Looking at faraway stuff - The Bear and Badger

cockbeard

Ultima Thule - Where my emotions are

cockbeard

Bloody page turn, oh well, do your own homework

Don't bother it's not that funny

Dinostar77

cockbeard wrote:

Ultima Thule - Where my emotions are

You've completely lost me. May have to explain to the uneducated.

cockbeard

Very far away

Dinostar77

Looks like New Horizons survived its flyby, unfortunately it will take till September 2020 to get all the data its captured from Ultima Thule.

Won't be in my lifetime, but it would be some achievement if we could get a space probe beyond the kupier belt and to the inferred neptune sized planet X thats been pulling on objects outhere.

https://www.nationalgeographic.com/science/2018/10/news-solar-system-object-pluto-planet-x-sun-space/

davyK

The pictures of Pluto I saw from that probe are stunning.

SpaceGazelle

Doesn't really belong here but hey.

SpaceGazelle

I like this pic, which shows the relative size of Andromeda in our night sky. We don't see it because the light from the stars in another galaxy are too weak for us to see but it's there, and you can see it in infrared with the right equipment.

Vela

You can see it with the naked eye where I live if you drive twenty minutes out of town. Obviously not that clear, but humbling to think that's light that has travelled for two million years before reaching us.

Roujin

Wow that's actually amazing. I had no idea it would be so large if we could see it properly, I always figured that the blob at the centre represented the whole thing when we see it.

Weirdly it makes the universe feel a little bit smaller all of a sudden.

SonicBoomBoy

That's pretty cool and humbling.

davyK

That's a gorgeous image.

Reminds of the scene at the end of Empire Strikes Back when the Millenium Falcon leaves to get Han Back and they are flying toward a spiral galaxy.

davyK

Also makes me wonder how dense it gets at in the big blob at the centre of a galaxy.

I remember a scifi short story about a planet in the centre of a galaxy that was so close to neigbouring stars that it was never properly dark - except for one time when the bodies aligned a particular way every few thousand years and the panic caused by a dark night with a beautiful view of the stars caused chaos and social breakdown.

SpaceGazelle

We had to model galaxies during my degree and when they collide none of the 100,000,000,000 stars in each galaxy actually hit each other. They don't pass straight through either due to gravitational forces, but there are no collisions. This is what will happen when Andromeda "hits" the Milky Way. The density of the Milky Way is about 1/5,000,000,000 kg/m^3 btw. Not very much.

There's a good chance that the Earth and it's inhabitants would only notice the difference because the constellations would slowly change.

SpaceGazelle

Actually this vid is better.

davyK

Cool!

cockbeard

Thank you, the first post got me intrigued as to how the vid would look and then there was no vid, I did call you a big tease before just closing the tab without posting

Dinostar77

Isn't the sun due to inflate into a red giant and shrink down to a white dwarf before the merging of andromeda and milky-way happens? mercury, venus, earth and mars will be gobbled up in the red giant phase.

I wonder what that extra heat would do to titan?

SpaceGazelle

The Sun expands about a billion yrs later.

Vela

Wasnt there some modelling in the recent news about the earlier collision between the LMC and our galaxy that would see us moved enough out of the way to delay the collision with Andromeda?

https://www.theguardian.com/science/2019/jan/04/nearby-galaxy-large-magellanic-cloud-set-to-collide-with-milky-way

If I understand this correctly it means we might execute a small sidestep before Andromeda comes back for a second swing.

GooberTheHat

If the universe is expanding, and everything is moving away from the big bang/centre, and the further out things are the faster they are moving...

... How is andromida and the milky-way moving closer together?

Vela

Local attraction due to gravity. The expansion becomes more significant on larger scales.

SpaceGazelle

Also, there is no centre.

SpaceGazelle

Insofar that everywhere is the centre.

Vela

SpaceGazelle wrote:

Insofar that everywhere is the centre.

Which is doubly confusing when you try to describe the shape of the universe (assuming its actually a hypersphere).

SpaceGazelle

Apparently, a small proportion of the population can visualise stuff like that.

Vela

SpaceGazelle wrote:

Apparently, a small proportion of the population can visualise stuff like that.

Wouldn't surprise me in the same sense there are people with synathsaesia, tetrachroma vision, eidetic memory and so on. Although we cannot ever observe a 4D shape can we, only projections?

SpaceGazelle

Yeah you can't see it, only do the maths. I can't remember how many dimensions string theory is currently working with but trying to think about what just one dimension actually is used to do my head in, back when I thought about stuff like that.

SpaceGazelle

One of the most useful ideas my lecturer (a cosmologist) told me was the idea of non-infinite dimensions. That is a dimension, or an imagined straight line, that is not infinitely long but "curves" a little. Eventually, if you follow it enough it becomes a circle. A square, when made large enough, becomes a sphere. A cube becomes the Universe.

Curiously, the "curved" aspect of a single dimension does not need a second dimension to be curved, and the Universe is actually 3D but "like it was" curved in a fourth dimension without actually needing a fourth dimension. Therefore you can do all the tensor calculations required for GR without resorting to an extra dimension.

Vela

I vaguely remember this stuff (tensors, intro to GR, de Sitter space but dont ask me to explain it) but this business about curved, finite dimensions - that's what essentially enables you to have an infinite but bounded universe, isnt it?

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