Size and Age of the Universe

[50bmg]

I just read an article called "Scientists pinpoint the farthest galaxy" at :

http://cosmiclog.msnbc.msn.com/_news/20 ... est-galaxy

It discussed Hubble finding a galaxy with redshift 8.55 in the Hubble ultra deep field image. My question is - If we pointed Hubble 180 degrees in exactly the opposite direction and made a similar observation and found another galaxy with similar redshift, wouldn't that make the universe at least 26 billion years old and destroy the current model of the universe that we understand? If not, I must have a fundamental misunderstanding somewhere. Could someone point me in the right direction?

[neufer]

I just read an article called "Scientists pinpoint the farthest galaxy" at :

http://cosmiclog.msnbc.msn.com/_news/20 ... est-galaxy

It discussed Hubble finding a galaxy with redshift 8.55 in the Hubble ultra deep field image. My question is - If we pointed Hubble 180 degrees in exactly the opposite direction and made a similar observation and found another galaxy with similar redshift, wouldn't that make the universe at least 26 billion years old and destroy the current model of the universe that we understand? If not, I must have a fundamental misunderstanding somewhere. Could someone point me in the right direction?

We are surrounded on all sides by distant galaxies that we see just as they were 13 billion years ago (though reddened a bit).

There is no reason to add up any of these 13 billion year time gaps.

(Feel free to subtract any two you like, however.)

[Chris Peterson]

I just read an article called "Scientists pinpoint the farthest galaxy" at :

http://cosmiclog.msnbc.msn.com/_news/20 ... est-galaxy

It discussed Hubble finding a galaxy with redshift 8.55 in the Hubble ultra deep field image. My question is - If we pointed Hubble 180 degrees in exactly the opposite direction and made a similar observation and found another galaxy with similar redshift, wouldn't that make the universe at least 26 billion years old and destroy the current model of the universe that we understand? If not, I must have a fundamental misunderstanding somewhere. Could someone point me in the right direction?

The two galaxies in question would not be able to see each other- they would be causally disconnected. The physical size of the Universe is much greater than 13 (or 26) billion light years. The observable Universe is bigger because you need to consider the comoving distance (the Universe was getting bigger even as light was moving through it); the Universe as a whole is probably much bigger even than that- possibly even infinite in extent.

[bystander]

I just read an article called "Scientists pinpoint the farthest galaxy" at :

http://cosmiclog.msnbc.msn.com/_news/20 ... est-galaxy

http://asterisk.apod.com/vie ... 31&t=21644

[neufer]

I just read an article called "Scientists pinpoint the farthest galaxy" at :

http://cosmiclog.msnbc.msn.com/_news/20 ... est-galaxy

It discussed Hubble finding a galaxy with redshift 8.55 in the Hubble ultra deep field image. My question is - If we pointed Hubble 180 degrees in exactly the opposite direction and made a similar observation and found another galaxy with similar redshift, wouldn't that make the universe at least 26 billion years old and destroy the current model of the universe that we understand? If not, I must have a fundamental misunderstanding somewhere. Could someone point me in the right direction?

The two galaxies in question would not be able to see each other- they would be causally disconnected.

We don't know that for sure, do we?

It's possible that the universe lies on a cylinder whose circumference is only slightly larger than the known universe
and that the two galaxies in question would be able to see each other better than they can see us.

[Ann]

I read an article somewhere where an astronomer discussed how big the universe really was. I think he made the assumption that our own universe "is all there is", or at least, that we aren't dicussing any other universes than our own. He assumed that all of it had been born in the Big Bang a little less than 14 billion years ago and had been expanding at a rate that was not constant, but which at least varied in the same way everywhere in the universe. In other words, he assumed that the acceleration of the expansion that we detect from our point of view can be detected also in other parts of the universe that are "as far away in spacetime" from the Big Bang as we are, even if those parts are so far away from us as to be "disconnected from us", so that we can never find any direct evidence of their existence.

Anyway. This astronomer discussed the question of how big the universe is, given the assumptions I have just stated. He arrived at a "size" of about 69 billion light years, I think. (But I may easily misremember this.) So according to him, a universe that is "only" a bit less than 14 billion years old can still be 69 billion light years in "diameter".

Any comments from you math whiz guys out there?

Ann

[bystander]

This astronomer discussed the question of how big the universe is, given the assumptions I have just stated. He arrived at a "size" of about 69 billion light years, I think. (But I may easily misremember this.) So according to him, a universe that is "only" a bit less than 14 billion years old can still be 69 billion light years in "diameter".

The comoving distance from Earth to the edge of the observable universe is about 14 billion parsecs (46.5 billion light-years) in any direction. The visible universe is thus a sphere with a diameter of about 28 billion parsecs (about 93 billion light-years).

[50bmg]

Asking the same question another way:

If the universe is only 13 billion years old (or, in other words, all matter in our visible universe was contained in a singularity 13 billion years ago at the time of the big bang), how can two galaxies be 26 billion light years apart if they can't move faster than the speed of light?

[neufer]

Asking the same question another way:

If the universe is only 13 billion years old (or, in other words, all matter in our visible universe was contained in a singularity 13 billion years ago at the time of the big bang), how can two galaxies be 26 billion light years apart if they can't move faster than the speed of light?

Space time itself is stretching like an expanding balloon.

The speed of light ONLY limits
the local propagation speeds across the surface of the balloon
it has nothing to do with the "global" expansion rate of the balloon itself.

[50bmg]

So the geometry of the universe is or can expand faster than the speed of light? Isn't that expansion a measured quantity? Is that quantity less than c? If so, for two galaxies to be further than 13 billion years apart would require either the big bang to have happened longer ago than we think, or matter moving faster than c - or, more likely, I am misunderstanding something.

[neufer]

So the geometry of the universe is or can expand faster than the speed of light?

The geometry of the universe DOES expand faster than the speed of light.

Isn't that expansion a measured quantity? Is that quantity less than c?

Small pieces of that expansion (which are all less than c) are measured quantities.

All the rest has to be surmised based upon mathematical models.

[Chris Peterson]

So the geometry of the universe is or can expand faster than the speed of light?

Yes.

Isn't that expansion a measured quantity? Is that quantity less than c?

It is measured. Hubble's law tells us that the rate of separation between two points is a function of their separation. Get far enough apart, and those points will be separating faster than c. In fact, that's what defines the size of the observable Universe. Points outside the observable Universe (which is different for every point) are simply moving faster than c, and are therefore causally disconnected.

In fact, there is no physical law being broken by two objects moving apart faster than c. The rules only require that information can't be transferred between them in that case.

If so, for two galaxies to be further than 13 billion years apart would require either the big bang to have happened longer ago than we think, or matter moving faster than c - or, more likely, I am misunderstanding something.

You aren't misunderstanding anything. Distantly separated matter is moving faster than c with respect to other matter.

[50bmg]

I believe this is the information that I was lacking, given by Chris above -

"In fact, there is no physical law being broken by two objects moving apart faster than c. The rules only require that information can't be transferred between them in that case."

I had understood before that no real objects could move faster than the speed of light regardless of the frame of reference - in other words, I thought that in the case of two spaceships moving at the speed of light in opposite directions, one could not observe the other traveling at 2c, which is true based on the statement above - the ships would be causally disconnected and would not observe each other at all. Am I understanding right? This would be the case of the galaxies in opposite directions, between which the geometry of the universe is expanding faster than the speed of light, so they appear to be further away than they could be based on the time they had to travel there and limited by the speed limit=c. Right? I'm sure someone could restate this in a simpler way.

I think (hope) I am understanding. Thanks for all the replies, I am new to this forum - it is sure nice to have a place like this.

[Ann]

I'm a non-mathematician, so be warned.

But two galaxies can certainly move away from each other faster than c, and they will indeed do that if they are sufficiently far apart. In that case, any intelligent beings inhabiting a world in one of those galaxies can never see or have any other knowledge of the other galaxy or any beings that may live on a planet in it. If we imagine two spaceships in two galaxies that are so far away that they are moving away from one another faster than c, then the two spaceships in the two galaxies are also moving away from each other faster than c.

But now let's toy with the (unlikely) idea that humans may one day learn how to build spaceships that move in our local universe at a speed that is close to c. Now imagine that we launch two such spaceships in opposite directions, both going away from us at a speed close to c. Let's imagine, too, that these spaceships are manned. Will the two crews of the two spaceships lose contact with each other because they are moving away from each other faster than c?

No. The way I understand Einstein's theory of relativity ( probably his theory of special relativity), two objects that are close together in the local universe can never move apart from each other faster than c. The crews of the spaceships may move away from the Earth in opposite directions at a speed close to c, but from their own point of view they are moving away from each other at a speed close to c, too.

Ann

[neufer]

Two galaxies can certainly move away from each other faster than c, and they will indeed do that if they are sufficiently far apart. In that case, any intelligent beings inhabiting a world in one of those galaxies can never see or have any other knowledge of the other galaxy or any beings that may live on a planet in it. If we imagine two spaceships in two galaxies that are so far away that they are moving away from one another faster than c, then the two spaceships in the two galaxies are also moving away from each other faster than c.

But now let's toy with the (unlikely) idea that humans may one day learn how to build spaceships that move in our local universe at a speed that is close to c. Now imagine that we launch two such spaceships in opposite directions, both going away from us at a speed close to c. Let's imagine, too, that these spaceships are manned. Will the two crews of the two spaceships lose contact with each other because they are moving away from each other faster than c?

No. The way I understand Einstein's theory of relativity (probably his theory of special relativity), two objects that are close together in the local universe can never move apart from each other faster than c. The crews of the spaceships may move away from the Earth in opposite directions at a speed close to c, but from their own point of view they are moving away from each other at a speed close to c, too.

Yes to all of the above.

You can even take your argument one step further and start one of your escaping spaceships on that distant (z=8.55) galaxy and she will still be causally connect to earth and earth's spaceships. Any two objects causally connected ANYTIME after the early inflation period of the universe remain causally connected in perpetuity(; or, at least, that was the situation PRIOR to the recent new 'dark energy' inflation period.) This includes spaceships descending into black holes which remain permanently frozen and plastered just outside the black hole's event horizon.

[dougettinger]

I just read an article called "Scientists pinpoint the farthest galaxy" at :

http://cosmiclog.msnbc.msn.com/_news/20 ... est-galaxy

It discussed Hubble finding a galaxy with redshift 8.55 in the Hubble ultra deep field image. My question is - If we pointed Hubble 180 degrees in exactly the opposite direction and made a similar observation and found another galaxy with similar redshift, wouldn't that make the universe at least 26 billion years old and destroy the current model of the universe that we understand? If not, I must have a fundamental misunderstanding somewhere. Could someone point me in the right direction?

We are surrounded on all sides by distant galaxies that we see just as they were 13 billion years ago (though reddened a bit).

There is no reason to add up any of these 13 billion year time gaps.

(Feel free to subtract any two you like, however.)

My mind became stretched by several billion light years after reading all the commentary of this topic. Hence, I totally forgot how we know the basic fact that the (local) universe is about 13 billion years old ? Please, reshape my mind before I become casually dis-connected. Thanks.

Doug Ettinger
Pittsburgh, PA

[Céline Richard]

Hi,

I read the Universe would be 13 billion years old in this topic, and would have a certain size. Actually, i wonder what does it mean.
I mean... if the Universe has a size, thus it is limited into space. Consecuently, what is there beyond the Universe: other Universes?
Otherwise, if the Universe has an age, so it is limited into time. Thus what was existing before our Universe, if the Big Bang has made everything; dark energy ready to convert itself into material?
Maybe both my hipotesis are false, but if someone has better ideas, please write it, i would thank you a lot because it interests me.
The Universe is full of so many misteries

Have a very good day!

Céline

[dougettinger]

Hi,
I read the Universe would be 13 billion years old in this topic, and would have a certain size. Actually, i wonder what does it mean.
I mean... if the Universe has a size, thus it is limited into space. Consecuently, what is there beyond the Universe: other Universes?
Otherwise, if the Universe has an age, so it is limited into time. Thus what was existing before our Universe, if the Big Bang has made everything; dark energy ready to convert itself into material?
Maybe both my hipotesis are false, but if someone has better ideas, please write it, i would thank you a lot because it interests me.
The Universe is full of so many misteries Have a very good day! Céline

Hello Celine, Before the Big Bang one can presume that there was only the Black Void; a void has nothing in it to measure time against; until you have points of interest such as stars or galaxies time simply does not exist. The universe may be much larger and older than we calculate. The given determined age is based on the observable cosmological background and the distant quasars and galaxies that have the most red shift. Interestingly, the theory of the evolution of stars and observations of aging white dwarfs reveals a similar age for the universe. Can there be any other Big Bangs besides the one that created us? The answer is anyone's guess. Are Big Bangs occurring now or before our Big Bang? Keep guessing with all the professional cosmologists.

The redshift is the stretching of light which is the rate of expansion of the universe. The outskirts of the universe are traveling very close to the speed of light which is the case in whatever direction we look from Earth. Picture pinpoint spots on the surface of a tiny balloon that are galaxies. As the balloon is inflated each of spots become farther apart from all other spots. This type of expansion is similar to the galaxies moving away from each other. If all the pinpoint spots were present at a singularity at time equals zero, then the inflation of the balloon has been taking place for over 13 billion years. The thing causing the inflation of the balloon is metaphorically Dark Energy. The skin of the balloon that is holding everything together is metaphorically Dark Matter.

Doug Ettinger
A low ranking science officer
Pittsburgh, PA

[bystander]

Before the Big Bang one can presume that there was only the Black Void; a void has nothing in it to measure time against; until you have points of interest such as stars or galaxies time simply does not exist.

Most proponents of BBT would say Space-Time began with the Big Bang. Why must we presume anything before the Big Bang. Certainly, our universe didn't exist then:

The universe may be much larger and older than we calculate. The given determined age is based on the observable cosmological background and the distant quasars and galaxies that have the most red shift. Interestingly, the theory of the evolution of stars and observations of aging white dwarfs reveals a similar age for the universe. Can there be any other Big Bangs besides the one that created us? The answer is anyone's guess. Are Big Bangs occurring now or before our Big Bang? Keep guessing with all the professional cosmologists.

http://asterisk.apod.com/vie ... 31&t=22115

[dougettinger]

I have read this very recent article and finding. Most of human knowledge is based on cyclic considerations: birth, death, rebirth, etc. Humans have a disdain for absolute beginnings and endings. Please choose what makes you the happiest or provides the most solace.

Doug Ettinger
Pittsburgh, PA

[BMAONE23]

If our understandings of Einsteinian theory is correct, We will never be able to produce enough energy to travel to our closest neighboring star over the span of a single lifetime nor will we be able to communicate or travel at speeds faster than light. Unless this barrier can be/is breached, does it really matter how old or insurmountably huge the universe is?

Does it matter that the farthest distant galaxy is 13.6gly distant or 14.2gly? We will likely never travel there so its absolute distance is both meaningless and likely unneeded. Could be a huge waste of time abd resources trying to figure this out.

We expend billions of dollars trying to prove ET's existance in the name of science.
We may be expending billions of dollars hiding the proof of their existance in the name of national security.
We also spend millions to discredit everyone who claims to have proof.
Seems like at least some of the expenditure is unnecessary.

Fun questions to ponder but do they carry any real bearing on what we accomplish, scientifically or otherwise?

[Chris Peterson]

If our understandings of Einsteinian theory is correct, We will never be able to produce enough energy to travel to our closest neighboring star over the span of a single lifetime nor will we be able to communicate or travel at speeds faster than light.

While it seems certain we won't ever travel or communicate faster than light, traveling to nearby stars in fairly short times from the viewpoint of the travelers (less than a few years) is certainly possible, and would require only moderate engineering advances over current technology.

Does it matter that the farthest distant galaxy is 13.6gly distant or 14.2gly? We will likely never travel there so its absolute distance is both meaningless and likely unneeded.

It matters very much- not because of issues of communication or travel, but because knowing these distances is key to our understanding the Universe. Or maybe it would be better to say the opposite- as we understand the Universe better, we also have better accuracies on the distances to other parts of the Universe.

We expend billions of dollars trying to prove ET's existance in the name of science.

No, we don't. The budgets of all the SETI projects together don't add up to more than a few million dollars, if that. This is below the noise threshold of research spending on astronomy. While the likelihood of success is small, the effect of discovering intelligent life would be profound, and even the absence of evidence adds to scientific knowledge.

[BMAONE23]

While I for one would like to travel to other star systems I know of few people (myself included) who would want to leave everyone and everything behind to travel to a near by star only to return home and find all their family and friends either dead or in their 90's. And traveling any further, given our current knowledge of physics, would assure the deaths of those responsible for the mission control functionality before the objective was ever met, possible several generations would live and die before the star system destination was reached.

[rstevenson]

This Wikipedia page gives an excellent description of the general problem of Interstellar Travel, including what our current and projected technologies could allow us to accomplish.

Rob

[Céline Richard]

Hello,

The redshift is the stretching of light which is the rate of expansion of the universe. The outskirts of the universe are traveling very close to the speed of light which is the case in whatever direction we look from Earth. Picture pinpoint spots on the surface of a tiny balloon that are galaxies. As the balloon is inflated each of spots become farther apart from all other spots. This type of expansion is similar to the galaxies moving away from each other. If all the pinpoint spots were present at a singularity at time equals zero, then the inflation of the balloon has been taking place for over 13 billion years. The thing causing the inflation of the balloon is metaphorically Dark Energy. The skin of the balloon that is holding everything together is metaphorically Dark Matter.

Thank you, it is very interesting and i understand a lot better now

Céline