP. In the first part of the post it is explicitly stated men should not talk over the fear of women. A message like yours seems to blame people just because they criticize the way of discussion in some places. I think it is obvious that men are influenced in a possible negative way, when they are always seen as danger. At least for me it probably contributed to my low self esteem, especially in all sex/gender related topics. I think, we as men do so much harm, I don’t want to take part in this. But i took it to the extreme, so I was ashamed of everything sexual about me. But as OP said, all of this doesn’t invalidate the feeling of any woman. But for example this situation here is not governed by fear, still it seems you can’t discuss the social effects of this sentiment “against” man, without discrediting the other side. Sure, violence done mainly to women is the most important topic. But if men always get portrayed as danger, I can understand some are open to other, more misogynist worldviews.