Talk:Outer space

Citation needed vs delete.

@Praemonitus @Nsae Comp This sentence was recently added without a source then marked as citation needed:

• Cosmic radiation in low Earth orbit is reduced due to being inside of the Van Allen belt, the lowest radiation belt of Earth's shielding magnetosphere.

I think its better to delete this sentence if sources cannot be added. Johnjbarton (talk) 16:31, 2 January 2025 (UTC)

I agree that new additions should be properly sourced. In this case it seemed like the wording is redundant with what follows, so I'm not sure it was an improvement. Praemonitus (talk) 17:27, 2 January 2025 (UTC)

I am sorry the use of "inside" was wrong, I meant "below" the inner V.A. belt, as of course the V.A. belt has high radiation. Sorry for that. But I dont see a problem with the paragraph as a whole. Citation about low Earth orbit and its bordering of the V.A. belt isnt a problem, e.g.:. Nsae Comp (talk) 01:40, 3 January 2025 (UTC)

Actually no, I don't think it does properly cite the statement. At least not the part I can access. All it says is that the Van Allen belt has a higher level of radiation, which can impact satellite safety. Praemonitus (talk) 02:22, 3 January 2025 (UTC)

What does it not state? Nsae Comp (talk) 04:49, 3 January 2025 (UTC)

Here's your statement: "Cosmic radiation in low Earth orbit is reduced due to being below the inner Van Allen belt, the lowest radiation belt of Earth's shielding magnetosphere." Where does the source state that the Van Allen belt reduces cosmic radiation? All I see is that the belt shows a higher radiation level than LEO. Your conclusion does not follow. All the source implies is that radiation accumulates in the belt. Praemonitus (talk) 03:18, 4 January 2025 (UTC)

Same is true for the para you took out: none is controversial and it is only a basic introducing statement, finding a reference shouldnt be a problem as far as I can see:

Living in outer space is shaped by the characteristic environment of outer space, particularly its microgravity (producing weightlessness) and its near perfect vacuum (supplying few and producing unhindered exposure to radiation and material from far away). Radiation is prevalent in outer space particularly beyond shielding magnetospheres, being one of the main challenges of sustained human spaceflight beyond low Earth orbit.

Nsae Comp (talk) 04:57, 3 January 2025 (UTC)

I agree that a short intro paragraph does not necessarily need citations, but this paragraph does much more and in my opinion it is controversial. The paragraph introduces contradictions (gravity <-> weightlessness) and ambiguous quantifications ("near perfect", "prevalent", "main challenges"). An introductory paragraph should be a completely neutral outline:

• Living in outer space is shaped by weightlessness, lack of atmosphere, and exposure to radiation.

Johnjbarton (talk) 15:39, 3 January 2025 (UTC)

Thank you for engaging about the content. Now I understand what you see controversial. I can relate. While I think the issues are not unsolvable I am going with your concise version, because with that the chapter doesnt right away start with the possibility of extremophiles living in space. Nsae Comp (talk) 19:57, 3 January 2025 (UTC)

References

The inner Van Allen radiation belt encompasses a significant part of low earth orbit, so the claim that "Cosmic radiation in low Earth orbit is reduced due to being below the inner Van Allen belt" is invalid and should be removed. Cf. D. N. Baker et al (2017).[1] Praemonitus (talk) 00:03, 5 January 2025 (UTC)

What is low Earth orbit?

The Wikipedia article for low Earth orbit states that it extends past 800 km, while the van Allen radiation belts drop down to 640 km. In the South Atlantic anomaly, the belt drops down to 200 km. Thus they overlap. Praemonitus (talk) 18:05, 9 March 2025 (UTC)

Earth orbit intro

Hi there again,

I really cant see how the first sentence of the chapter Earth orbit is easily comprehensible.

Thats why I tried to be more illustrating with the following (taken out) text:"To achieve orbital spaceflight and accelerate beyond sub-orbital spaceflight a spacecraft needs to leave the denser part of the atmosphere, reaching the edge of space at 100 km altitude, and accelerate equal or beyond the centripetal acceleration due to gravity, producing an arcing trajectory." Nsae Comp (talk) 04:18, 11 March 2025 (UTC)

Okay, well it need some edits. The statement "accelerate beyond sub-orbital spaceflight" is redundant with "achieve orbital spaceflight". The segment stating, "accelerate equal or beyond the centripetal acceleration due to gravity" doesn't make sense. It's the tangential velocity (in conjunction with gravity) that produces the centrifugal acceleration. The current wording is more accurate. Praemonitus (talk) 15:50, 11 March 2025 (UTC)

Neither your proposal nor the current jargon-y first sentence

• A spacecraft enters Earth orbit when its centripetal acceleration due to gravity is less than or equal to the centrifugal acceleration due to the horizontal component of its velocity.

gets across the essential character of orbit. Spacecraft continually fall due to gravity: to orbit requires a specific speed perpendicular to the force of gravity, a speed so high that the spacecraft falls around the curve of its orbit. This speed is so high it cannot be maintained in Earth's atmosphere. We need sources that give this concept. Johnjbarton (talk) 15:52, 11 March 2025 (UTC)

The 'horizontal' should probably be changed to 'tangential', as the former depends on a frame of reference. Praemonitus (talk) 15:56, 11 March 2025 (UTC)

I'll take a crack using Newton's example:

When a launched rocket terminates its thrust, it is going to follow an arc-like trajectory back toward the ground, under the influence of the Earth's gravitational force. At orbital velocity, the curvature of this arc can be set to parallel the curvature of the planet underneath, and the spacecraft will be in orbit. That is, the spacecraft enters Earth orbit when its centripetal acceleration due to gravity is less than or equal to the centrifugal acceleration due to the tangential component of its velocity.

— Praemonitus (talk) 17:49, 11 March 2025 (UTC)

I like part of your proposal. I think invoking a fictitious force is confusing and unnecessary.

• When rocket is launched its thrust must both counter gravity and accelerate it to orbital velocity. When the rocket terminates its thrust, it is going to follow an arc-like trajectory back toward the ground under the influence of the Earth's gravitational force. In orbit, the curvature of this arc parallels the curvature of the planet underneath. That is, a spacecraft successfully enters Earth orbit when its acceleration due to gravity pushes the craft down just enough to prevent its momentum from carrying it off into outer space. (https://www.nesdis.noaa.gov/news/why-dont-satellites-fall-out-of-the-sky)

Johnjbarton (talk) 18:37, 11 March 2025 (UTC)

I don't agree with your first sentence because a rocket launch does not necessarily mean it is going to reach orbital velocity. The point was to present the general case of the rocket following an arc, followed by the special case of achieving orbital velocity. Praemonitus (talk) 00:51, 12 March 2025 (UTC)

The name of the section is "Earth orbit". So we could start "When a rocket is launch to achieve orbit,..." Johnjbarton (talk) 01:00, 12 March 2025 (UTC)

Okay, but the second sentence should start with 'After' (to avoid the repetition). Praemonitus (talk) 02:31, 12 March 2025 (UTC)

I put that version in. Johnjbarton (talk) 02:41, 12 March 2025 (UTC)

", the curvature of this arc will tend to parallel the curvature of the planet underneath." is that true? Pertubation is a component, but the curvature of the planet isnt the factor, it is the distribution of its mass, its density distribution. Nsae Comp (talk) 18:49, 15 March 2025 (UTC)

All it's saying is the orbit doesn't plummet into the ground or fly off into space. It's a simple explanation, which is what you want for an intro. No need to over think it. (I suppose it could say "...will tend to follow the curve..." so the wording is more clearly simplified.)

Or we could de-nerdify it even further and just say, "For a circular orbit, the curvature of this arc will parallel the curve of the planet underneath." Praemonitus (talk) 20:09, 15 March 2025 (UTC)

I tried an even simpler version. Johnjbarton (talk) 00:55, 16 March 2025 (UTC)

I have several issues with this version. Firstly what is it for anyway? Is it to describe Earth orbit or Human access to it? I more and more think its fine to take the whole para out and start right away with the second. Otherwise I have a revised proposal very much shortened:"To reach Earth orbit from the surface a spacecraft must be accelerated to orbital speed."

or a longer more precise proposal including non-trivial components like drag and perturbation, but most importantly one that does not say that orbits are curved like the planets below, that is back to ancient understanding of orbits, closed orbits are mostly elliptical, plus merging the sentence about leaving Earth orbit and falling toward Earth by focusing on falling at a speed lower than escape velocity:"To reach Earth orbit from the surface a spacecraft must be accelerated to orbital speed. The spacecraft successfully enters orbit when it does not reach escape velocity and falls toward Earth due to its gravitational pull, but at the same time does not intersect and reach the surface. Therefore an achieved orbit takes the spaceship on a flightpath which follows a closed curved trajectory under the influence of the Earth's gravitational force. Subsequently orbits are maintained by station keeping, countering orbital degradation in the presence of drag and perturbation." Nsae Comp (talk) 02:26, 16 March 2025 (UTC)

No, that's far too much detail for this page. The article is about outer space so it should focus on that, providing just enough detail to explain in simple terms how a spacecraft achieves orbit. The reader can go to the Earth orbit for more details. Praemonitus (talk) 03:23, 16 March 2025 (UTC)

I agree with Praemonitus. Johnjbarton (talk) 17:38, 16 March 2025 (UTC)

Semi-protected edit request on 1 May 2025

SpaceIzAlwaysCool (talk) 02:26, 1 May 2025 (UTC) There is more stars of space than grains of sand on beaches

 Not done: it's not clear what changes you want to be made. Please mention the specific changes in a "change X to Y" format and provide a reliable source if appropriate. Cannolis (talk) 07:32, 1 May 2025 (UTC)

The statement is true and is mentioned on the star article, but it is unclear what that has to do with outer space. Praemonitus (talk) 14:01, 1 May 2025 (UTC)

Contradiction

The article currently defines interplanetary space as "the space dominated by the gravitation of the Sun", but interstellar space as " the physical space outside of the bubbles of plasma known as astrospheres, formed by stellar winds originating from individual stars, or formed by solar wind emanating from the Sun." The gravitational influence of the Sun extends hundreds of times farther out than the heliosphere. So which is it? The region of the heliosphere, or the region of the Sun's gravitational influence? Serendi^podous 11:51, 2 May 2025 (UTC)

Good point. The first can be corrected by removing "the space", so it then matches the reference. I went ahead and made the change. Thanks. Praemonitus (talk) 13:44, 2 May 2025 (UTC)