- Roman Cieciak
- Krakow
- Poland
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How do the cosmologists account for the time gap of the distant galaxies' images?
First of all I am no phisycist of any kind, I am just a physics enthusiast.
The question that is bugging me in the notion of ever accelerating expantion of the universe is how do we know that the universe is accelerating right now. The images of the furthest galaxies are bilions years old and they are images of the younger universe, a universe that perhaps was 'still exploding', the force that caused the Big Bang was still effecting the matter in the universe. Hence it's only natural that those distant objects appear to be moving away from each other faster than the ones that are closer to us.
We don't and won't know what happens there 'now' and this might be the problem. Not "we're too late to see what happened" but "we're too soon to see what the outcome is/will be".
Please, let me know what is unclear and/or wrong in my reasoning, I'll try my best to lay out my idea.
David Martin
When we look out at the distant parts of the universe we are basiclly looking back in time!
Ted Froberg
David Martin
'Red shift' refers to how the light we observe is 'shifted' towards the Red end of the spectrum. Like the sound of a train as it goes pass, the waves get spread out lowering the pitch. Light also comes to us as waves. As the source speeds away from us we see these waves slowing down and therefor at a lower frequency (More reddy). The Red shift doesn't get older, what changes is the amount of Red Shift we measure.
The Shift towards Red is greater at further distances because the further we look out we see those objects moving away from us faster than ones closer to us. The fact that the Red Shift has been mearsured as increasing is evidence that the expansion is speeding up, not slowing down... If it were slowing down the observed Red Shift would decrease.
Roman Cieciak
As you say "The Shift towards Red is greater at further distances because the further we look out we see those objects moving away from us faster than ones closer to us." but those objects are also more distant in time. Their red-shifted light was emitted earlier than the light of those closer objects.
Ted Froberg
Then the logical observer in a linear world (call him a linear observer) makes the following deductions:
If objects at the fringe of our universe are moving apart faster, we might conclude that the distance between objects near the edge of the universe (call it the mass horizon) is greater than that near the center of the universe where expansion occurs more slowly. The linear observer then deduces that the "mass denisity" of the universe decreases toward the mass horizon. Further, as the mass density decreases, the linear observer concludes that space shrinks and the passage of time accelerates near the mass horizon. The linear observer pauses here to recognize that, although space shrinks, distances should not change because measuring sticks also shrink. However, if the passage of time accelerates, then more time should elapse as light travels those distances and, measured in light-years, those distances should be greater. Unless ... the acceleration in the passage of time allows light to travel faster, rendering the measured distance no different.
The linear observer notes here that beyond the mass horizon, time accelerates until eternity elapses in what seems an instant here on earth, rendering the universe's "edge" infinitly distant.
So, as seen from the center of the universe by a linear observer, is the expansion of the universe just a relativistic illusion? Perhaps the terms "here," "there," "now," and "then" are meaningless in a universe where time and space are not absolute.
Ted Froberg
Heather Jones
Ted Froberg
The farther away one peers into the universe, the further back in time one is looking. The logical deduction is, if those farthest objects are moving away faster than the objects closer to us (as observed by their red shift), then the rate of expansion was greater in the distant past than it was in the more recent past. And a casual observer would resonably conclude that the expansion is slowing down. So why are we told just the opposite?
Any physicists want to answer this question? What's the logic?
David Martin
Exponential growth! Example:
1. |-|--|---|----|...
2. |--|----|------|--------|...
3. |----|--------|------------|----------------|...
4. |--------|----------------|------------------------|------------------------------------|...
The vertical lines " | " are set markers from a base and are galaxies. At each step the distance between each marker has been doubled. And you can clearly see the amount the last marker (Lets say the edge of the universe) is getting is faster and further away at each step than the ones nearer the base line.
So the Red-Shift between each galaxy gets more the further you look out. This is not the only thing that is happening - Dark Energy is a constant 'Push' and is the force that is driving the speed-up of the expansion of the universe.
How that helps. :)
Ted Froberg
David Martin
David Martin
The colours of the light that left those distant objects is/was 'Normal' in colour when it left. It is only shifted on it's way here by the expansion of the universe.
Victor Valentour