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General questions about SpaceEngine

Posted: 07 Sep 2018 20:28
by Gnargenox
Thanks again Watsisname!

The distance noted on the left side of the screen to other galaxies is the distance (time) light has traveled or is it a comoving radial distance for right now? Meaning, is the expansion of the universe included? Also, is the Space Engine universe flat or open?

General questions about SpaceEngine

Posted: 08 Sep 2018 01:33
by Watsisname
Sure thing, Gnargenox! :)

I want to explain a little further with the galaxy motion, since I was in a rush earlier, that there are really two motions to think about.  One is their physical motion through space (the "peculiar velocity, which is usually a few hundred km/s with respect to the cluster center), and the other is the "recession velocity" due to cosmic expansion.

Peculiar velocity perpendicular to our line of sight changes their location on the sky, but is way too small of a shift to be measured.  The radial component of it measurable, as a Doppler shift.  That shift is in addition to the redshift caused by cosmic expansion, which is why galaxy clusters in redshift-derived maps like this one to appear smeared radially.  But otherwise none of these motions change the observed galaxy position over human timescales.

The expansion does have an interesting side-effect though in that it changes the relationship between distance and apparent angular size of an object.  If you try calculating the size of a galaxy in the usual way as its distance times the tangent of its angular size, then you'll get the wrong answer (and more severely so at greater distances -- beyond a certain point the angular size even starts increasing!)  In cosmology we define a new "angular diameter distance" to correct for this, so that the Euclidean relationship holds.

Gnargenox wrote:
Source of the post The distance noted on the left side of the screen to other galaxies is the distance (time) light has traveled or is it a comoving radial distance for right now? Meaning, is the expansion of the universe included?


From what I can tell I think the distances to catalog objects are generally given in terms of light travel time.  At least, for the few distant catalog galaxies that I checked which have redshifts, I get good agreement between the stated distances and what I calculate for light travel time in a flat LCDM cosmological model with Omega_M = 0.3 and H0 = 70 km/s/Mpc.  The comoving distance would be slightly greater.

However, the catalog galaxies in SE are nearby enough (redshift z less than about 0.2) that the difference between their distance in terms of light travel time or by comoving distance is very small -- I would even say it is unimportant.  In fact the uncertainties in the cosmological parameters (like the value for Hubble constant) can matter more.

What about the distances for procedural galaxies?  For them I would say its up to your imagination.  So far, Space Engine shows the cosmic expansion effect of reddening the color of distant galaxies.  Although the SE universe didn't really expand or simulate the light travelling to you, if you like to think that the light is redder because the space expanded and so those galaxies are actually farther away than you'd think from light travel time, then go for it!

I would call the Space Engine universe a static, flat, Euclidean rendition of the universe.  There are still some cosmological expansion effects that are not shown, even aside from having the universe grow larger with time.  (Like the weird way angular sizes are distorted over great distances that I mentioned earlier.)

General questions about SpaceEngine

Posted: 11 Sep 2018 22:58
by atuhalpa
What are some graphic settings that users like for different situations?

General questions about SpaceEngine

Posted: 30 Sep 2018 04:13
by Eboreus
I suppose that star with RS number are the generic ones? And does genereic mean they and their planetary system are different for each user? Or does SE provide a consistent universe which can be explored bey all users?

Exoplanets seem to be not very much up to date. As an example: Proxima Centauri b is a confirmed exoplanet and it is contained in SE. But in SE it is a giant monster while in reality it is very likely (about 90% probability) below 3 Earth masses. Also I think it's not very likely that there are no other (generic) planets in the Centauri triple. Proxima is extremely far vom the Alpha double (and may be even just a close passage), and the two Alpha stars are also very, very far from each other, so they both could very well have their own planetary systems.

General questions about SpaceEngine

Posted: 30 Sep 2018 09:27
by Eboreus
And another question: is there any effective way to search for temperate Terras with terrestrial life? You can use the filter setting in the star browser to show only them (with the default criteria like diameter, mass etc.), but they are obviously extremely rare. From each star you can search a globe with the diameter of 100 to 120 light years before you hit the 10.000 barrier. After having searched maybe 150.000 stars this way jumping randomly through space I haven't found any. So, is there any better way of searching?

General questions about SpaceEngine

Posted: 30 Sep 2018 13:48
by Stellarator
Eboreus wrote:
Source of the post is there any effective way to search for temperate Terras with terrestrial life?


Not really. The filter is probably the best way for now. In the new upcoming version of Space Engine (0990) you will be able to search by atmospheric content, so that'll be useful for this sort of thing. And besides, none of the Terra's in the SE 0980 universe are habitable for humans anyway, since apparently that universe has an overabundance of CO2 and SO2 in its planetary atmospheres. 

General questions about SpaceEngine

Posted: 30 Sep 2018 15:03
by Eboreus
But the search for atmospheric content would probably still be limited by the 10.000-barrier of the star browser?

General questions about SpaceEngine

Posted: 30 Sep 2018 15:38
by Mosfet
Eboreus wrote:
Source of the post  does SE provide a consistent universe which can be explored bey all users?

Space Engine universe is consistent for all players using the same version, unless you use some mod involving galaxies, for example. This could alter the ID of existing ones, or, by changing their appearance, the number of stars and planets.

General questions about SpaceEngine

Posted: 30 Sep 2018 22:45
by Eboreus
Ah, thanks. :)

General questions about SpaceEngine

Posted: 08 Oct 2018 09:46
by ChickenSplash
quick question, is the amazing beautiful game ever be uploaded on steam?

General questions about SpaceEngine

Posted: 08 Oct 2018 15:41
by Mosfet

General questions about SpaceEngine

Posted: 08 Oct 2018 18:17
by DoctorOfSpace
ChickenSplash, SpaceEngine is already on Steam, it is currently hidden and in private testing. 

General questions about SpaceEngine

Posted: 08 Oct 2018 20:04
by vlad01
Will 0.990 be available as stand alone like previous versions?

General questions about SpaceEngine

Posted: 20 Oct 2018 15:47
by NathanKerbonaut
Does 0990 in VR have the ability to manually change the scale of the universe?

I realized how nice of a feature this is while playing other games in VR. In Universe Sandbox 2 you can scale the universe as small as you want or as big as 1:1. This allows me, for example, to fit the entire solar system in my hand or to be at human-scale on the surface of a planet. Very useful for getting different perspectives of the universe, which in my opinion enhances the exploration aspect greatly. I'd love to see something similar implemented in SE.

Google Earth VR, on the other hand, scales the world automatically based on altitude, which works fine in this situation, but its a level of control I wish I had at times.

General questions about SpaceEngine

Posted: 20 Oct 2018 21:53
by JackDole
NathanKerbonaut wrote:
Source of the post Does 0990 in VR have the ability to manually change the scale of the universe?


I suppose you mean what is called 'Stereobase'.
If you have two windows for Crossview / Parallelview, you can change them with 'Shift mouse wheel' or with 'Shift + / Shift -'.
I suppose that works in VR too.