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[RobbW]

I was reading an article and its user comments on Space.com today about the possibility of intelligent life existing outside our solar system, and whether that civilization would be benevolent or malevolent if we were to ever meet up. There were many distances (in light years) bantered about with regards to how far ET would have to travel to meet us. For whatever reason, that got me thinking about the size and age of the universe.

I recall reading an article on NASA's site about the farthest celestial object that they have been able to observe to date. I remember them stating it was something close to 14 billion light years away. Therefore, the universe must be nearly 14 billion years old.

Well, what I'm wondering is what happens if they take that same telescope and turn it exactly 180 degrees in the opposite direction? What would be the farthest object they could observe in that direction? Wouldn't the hypothetical age of the universe be at least that original 14 billion years plus however many billions of light years they observed an object in the opposite direction?

Or am I completely missing something about how they determined that the farthest observed object was nearly 14 billion light years away?

[patrickm]

Alright, I'll give it a go, but this is from my super primitive, book learning and may be completely incorrect. How's the for a disclaimer?

First, we're not in the center of the Universe. We can only observe two wedges of the Universe perpendicular to the plane of the Milky Way.

Second, the 1995 Hubble Deep Field shot very near the edge of the observable universe. That's about 13 billion years back. It shot in a starless area near Ursa Major. The 2003-4 Hubble Ultra Deep Field shots were taken in a starless area near Orion. The galaxies start to appear adolescent and malformed.





So the Universe should be about 27bly in diameter, right? Except it ain't. It's somewhere between 152bly and 192bly in diameter. This is because the Universe is not static but expanding, so a photon of light. This turns into a calculus problem to account for a photon moving through expanding space. I sort of get that from my HS calculus, but I can't get much past that.

James Webb Space Telescope launched later this year will look past this and in much greater detail. That should be freaky!

I'm not even gonna get into Hawking, multiverses, and flat or curved space because that's to F'd up for my pea brain.

Did I get anywhere close to helping you toward and answer?
p

[RobbW]

Thanks for the stab at it, Patrick! I figured it HAS to be older than the accepted 13 billion years old. If you take a picture in one direction and see an object 13 billion light years away, and look in the opposite direction and see nothing but distant galaxies, then the universe HAS to be more than 13 billion years old!!! Personally, I think the universe keeps blowing up (Big Bang) and expanding until it can no longer sustain such expansion and then starts collapsing on itself. It collapses to a singular point until it can't hold the energy anymore and then explodes again. I bet the Big Band has probably occurred several times in the nearly infinite lifetime of the universe. I really don't know. It is WAY too much for the puny human mind to comprehend!

[patrickm]

Hey Robb,
They're not saying that those figures show that the universe is older than 13.75BY, only that because it has expanded that the most distant objects are much further away than 13BY.

Also, if the Universe expands and contracts, which seems to not be the most recent prevailing wisdom, then wouldn't each new expansion from the singularity count as a new Universe?

I think prevailing wisdom is that the universe will just continue to expand and fizzle out as stars die off, and everything is too far away from everything else for gravity to pull it back together again.

Who will see the last planetary nebula?

Which star will be the last supernova?

Eek! Off to bed.
P

[Paulie pchris00]

I get cosmology at it's most basic, but my head starts to spin if I think about it too much. And don't even get me started thinking about how the universe has no center. (How could of the that be?!?) Patrick's explanation of the expanding universe is basically correct (I don't know the exact numbers involved, so it could be dead-on accurate. Photons further away than 13.6 or 13.7 billion light years are beyond our observation simply because there has not been enough time for them to reach us. Photons within that 13 billion or so light year bubble are then the "observable universe." Presumably, galaxies within our universe but outside our ability to observe are much the same as those that we can see.

I started to read a book a couple years ago (and Astronomy Magazine ran an article based on the premise of the book around the same time) hypothesizing that the universe is of an infinite age, that there have been multiple Big Bangs, then a collapsing universe led to another Big Bang, and started the process over again. I gave up on it because we live in a universe that almost certainly will expand forever, not contract. Why should things be different this time around, if ever previous incarnation has led to a collapsing universe?

For us amateurs, our telescopes are suited at best for seeing galaxies out to maybe 100 million light years. Personally, I think the furthest I have ever seen is probably M51, which if I recall is about 25 million light years from us. Mostly though, I'm observing our solar system and our neighborhood inside the Milky Way. Those distances are vast, but vaguely comprehensible. Maybe it's a good thing that most of us aren't capable of seeing to the HST Deep Field or Ultra Deep Field. Our heads might explode. I think mine would...