Spaces can be either finitely extended or infinitely extended. We can easily observe when those spaces which are finitely extended, expand, by simply observing the expanse they occupy at different times are different in size. But what does an infinitely extended space expands mean ? For instance space of cosmology or the universe.
You input is much appreciated.
This is an excellent question with many possible answers. In addition to @José Eduardo Jorge's helpful and insightful answer, there is a bit more to consider.
From my perspective, the notion of infinitely extended is not something that occurs in the physical world. In other words, from my perspective, all extensions and expansions--no matter how far reaching--are finite in extent.
More to the point, a supposition about infinite time is considered in
https://www.researchgate.net/publication/45863899_Possible_Anthropic_Support_for_a_Decaying_Universe_A_Cosmic_Doomsday_Argument
Infinity does not enter into the picture in Roger Penrose's holographic universe in
https://www.researchgate.net/publication/282010229_Roger_Penrose_the_Quantum_Big_Bang_of_Creation_and_the_Holographic_Universe
An interesting related topic is empty space which has more energy than everything in it:
http://scienceblogs.com/startswithabang/2012/07/26/empty-space-has-more-energy-than-everything-in-the-universe-combined/
Article Possible Anthropic Support for a Decaying Universe: A Cosmic...
Research Roger Penrose, the Quantum Big Bang of Creation and the Holo...
Dear Dejenie:
In my understanding, an infinitely expanding space at the cosmological level means that every object in the Universe is moving away from every other object. We cannot see this expansion directly, but verify it in an indirect way observing the red-shift of light from distant galaxies..
https://en.wikipedia.org/wiki/Redshift
This is an excellent question with many possible answers. In addition to @José Eduardo Jorge's helpful and insightful answer, there is a bit more to consider.
From my perspective, the notion of infinitely extended is not something that occurs in the physical world. In other words, from my perspective, all extensions and expansions--no matter how far reaching--are finite in extent.
More to the point, a supposition about infinite time is considered in
https://www.researchgate.net/publication/45863899_Possible_Anthropic_Support_for_a_Decaying_Universe_A_Cosmic_Doomsday_Argument
Infinity does not enter into the picture in Roger Penrose's holographic universe in
https://www.researchgate.net/publication/282010229_Roger_Penrose_the_Quantum_Big_Bang_of_Creation_and_the_Holographic_Universe
An interesting related topic is empty space which has more energy than everything in it:
http://scienceblogs.com/startswithabang/2012/07/26/empty-space-has-more-energy-than-everything-in-the-universe-combined/
Article Possible Anthropic Support for a Decaying Universe: A Cosmic...
Research Roger Penrose, the Quantum Big Bang of Creation and the Holo...
Dear Dejenie A. Lakew
Thank you for inviting me to participate in the question, which I paraphrase as follows:
What makes a domain is infinitely extended, which means its breadth?
In my view, the question has two basic answers, and probably more subordinate.
- Even in the astronomical and according to the Theory of Relativity and quantum mechanics perspective, it is accepted that the universe has 3 known on earth spatial dimensions, plus a different time, that is, the universe-Space-Time "4D". This can also be verifiable by astronomical observations and using mathematical tool man created for this purpose.
regards
Jose Luis
Estimado Dejenie A. Lakew
Gracias por invitarme a participar en la pregunta, la cual parafraseo de la siguiente forma:
¿Qué hace que un dominio esté infinitamente extendido y que significa su amplitud?
A mi parecer, la pregunta tiene dos respuestas básicas, y probablemente más subordinadas.
Saludos
José Luis
Dear all,
Thank you for your answers and valuable resources.
Dear Jose,
I think what you said the red shift is where we observe the further separation of galaxies over time.
Dear James,
Dan Page's suggestion that the universe is decaying with some rate which he approximated to be around 20 billion years contrary to the common belief that the universe is expanding and in his own words, his predictions require unnatural tuning and would not be explained in human's consciousness and understanding, but that amounts to religious toning. Penrose's theory is that the universe existed before and died to a singularity, and it started from a singularity and dying to be a singularity which is a cyclical or periodic existence, which simply puts the universe to be finite in all dimensions. But I am wandering what the space outside of the universe where the universe if expanding in to and that outer space is what I see endless or infinite and unreachable.
Regards,
Dear Jose Luis,
Thank you for your detailed, categorized and well elaborated answers.
Regards,
The universe is an example of an infinitely expanded domain, since its very begining, in the Big Bang. Fisychists say that the universe is expanding.
Dear Cesar,
There are other physicists who say the universe is decaying which will be finished in the next 20 billion years. Dan Page of the University of Alberta, whose article is shared by dear James above is one such physicist and Penorse is another, who says the universe is always in finite domain which collapses and explodes in a cyclical ways, which might have been that way for all time with no beginning and no end.
How could such divergent thoughts exist as scientific theories that are valid ? It seems that cosmology and physics is one of the fields of study where every person can come up with his/her own theory and enjoy the joy t that comes from the mathematical expressions of the theories not the actual empirical truth of that theory.
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