We don´t!

As long as we cannot carry out at least one measurement relating every place in the universe, Xavier is correct, I'm afraid. And even if we could, measurements would be constrained to the observable universe. We have to stick to the assumption that laws governing events in the universe are the same as on or near earth.

Therefore, we have such theories as given in the link below.

http://www.nature.com/news/simulations-back-up-theory-that-universe-is-a-hologram-1.14328

Interesting question, indeed. The current cosmological paradigm argues that homogeneity exists through out all our universe, so the laws are everywhere the same independently from the place where they have been deduced or discovered or invented. But we can find counterarguments:

1)Let's suppose that we live in the neighborhood of a big black hole (not near the horizon, but a safe distance away) and our scientific background has not discovered yet the term of 'black hole'. What kind of laws can we observe there? Surely we shall observe a dominant direction towards the (unknown to us) black hole. Is this a universal law? Surely not.

2)Let's suppose now for our current knowledge status that we live closer to an unknown 'entity', probably similar to a black hole but for other reasons. What kind of laws can we derive? Are there applicable outside our isolated local neighborhood? Here is the question...

Just to go a step forward:

What does exactly guarantee that our observation of 'universe expansion' is a global and not a local phenomenon?

I would suggest reading the book "Time Reborn" by theoretical physicist Lee Smolin. He expresses some concerns on why we cannot easily extend simple physics considerations to the whole Universe at once (e.g. the problems with the concept of time arising when you try to apply quantum mechanics as is to the Universe). I found this discussion, as well as the whole book, incredibly interesting.

You should go to Hindu Philosophy. try to read "Geeta" http://ebooks.iskcondesiretree.info/pdf/00_-_Srila_Prabhupada/Bhagavad_Gita/Bhagavad_Gita_As_It_Is.pdf

or

Lectures of "Swami Vivekanand"

Cosmology, as a science, was born with the Einstein´s field equations. Two cosmological equations were derived applied to the universe as a whole. On the other hand the Einstein´s field equations have a local application, that is Einstein special relativity that are subject to laboratory experimental verification, like the particle accelerators. In cosmology we can not do experiments, just observations via all kind of telescopes on earth or satellites. And the two cosmological equations predict a lot of things that may be observed, and viceversa, a lot of observations that may be explained. Nevertheless there are a lot of predictions not yet observed and a lot of observations not yet explained. This is the job of the scientific method that we are constantly applying when doing research.

Dear Oscar Chavoya-Aceves,

We do not know if a statement that refers to the entire universe is true. We just assume such statements. Hence the standard model of cosmology is based on the statements that Universe is the same everywhere (homogenenous) and in all the direction (isotropic). But such statements can be very suggestive as explained for instance in http://www.newscientist.com/article/mg21028061.400-empty-universe-cosmology-in-the-year-100-billion.html

Because of Universe accelerated expansion, it is possible that in 100 billion years, no galaxy be visible in our observable Universe. Cosmologists at that time (if any !) could then make the wrong statement that we live in an empty Universe.

In my own opinion, the relative variance is true, which is indepenent of the reference you choose

Our capacity to observe conditions throughout the universe is temporally limited at small scales, but at increasingly larger scales it is temporally increasingly varied. As a result, conditional statements about the universe that are not anywhere observationally falsified can be reasonably be considered to be universal, at least for the periods and scales observed.

We never know with certainty that any universal statement is true, and even my statement that we never know that universal statements are true is not uttered based certainty. Therefore your question may never authentically arise lol.

You can certainly know when one of these statements is FALSE. But you will never be able to prove that something in science is TRUE: Science is always exposed to the risk that more accurate or different measures show a previously unnoticed departure from experiment. This is Karl Popper's falsability paradigm.

The "entire universe" is, by local definition, all-that-is. That, in itself, is a statement about it. Beyond that, how about Bell's Inequality?

Cyril-Mary Olatunji

Apparently the question makes sense, considering that you answered.

@Jonathan Gagné

Thanks for the reference.

because the Universe is not filled with local observers observing local physics -

that Universe is causally impossible. All observer have horizons on them of size c/H_o but the physics and constants of nature within each horizon are the same - otherwise if you change horizons the physics would change. Good for sci fi novels but not for a physical Universe.

well I don't know what an objective reality is - I can't measure that,

I can only measure by detector based reality which just may be Descartes Evil Genius running around and fooling me all of the time.

How do we know that a statement that refers to the entire universe is true?

The statements that are implied in the cosmological models of the universe are scientific and based on the Einstein general relativity field equations. Problem: quantum mechanics is there to stay and we still have not succeded in integrating the two approaches to nature, once and for all. We are sure that the universe, call it nature, is one, integrated, and in a way based in a unified underpinning TOE, theory of everything. One starting step is to quantize, to introduce the quantum principles we are sure to hold, in the cosmological models. I am sure that once the first step is succesfully made the whole picture will change and improve in a relatively short time. So far there is not yet a succesful first step.

The concept of "truth" means following a predicted behavior. If it follows that, the prediction is true, If there is no way of making a prediction, and then observing

to see if the prediction is fulfilled, then the process is impossible, and there is neither truth nor falsity associated with the issue. The best description I know of the issue is in Mark Twain;s Connecticut Yankee in the Court of King Arthur. Here he tested someone who claimed they could determine things happening at a distance by asking what he was doing with his hand behind his back.

Dear Oscar,

When we claim that "Y is false", and Y turns out to be false, then our first statement represents a true statement. Regardless what we don't like to think, there are few statements that we can say about the universe that can be verified true. I first quote "the aim of a science is to discover which of the propositions in its domain are true, i.e., which propositions possess the property of truth" - R. Audi, The Cambridge Dictionary of Philosophy, Second Edition, p. 929.

Thus in science, one may safely find a way to use the word "true" about causality of natural phenomenology for example. As well as few more situations as:

a) The famous singular and nomic causation signified that true behind a natural system maybe well understood if enough data about that system was collected, a principal that used majorly by instrumentalists.

b) Scientific pragmatism is a method originates from philosophical point of view that one takes from phenomenology the truth he requires for practical use. In other words, there are true things in nature depending on his needs.

c) Subjectivism of science, by all means defines truth as theory predicts regardless its objective meaning.

.. etc. In quantum theory, for example, the true about a microscopic entity is found when its wavefunction (as a proper function) is fully found. The illusion, I think, is not due to definition of the truth value found in nature; rather it is about absolute truth of it– purely objective truth, which are observer independent and conditions invariant.

Some predictions can be measured, like Hubble experiment, confirming Friedman prediction of the expanding Universe. Other predictions, especially about black holes are hard to measure, other than nothing is coming out of them.

It has been stated in the beginning that scientists only can reject hypotheses, never demonstrate they are true. However, others might think that scientists will never be able to demonstrate that a hypothesis is false, for instance because of constraints at the biology-based perception level always creating biases in perception and how the world is peceived. Can an ant scientifically demonstrate that a human-made table does not exist?

Hypothesis, if they pertain to a scientific theory, have to be constantly validated i.e. checked by different scientists. The hypothes will never be demostrated to be true because for that we need an infinite number of experiments and we do not have either time nor money to do that. All we can do is to keep validating the hypothesis, until may be some time arrives and it can not be validated, it has then be falsified. Then the scientists have to go back to the blackboard and generate a falsifiable theory and start again. Scientists can demostrate that a hypothesis is false, it is their job, and they are doing this every day. As far as ants is concerned, I do not know any scientific paper published in any peer reviewed journal and written by an ant.

Dear Antonio,

At certain scales of analysis or perception, humans are probably at a limited mental level compared to other living beings in the universe (billions of billions of stars with billions of billions of planets..). Perhaps for some living beings, we are not more than symbolic ants. I am confident that at certain scales of analyses, humans are not able to falsify hypotheses, and one of the potential causes are mental/perception constraints.

Herewith an example I gave already before:

The empirical approach in science is principally based on analysis of perceived patterns reflected or produced by matter, like material, soil, crystal, liquids or any living being. Sophisticated science tools, such as a hubble telescope, electronic microscopes, spectrometers, cameras, binoculars.... are always used to observe matter from a distance. Because physics of reflectance patterns of light, or any other transmitted form of energy reflected from or produced by matter, apparently differs from physics of matter per se, empirical observation from any distance will not give direct access to matter physics per se. Thus empirical science observation suffers from bias due to methodology based on perception not giving full access to fundamental structures and organisations in nature/the universe.

Dear Marcel,

Dear All,

What you have written is really fascinating as a hypothesis but the scientific evidences for it are as difficult and complicated to understand and prove as those for the universe. Regarding human perceiving and evaluating its efficacy on the basis of how the human population are able to understand and know the statements of universe, these statements cannot be true for the majority of people. However, truth must be objective but because of our subjective ignorance we – humans – cannot recognise it.

Dear Marcel,

The scale of mental levels in the universe must be very large, and we do not know where we are in these scale right now. Certainly we do know where we are at the scale here on earth, we are very good observers and have an ample field for study here. We do not know yet what is going on in other planets. So far only imagination and risky extrapolation is possible. And as far as humans not able to falsify hypothesis statistically this may be true, but another potential cause (besides mental/perception constraints) is the state of the technical possibilities that we have available right now. Extrapolating and using a good hystoric reference, based on the known evolution in both technical improvements and decrease in mental/perception constraints, we can say that in time we will arrive at a higher and higher mental level and technical improvements. Look for example the field of comunication all over the world. And if we advance in ethics, we may feed all humans because there is enough food for all humanity, if it were properly distributed. We may be populating other planets not so far in the future. To be precise, just for curiosity, in our visible universe there are one hundred thousand of millions of galaxies (10^11), and each galaxy has the same amount of solar systems. So you are right, in our visible universe there may be 10^22 planets the majority of them with living beings.

Dear Antonio,

for me it is already facinating that humans are able to put a human-made object on another planet in our solar system. Little step by little step humans will understand more and more. The potential problem is that many scientists want to run before they can walk, perhaps because of social pressures or funding agencies that do not truly understand how research is conducted in practice.....

Dear Antonio,

You have written that we – humans - are “very good observers and have an ample field for study here”. I think at population level we are not very good observers – only some of us are so. And regarding thinking we are very weak even at our own level. As to our ethical abilities you are – unfortunately – right. Considering that ethical capacity is an innate part of human intelligence, the recognition and use of truth are hugely hampered here.

Dear Andras,

Because of our biology we only perceive Earthly phenomena from the past (e.g. caused by the relatively short transmission distance between an 'object' and the position of the brain transforming perceived stimuli into....), like astronomists watching the universe only studying phenomena from the past (e.g. caused by the relatively long transmission distance between an 'object' and the position of the brain transforming perceived stimuli into...)....

Cheers

Dear Marcel,

My desires is that humans should conclude and reflect rightly according to our modest biological capacities at the widest population level as cognition is a socially and timely determined process.

Dear Andras,

Democratic science: unusual theories that might be considered scientifically correct in the future will therefore be counter-selected hampering science progress at the theoretical level? Some people claim that only those hypotheses should be published that can be (experimentally) tested.

Dear Oscar, 

I could address you to our works V.E. Ostrovskii, E.A. Kadyshevich, EPSC Abstracts, v.9, EPSC2014-653, 2014 and Elena A. Kadyshevich, Victor E. Ostrovskii, Adv. Plasma Astrophys., Proc. IAU Symp. № 274, 2010, pp. 95-102 and to the publications of the same authors between these two ones (all are available at the RG site). 

this link is useful

https://www.space.com › Science & Astronomy

regards

Agree with Michael Brückner

regards

We can certainly hypothesize about a universe of sextillion times sextillion stars, but that's about all we can know. A hypothesis is not an exactitude.