The Absolute Maximums of Time and Space Relativity
The Absolute Maximums of Time and Space Relativity
Just because time is relative does not mean time is subjective. Time is a fundamental objective part of reality, and time and distance relativity is probably less weird than you think it is. There …
I'm not an astrophysicist nor a relativity theorist, but this makes absolutely no sense.. The article writes,
When we say that the Earth is 4.5 billion years old, technically we mean 4.5 billion years is the maximum amount of relative time any thing could have experienced since the Earth was formed.
If by "Earth is 4.5 billion years old" it means the time lapse as experienced on earth -- in other words, as measured by a clock on earth, then the clock is in the rest frame and therefore measures the shortest possible time duration among all clocks in other (moving) inertial frames, not "the maximum amount of relative time" (special relativity). I think the author is confusing this with the twin paradox where the traveling twin ages slower. The talk of
There is a maximum amount of relative time that can be experienced between any two points in time (no time dilation). There is a maximum relative distance between any two points in space (no length contraction)
is also troublesome -- what is even "two points in time (no time dilation)"? One should instead be talking about two events and their space-time coordinates
If by “Earth is 4.5 billion years old” it means the time lapse as experienced on earth
Nope. It means that 4.5 billion years is the roughly the MAXIMUM amount of relative time anything anywhere in the universe in any frame of reference could have experienced since the creation of the Earth. Now obviously it is true that Earth's reference frame is close enough to that maximum such that the difference is a rounding error of the 4.5 billion years figure. But there is literally nothing in the universe that could have experienced 5 billion years of time since the creation of the Earth, although it is certainly possible to experience only 4 billion years. It is also true that 13.8 billion years is the maximum amount of relative time anything in the observable universe in any frame of reference could have experienced since the big bang.
I think the author is confusing this with the twin paradox where the traveling twin ages slower.
I think the author means exactly what he said. Experiencing 5 billion years (more than the maximum) since the Earth's formation would be impossible in all frames of reference - but experiencing 4 billion (less than the maximum) is possible.
“what is even two points in time”
You don't understand what a point in time means? It is well understood by astrophysicists that there is a maximum amount of relative time that can be experienced between any 2 points in time, just as there is a maximum amount of relative distance that can be experienced between any 2 points in space (no length contraction). It is impossible for time dilation and/or length contraction to be negative.
One should instead be talking about two events and their space-time coordinates
You can talk about that if you want. But then you probably won't learn anything new. This article talks about the implications of the well understood facts by astrophysicists that there exists a maximum relative length between any 2 points in space and also between any 2 points in time and how length contraction is related to time dilation.
It means that 4.5 billion years is the roughly the MAXIMUM amount of relative time anything anywhere in the universe in any frame of reference could have experienced since the creation of the Earth.
Another confusing thing is that NO ONE calculates the age of the Earth this way. People do things like measure isotopes and radioactive decay rates, which gives you the Earth's age in its own reference frame. No one is messing about with measuring the CMB or calculating galactic flow rates or some such.
True, for the Earth "the difference is a rounding error". But imagine if the Earth formed 10 billion years ago, then between age 500 million and 1000 million years some alien pranksters accelerated Earth to near lightspeed and took it on a joy ride around the universe for 6 billion years, then put it back here. All our measurements would still show the Earth is 4.5 billion years old, yet by the article's calculation it would be 10 billion years old, disproving the article's entire point!
I think the author just got confused. The only context where the "maximum amount of relative time" concept comes up is in calculating the age of the universe. It is objectively 13.8GY. There we do look at the CMB to make corrections for our relative speed! This way all observers will agree on that number regardless of their speed, even if their own clocks show less. But the author heard that, got excited, and started trying to apply it to the age of Earth, where it doesn't serve any use.
Hey, you seem to have a better understanding of the stuff, so perhaps you could point me in the right direction? Here's my confusion: Let's say at the inception of the earth, a clock started ticking (event 1), and let's count earth's age as up to the moment I made the post right next to that same clock (event 2). By special relativity (so obviously ignoring gravity etc), the interval between the two events is
s^2 = t^2 - x^2wheretis the time elapsed on the clock, andx = 0is the distance traveled by the clock in its own frame (earth's frame), which is zero. For an observer moving at a constant speed relative to earth, the clock has moved, sox' != 0(using'for the moving frame), but the intervalsis the same in both frames, so the time elapsed in the moving observer's frame, between the same two events, must be greater than on the earth clock,t'^2 = s^2 + x'^2 > s^2 = t^2. In other words earth appears older (as measured by the relative time between the said two events) to the moving observer than to someone living on earth. This is where my comment about "two points in time" come from: without the spatial information, I wouldn't be able to compare different relative times and pick its maximum.I'm obviously not an astrophysicist and not familiar with the "well understood facts by astrophysicists" of maximum relative time/space. I suspect from your comment that my interpretation of "relative time" is wrong, but if you could point me to some accessible references, that would be very much appreciated!