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pfildozer12 t1_j0ndi49 wrote

No, the local group of galaxies, and the stars within those galaxies, are gravitational bound to each other. That overcomes the expansion due to dark energy and local distances stay the same.


Oberic t1_j0nklws wrote

It's like that cotton spider web stuff. You can stretch it out like crazy, but there's still strings connected together and clumping in spots.


samuelcook t1_j0o3dyw wrote

How far would we need to travel in order for us to start including expansion in our calculations? Is it further than our obversable universe?


TheStarsFell t1_j0o9td8 wrote

I don't really think that the expansion of the Universe would ever need to be considered, even if we traveled between, say, our galaxy and Andromeda (which will likely never be possible). Even if we traveled between five or six galaxies in our local galactic cluster, that's still a very small distance when you consider that the observable Universe is 90+ billion light years across.


Thocc-a-block t1_j0oup7l wrote

Isn’t the expansion of the universe faster than the speed of light 🤔


midnight_mechanic t1_j0p0sm3 wrote

Over very large distances it is. That's literally the boundary of the "observable universe". Everything past that is moving away from us faster than the speed of light.

The rate of expansion of the universe is increasing as well, so stars and galaxies are constantly moving beyond this boundary. In the far far distant future, whoever lives on earth, if it even still exists, won't have any way to tell that anything beyond the local group exists or ever did exist.


midnight_mechanic t1_j0p2zg4 wrote

We can't travel beyond the edge of the observable universe. That space is expanding away from us faster than the speed of light.

There's only three conceivable ways that we could ever travel outside our local group

  1. we create some generation ship that travels at a significant fraction of the speed of light. It would take 50 or 100 million years for that ship to travel to the Vergo Cluster of Galaxies, which is the next closest large galaxy group to us.

  2. we create some faster than light warp drive mechanism. Recent calculations have suggested that it might be possible if we could convert the entire mass of Jupiter into energy. For this we would be limited by the speed the warp drive is able to provide. If it was even some single digit multiple of the speed of light, it would still take 5 to 10 million years to reach the Vergo Cluster.

  3. we create a worm hole that allows us to travel any distance very quickly. This would also require negative energy or negative mass to hold the wormhole open. We don't have a theory of quantum gravity that could even tell us if this is possible, but most current theories say that any wormhole would collapse immediately, or not allow mass (or possibly even light) to travel across it.

Keep in mind that due to relativistic time dilation, traveling faster than light is basically the same as traveling back in time. Also wormholes could theoretically be manipulated to create time portals that allow forward and backward movement in time.

Anyways, the Vergo Cluster is loosely gravitationally bound to our own local group. If you wanted to travel to a galaxy that was not gravitationally bound to us in some way, that might take 50 to 500 million years of travel (depending if faster than light travel is possible), mostly through voids of interstellar space. That would require taking the expansion of the universe into account for trajectory calculations.


twilight-actual t1_j0nnypa wrote

The expansion of the universe is 73 kilometers per second per megaparsec plus or minus 1. There are 3.3 light years to a parsec. So a megaparsec would be 3,300 light years. At the scale of the solar system, the amount of displacement would be negligible.


Character_Pop_6628 t1_j0ng10w wrote

Between galaxies which are gravitationally-bound it should not. When moving through intergalactic clusters which are not gravitationally-bound, yes. The problem is, compared to the speed of light (the cosmic speed-limit) the expansion of the universe in these areas prevents any relative motion when traversing toward an object on the other side which is being thrown in the opposite direction. When moving laterally between galaxies which are weakly gravitationally-bound the effect will be minimal given light-speed is so slow to cross the distance over millions of years, most other forces will have a greater influence


NotTheMarmot t1_j0ndhuq wrote

Not within say, a solar system I think. Most of the objects are gravitationally bound. This may be true for the whole galaxy too, actually.


Argomenon t1_j0nr2a3 wrote

No, and it’s exactly because of what you suspected: we are operating in a too small area for the expansion of the universe to affect space travel much at all.

Here’s why: the gravity exerted between the galaxies within our Local Galactic Group is stronger than the Dark Energy pushing the universe apart. The LGC is 10 million light years in diameter while our closest star is 4.25 light years. If the expansion of the universe doesn’t affect galaxies within millions of light years from us, and we’re unlikely to even travel 4.25 light years away, this expansion doesn’t matter when considering human space travel.

For more context, our Local Galactic Group is a region of 30 major and hundreds of minor galaxies, of which the Milky Way is the second largest, and it extends for 10 million light years.

And regarding human space travel: We won’t even go to the nearest solar system anytime soon because the closest star to us, Proxima Centauri, is 4.25 light years away. The Voyager 1 would take 73,000 to reach it going 61,500 km/h and the fastest manned space flight was Apollo 10 at just under 40,000 km/h.


BigTastey2 t1_j0ncoe7 wrote

No idea - if pressured to guess I’d say no. My understanding of the subject is that the fabric of space itself is expanding, not just the contents in it, right? Like the inflating balloon example. So relative to a position the direction/azimuth of a spacecraft shouldn’t change because it’s a rising tide lifts all boats kind thing, right? Anyway. What you’ve just finished reading is why I’m not an astrophysicist.


CremePuffBandit t1_j0ndoy3 wrote

Not unless we start sending intergalactic probes.


bookers555 t1_j0noyv4 wrote

Not even that, the probes would need to leave the entire Local Group and it's gravitational pull behind for expansion to need to be taken into account.


mmm2412 t1_j0o13n0 wrote

I think you are vastly overestimating our space flight ability.


Distinct-Educator-52 t1_j0nlds5 wrote

So to answer, our local space is too "local" and the time of travel is too "short" to have universal expansion be a factor. Like was said earlier with some excellent answers, it's all good in the local cluster.


tehdamonkey t1_j0nxfem wrote

Yes and no, In an interstellar or intergalactic trip you would need to go by way points along the path. At each way point you would need to recalculate your journey based on your location and things that have changed in your path. Over that huge span of time there would be events like supernovas, stellar collapse, black holes, etc.. that might occur and force course corrections. The expansion of the universe is a bit of a constant so it would not be too much of a variable depending on the distance and time traveled. It would be in the consideration, but at each way point would be reset naturally.


Gorrium t1_j0o44gy wrote

No, expansion mostly takes place between galaxies not within. Even in galaxy clusters expansion is limited


bears5975 t1_j0nt9a3 wrote

Novice here but at the edge of the “known”universe which would take roughly 38-43 billion light years to reach and is supposedly expanding away, the forces there we will never experience physically or inside a spacecraft flying within our “local group”.


DisillusionedBook t1_j0nyuwa wrote

Definitely not. The local gravitational area of our galaxy is not under the influence of universe expansion at all. There's nothing to measure locally


space-ModTeam t1_j0p3494 wrote

Hello u/andreasdagen, your submission "Is the expansion of the universe significant enough to be included when calculating the trajectory of spacecrafts?" has been removed from r/space because:

  • Such questions should be asked in the "All space questions" thread stickied at the top of the sub.

Please read the rules in the sidebar and check r/space for duplicate submissions before posting. If you have any questions about this removal please message the r/space moderators. Thank you.


Grimsage777 t1_j0nqi7f wrote

For most spacecraft trajectories within the solar system, the expansion of the universe is not significant and can be safely ignored. The gravitational forces of the sun and planets, as well as other factors such as atmospheric drag and solar radiation pressure, are typically much more important for determining spacecraft trajectories within the solar system.

That being said, the expansion of the universe can be important for certain types of spacecraft missions, such as those that are designed to study the expansion of the universe itself or those that are designed to travel to other galaxies. In these cases, the expansion of the universe must be taken into account in the spacecraft's trajectory calculation.


NotAHamsterAtAll t1_j0nitxo wrote

An expanding universe has never been measured. It is just a hypothesis inferred from redshifting of distant light + Big Bang hypothesis, nothing more.

To explain the issue of why the expansion isn't measurable, a bullshit explanation about galaxies being "gravitationally bound" has been introduced.

In short; no adjustments are needed, as spacecrafts does not need to adjust for hypothetical forces.


BasicHelicopter7711 t1_j0nphhc wrote

Way to broadcast your ignorance mate.


IFrickinLovePorn t1_j0nu3xn wrote

Wil the expanse of the universe impact the rate to which his ignorance can spread?


NotAHamsterAtAll t1_j0otucs wrote

I will as long as people still buy into the hopeless Big Bang hypothesis

or dark energy is actually found.

Whatever comes first.

In the meantime enjoy the modern creation mythos, its even less likely than the one found in any old religion.