Conflicting Information about the Universe

I watch a lot Discovery, National Geographic, History and Science channel programs and I'm getting aggravated by all the conflicting information and statements I hear regarding the universe.

For instance:

A. Galaxies

1. The universe is expanding and "Each galaxy is moving away from all the others." I have heard this statement many times without caveat.

2. Then I hear that our Milkyway Galaxy is the product of many collisions with other galaxies and we are headed for another collision in the future.

3. Then, I find that we can see several galaxies in the process of colliding.

4. Then I hear that Hubble found every galaxy he viewed was red-shifted indicating that they are all moving away from our galaxy.

At no time have I heard anyone say the words "most, some, usually, as a rule", or any other indication that what they were saying was not absolute.

B. Gravity

1. Gravity "pulls" us to the surface of our planet. That gravity is actually stronger at my feet than at my head. The higher we go the less the effect of gravity.

2. Gravity "pushes" us down to the surface of the earth. This would then seem, to me, that the effect would be greater on my head than at my feet?

3. To escape the Earth's gravitational field one must achieve a speed of about 11.2 kilometers per second. I find this somewhat confusing. If i were to ascend at the rate of 1,000 feet per minute (or any speed, for that matter) and my engine was not dependent on conventional rocket fuels and oxygen, why could I not continue at this speed and eventually exit the gravitational field? Why is speed relevant. If gravity is strongest at the surface of the planet, it would seem that less energy would be required the higher I ascend.

4. Gravity Question: Suppose I drilled a tunnel to the center of the earth (hypothetical). Would gravity gradually decrease the deeper I go because the mass between me and the center decreases with depth?

Perhaps these are stupid questions, if so, please excuse my ignorance, but these questions have perplexed me for many years.

These are fantastic questions. I cannot answer any of them but I am looking forward to all the other questions that you may have and of course the answers if any come.

Nice trains of thought going on there

I know gravity pulls us to the earth, and decreases with distance. It's like a magnet, but a magnet has a very concentrated, very limited pulling range. Whilst mass gives a very weak force, but with a very large range.

As for speed you need to travelling vertically at more than 11.2km per second, in order for all the energy (from any extra thrust) to just go towards making you travel up faster-get lost by atmospheric friction.

Also: The pull of the earths gravity is very strong, and extends far out into space. It's only because we are attrracted to other bodies like the moon, mars, sun ect, that orbit is about 80km. So if we had less planets, then orbit would be much higher (since there pull would be weaker).

Really interesting questions thought about a lot of this myself although admittedly haven't noticed the conflicting ideas until you pointed them out (I find it all confusing at the best of times). The one question that gets me is also about the need for a particular speed to escape the gravitation pull. I know there are planes that can fly up to the atmosphere, maybe they need that extra kick to get them out ?


Also, I heard a while back that there was a galaxy heading straight for our own. There is a lot of information about colliding galaxies, so to say they move away from each other makes no sense to me.

[edit on 14-4-2010 by eyesdown]

Edit to add link, it seems good old yahoo answers has a good discussion on how galaxies can collide in an ever expanding universe link



[edit on 14-4-2010 by eyesdown]

reply to post by Hopup Dave


sometime last century scientists came up with the theory of the big bang. what caused it they dont go there. and it is just another theory. therefore they reasoned that galaxies must be all moving outwards. they support this with the red shift idea. i cant remember who, but someone pointed out (scientist) that this was not a reliable indicator due to some change occurring timewise with light.

they also admit to galaxies colliding and are supposed to have pix of that phenomena. i think there are lots of holes in their theories too.

a fresh look at many things in our galaxy can be seen at thunderbolts.info... -and gives much sustaining food for thought. here is their opening paragraph.

“From the smallest particle to the largest galactic formation, a web of electrical circuitry connects and unifies all of nature, organizing galaxies, energizing stars, giving birth to planets and, on our own world, controlling weather and animating biological organisms. There are no isolated islands in an electric universe”.

happy reading.

Originally posted by Hopup Dave

4. Then I hear that Hubble found every galaxy he viewed was red-shifted indicating that they are all moving away from our galaxy.

I find this puzzling too.

If every galaxy is red-shifted (moving away from Hubbles viewpoint), then that would imply that where the Hubble is sitting is the center of the universe?

If a galaxy is going to collide with our milky way in the future, Then shouldn't it be blue-shifted as it is coming right for us?

reply to post by All_Truth_Soon


Thanks for that! At least I don't feel like I'm the only one who would like some straight answers.

I like Michio Kaku but I find some things he says to be contradictory to everything I have heard up till now. He is the one that said gravity "pushes" instead of "pulls". I think gravity is the hardest to get my head around.

reply to post by CitizenNum287119327


That's exactly what I would think, blue shifted instead of red for the Andromeda Galaxy which is supposed to collide with our Milky Way.

I hope some of our resident experts can shed some light on this.

Originally posted by Hopup Dave
reply to post by CitizenNum287119327

 

That's exactly what I would think, blue shifted instead of red for the Andromeda Galaxy which is supposed to collide with our Milky Way.

I hope some of our resident experts can shed some light on this.

This article sums it up:
- There are blueshifted galaxies, one of them is Andromeda, most of them are close to the milky way.
- All galaxies that are far far away are redshifted (or at least all far far away galaxies we have analyzed so far)

What the article doesn't say:
- Two galaxies do not need to be heading towards each other for them to be on a collision course. Think about comets, they have weird orbits around the Sun, there are times when comets fly away from the Sun but eventually end up returning so velocity vectors need not be pointing towards the Sun at all times. Same is true for galaxies. They do, however, need to be accelerating towards each other.

3. To escape the Earth's gravitational field one must achieve a speed of about 11.2 kilometers per second. I find this somewhat confusing. If i were to ascend at the rate of 1,000 feet per minute (or any speed, for that matter) and my engine was not dependent on conventional rocket fuels and oxygen, why could I not continue at this speed and eventually exit the gravitational field? Why is speed relevant. If gravity is strongest at the surface of the planet, it would seem that less energy would be required the higher I ascend.

The 11.2km/s is if you are starting from the surface of the Earth and do not apply an upward force after launch - pretty much like throwing a rock.

If you were flying at a constant 1000 feet/minute away from the Earth, then you are applying a force and you will eventually escape Earth's gravity.

4. Gravity Question: Suppose I drilled a tunnel to the center of the earth (hypothetical). Would gravity gradually decrease the deeper I go because the mass between me and the center decreases with depth?

Yup, also, the earth above you would be pulling you more and more as you go.

As to if gravity ether pushes or pulls, I personally like to go with pulls, but some (very few) may say it pushes, and another bunch will say neither and state is just space twisting bringing us together or something along those lines.


[edit on 14-4-2010 by daniel_g]

reply to post by daniel_g


I think daniel_g did a good job answering the OP questions.

Technically they should say something like "most" when they refer to galaxies moving away from each other, but the OP is right, they don't always do that.

The expansion is somewhat, but not completely linear with distance as this graph shows:

[atsimg]http://files.abovetopsecret.com/images/member/5179db75884a.gif[/atsimg]

Everything off the line is an exception to the Hubble constant and most observations are off the line. Still, it's a pretty linear relationship.

And the galaxies are gravitationally being drawn into superclusters of galaxies, so while they appear to be generally moving apart, some are moving closer together, just like the example given of our milky way galaxy, and the Andromeda galaxy.


[edit on 14-4-2010 by Arbitrageur]

reply to post by daniel_g


Thanks for the link, Daniel_q. That is pretty much what I thought was happening, but to listen to those experts on TV, they always say "everything" is moving away from "everything". Very misleading and confusing.

Thanks also for the explanation about gravity, and, especially about escape velocity. I'll ponder on that for a while.

reply to post by Arbitrageur


Okay, now I see the graphic representation of the Hubble Constant and I have a better understanding. Like all rules, there are exceptions. That's why these experts should be careful when using words like "everything", "always" and "never".

Thanks for the replies...most helpful!