Realistic Window View from a Starship: Gravity, Rotation, and Blue/Red Shifting

[Grasshopper]

TL;DR Summary

Movies and other media depict stars moving by as if you were on a boat. What does it really look like?

I have my own intuition on things, which I hope to correct if I’m wrong.

For example, the most obvious thing is that stars won’t fly in a straight line from the front of the craft to the back if you look out the side window because the craft would be rotating to simulate Earth’s gravity.

So, assuming the ship moves forward perpendicularly to its rotation, if you’re looking out the side window, the stars should move from up to down, should they not? The spaceship pushes up against your feet to simulate gravity, so the ship is rotating “upwards,” so the stars move downwards (and back, over long periods of time as the ship moves toward its destination). And then they appear again up high on the window after a rotation is completed, just like what happens here on Earth.

If this is true, would you see the stars somewhat blue shifted when they are up high in the window and red shifted when they are low in the window? I reason that because when they are high in the window, you are momentarily moving toward them, and when they’re low you’re momentarily moving away.

Unless I’m envisioning it wrong. Or unless the rotation would have to be absurd to notice a difference.

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If, on the other hand, you look in the direction the ship is traveling (perpendicular to the rotation), the stars ought to just move in circles across your window, right?I guess I can see why media tends to show stars flying by from the front of the craft to the back. It makes it look like the craft is going forward. But surely a real starship would be constantly rotating.

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Lastly, is there a formula that tells what the magnitude of rotation must be in order to simulate 1 G that is dependent on the radius and/or mass of the starship? I’m thinking you want 9.8m/s^2, but if you have a really big ship, maybe somewhat less. Earth’s rotation is only 0.039 m/s^2 if I recall correctly. I guess an angular velocity to force equation would show the way.

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As always, thanks! And any further insight or corrections are appreciated.

 

[jedishrfu]

An interesting question, it depends on how fast you're traveling, how far away things are and how fast you're rotating for artificial gravity.

If you're in a car or train. Close up things whizz by really fast whereas faraway things appear to stay where they are but slowly rotate. First you might see the side of a house, then the front and then the other side and the house will appear to get larger and larger and then smaller and smaller. This effect you might see as you pass a planet, asteroid or moon.

The stars are so distant that you won't see much motion at all. If you travel really really far from Earth then you might notice that the constellations look a little different if you can identify them amid the myriad of stars you'll now be able to see.

If you ship is rotating around its axis of direction then of course you'll see the stars move by your window either from top to bottom or bottom to top depending on the window. You'll not see a blue or red shift as that would imply you are rotating at very high relativistic speeds ie a fair percentage of light's speed like maybe 80% or more.

Considering relativistic speeds then other things come into play. Here's an article on some of those things:

https://www.universetoday.com/14751...s-like-traveling-close-to-the-speed-of-light/

 

[DrStupid]

Summary:: Movies and other media depict stars moving by as if you were on a boat. What does it really look like?
[...]
For example, the most obvious thing is that stars won’t fly in a straight line from the front of the craft to the back if you look out the side window because the craft would be rotating to simulate Earth’s gravity.

Which "movies and other media" are you referring to? Where stars (or other stuff) is flying from the front the back there is usually artificial gravity (e.g. in Star Trek). I didn't check movies with simulated gravity but I would expect them to show the resulting apparent movement of the stars correctly (except for low-budget films).

So, assuming the ship moves forward perpendicularly to its rotation, if you’re looking out the side window, the stars should move from up to down, should they not?

Depending on the position and size of the window as well as on its distance from the axis and the camera the stars could also appear to move diagonal, horizontal or in circles.

If this is true, would you see the stars somewhat blue shifted when they are up high in the window and red shifted when they are low in the window?

Rotation for simulated gravity wouldn't result in noticable blue- or redshift. But you would see the stars blue- or red-shifted if the ship is fast enough to see them moving from the front to the back. In that case you might even see blue-shifted background radiation (currently I'm to lazy to do the math).

Lastly, is there a formula that tells what the magnitude of rotation must be in order to simulate 1 G that is dependent on the radius and/or mass of the starship?

##\omega = \sqrt {\frac{g}{r}}##

 

[Grasshopper]

Thanks. These are excellent answers.

DrStupid: Star Trek has managed to back most of its lore with plausible scientific explanations, so I’m not referring specifically to that series.

But, if you were to look up, for example, YouTube videos such as this:

Starship White Noise | Sleep, Study, Focus | Spaceship Lounge Sound 10 Hours

you’d find really beautiful animations that just aren’t particularly realistic.

Here’s another.Yeah, I suppose you can posit some as yet discovered way to simulate gravity, but I don’t think the thought is crossing any of the minds of these artists. I mean, many times the stars fly by like specs of dust, which is insane.Speaking of which, here’s a followup question.

One thing that’s been hovering around my head for a while now is this: IF the universe allows for (and if we discover) a way to create the Alcubierre drive, would it also be possible to use the same technology to create gravity? Or am I very badly misunderstanding what Alcubierre drives do? (I’m under the impression they bend spacetime to reduce travel time, and if so, as why couldn’t they do the same thing to imitate gravity? ).

Anyhow, again, thanks to all who reply.

 

[DrStupid]

But, if you were to look up, for example, YouTube videos such as this:

Starship White Noise | Sleep, Study, Focus | Spaceship Lounge Sound 10 Hours

you’d find really beautiful animations that just aren’t particularly realistic.

Here’s another.

That doesn't look like a serious attempt to show stars as seen from a space ship. It's just a visual effect that has a remote similarity with stars - just like the classic stars screensaver from Windows XP.

 

[glappkaeft]

The most forgotten thing. If you have the lights on in the spaceship and are watching with your naked eyes you won't see anything unless you are near a star.

 

[Keith_McClary]

https://math.ucr.edu/home/baez/physics/Relativity/SR/Spaceship/spaceship.html

 

[Grasshopper]

The most forgotten thing. If you have the lights on in the spaceship and are watching with your naked eyes you won't see anything unless you are near a star.

Would distant star light provide a little light?

 

[jedishrfu]

Would distant star light provide a little light?

Not enough to see anything.

 

[Vanadium 50]

Would distant star light provide a little light?

Look out your window at night. See many stars?

 

[jedishrfu]

Look out your window at night. See many stars?

You said what I wanted to say. :-)

The nightsky in many cities and suburbs is so swamped with light you'd think there was only a dozen stars at most and wondered where all the constellations went.

 

[Grasshopper]

Look out your window at night. See many stars?

In the right place you can see a lot of them. But I’ve so rarely been in a place without city lights when the moon is at a minimum. But even then it seems the moon is the dominant light source, so their contribution has to be tiny

However, Keith’s article suggests if you go fast enough the stars appear to contract toward your direction of motion. So would there be more star light than there “should” be? But on the other hand, how many of these stars are blue shifted into invisibility? But then again, how much invisible light is shifted into the visible spectrum. And even more curious, what about the CMB? At some point would that become the dominant light source?

Now I’m curious about how we could determine the speed at which stellar light (or other sources) is maximized. I wonder if someone has considered this question in a thesis research project.

 

[Vanadium 50]

In the right place you can see a lot of them.

From inside? Looking out a window? You know, like they show on TV looking out the window from a well-lit spaceship? Nope.

Look at most of the moon landing pictures. A few show stars, but most do not. It's too bright.

 

[Filip Larsen]

In case you are also considering a spacecraft moving at significant linear relativistic speeds (relative to the stars in our galaxy) you can expect visible changes to geometry (position of stars) and their color (blue/red shift).

I recall someone who made an animation or video of this some years ago, but unfortunately I'm not able to locate it from a quick search. Instead I found this nice looking four-part blog Celestial View From A Relativistic Starship (I understand the author is an MD; as far as my engineering eye can spot from a quick glance the conclusions looks OK).

 

[Grasshopper]

From inside? Looking out a window? You know, like they show on TV looking out the window from a well-lit spaceship? Nope.

Look at most of the moon landing pictures. A few show stars, but most do not. It's too bright.

Yes. But I thought you guys meant if all interior lights are off. I imagine the stars should being at least a little light. But again, it’s probably a very small amount.

But yes, through a window whatever star light would get in must it must be minuscule (spaceship lights off).

 

[Grasshopper]

In case you are also considering a spacecraft moving at significant linear relativistic speeds (relative to the stars in our galaxy) you can expect visible changes to geometry (position of stars) and their color (blue/red shift).

I recall someone who made an animation or video of this some years ago, but unfortunately I'm not able to locate it from a quick search. Instead I found this nice looking four-part blog Celestial View From A Relativistic Starship (I understand the author is an MD; as far as my engineering eye can spot from a quick glance the conclusions looks OK).

What did you think about the link posted by Keith_McClary? (Post 7)

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So since stellar aberration and blueshift affect which stars (and other sources of EM radiation) are visible, should there not be a point dependent upon velocity in which the light seen from the front of the spaceship is maximized? I think in Keith’s article is makes a claim about the velocity in which all EM waves are blue shifted into invisibility, so surely there is a point of maximum visible light.

 

[Keith_McClary]

https://math.ucr.edu/home/baez/physics/Relativity/SR/Spaceship/spaceship.html
There are some videos

stars (and other sources of EM radiation) are visible

You would have to know the intensity as a function of frequency. I don't know the terminology, so I can't google it.

 

[Filip Larsen]

What did you think about the link posted by Keith_McClary? (Post 7)

Ah, that is nice too, but its not the animation I was thinking of in my post in case that is what you are asking.

By the way, I read the link in post 7 as the usual reference to the relativistic rocket math. Comparing the two links I think I can see why that is an easy mistake to make :
https://math.ucr.edu/home/baez/physics/Relativity/SR/Rocket/rocket.html
https://math.ucr.edu/home/baez/physics/Relativity/SR/Spaceship/spaceship.html

 

[.Scott]

If the spacecraft is rotating to induce artificial gravity, the period of rotation is likely short enough to make viewing the outside very uncomfortable. I would recommend that when artificial gravity is used, that artificial windows be used as well - that way you can get a nice steady image - and no motion sickness.

If the rotation is less that about four revolutions per hour, there should be little problem. Though many people cannot tolerate those rotating restaurants that average less than one turn per hour.

Four revolutions per hour would imply a pretty large ship (or two or more sections connected through long cables) and/or less than 1G of simulated gravity.

 

[pervect]

It seems to be paywalled nowadays, but "In search of the ’’starbow’’: The appearance of the starfield from a relativistic spaceship", https://aapt.scitation".org/doi/10.1119/1.11834 is an interesting paper I've seen on the topic from the American Journal of Physics - it used to be more accesssible in days past.

I'll quote the abstract below:

One prediction for the appearance of the starfield from a moving reference frame has been circulated widely despite physically objectionable features. We reexamine the physical basis for this effect. To the well‐known aberation and Doppler effects we add the transformation of intensity of light upon a change of reference frame. We integrate the transformed spectrum of a star, represented as a blackbody, over the response function of the human eye. We present a one‐parameter function to represent the dependence of the apparent visual magnitude of different stars upon Doppler factor. We conclude with a sequence of computer‐generated figures to show the appearance of Earth’s starfield at various velocities. A ’’starbow’’ does not appear.

"The myth of the starbow", https://oikofuge.com/the-myth-of-the-starbow/ has some interesting images that match my recollections of the above paper, but I'm not sure of the image sources. It seems to be more of a popularization than a primary source, but a very brief scan didn't find anything that looked too crazy. It has an interesting reference to a paper by Sanger that I have not seen mentioned before, https://ui.adsabs.harvard.edu/abs/1962JBIS...18..273S/abstract, which may shed some light on the origin of the whole concept. However, it was claimed to be in error.

Google also finds "A brief history of the star bow", https://www.osa-opn.org/home/articl...s/light_touch/a_brief_history_of_the_starbow/. It also appears to be a popularization as nearly as I can tell. The abstract is very short but looks like it might have some more interesting references.

The rise and fall—and rise again—of an intriguing concept about relativistic space travel.

Finally, http://t.nomoto.org/HippLiner/GHOU2007ProcNomoto080321web.pdf talks about an educational simulator. I'm not sure of the source, it cryptically references Proc. of the GHOU 2007 in Tokyo .

None of these papers considers rotating spaceships - that's a rather unusual assumption.

 

[Keith_McClary]

It seems to be paywalled nowadays

It's on a university website (so it must be legit).

 

[Filip Larsen]

Four revolutions per hour would imply a pretty large ship (or two or more sections connected through long cables) and/or less than 1G of simulated gravity.

Depending on the g-load faster rotation should be acceptable too, say on the order 1 RPM. I am not aware if there is any current research of this (rather likely since rotation it a relevant option for a manned Mars mission), but at least I found this paper from 2006 by Hall that references and discuss some of the research I remember seeing years back.

 

[.Scott]

Depending on the g-load faster rotation should be acceptable too, say on the order 1 RPM. I am not aware if there is any current research of this (rather likely since rotation it a relevant option for a manned Mars mission), but at least I found this paper from 2006 by Hall that references and discuss some of the research I remember seeing years back.

1 RPM should be fine - as long as there is no outside window.
The standard turning rate for an aircraft is 0.5 RPM - more than that is getting aerobatic (and fun for some).

I visited a carnival "ride" where people simply stood and watched a wrap-around video. Within a couple of minutes, I was the only one left standing. I have done some aerobatic pilot training - so perhaps that helped.

If the window stayed on the night side of the ship during rotation, 1 RPM might would be okay for a few minutes - and with practice, certainly longer than that. But if the sun was in view, you would want to keep the shade down - otherwise you would have an intense spot light continuously circling your room.