Starship Asterisk*

https://www.youtube.com/watch?v=32c7espw_jQ

Moon - Close Up View - Real Sound. HD
Our Universe is not silent..
Although space is a vacuum, that does not mean there is no sound in it.
s t a r d u s t 2018. 9. 18.

in this video at 15 min. run, there appears two white squares superimposed in the shadow of a crator lowest right. what is it?

CuriousChimp wrote: ↑Thu Mar 26, 2020 2:06 pm Are we sure that our big bully of a neighbour is coming here?

From their point of view, the Milky Way is the bully.

CuriousChimp wrote: ↑Thu Mar 26, 2020 2:06 pm Are we certain she's part of the Milky Way Local Group, even? Might it not be that The Lady is the core galaxy of her own local group and that they are just passing by?

There are many, many fine examples, and APoD shows lots of the prettier ones, of pairs and multiples of huge star clouds whizzing by each other without being related. Might lovely Andromeda and us be one of those?

Membership is not the issue. Gravity is.

CuriousChimp wrote: ↑Thu Mar 26, 2020 2:06 pm If not, why am I so sceptical?

Wishful thinking? I had been skeptical, too, but not about a future interaction. We’ve known about M31’s blueshift for more than a century. What I’ve been skeptical about was whether the interaction would take the form of a direct collision; for that knowledge, we would need to know M31’s proper motion—from a distance of 2.5 million light years. What I’m reading is that the Hubble Space Telescope has ruled out any proper motion large enough too avoid a collision.

CuriousChimp wrote: ↑Thu Mar 26, 2020 2:06 pm Another weird thought ... five milliards of years is a strangely specific number. By an interesting coincidence it is also roughly the expected lifespan of Sol, that shiny, bright thing that keeps us all cosy and warm. With a possible galactic-sized catastrophe and the end of our Sun coming it is almost as though the cosmos is waving a sign at us; telling us to get the hades out of here before it smooshes us.

I wonder whether Man is clever enough to see the signs and to heed them?

The collision between the Milky Way and M31 will have no consequences for any hypothetical civilization in our solar system—other than prettier night skies. There will not likely be any civilization on Earth anyway, since the Sun’s Goldilocks zone will have expanded beyond Earth’s orbit 4,000 million years previously. Events 1,000 million or 5,000 million years hence are not signs for us in the present, so long as we are creating our own more immediate signs by destroying our environment.

What a night sky it would be! 5 Billion years...pretty funny when our survival pivots on a possible mere 100 years .No negativity here..just being realistic.

Cousin Ricky wrote: ↑Fri Mar 27, 2020 1:50 pm The collision between the Milky Way and M31 will have no consequences for any hypothetical civilization in our solar system—other than prettier night skies.

As a matter of statistical likelihood, that's true. But it does depend upon what part of Andromeda passes through whatever part of the Milky Way our system is in come that time. Areas that are dense with stars are likely to have devastating consequences on planetary systems. Our region would not need to get much denser- perhaps stars a light year apart instead of several light years- to tip our substantially stable planetary orbits into chaos. There's probably not much life that can survive its home planet shifting to a new distance from its parent star.

I particularly liked this image because in 12 years of teaching astronomy, one thing I tried to get across to my students was that the universe was not so big as many tried to paint it, and that it was comprehensible. One way I tried to do this was to show them an image of the Andromeda galaxy. Then, I would explain that it was approximately 10X the angular size of the setting sun -- something they have all seen and can relate to. Then I tried to get them to imagine replacing the setting sun with the Andromeda galaxy. By doing so, clearly they could imagine the Andromeda galaxy 10X larger than the setting sun and then realize it was actually quite a nearby large galaxy. Then, finally, I explained that the edge of the observable universe was only 5000X farther away than the Andromeda galaxy -- which is actually not that far away in cosmic terms.

Thanks for a very nice image!

triastro wrote: ↑Sat Mar 28, 2020 10:18 pm I particularly liked this image because in 12 years of teaching astronomy, one thing I tried to get across to my students was that the universe was not so big as many tried to paint it, and that it was comprehensible. One way I tried to do this was to show them an image of the Andromeda galaxy. Then, I would explain that it was approximately 10X the angular size of the setting sun -- something they have all seen and can relate to. Then I tried to get them to imagine replacing the setting sun with the Andromeda galaxy. By doing so, clearly they could imagine the Andromeda galaxy 10X larger than the setting sun and then realize it was actually quite a nearby large galaxy. Then, finally, I explained that the edge of the observable universe was only 5000X farther away than the Andromeda galaxy -- which is actually not that far away in cosmic terms.

Thanks for a very nice image!

The edge of the observable universe is 46.5 billion ly away, which is 18,600 times farther away than Andromeda galaxy.

Getting to the edge of the observable universe would require an instantaneous jump of 46.5 billion ly... anything slower than that will pose problems, as that edge is moving away from us at the speed of light. And, of course, as you traveled towards that "edge", you would always be at the center of your own observable universe. You could be at the edge of ours, and you'd never know it. Indeed, we ourselves are at the edge of the observable universe for observers in other locations.

Chris,
Thanks, for the response. Yes, indeed, the true edge is as you have described. What I was trying to relate to my students was the apparent edge based on the 13.8 billion year age of the universe, as opposed to the edge that occurs due to the expansion of the universe since it was created. Either way, 5000X or 18,600X, the size of the universe relative to the current distance to Andromeda is comprehensible, with Andromeda basically in our backyard, looming 10X the angular size of the sun or the full moon, and the edge of the universe only 18,600X farther away!

Best regards.