up or down- more astronomy Q's

Factual Questions
1

Here I go again.

  1. Is there an up or down in space - assuming you’re not worried about come back down here.
    Just because we have a mag. north, does that mean anything beyond here?
    Or in other words - pictures show the Milky Way as illustrated looking down - how do we know which side is up - if it really matters at all.

  2. Movies always have sound effects for exploding space ships, but would any sound be heard in the vacum of space?
    If so how much of a sound might we hear?

2
  1. No, basically there’s no “up” or “down” in space.
    However, your question about the Milky Way appears to be “from above” or “below” - relative to the camera. But, you forgot to ask…how do we know what the Milky Way looks like if no spaceship has left the Milky Way??? (I forget the answer to this. Something to do with light received gives us an image of the Milky Way…but since we’re out on one spiral arm, wouldn’t our picture be an incomplete picture? We wouldn’t be able to see across the center (i.e.: the disk) of our galaxy due to the high density of stellar matter.)

2a. Mag north means nothing once leaving the earth. Even Polaris would be just another star - one among many.
2b. Say, how do you know the picture isn’t taken looking upward? Or, could it be sideways looking onwards? Who’s to say how the Milky Way is oriented? The orientation would have to be expressed relative to another object.

  1. Explosions have no sound in space…makes for very boring movies. I always used to laugh to myself about this when watching sci-fi movies, like Star Wars.
  • Jinx
3

  1. No. Up or down have no meaning unless you have a point of reference. On earth, that point is the Earth’s centre of gravity. In space, there is no such point. I guess you could say one side of our galaxy is ‘up’ and the other is ‘down’, but it would have no meaning, as it would not be consistent with our terrestrial definition of up and down. As to magnetic north, I am not quite sure what you are asking.

  2. None. Sound is propagated through a medium. The vacuum of space is the absence of any medium. (OK, technically there are a few H atoms and dust particles here and there, but not enough to sustain the propagation of sound.)
    -Oli

4

Damn…too slow.
-Oli

5

You’re right. Any picture you see of the Milky Way from the outside is an artist’s interpretation. The same is true of the Solar System. But we do know a good bit about the structure despite not having a photograph. There is no doubt that it’s a spiral galaxy.

6

Staff Report: How do we know what shape the Milky Way is?

7

A recent thread about how we know we’re in a spiral galaxy: http://boards.straightdope.com/sdmb/showthread.php?&threadid=140488

The Earth’s magnetic field would be detectable from orbit, so compasses would still work out there. If you get far enough away from Earth, they’ll start to be affected by other magnetic fields such as the Sun’s and the galaxy’s. But those are not simple dipoles, so they will not be much good for telling which way is north.

8

I always wondered why the ships in Star Trek would encounter each other the same way up…

9

It wouldn’t do to go out there and forget about Magnetars either. Suck the pens right out of your pocket from halfway to the moon, the little bastards :wink:

10

Not only would they be silent, but they would also look different and would do much less damage (since there isn’t a shock wave).

11

No billows in space, since there’s no atmosphere. But explosions can still look pretty cool - check out photos of nova/supernova remnants. (Maybe because of magnetic field effects?)

12

You could counter this by saying that there is no way anyone is ever going to be sitting around in the vacuum of space to experience no sound. So every possible simulated viewpoint should be from an enclosed location, be it space suit or space craft.

In this case you could hear the explosion as particles (either solid or gas) from it struck you. It would, however, be significantly quieter than explosions on Earth and sound very different.

13

And due to those odd atoms here and there in space, it’s still possible to get “sound” transmitted, but you need a friggin’ huge explosion to do it. I’m not talking mere piddling nukes here, or exploding spaceships… I mean supernovae. Supernovae do, indeed, produce shock waves which travel through space.

14

Er, I’d just like to point out here, that space is not “empty”. There’s an awful lot of gas and dust out there. And, so, like Chronos points out, supernovae produce shock waves. Also depending on where you are in space, you get some pretty impresive shock waves, and not just from supernovae. When you get jets from radio galaxies which decelerate suddenly, these billow out, probably get shocked (and so produce a shock wave), produce shock waves, and loads of other interesting phenomena.

But, to answer the OP, up and down are simply a by-product of your frame of reference, and gravity. Think about it - if ther was no gravity, we’d have no way of telling the orientation of something. In a free-falling lift, you can’t tell if you’re moving up or down. The same way, without gravity, there is no concept really of up and down. (Until you get close to a black hole, and then everything goes kooky again!)

15

Shock Waves? That brings up another thought…
What precautions does the space program take to lessen the effect of a grande shockwave that you can’t see?
Or are these minute by the time they reach the astronauts who are orbiting and doing space station repairs?