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Quarlep
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Is space time has a energy itself ?
Thanks
Thanks
wabbit said:You can interpret the cosmological constant as an energy density of spacetime, which is fine though only one way to see it.
Hi Q,Quarlep said:If space-time has energy density it means it has a energy isn't it ?
Thank you very much. I am 18 years old so let me be repeat this knowladge.As I understood that space-time itself have a energy density which is cosmological constant but you said that's not quite true cause that lambda is a curvature of universe. Its smthing like constant and you showed me a graph but I dindt understand the main idea cause my english ls bad can you explain me simpler.marcus said:The present rate of distance growth is 1/144 % per million years and the longterm residual rate it is tending towards is 1/173%. That is what you get from Einstein's Lambda constant. But I'd like to show a curve that plots the history of that growth rate say from year 1 million up to the present, and on into the future some so you can see it leveling out.
If I have 100 $ than I l ll have (in %4 growth per year) I ll have 104$ than 104+104/25 so 108.16 isn't itmarcus said:Do you know what a growth rate is? It is a number per unit time. Like "4% per year".
That means 0.04 per year.
Something grows by 1/25 of its size per year.
Quarlep said:Whats the y-axis on this graph you are trying to tell me change in time and change in smthing but I didnt understand the other y-axis excuse me but what's means present rate of distance growth 1/144% per million years and what's the grow rate why there's % (these question can be simple or stupid but I don't have enough english and cosmolgy knowladge to learn understand it)
Thanks for help
Yes that is right.Quarlep said:If I have 100 $ than I l ll have (in %4 growth per year) I ll have 104$ than 104+104/25 so 108.16 isn't it
I think you are getting the idea.Quarlep said:So now our universe diameter is r and we are multiplying it 1/144 per billion years(that grow rate is diameter of universe isn't it) after billion year we will multiply it 1/173 per billion year than we will multply it some number which your graphs show
I understand your idea.I can get used to think time measured in Qdays I guess. 1 Qday is 17.3 billion years. 1/Qday is expansion rate that's why graph is look like 1/x graph. This graph is y=1/Qday isn't itmarcus said:I should make you a table for converting time (in usual scale of billions of years) to time on the x-axis scale.
To convert you have to divide by 17.3.
Imagine that we have a new unit of time called the UNIVERSE DAY, it is 17.3 billion years long. Or we will name it after you and call it a QDAY.
Now the present age of the universe is 0.8 Qdays.
Can you get used to thinking of time measured in Qdays? That is what the x-axis of that plot measures.
Yeah, Marcus has a habit of doing thatwabbit said:Thanks, sounds like a much better way to put it than my "yes in a sense but..." contorsions
Good.Quarlep said:Now we have a galaxie which distance is 1 billion light year away...
So If I get it when x=0.23 than distance from galaxy is 0.5 light [billion] years. and that day universe is 0.23xQday=4 billion years after universe created
So there's no energy in space-time this lambda is a geometric thing which we discussed.Theres no energy density too. Its a wrong idea.marcus said:Hi Q,
So far the observations are consistent with the cosmological constant interpretation. IOW not necessarily anything we would recognize as energy (in the usual senses) but better thought of as an intrinsic tendency for distances to expand at a small permanent rate (not affected by matter and radiation).
The present rate of expansion is somewhat higher and is observed to be gradually declining as if it is going to level off at this small residual rate. That's all we know--what we observe. We don't observe any energy, we see a longterm trend in geometry. I'll give you some numbers to make this more definite.
Quarlep said:So there's no energy in space-time this lambda is a geometric thing which we discussed.Theres no energy density too. Its a wrong idea.
Yes the second graph includes the effect of Lambda, that is why it changes from convex to concave around x=.45Quarlep said:Your second graph shows us the observable universe include lambda isn't it ? And ls 1/Qday a Hubble constant or that's lamda
marcus said:Quarlep, this might sound like it is unrelated to the discussion but I'm interested to know. Did you learn some differential calculus already?
For example, did you learn that the slope of the sin(x) is equal to the cos(x)? You sound like someone who has learned some calculus as well as trig.
For doing calculus, it is best to measure angle in radians, not in degrees.
I will denote the derivative or slope of a curve by the ' so the slope of f(x) can be written simply as f'(x)
and then
sin'(x) = cos(x)
and
cos'(x) = - sin(x)
Is all that familiar to you?