Given that the universe is 13.798±0.037 billion years old, if a galaxy is 13.798±0.037 billion light years plus one light day in distance from the earth…..does that mean that tomorrow that galaxy should be visible from earth for the first time?
Skeptic Pete said:
Given that the universe is 13.798±0.037 billion years old, if a galaxy is 13.798±0.037 billion light years plus one light day in distance from the earth…..does that mean that tomorrow that galaxy should be visible from earth for the first time?
By rights there should be stuff appearing all the time
wookiemeister said:
By rights there should be stuff appearing all the time
Well yeah, that’s what I was thinking. I wondered why I’d never really heard of it happening, but I suppose it’s only theoretical, and would only be noticed with telescopes like Hubble deep field images.
it is more complicated than that. the universe is expanding so a galaxy that was 13.7 bly away 13.7 billion years ago is actually further away than 13.7 billion light years now. more like 47 billion light years. and at the edge of our observable universe. so the light hasn’t actually reached us yet. for us to see light that has traveled 13.7 bly the galaxy would have been a lot closer to us when it emitted that light. also the only “light” we see from that long ago is the cmbr as there were no stars or galaxies around at that time. so currently we see the furthest galaxies which are 47 bly away that emitted their light a few million years after the BB and we wont see anything further away because the expansion of space exceeds the speed of light.
z8_GND_5296 is a galaxy discovered in October 2013 which has the highest redshift that has been confirmed through the Lyman-alpha emission line of hydrogen, placing it among the oldest and most distant known galaxies at approximately 13.1 gigalight-years (4.0×109 pc) from Earth. It is “seen as it was at a time just 700 million years after the Big Bang when the universe was only about 5 percent of its current age of 13.8 billion years”. The galaxy is at a redshift of 7.51, and it is neighbour to what was announced then as second most distant galaxy with a redshift of 7.2. The galaxy in its observable timeframe was producing stars at a phenomenal rate, equivalent in mass to about 300 suns per year.
The light reaching Earth from z8_GND_5296 shows its position over 13 billion years ago, having traveled a distance of more than 13 billion light-years (13 gigalight-years). Due to the expansion of the universe, this position is now at about 30 gigalight-years (9.2 Gpc) (comoving distance) from Earth.
http://en.wikipedia.org/wiki/Z8_GND_5296
so currently we see the furthest galaxies, which are 47 bly away, now…
this position is now at about 30 gigalight-years
so there is 17 bly that we don’t see. and wont.
:-)
Does Olbers limit ring a bell with anyone? (not sure of the spelling of Olbers)
ChrispenEvan said:
it is more complicated than that. the universe is expanding so a galaxy that was 13.7 bly away 13.7 billion years ago is actually further away than 13.7 billion light years now. more like 47 billion light years. and at the edge of our observable universe. so the light hasn’t actually reached us yet. for us to see light that has traveled 13.7 bly the galaxy would have been a lot closer to us when it emitted that light. also the only “light” we see from that long ago is the cmbr as there were no stars or galaxies around at that time. so currently we see the furthest galaxies which are 47 bly away that emitted their light a few million years after the BB and we wont see anything further away because the expansion of space exceeds the speed of light.
Oh dear. That does my head in.
Have they figured out yet if the expansion is only one way. Bit sad if it is, the only reality will be dry cold motes at impossible distances to each other and no light or life. Bit of a waste really.
You won’t see any galaxies until they first come into being and start emitting light, i.e., no light that took longer than that to reach Earth will be light from galaxies.
AwesomeO said:
Have they figured out yet if the expansion is only one way. Bit sad if it is, the only reality will be dry cold motes at impossible distances to each other and no light or life. Bit of a waste really.
Yes, the universe is expected to expand indefinitely.
Bubblecar said:
AwesomeO said:
Have they figured out yet if the expansion is only one way. Bit sad if it is, the only reality will be dry cold motes at impossible distances to each other and no light or life. Bit of a waste really.
Yes, the universe is expected to expand indefinitely.
Wonder how many universes there are?
bob(from black rock) said:
Bubblecar said:
AwesomeO said:
Have they figured out yet if the expansion is only one way. Bit sad if it is, the only reality will be dry cold motes at impossible distances to each other and no light or life. Bit of a waste really.
Yes, the universe is expected to expand indefinitely.
Wonder how many universes there are?
It’s increasingly becoming the orthodoxy that we’re probably part of a multiverse of countless universes.
Bubblecar said:
bob(from black rock) said:
Bubblecar said:Yes, the universe is expected to expand indefinitely.
Wonder how many universes there are?
It’s increasingly becoming the orthodoxy that we’re probably part of a multiverse of countless universes.
What does that mean though? Pinheads of energy we cannot perceive that make the maths work or real universes with real worlds and their own living things?
Bubblecar said:
bob(from black rock) said:
Bubblecar said:Yes, the universe is expected to expand indefinitely.
Wonder how many universes there are?
It’s increasingly becoming the orthodoxy that we’re probably part of a multiverse of countless universes.
http://www.thedailymash.co.uk/news/science-technology/parallel-universe-brian-coxes-are-cooler-and-more-famous-2014092591037
Recommended for Pete: an introduction to cosmology by Victor Stenger, a physicist & one of the New Atheists (who died last month):
http://www.bookdepository.com/God-Multiverse-Victor-Stenger/9781616149703
I started it the other night, seems a very clear and helpful introduction to the latest thinking.
AwesomeO said:
What does that mean though? Pinheads of energy we cannot perceive that make the maths work or real universes with real worlds and their own living things?
Real universes like ours and also probably countless ones completely different from ours :)
Here’s Max Tegmark’s site which introduces some of the ideas:
http://space.mit.edu/home/tegmark/crazy.html
Bubblecar said:
AwesomeO said:
What does that mean though? Pinheads of energy we cannot perceive that make the maths work or real universes with real worlds and their own living things?
Real universes like ours and also probably countless ones completely different from ours :)
Here’s Max Tegmark’s site which introduces some of the ideas:
http://space.mit.edu/home/tegmark/crazy.html
Completely different including physics?
AwesomeO said:
Completely different including physics?
In Tegmark’s scheme, The Level 4 Multiverse has different fundamental equations of physics, but that’s getting into very speculative realms.
Bit sad if it is, the only reality will be dry cold motes at impossible distances to each other and no light or life. Bit of a waste really.
a few trillion years down the track. and life would have ended long before then. but ye, in the future up and coming civilisation wont have a BB cosmology because their galaxy will be all they know and the radiation from it will swamp the cmbr.
olbers paradox. yes i have heard of it.
Has this question been answered satisfactorily?
Anything we see near the edgeof the visible universe is going to be a very young object because we look back in time as we look through space and we are seeing it at as it was at a time when the Universe is very young.
Thinking in terms of days is not very helpful since things don’t change very much. Lets say the Universe is 13.7b years old and the earliest galaxies 13.2b years.
Now imagine we keep watching for 1b years. Now the universe is 14.7b years old, we will be detecting young galaxies at a distance of 14.2b ly away (beyond our current limit) and those young objects we saw at 13.2 bly will be 1 billion years old (and we will have watched that evolution).
A further question, is the expansion of the universe something we can measure locally?
Is the distance between planetary bodies in our own solar system expanding or does our suns gravity field counteract this. The same goes for local stars
Cymek said:
A further question, is the expansion of the universe something we can measure locally?
Is the distance between planetary bodies in our own solar system expanding or does our suns gravity field counteract this. The same goes for local stars
The expansion doesn’t occur at that scale, or even at the scale of stars within a galaxy or galaxies within a local group of galaxies.
It is something that only shows up on a scale of tens of millions to billions of light years.
wookiemeister said:
Skeptic Pete said:
Given that the universe is 13.798±0.037 billion years old, if a galaxy is 13.798±0.037 billion light years plus one light day in distance from the earth…..does that mean that tomorrow that galaxy should be visible from earth for the first time?
Yes
You should have heard of this, it’s what led to a paradox that was only resolved when cosmic inflation was invented.
One description of the paradox runs as such. Distant galaxies are appearing at the edge of the visible universe all the time, therefore they can’t be causally connected with the nearby universe because causality can’t travel faster than the speed of light. So, because there is no causal connection between us and the distant universe in different directions, the universe ought to look different in different directions. But it doesn’t, the distant universe looks the same in each direction. Hence the paradox.
The solution was cosmic inflation. The galaxies that are just now appearing from over the horizon of the visible universe were once close enough to be connected by causality. Cosmic inflation pushed material from inside the visible horizon of the universe out, and it is now just floating back in again.