The expanding Universe.

[Harvin87]

I assume there's already a thread on this subject or at least was boarded at least a couple of times but I will give it a new try.

I was reading about the Hubble's Law:

Spoiler :

All objects observed in deep space (interstellar space) are found to have a doppler shift observable relative velocity to the earth, and to each other. And, that this doppler-shift measured velocity, of various galaxies receding from the Earth is proportional to their distance from the Earth and all other interstellar bodies

My question would be: Is the velocity of galaxies uniform? this meaning that it will always respond to the constant and thus the universe will continue to expand forever? or will the galaxies at some point in distant future be started to be pulled back by the own inertia of their movement? That's what scientist called "The big Crunch" right? thanks a lot for the help.

P.S. Sorry if my terms are not the most precise.

 

[uppi]

If I had proof for either possibility, I would be waiting for my Nobel prize instead of posting here.

 

[Harvin87]

Aha... so I'm on the right track...

 

[Souron]

Distant galaxies have been observed to be speeding up, so the Big Crunch is out the window, as far as agreeing with current theory. Of course it's still possible that this expansion is not an eternal force, but so far the simplest explanation is that it is.

 

[Ziggy Stardust]

Yeah, that's one of the puzzles of the Universe. They needed to introduce the unknown Dark Energy to account for the increasing speed.

As an aside, I recently watched a Docu about this and they said the nearest galaxy was moving away from us a million miles an hour. I was thinking the moon is roughly a quarter of that away from us, so the galaxy is moving twice to the moon and back per hour. That's slower than I'd thought it would be now I had a reference.

Then it struck me that I considered a million miles an hour relatively slow.

 

[Samez]

Perhaps a bit OT but still very interesting

Link to video.

 

[Harvin87]

In deed very interesting... I liked the joke about the milky-way... .

 

[Bluemofia]

Yeah, that's one of the puzzles of the Universe. They needed to introduce the unknown Dark Energy to account for the increasing speed.

As an aside, I recently watched a Docu about this and they said the nearest galaxy was moving away from us a million miles an hour. I was thinking the moon is roughly a quarter of that away from us, so the galaxy is moving twice to the moon and back per hour. That's slower than I'd thought it would be now I had a reference.

Then it struck me that I considered a million miles an hour relatively slow.

They referring to Andromeda? Andromeda is actually moving towards us.

If they are referring to the small satellite galaxies, those are either in orbit, or being eaten by us. Or both. (and by us, I mean the Milky Way)

 

[Harvin87]

yea, What can we expect about Andromeda?,

 

[emzie]

yea, What can we expect about Andromeda?,

They merge, probably. They have so much inertia that they fly though one another, then gravity overcomes that, and they're pulled back together. It's beautiful to watch the simulations.


Link to video.

There would be few collisions of stars. There's a surprising amount of nothing between each little burning ball of hydrogen. The collisions that might happen would probably be something amazing. Some stars will be thrown into intergalactic space -- there's actually a lot of stars in intergalactic space and they were probably all tossed there by events like this. As far as I know, it's still thought that galaxies form stars, not the other way around, so these outcast stars (which have been photographed by Hubble) have migrated to their current location.

It's moot though. By the time any of this happens, Earth will be gone and our sun a white dwarf.

 

[deanej]

The collision will happen in about 4.5 billion years. The sun won't even be fusing helium yet. Moot though - the increasing luminosity will have made Earth uninhabatable about a couple billion years from now.

 

[PiTiFUL]

Personally I think the whole expanding universe theory is going to end up being a flat earth theory, total bunk. Everytime new data goes against the big bang instead of dumping the theory they invent something to change the parameters, just another case of dogma. I lean more towards some form of tired light to explain red shift.

 

[deanej]

I agree. There are plenty of alternatives to the big bang that don't require inflation, dark energy, etc. Whatever happened to "the simplest explanation is usually the best one"?

 

[Souron]

Personally I think the whole expanding universe theory is going to end up being a flat earth theory, total bunk. Everytime new data goes against the big bang instead of dumping the theory they invent something to change the parameters, just another case of dogma. I lean more towards some form of tired light to explain red shift.

The Doppler effect is easily demonstrable. The simplest way is to listen to cars speeding past you as you stand on a busy road. The sound the car seems to make changes drastically as a car passes you in more than just volume. It is only consistent that light from the past should behave the same way.

New evidence does not make the old evidence go away. The reasons that motivated the Big bang when it was first accepted are still true today.

I agree. There are plenty of alternatives to the big bang that don't require inflation, dark energy, etc. Whatever happened to "the simplest explanation is usually the best one"?

It is the simplest. If you are going to dismiss an accepted scientific theory, you need to be well versed in the ideas that motivate the theory in the first place. Otherwise you are much more likely to be ignorant of either the experimental evidence or of the tenants of the theory itself.

 

[deanej]

It is the simplest. If you are going to dismiss an accepted scientific theory, you need to be well versed in the ideas that motivate the theory in the first place. Otherwise you are much more likely to be ignorant of either the experimental evidence or of the tenants of the theory itself.

Are you even aware of the alternatives? IMO this one is infinitely superior to the big bang model: http://discovermagazine.com/2004/feb/cover

I always love how science claims to be accepting of new ideas and then immediately tells anyone who contradicts established scientific doctrine that they are wrong.

 

[ParadigmShifter]

I'm more into lots of little bangs rather than a big bang being the alternative theory.

EDIT: I took loads of drugs when I was young though

 

[uppi]

Are you even aware of the alternatives? IMO this one is infinitely superior to the big bang model: http://discovermagazine.com/2004/feb/cover

I always love how science claims to be accepting of new ideas and then immediately tells anyone who contradicts established scientific doctrine that they are wrong.

Infinitely superior? Not a chance. It is wild speculation, nothing more.

And that speculation does contain the Big Bang, it just tries to find some sort of cause for it.

The Big Bang theory is science, this is not.

 

[PiTiFUL]

The Doppler effect is easily demonstrable. The simplest way is to listen to cars speeding past you as you stand on a busy road. The sound the car seems to make changes drastically as a car passes you in more than just volume. It is only consistent that light from the past should behave the same way.

New evidence does not make the old evidence go away. The reasons that motivated the Big bang when it was first accepted are still true today.

Yes I understand the theory is redshift is a doppler effect, I disagree with that conclusion. Redshift can also be a gravitational effect, but I think the redshift is infact just reddening.

New evidence doesnt make old evidence go away but it does disprove theorys. Thats the whole point of scientific method, create a theory then try to prove or disprove it with evidence. They calculated based on 'doppler redshift' how fast the universe is expanding. Then they found that based on the mass present that the universe could not possibly be expanding that fast, it defied general relativity. Now we know based on local observations that general relativity is a pretty sound theory so that means the 'doppler redshift' assumption is wrong. So did they, based on new evidence, scrap the big bang, nope they invented an unprovable, untestable, 'magic' ... dark energy, and thats not the first time theyve made up stuff to make the theory 'fit'

I always love how science claims to be accepting of new ideas and then immediately tells anyone who contradicts established scientific doctrine that they are wrong.

Dogma, not the first time scientists have refused to change because of that, nor will it be the last.

The Big Bang theory is science

Big Bang Theory is a theory, not a fact. May prove out in the end, but I dont think it will stand the test of time... heh CIV pun

 

[Bluemofia]

Are you even aware of the alternatives? IMO this one is infinitely superior to the big bang model: http://discovermagazine.com/2004/feb/cover

I always love how science claims to be accepting of new ideas and then immediately tells anyone who contradicts established scientific doctrine that they are wrong.

Eh, I wouldn't say infinitely superior, but it is a more elegant solution that I myself find rather philosophically pleasing. (Not that it has any weight in science)

It isn't "mainstream" much like Big Bang Theory wasn't mainstream also in competition with Steady State before being definitively defeated. (note, for a theory to be discarded in favor of a new one, the new one must be able to explain the facts better, not just provide a simpler explanation for the same stuff as is the current case with the cyclic model.)

This one can be tested however, by observing if there is B polarization of the CMB (which one of my friends is working on that for her undergraduate work) or gravitational wave signatures (more specifically, lack of.).

So it might be a few more years before we can decide whether or not this one is better, but until then, we'll keep with the old model simply because there's no other model that describes it better.

 

[Harvin87]

I stay with the post above.
nice one.