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Comment by rackforms | Hacker News Reader

Neat! My favorite way to show the impossibly large scale of our universe: http://spaceengine.org/. Set your speed to 10 light years per second and watch the Andromeda galaxy just sit there.

Also fun to see how slow even the speed of light is. Start at the sun and head for earth. Once you reach Earth marvel at how fast you had been going.

Head towards Jupiter and, once again, marvel at how impossibly slow your going compared to even the nearest background stars.

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> the impossibly large scale of our universe

The other planets are far away, other solar systems are far away, and the galaxy is huge.

But after that, the neighboring galaxies are surprisingly close. If we take 150k light years to be the diameter of Milky Way, and Andromeda is 2500k light years away, the distance between galaxies is less than 20 times the diameter of our galaxy.

I'd love to play with this but it's Windows only :(

Playing with its zoom function is fun (Page Up/Down/Home). You can basically reproduce the Hubble Deep Field with it by bumping up the galaxy magnitude limit (F8) and zooming in until the indicator in the lower right reads around 2'30".

And of course you can click on a galaxy and fly to it with a press of the g key. Watching thousands of galaxies zip by like stars in Star Trek is pretty mindboggling (also note that high warp is somewhere around 20 AU/sec using the TNG scale...)

Example I made a few days ago: https://imgur.com/a/xyZe8

Celestia is worth checking out as well: https://celestiaproject.net/

Not nearly in same league as Space Engine. I installed both just now. Celestia is already uninstalled after 5 minutes. It's too basic and the navigation controls are lacking compared with SpaceEngine - which is remarkable in how well it allows you to fly great distances at enormous speeds, with easy adjustment to for slowing down and re-positioning.

Sadly only for Windows, it looks like a very compelling package though!

OK, there is something scary in warping to, let's say, Proxima Cen, spawning an alien ship, and locking on to our solar system.

This is inaccurate. At even 1g acceleration Andromeda is just 28 years away. At 10 light years per second you would have passed it many many years ago.

Uhm, no? He's talking about a constant speed of 1 LY/s, and not an acceleration.

And what he said was nonsense; 10 LY/s is faster than light; you must be a hypothetical particle with some crazy properties and our math really breaks down at that point.

In space you need to think in terms of relative velocities less than c and acceleration. To get a reasonable sense of how far away Andromeda is consider how long it will take to get there, which is just a few years.

Are you talking about the Andromeda Galaxy? The one that is 2,500,000 light years away? At a constant 10 light years per second speed, that's 69 hours.

Also, even ignoring relativistic effects, it would take a very long time to get there at 1g acceleration.

d = a * t² / 2

2.3652e22 meters = 9.80665 m/s² * t² / 2

4.7304e22 meters = 9.80665 m/s² * t²

4.8237e21 s² = t²

6.9453e10 seconds = t

That's about 2200 years, not 28.

Why would you ignore relativistic effects?

Try entering the numbers here: http://nathangeffen.webfactional.com/spacetravel/spacetravel...

I think that taking traveler time instead of observer time when the discussion is scale of the universe isn't what people would expect. But I do agree that ignoring the relativity here is silly -- of course it makes the observer time close to the 2.5 million years you would expect given its distance.

And thanks for the site. Do you know whether it takes into account deceleration? Because getting to Andromeda at .99c isn't going to do much good unless you're heading somewhere else...

> Do you know whether it takes into account deceleration?

Looks like it does. If I plug in a distance of 980m and acceleration of 9.8m/s^2, it gives a 20s time. That's 10s of acceleration (0.5 * 9.8 * 100 == 490m traveled) and 10s of deceleration.

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