/sci/ - Science & Math

>>6410611
http://en.wikipedia.org/wiki/Hubble%27s_law

I googled "how to calculate the expansion of the universe"

>>6410614
>http://en.wikipedia.org/wiki/Hubble%27s_law
fuck.. had that page open but totally ignored it.

http://en.wikipedia.org/wiki/Friedmann_equations

Overly complicated Friedmann took too much time..

OP here,

I suck at maths, can someone calculate me the current expansion rate in lightyears/s

>>6410633
yes

>>6410648
I appreciate, Thank you. Waiting patiently. :)

>>6410633
The unit isn't [distance]/[time], it's 1/[time]. You cannot convert 2×10^-18 per second into light years per second. It's usually given as 70 km/s/Mpc (kilometers per second per megaparsec), where both kilometer and megaparsec measure distance. This would be 7.399×10^-12 ly/s/Mpc, if you need that for some reason.

>>6410652
I thought the universe expands in velocity (which should be expressed in distance/time).

May I ask why isn't it possible to calculate the expansion rate in distance/time (preferably in lightyears/s , c/s)

>>6410652
As I read this again, I think this means that we don't really know the acceleration speed(velocity) that universe expands in.

As we have 1/s (units / second) this means there isn't anything concrete, am I right? Or Does this mean we Can't tell if the universe expands in linear way (calculatable)?

>>6410611
http://www.einsteins-theory-of-relativity-4engineers.com/CosmoLean_A20.html

from PhysicsForums > Cosmology

>>6410667
(Disclaimer: I don't know what the fuck I'm talking about. I'm just going by the Wikipedia page linked.)

Oh, it's concrete. You just can't give the value as straight up velocity since every point of the universe is moving away from every other point. The points farther away are moving away from you faster than the ones closer by. That 70 km/s/Mpc is the velocity of a galaxy one megaparsec (3.09×10^19 km) away. and that 2×10^-18 is the relative velocity, in m/s, of two points one meter apart.

>>6410670
>http://www.einsteins-theory-of-relativity-4engineers.com/CosmoLean_A20.html

Looks like very good script.

I am looking for the current acceleration/velocity (v=distance/time, a=v^2) of the universe.
I am unsure though about those values that the script gives/shows,


Hubble constant (km/s/Mpc):
70.36
Is this the current one? Is it possible to convert this into normal velocity? Preferably into form of lightyears/second.

>>6410663
>>6410667
>>6410667
remember: the further two points are, the faster they get away from each other.

for example, 7.4e-12 ly/s/Mpc means that for two points at one Mpc of distance will see their mutual distance increase at a rate of 7.4e12 ly/s.

if the were at 2Mpc of distance, the rate would become 14.8e-12ly/s

>>6410678
no intention to offend you, but it sounds like you are not prepared to interpret results or values regarding the expansion of the universe. It is more complicated conceptually compared to what one would think. It's not about movement or speeds, these things in their intuitive form from newtonian mechanics loose all simple meaning in a GR context.

Just study a bit - just a bit - of general relativity, skim Hobson's introduction, and understand. Then you will be able to make sense of numbers, I guarantee.

>>6410633
Each light year distance expands about 2cm/s.
The distance of the observable universe reaches 46 billion lightyears, so the very edge is moving away from us at about 3x the speed of light

>>6410694
:D Go study yourself.

I have studied my part, I am interpreting very complex things in the simplest form which is Truth. (According to top scientists; If you can explain something to the simplest mind it means you can completely understand it.)

I don't need you Phd in fysics neither mathematics.

Sorry for sounding overconfident, but thats the game in the world. ;)

>>6410701
>so the very edge is moving away from us at about 3x the speed of light

This is what I was searching. Can you explain to others (and well for my feeling for a source) for myself too how did you come up with this result, in more detail? Please. :)

>>6410754
Most of all you sound underage

>>6410754
>I don't need you** Phd in fysics neither mathematics.

your*

>>6410763
"age argument"

>>>/b/

K as in Okay. Its okay to be ignorant.
Whatever suits you. It's not my place to be
your Messiah, go find the truth, its out there.

>>6410754

>;)

>>>leddit

>>6410756
>This is what I was searching.

But that's not what you asked. You asked the expansion rate, which is about 2cm/s/lightyear. The rate of expansion is not a speed.

>how did you come up with this result

He multiplied the rate by 46 billion lightyears.

>>6410754
what the actual fuck
thats it, enough of this shithole

>>6410796
>You asked the expansion rate

This was poorly expressed on my behalf. Sorry.

I wanted the expansion rate converted into linear velocity,

>>6410678
>Hubble constant (km/s/Mpc):
70.36
Is this the current one? Is it possible to convert this into normal velocity? Preferably into form of lightyears/second.

Which should be easily possible?

As object expands in to every direction if we compare the size of the object yesterday and today we get the (quite) current velocity.

I know the universe isn't perfectly round, but I dont need the most perfect answer.
>>6410803
Well if you didn't know, "haters gonna hate" is actually true and haters(enemies) show your colours (what you are?).

And as I see, I want to be your exact opposite. Not going to even argument this, go figure.

>>6410827
>Is it possible to convert this into normal velocity?
You need a distance. The Hubble expansion say's the further the object the faster it recedes, you need a distance.

>As object expands in to every direction if we compare the size of the object yesterday and today we get the (quite) current velocity.
This only applies to structure on cosmic scales.

>>6410701
>>6410796
>46 billion lightyears.

Is this the radius of the current universe or diameter?

>>6410834
Can't we detect the comparable galaxys current distance and distance later -> leading to the velocity?

>>6410701
>the very edge is moving away from us at about 3x the speed of light

Where is this number coming from

>>6410847
>Can't we detect the comparable galaxys current distance and distance later -> leading to the velocity?

Yes, and that is what Hubble's Constant is. Thing is, the farther away two galaxies are from each other, the faster they'll be moving in relation to each other. Two points one meter apart will be moving away from each other at 2×10^-18 m/s (which is a very small number), and two points one light year apart will be moving away from each other at 2 cm/s. Two points one megaparsec apart (this is the kind of distance you can find between two galaxies) will be moving away from each other at 70 km/s.

>>6410847
There is no such thing as the "velocity of the expansion of the universe".

If you pick two galaxies and measure their distance twice, you are indeed going to find a velocity. But it is not the rate of expansion of the universe. It is just the velocity BETWEEN THOSE TWO PARTICULAR GALAXIES.
If you do the same thing with different galaxies, you are going to get a completely different velocity.

The only way to measure the expansion rate of the universe is with Hubble's constant, which is expressed in km/s/Mpc.
It is a velocity over a distance, precisely because the velocity between two galaxies DEPENDS on the distance between them.

In short, the more distance is between two galaxies, the faster they will move away from each other.


Now, if you are given two particular galaxies, and you want to calculate the velocity induced by expansion between those two galaxies, you just have to multiple Hubble's constant by the distance between the galaxies.

This is how he got the number of "3x the speed of light". He considered two points at each side of the observable universe, ie, the distance between them is 46 billion lightyears. And he multiplied this distance by Hubble's constant. This gives 3x the speed of light.
It is NOT a conversion, it is a different quantity