Whats in 'Outer Space'?

[caleb]

Just wondering, would their be any asteroids, planets or even stars/solar systems outside of a galaxy? Would the radiation be ENORMOUS here.

And like the Sun and Earth which produce a magnetic field, do galaxies produce them?

[OneOfOne (Trevor)]

Most of intergalactic space would be largely empty, with the exception of the occasional hydrogen molecule or other atom. If there had been a recent, ie. last couple of billion years, nearby collision between galaxies, there would be isolated pockets of ejected stars. Imagine if we were unfortunate to be one of these, if you looked into the sky you would see nothing but a handful of other orphaned stars, probably thousands of light years away and the odd galaxy. It would be a very lonely place.

Galaxies do produce magnetic fields, if they have an active core they produce massive fields.

[caleb]

Would this hydrogen atom slice through a spaceship?

And would it be the same 'outside' of a galaxy as the space outside a solar system, beyond the heliosphere?

[OneOfOne (Trevor)]

At the normal speeds of current space travel, individual atoms would not create a major problem, near light speed however, even a molecule of hydrogen would pack a bit of a punch, however, it you were able to travel near light speed, you would become very small (this is a relativistic effect that would only become significant when you are within a few percent of c) and so a much smaller target.

I expect that interstellar space would contain much more matter than intergalactic space, although it can't be very much, otherwise even the 4 light years of even a very thin gas between us and Alpha Centauri would block a huge amount of light. Matter near the central plane of our galaxy causes severe light loss to stars located in the plane and can easily amount to one or to magnitudes.

[caleb]

Hmmm, I thought as you neared c you gained mass, and at c, you would fall in on yourself, I'm guessing forming a black hole?? Anyone...

Well you cleared up my main question, what are your sources by the way?

[mithrandir (Andrew)]

Originally Posted by caleb

Hmmm, I thought as you neared c you gained mass, and at c, you would fall in on yourself, I'm guessing forming a black hole?? Anyone...

To collapse into a black hole your mass has to exceed the Chandrasekhar limit - considered to be about 1.4 times the mass of the sun.

Assume a rest mass of 100kg, Trying to determine the necessary speed you would need to achieve 2.7846e30kg,
v/c=sqrt(1-(100/2.7846e30)^2)
rounding errors hide any difference from c.

You would have had to expend 2.7846e33*3e10*3e10 g*cm2 = 2.50614e54 ergs (I think that's the right number of zeroes).

Where did you get all that energy? Your rest mass of 100kg means you were not carrying it in any form when you started.

[sjastro]

Originally Posted by caleb

Hmmm, I thought as you neared c you gained mass, and at c, you would fall in on yourself, I'm guessing forming a black hole?? Anyone...

Well you cleared up my main question, what are your sources by the way?

An object's "rest mass" will not increase when accelerated to velocities approaching c.

An objects relativistic mass is simply the objects rest mass + kinetic energy.
At speeds approaching c, increase in relativistic mass is taken up by the kinetic energy, rest mass doesn't change hence the object will not collapse into a black hole.

Regards

Steven

[renormalised (Carl)]

Originally Posted by sjastro

An object's "rest mass" will not increase when accelerated to velocities approaching c.

An objects relativistic mass is simply the objects rest mass + kinetic energy.
At speeds approaching c, increase in relativistic mass is taken up by the kinetic energy, rest mass doesn't change hence the object will not collapse into a black hole.

Regards

Steven

Unless, of course, he starts eating a lot

[freespace]

Originally Posted by OneOfOne

At the normal speeds of current space travel, individual atoms would not create a major problem, near light speed however, even a molecule of hydrogen would pack a bit of a punch, however, it you were able to travel near light speed, you would become very small (this is a relativistic effect that would only become significant when you are within a few percent of c) and so a much smaller target.

Length contraction is along the direction of travel, so your cross sectional area is the same. The risk of hitting a mote of dust head on is thus the same as if you were travelling at non-relativistic speeds.

Put it another way, you don't avoid collision with an object by accelerating towards it

[xelasnave]

Interesting to see this post as since I was here last most of my time has been applied to considering what is in the remotest part of space and what one could expect to find in the supreme realm of nothing.

The fact is there will be heaps..consider the electromagnetic radiation passing by at any point.... seemingly limitless on my estimation...
when one thinks what a grain of sand held at arms lenght will hide.. (that was the approximate field of view for the Hubble Deep field)... I translate that to mean that wherever we look one grain of sand hides some 2000 galaxies as established and probably many more than that... and given they (Hubble team) picked the darkest spot etc for the deep field exposures one could reasonably assume that our grain of sand will hide that many galaxies wherever we hold our arm... now if we go to the regions of our universxe where we can examine nothing..the voids... then I expect that there our arm length holding the grain of sand will also hide many galaxies..in any direction the galaxies and the energy they send to where we observe even in the middle of the largest void is mind boggling...my point is simply that in the middle of nothing the energy passing thru from everywhere is for practical purposes near infinite... we may find only one hydrogen atom every 4 light years or so (whatever) but the energy will be jam packed at any and every point...in fact when you think it thru there is so much passing by it is wonderous that it all manages to fit

As to a hydrongen atom travelling at speed I often wonder if the hydrogen in a hydrogen bomb is there not for any energy release via the conversion to helium thing as we all believe but that the hydrogen forms merely a schrapnel jacket.much like placing bolts and nails in a fertilizer bomb...being so small those atoms must get up some speed and imagine just one hitting anything at near c... E=MC^2 would suggest that I feel... so how fast do the hydrogen atoms accelerate to??? and what if just one hit a gum tree..would it do any damage??
alex

[OneOfOne (Trevor)]

Originally Posted by freespace

Length contraction is along the direction of travel, so your cross sectional area is the same. The risk of hitting a mote of dust head on is thus the same as if you were travelling at non-relativistic speeds.

Put it another way, you don't avoid collision with an object by accelerating towards it

Oops, 90 degrees out of phase, yes, you will get shorter but no thinner! I knew contraction only happened in one direction but got the wrong direction.

[Astro78]

I would think the raditation (whether if we saw it live or not) would be far lower, than within a galaxy.

I would also think that if we could prove an interaction between our solar system bodies and their independant magnetic fields, your answer would be yes.

No chance of it cutting through more than a relatively small number of atoms making up the hull of the ship Although the damage would increase, I believe, to something relative to a circle (I bet).