As always, there is a relevant xkcd for this: https://xkcd.com/2608/
lurker2718
joined 2 years ago
The AI needs help to cut the loop, perhaps it needs a new set of knives?
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
It needs thrusters, because there are still some small forces acting on the probe. For example, asymmetrical emission thermal radiation may rotate the probe slowly. This accelerated the Pioneer probes somewhat, see Pioneer anomaly. So without correction you can't keep the orientation for years. Every tiny force would accumulate over this timescale.
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
If you haven't read it already, try the new book "Project Hail Mary" also by Andy Weir. I found it even more enthralling.
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?
Gases we emit into the atmosphere are well mixed over the whole globe in a relatively short time span over a few years or faster. So these refrigerants are in the same concentration over Antarctica as over inhabitated land. However, the ozone depletion effect of the gases is dependent on a lot of factors. One of them are stratospheric clouds, which seem to be one reason for the hole above Antarctica.
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Der Artikel scheint sehr ungenau zu sein, da Spannungsregelung und Momentanreserve nicht differenziert wird. Den originalen Bericht auf spanisch habe ich noch nicht gelesen, aber laut diesem Bericht, lag es eben an Überspannung bzw Probleme bei der Blindleistung.
Momentanreserve entsteht durch Schwungmasse der Generatoren, und liefert innerhalb von Sekunden Energie. Blindleistung liefert/verbraucht Energie bei jeder schwingung der Netzfrequenz, bereits über eine Periode von 20 Millisekunden gemittelt ergibt sich 0 ausgetauschte Energie.
Der Unterschied ist wichtig wenn andere Länder und Möglichkeiten zur Vermeidung betrachtet werden. Eine Photovoltaikanlage kann nicht einfach mal einige Sekunden mehr Leistung liefern um Momentanreserve zu bilden. Aber Blindleistung ist einfach einzubauen. In Österreich und Deutschland etwa müssen alle Wechselrichter über wenigen kW Leistung, also selbst mittelgroße Heimanlagen, die Funktion haben, damit die Spannung zu stabilisieren.
Dass dies in Spanien scheinbar nicht so vorausschauend gelöst wurde, ist hier relativ gut beschrieben, mit einigen technischen Links
Edit: Ich hab mir den Bericht angeschaut und mit automatischer Übersetzung und ChatGPT versucht zu verstehen. Darin steht, dass ein Anstieg der Spannung das Problem war, eben nicht Schwungmasse, also Momentanreserve. Die Netzfrequenz ist erst abgefallen als sich Kraftwerke getrennt haben. Aber generell haben einige sachen zusammengespielt.