Given that time itself is relative to each observers and is dependent on relative velocity through space and the effect of mass proximity, and considering that all mass bodies are moving away from each other at increasing speeds; how then can we, from our observer perspective, be sure that our estimate of the age of the universe is correct?
@divegeester saidWe can't. We estimate, based on the size and the acceleration we currently observe. Reverse the acceleration back to a theoretical minimum size, as a thought experiment, and that yields a rough number, give or take a few million years.
Given that time itself is relative to each observers and is dependent on relative velocity through space and the effect of mass proximity, and considering that all mass bodies are moving away from each other at increasing speeds; how then can we, from our observer perspective, be sure that our estimate of the age of the universe is correct?
@moonbus saidI get the reversing of expansion in order to track back to a start point. But this on its own seems to ignore the relativity of time across the expanse of the cosmos.
We can't. We estimate, based on the size and the acceleration we currently observe. Reverse the acceleration back to a theoretical minimum size, as a thought experiment, and that yields a rough number, give or take a few million years.
@divegeester
What is it about "the relativity of time" makes you think the thought experiment is not a valid method or does not yield a correct result ? "The relativity of time" does not mean that we do not know when the 8:02 departs from King's Cross or when Halley's Comet is due to return or how long the half-life of thorium is.
@moonbus saidThe relativity of it. This is, relative time means that our perspective of the passage of time is relative to our situation and the passage of time for everything else in the universe is relative to that. Therefore as time is not a constant it cannot be possible to measure “age” of things far away and in a different spacetime dynamic.
@divegeester
What is it about "the relativity of time" makes you think the thought experiment is not a valid method or does not yield a correct result ?
@divegeester saidYour contention is not strictly correct. You apparently think there is no such thing as objectively verifiable truth because "everything is relative." An example may clear this up.
The relativity of it. This is, relative time means that our perspective of the passage of time is relative to our situation and the passage of time for everything else in the universe is relative to that. Therefore as time is not a constant it cannot be possible to measure “age” of things far away and in a different spacetime dynamic.
Suppose a star goes nova in some galaxy. Suppose another star goes nova in another galaxy far far away. Now, an observer who happens to be closer to star-1 than to star-2 will receive the light of the nova-1 before he receives the light from nova-2, and will therefore think, relatively to his own position, that star-1 exploded before star-2. Whereas, an observer who happens to be nearer to star-2 will think, relative to his position, that star-2 exploded first. Whereas, for some third observer, the light from both stars will arrive simultaneously, and he will think, relative to his position, that the stars exploded at the same time.
Does this mean that no one can ever determine which star exploded first? No, it does not. We can measure the red shift in the light coming from both stars, wherever we happen to be in the universe, regardless which light happened to arrive at our position first, and by comparing the red shifts we can determine how far away each star was when that light was emitted. Because the speed of light is a constant (that is not relative to an observer's position!), the distance (based on red shift) also tells us when the explosion's light was emitted. Compare the two, and you know which one exploded first, even if the light arrives in a different (non-chronological) order at your position.
Same argument applies to the age of the universe.
Furthermore, while velocity is relative (to some frame of reference or to some other object), acceleration is not. So it is simply not true that "everything is relative". Acceleration is measurable, and the expansion (or "inflation" ) of the universe is one such parameter which is not relative to an observer's position.
@moonbus saidIt’s not about light travel time determining time of event, this is about the effect of the dilation of time relative to the speed of travel of massive objects and their proximity to each other and the effect of gravity on time also.
Your contention is not strictly correct. You apparently think there is no such thing as objectively verifiable truth because "everything is relative." An example may clear this up.
Suppose a star goes nova in some galaxy. Suppose another star goes nova in another galaxy far far away. Now, an observer who happens to be closer to star-1 than to star-2 will receive the light ...[text shortened]... "inflation" ) of the universe is one such parameter which is not relative to an observer's position.
@divegeester saidThe inflation of the universe is not "a massive object" subject to time dilation. It is also not subject to the maximum speed of light; the early universe inflated faster than the speed of light.
It’s not about light travel time determining time of event, this is about the effect of the dilation of time relative to the speed of travel of massive objects and their proximity to each other and the effect of gravity on time also.
What 'effect' do you suppose gravity has on time ?? Gravity is not a force, the way electromagnetism is. What we call "gravity" is a curvature of space.
@moonbus saidOk I see the problem here with you not understanding the initial premise.
What 'effect' do you suppose gravity has on time ?? Gravity is not a force, the way electromagnetism is. What we call "gravity" is a curvature of space.
Have a read up.
https://en.wikipedia.org/wiki/Gravitational_time_dilation
https://en.wikipedia.org/wiki/Time_dilation
@divegeester
All of you are extremely impressive, I can’t help but to subscribe to your every theory. Me, I don’t even know if I am using the word theory correctly.! Cool stuff. I mean, am I to understand that there is no end to the universe and it just goes on forever and ever and ever after that.?
Further query: I would think that given all of the space and distance and millions and billions of things that float in space like earth, that there is an agreement on this forum that there is life out there…. I don’t mean microbes and amoeba and slimy stuff in a pool of water. There are societies out there……
@AverageJoe1 saidYou wouldn’t get an answer from the topic of this thread.
@divegeester
I mean, am I to understand that there is no end to the universe and it just goes on forever and ever and ever after that.?
The universe is finite but expanding, therefore if it continues to expand it will “go on forever”.
However the expanding universe is probably (according to theory**) more or less spherical, like the earth is more or less spherical. This means that if you left earth in a super fast spaceship and set off in one direction and kept going you would eventually come back on yourself, like you would on earth.
** other theories of the shape of the universe are available.
@AverageJoe1 saidThere is so far no evidence of life elsewhere in the universe; however we can only examine a tiny part of it for such evidence.
@divegeester
Further query: I would think that given all of the space and distance and millions and billions of things that float in space like earth, that there is an agreement on this forum that there is life out there…. I don’t mean microbes and amoeba and slimy stuff in a pool of water. There are societies out there……
One theory goes that if there was other life in the universe then we will never find it. The rationale being that it is not just the unimaginable size of the universe which is the problem, but also it’s age. Whereby if life arose elsewhere the chances of it happening within the timeframe of our existence here on earth is infinitesimally small. Add to that the size of the universe and the theory goes that we are effectively alone, and always will be. Eventually we will destroy ourselves or be destroyed by a cosmic event or in time the Sun will expand in its red giant stage and burn earth to a crisp.
We are a very short lived speck of life.
@divegeester saidTell this neophyte, how in the HELL does sun just burn and burn, keep on burning. Should it not have burned up by now.? I googled it has been burning 4.5 B YEARS!
There is so far no evidence of life elsewhere in the universe; however we can only examine a tiny part of it for such evidence.
One theory goes that if there was other life in the universe then we will never find it. The rationale being that it is not just the unimaginable size of the universe which is the problem, but also it’s age. Whereby if life arose elsewhere th ...[text shortened]... xpand in its red giant stage and burn earth to a crisp.
We are a very short lived speck of life.
@AverageJoe1
I gather you never took a single science class in high school. Do you know just what Einstein's equation E=MC^2 is all about?
Ever hear of the word in physics called fusion? Is that maybe a tiny hint as to what is going on inside the sun, why it has been burning for billions of years and will keep on burning for at least another billion years? Energy= Mass (in Kilograms) times the square of the speed of light (C^2) in meters per second, which is roughly 300 million times 300 million which means if totally converted, one kilogram of stuff will release 9 E16 joules. Or watt seconds, that is 9 followed by 16 zeros. A trillion is 1 E12, so 9E16 is 9000 trillion watt seconds, which is the same as one watt running for 9000 trillion seconds or about 2.7 billion years. Remember, that is totally converting only one kilogram into energy.
Now the mass of the sun is about 2E30 kilograms so it could produce 2E30 watts for 2.7 billion years. The sun produces 3.8 E26 Joules (watt seconds) per second. So that means fusion is only one ish percent efficient at releasing energy. If you want total conversion you would have to have an anti particle hit a regular particle. But that 1 odd percent is enough to run the sun for a lot more than 4 or 5 billion years. 1 Joule is the energy contained if you had one watt running for one second, like in electricity, 1 volt at 1 amp for one second, that is one Joule.
Joule is a scientist who showed how much heat energy is given off by electricity running through a resistance, like a resistor.