something to think about

is it possible that the milky way would be impossible to exit from inside or in turn enter from outside

think about it the earth creates some extremely strong atmospheric forces and its tiny

just like the earth is a object in a galaxy a galaxy is an object in the universe so I don’t see why it would be any different..

imagine the force created by something the mass of an entire galaxy.. would be pretty hard to counter I would imagine


im sure its probably been brought up before but i havent heard anyone talk about it so would be intresting to gain some insight! so cheers yall in advance

reply to post by dilapidated


I thought we are actually alien to this galaxy. Arnt we originally from as small galaxy that merged into the milky way?

Actually the Milky Way has captured 7 or 8 dwarf galexies.

The poster above me is referring to the idea that our solar system is native of the intersecting Sagittarius Dwarf Galaxy which Phil Plait explains why this isn't so.

The further out from the center of a spiral galaxy (super massive black hole) you are the less gravitational force there is for you to breach. Also consider the idea of breaching a spiral galaxy from the poles, instead of it's ecliptic.

I do think that it is an interesting idea.
And i would agree, that sticking to conventional methods, it would require an unimaginable amount of force/fuel/energy/technology to break through it.

But perhaps our ideas of space travel are relatively immature in the grand scheme of the information and possibilities that are out there.

Perhaps it is as easy as 'imagining' it.'

Ha! Wouldn't that be cool?

Astral projection would be a good start.

Originally posted by dilapidated

think about it the earth creates some extremely strong atmospheric forces and its tiny

And yet we still have no problem leaving the Earth.
"Atmospheric forces" aren't really a concern, as far as the galaxy is concerned. Along the galactic plane, at the outer edge of the galaxy, the escape velocity is about 630 km/s. All the spaceship would need to do is reach this velocity for a second, and then they could cut their engines if they wanted to... they would continue to drift away and would never be pulled back in.
Besides, the escape velocity decreases above and below the galactic plane. So, if a spacecraft wanted to leave the galaxy straight "up" or "down" (relative to the galactic plane) from wherever they were, they would have very little trouble doing so.

reply to post by CLPrime


So your line of thinking is to breach the galaxy perpendicular to the galactic plane, the ecliptic as it is, requiring much less energy. That idea is where my logic resides.

The idea of the emptier void between galaxies as having most of the unmeasurable untapped energy of the universe has also crossed my mind, when one thinks of the expansion of space scenarios. Intermingling dark energy and dark matter may be the real binding forces of galactic structure more so than the gravitational field, especially when one considers the gravitational drop-off per distance formula. (I daydream of being whisked away at impossible speeds in the void of intergalactic space, where our known ToR may be less of a roadblock*).

*to be taken with a grain of salt

Originally posted by Illustronic
reply to post by CLPrime

 

the ecliptic as it is

It would be the ecliptic if we were speaking of the plane the Earth orbits in.

Intermingling dark energy and dark matter may be the real binding forces of galactic structure more so than the gravitational field, especially when one considers the gravitational drop-off per distance formula.

That's certainly the current prevailing theory. Though, you have to realize, dark matter is introduced because of its additional gravitational field. This is what accounts for the observed gravitational drop-off per distance signature of the galaxies we see...which is actually less of a drop-off than it should be (due to the presence of dark matter).

reply to post by CLPrime

Originally posted by Illustronic
Intermingling dark energy and dark matter may be the real binding forces of galactic structure more so than the gravitational field,

That's certainly the current prevailing theory. Though, you have to realize, dark matter is introduced because of its additional gravitational field.

This is a reason that I don't like the theory of dark matter. How can dark matter be the real binding galactic force over gravity when dark matter is said to only effect things gravitationally? Can't see it nor measure it in any way except that we see a gravitational anomaly. Perhaps this anomaly is due to something different all together.

What about galactic time dilation? How would this effect an extra-galactic spaceship?

Time slows down due to both acceleration and gravity and our galaxy has a huge amount of both. Rotational motion is considered an acceleration and the Milky Way is essentially accelerating a galactic amount of mass. So if we were to remove ourselves from this galactic acceleration how much would time speed up? Would the effects be small or so much to the point that it creates difficulties in attempting to enter/reenter a galaxy?

reply to post by Devino


You're really stuck on this dark matter issue, aren't you?
There are two possible explanations for the anomalous rotation curves of galaxies: either dark matter, or some form of modified gravity. However, there has also been observed an anomaly in the galaxy profiles (off-center mass which can't be accounted for by the mass we see) which can't be explained by any form of modified gravity. This leaves dark matter - matter which has mass, so it has gravity, but which has no other significant interaction with the matter around it - as the only possible explanation.

reply to post by CLPrime

You're really stuck on this dark matter issue, aren't you?

Yes, I suppose I am. It's just that I haven't found an explanation that makes sense to me yet and I have tried.

This leaves dark matter - matter which has mass, so it has gravity,

How can mass be undetectable in every way except gravitationally? This sounds more like the description of a black hole yet spread out over a huge and diffuse area.

reply to post by Devino


The only way mass is detectable is by gravity. All other characteristics that we detect - they're not a result of mass, they're a result of things like charge (and resultant EM fields), or particle interactions. This would suggest that dark matter has mass, but may have no charge (it may be comprised of electrically neutral particles), and it doesn't interact strongly (if at all) with other particles by any means other than gravitationally.

And we know that things like this exist. Take neutrinos. They hardly interact with anything. It's not a stretch at all to say that dark matter is like neutrinos on steroids - larger mass, but with even less of an interaction with other particles.

Originally posted by Devino

What about galactic time dilation?

At our location, the rotational time dilation is 0.99999973073865. That is, over the entire history of the planet, we've gained a little over 1200 years compared to someone at the center of the galaxy.

reply to post by CLPrime

Is there such a thing as mass with no charge? I had assumed they were synonymous.

The problem with neutrinos is that they can be detected, although being very difficult, yet they have an extremely small amount of mass which means an extremely small gravitational interaction. I would think it a leap of faith to consider that there are much larger things out there that have no other interaction with "charged" mass except gravity.

reply to post by CLPrime

over the entire history of the planet, we've gained a little over 1200 years compared to someone at the center of the galaxy.

What about as compared to someone outside of the influence of the galaxy?

Originally posted by Devino
reply to post by CLPrime

 

Is there such a thing as mass with no charge? I had assumed they were synonymous.

That's quite the assumption.
Neutrinos have no charge. The Z boson is one of the heaviest known fundamental particles, yet it has no charge.
Also, neutrons, of course, have no charge.

The theoretical particles comprising dark matter are called WIMPs - weakly interacting massive particles.

There are 4 ways a particle can interact - gravitationally, electromagnetically, or through the strong or weak nuclear forces:
- the weak nuclear force is a result of momentum conservation in decay processes - therefore, it's bound to exist for every particle (even weakly-interacting ones)
- the gravitational force is a result of the presence of mass - if a particle has mass, it has gravity
- the electromagnetic force is a result of charge - if a particle has no charge, it has no EM interactiong
- the strong force is a result of colour charge, and is mediated by gluons, between quarks - if matter is not composed of quarks, it does not interact via the strong force

Therefore, if you have a massive (GeV-range) particle that has no charge and is not a quark, you have a WIMP, and, therefore, dark matter.

reply to post by Devino


Rotationally speaking, it's the same...both at the center of the galaxy and outside the galaxy, the other person is at rest.
Gravitationally speaking, I'm not sure. The only mass which has any time dilation effect on us would be that which is within our galactic orbit (that is, the mass within a radius of 26400 light-years), and I have no idea how much mass that is. It's also in the form of a disc, so it's not as simple as a sphere.

Taking it to extremes, though, we can assume that the entire mass of the galaxy (1.4*10^42 kg) is contained in a sphere with a radius of 26400 ly (2.5*10^20 m). This results in a time dilation of 0.99999583775928, or a loss of 18730 years over the history of the planet. Combined with the rotational time dilation, that's a net loss of 17518 years.
The point: such effects are negligible, even on the galactic scale.

reply to post by CLPrime

Neutrinos are defined to be electrically neutral. Do you consider this the same as no electric charge?
When I look up the definition of "electrically neutral" this is what I find.

Electric Charge
A form of charge, designated positive, negative, or zero, found on the elementary particles that make up all known matter.
...
Electric charge is a basic property of elementary particles of matter. The protons in an atom, for example, have a positive charge, the electrons have a negative charge, and the neutrons have zero charge

www.thefreedictionary.com...
A zero charge is considered having no net charge but is this the same as having no charge?

My point, however, was that I never had considered mass to be observed to not interact with the other forces of nature or essentially be invisible.

Thanks again for you time CLPrime, I always enjoy reading your replies.

Originally posted by Devino

A zero charge is considered having no net charge but is this the same as having no charge?

When we're talking about a fundamental particle... yes, of course. A fundamental particle is not composed of anything else, so its charge is intrinsic...and, so, a neutral charge means the particle has no charge (and therefore no EM interaction with other particles).

My point, however, was that I never had considered mass to be observed to not interact with the other forces of nature or essentially be invisible.

What you have to keep in mind is that matter is not mass. Matter has mass, but mass is the property that determines gravitational attraction and no other interaction. The other interactions are determined by other factors - as I said, charge (EM) and colour charge (strong force). These are all qualities of matter. But, matter does not have to have charge, nor colour charge. And, if it doesn't, then it is weakly interacting (interacting only through gravity and the weak force). Matter which has sufficient mass and no charge of any kind is "dark matter".

Thanks again for you time CLPrime, I always enjoy reading your replies.

No problem. I always enjoy replying...even if I do sound annoyed

I would think of this in the most simplistic of terms. Yes, being of the most simple of minds.

Would it not be easier to enter the galaxy than to exit ? Seems that should be the case when we see that most galaxys seem to be of the spiral kind.