lurker2718

joined 1 year ago
[–] [email protected] 7 points 1 month ago

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.

[–] [email protected] 4 points 4 months ago (1 children)

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.

[–] [email protected] 13 points 5 months ago (1 children)

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.

[–] [email protected] 1 points 6 months ago

Yes. One place in space has different temperatures. I would assume even individual particles are not distributed by a Maxwell distribution, so the concept of temperature is hard to apply. The background radiation has one temperature. If you add the sun, however, you already have a problem as the sun radiation is not in thermal equilibrium. So depending on how you look at it, you get different temperatures. The particles have a high energy, so also a high temperature. But they are so rare, that radiation is the dominant mode of heat transfer and determines the temperature of a thermometer placed in space.

[–] [email protected] 2 points 6 months ago (1 children)

I think it is actually the other way around. You can consider the air inside the balloon to have internal energy from the heat. And additionally you have to make room for the balloon in the atmosphere, so you have removed the atmosphere from the volume the balloon takes, which also needs energy. If you consider both you arrive at the concept of enthalpy (H = U + pV), which is very useful for reactions in the atmosphere as pressure is constant. For this example it is not that useful as outside pressure changes when the balloon rises.

Another way to see it, the pressure has no "real" energy. In a ideal gas, the only energy comes from the kinetic or movement energy of the atoms. Each time a gas molecule is hits the balloon envelope it transfers some momentum. The cumulative effect of the constant collisions is the pressure of the gas. If the balloon is now expanding slowly, each collisions also tranfers some energy, in sum building the work the system has to do to the atmosphere. Leading to a decrease in internal, so "real" energy in the balloon. This corresponds to a decrease in temperature.

[–] [email protected] 2 points 6 months ago (1 children)

The stratosphere is heated not by the ground but directly from solar radiation leading to higher power input at the upper layers. So the top is hotter and now convection never starts and you get no cooling of the air when rising.

[–] [email protected] 8 points 6 months ago (5 children)

While I agree in general, one point is a bit to simplified in my opinion

In other words, there are fewer air molecules per cubic foot (volume of air). The molecules are farther apart and can hold less heat energy. Because "heat" is what we say when we mean molecules are moving around.

Less molecules mean less heat, it has nothing to do with the temperature, if you just decrease the density by removing half the molecules, you have the same temperature.

It cools down because it expands adiabatically. Consider a very thin balloon filled with air which is warmer than the surrounding. This now rises up, but as it does, the pressure decreases, causing the balloon to expand. During this expansion, the balloon transfers energy away from itself, because it has to push away air, to make room for expanding in the surrounding. This work cools the air inside the balloon. Assuming the air inside is dry, it would cool around 10 °C per km it rises. Now if you think about it, the balloon just stopped the inside from mixing with the outside. If you look at a large "piece" of air, it does not mix very fast, so you can remove the balloon and just consider what happens with warm air heated from the ground.

Now this does not mean, it has to be cooler when higher up. The same points hold, inside a house, but there it is often warmer when higher.

The best explaination is when looking where the heat comes from and goes too from the air. The atmosphere is mostly heated from the surface of earth, so the bottom and cooled from the upper layers. So naturally it gets hotter where it is heated. The question is now by how much? There are three modes of heat transfer in the atmosphere: radiation, conduction and convection. The first two are very slow. Connection is fast but has limits. Consider the piece of air, if it rises, it cools. So at some place it may be the same temperature as the surrounding air, so it stops rising. This means the convection works only when the air gets cooler by 10 °C/km going up (~6.5°C when the air is moist and precipation happens). So this temperature gradient is observable very often.

[–] [email protected] 7 points 7 months ago

Yes, the file itself (so the data and inode) is not gone as long as the handles live on. Only the reference is gone. You canstill recover the file. https://superuser.com/questions/283102/how-to-recover-deleted-file-if-it-is-still-opened-by-some-process#600743

[–] [email protected] 3 points 8 months ago* (last edited 8 months ago)

Dann sind aber die Effekte durch Windräder und Katzen auch nicht vergleichbar, die treffen nämlich sehr unterschiedliche Arten.

Insofern ist der Vergleich mit Hühnern auch nicht schlechter als so.

[–] [email protected] 2 points 8 months ago* (last edited 8 months ago)

Ich hab den Hinweis auf diese Studie in Wikipedia gelesen, wonach steht:

Auszug aus WikipediaIn einer Pressemitteilung stellte das Forschungsprojekt Life-Eurokite nach der Ausstrahlung des frontal-Berichts klar, „Diese Ergebnisse sind nicht per se auf die aktuelle Debatte um Todesursachen vom Rotmilan in Deutschland übertragbar (auch wenn dies im Beitrag so dargestellt wurde), da die Todesursachen in Europa ungleichmäßig verteilt sind. So treten bspw. Vergiftungen und illegale Abschüsse sowie der Stromschlag an Elektroleitungen in Deutschland wesentlich seltener auf als in anderen europäischen Staaten“ und kommt zum Schluss „Es ist zum derzeitigen Projektstand nicht auszuschließen, dass es in Zukunft zu Verschiebungen bei der Häufigkeit der Todesursachen kommt.“

Soweit ich mich damit beschäftigt hab ist es nicht so klar wie ein kleines problem es wirklich ist. Deswegen ist es gut wenn weiter an diesen punkten geforscht wird. Ich stimme gern zu, dass das problem wesentlich übertrieben wird in der Gesellschaft. Und dass es den Ausbau der Windkraft nicht verlangsamen darf.

[–] [email protected] 2 points 8 months ago (2 children)

Der Vergleich hinkt. Die unterschiedlichen Ursachen treffen verschiedene Vogelarten deutlich anders. Für gewisse Arten (zb Rotmilan) macht Windkraft derzeit einige Prozent der durch Menschen verursachten Tode aus. Das ist derzeit noch kein großes Problem, wird allerdings die Windkraft hoffentlich stark ausgebaut, so ist es nicht mehr zu vernachlässigen. Damit sollte man sich auch jetzt schon Gedanken machen, wie das Problem verhindert werden kann.

Natürlich heißt dass nicht dass deswegen der Windradausbau stark eingeschränkt werden soll Auch sollte nicht dieser Ursache des Sterbens mehr Aufmerksamkeit geschenkt wird wie den anderen Ursachen, was derzeit passiert. Aber nur die Summe der Vögel zu vergleichen macht meiner Meinung nach wenig Sinn, da diese sehr unterschiedliche Lebensweisen, Häufigkeiten und Gefährdungen haben.

[–] [email protected] 1 points 8 months ago (1 children)

The problem is the size of the sun. If you could look at the sun (don't, try the moon its approximately the same size in the sky), you see it has a relatively large angular size. Its not just a point in the sky.

So the problem, the rays from one point of the sun are almost parallel. But the rays from the different points of the sun are not. So they also aren't parallel after your mirror. They spread in an angle similar to the size of the sun on the sky. And this is much larger than a satellite. So you cannot focus all energy on a satellite.

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