2007-01-02 13:33:58 · 7 answers · asked by Anonymous in Science & Mathematics ➔ Astronomy & Space
Caution! Caution! When you read or hear facts about the universe like its size, age, expansion rate, etc., you're hearing about the OBSERVABLE universe. We have measured the distance to the most distant objects we can currently see and determined how fast they're receding from us (..these distances are determined by measuring the redshift of these objects..) All these objects are embedded in space like everything else therefore move away from us dependant on how fast space is expanding. Science has determined that the farther away some object is in space the faster will be its recessional velocity. The actuall number is an increase of 70 km/sec for every additional 3.26-million light years. According to this so-called "Hubble Constant," there is a huge volume of space receding from us faster than the speed of light. Any objects in that space will never be visible to us because light can never get back to us.
2007-01-02 15:21:41 · answer #1 · answered by Chug-a-Lug 7 · 0⤊ 0⤋
the estimated 15 billion years is just a coarse look on things, based on different observations.
its a theory.
astronomers observe specific stars in other galaxies called cepheides, having a well known energy output, which makes them capable to calculate distances between galaxies since those stars appear fainter in the distance.
Then it was figured that distant galaxies have a redshift, telling us that they move away from us, or better the space itself expands.
Then it was figured that in the far distance is a wall of background radiation, and first galaxies are at a specific distance away from that wall.
This all is put into this calculation, along with observed distribution of matter and so on. And we get a scenario like 'we had a big bang, with a singularity as a source, and since then the universe expanded to its current stage.
this is ONE theory
other theories emerge here and then, but they yet all failed because there were a few things proofed to be wrong in them.
about the exact age, and how sure we are ?
no idea, maybe just tomorrow someone has a better idea how to put things together in a new model
2007-01-02 23:54:42 · answer #2 · answered by blondnirvana 5 · 1⤊ 0⤋
What astronomers are "really" implying when they say our Universe is 15 billion years old is that they are observing the outer boundary of our Universe when measured as 15 billion light years in distance from us !
2007-01-03 06:23:54 · answer #3 · answered by Anonymous · 0⤊ 0⤋
It is only an estimate, they can't be sure for sure!
It is possible to trigonomically measure deep space objects like galaxies, stars, quasars from several different observatories and then calculate a distance from the Earth.
This figure, however, is not reliable because something as simple as a slight wave abberation in the mirror or lens of a telescope can throw off the calculations.
Also we are talking about triangulating 15 billion lights years (that's like 900 billion trillion miles away) with a base of only 8,000 miles. That leaves a lot of room for "error."
How much room? +- 50% is not unreasonable or unrealistic.
2007-01-02 22:00:49 · answer #4 · answered by Anonymous · 0⤊ 1⤋
The current estimate is about 13.7 BY:
http://en.wikipedia.org/wiki/Age_of_the_universe
The age estimate from the expansion of the universe is somewhat uncertain, since the expansion rate appears to have been changing:
http://en.wikipedia.org/wiki/Expansion_of_the_universe
2007-01-02 23:00:13 · answer #5 · answered by arbiter007 6 · 0⤊ 0⤋
The farthest-away objects we can see are about 13.7 billion light years, thus it took 13.7 b.y. for their light to get to us.
2007-01-02 23:18:13 · answer #6 · answered by grotereber 3 · 0⤊ 0⤋
Just guessing...
Radioactive elements life?
Speed of galaxies away from our own?
2007-01-02 21:47:41 · answer #7 · answered by PragmaticAlien 5 · 0⤊ 0⤋