Comment on well?
Johanno@feddit.org 2 days agoWe have a theory for expansion of the universe. It is called “the big bang theory”.
However according to the math our universe should slow down expanding, but we can observe it is speeding up. Solution? Dark Energy.
There are models that try to simulate the orbits and shit of things we can see. Now those models aren’t working however… Solution? Dark matter.
This is very run down concept of what dark matter and energy is. Basically shit we need for the math to work out to the observation we make.
However I don’t think we are inside a black hole. This would mean that instead of mostly nothing our universe would be cramped with matter…
There’s also been some major leaps in dark matter physics in the last few years. Revisiting primordial black holes using lasers and microlensing might actually be able to get supporting evidence here before long if the hypothesis holds.
PBS Space Time has a good video breaking this possibility and methodology down.
Difference being that we understand dark matter exponentially more than dark energy. We can actually observe it’s gravity affecting light.
There’s also cyclic conformal universe theory, put forth by Penrose.
Where once you have an empty enough space… its mathematically indistinguishable from a singularity.
So, if its true, then yeah, we could be inside of a blackhole/singularity.
At this point, that doesn’t really matter.
So, dark matter and energy is the Universe’s theorized version of the Kelevin (from The Office).
faultyproboscus@sh.itjust.works 2 days ago
If you take all the mass in our universe and run it through the Schwarzschild equation, you get a black hole with about the same radius as our observable universe.
Things don’t need to be tightly packed to be a black hole, there just needs to be enough stuff in an area.
cptspike@lemmy.world 2 days ago
How do we predict the total mass of the universe?
faultyproboscus@sh.itjust.works 2 days ago
I think it’s a combination of at least three things.
Cosmic Microwave Background radiation gives us a pretty good idea of the energy/mass density in the universe at a fixed point and age of the universe. If you take the densities estimated from the CMB and multiply it by the estimated size of the universe at the time the CMB (380k years after the Big Bang), then you get the total mass.
Second, we can just look for what we can see. I think there have been large-scale surveys done to estimate total mass/energy in the universe.
The third estimate has to do with something called ‘critical mass’ - we observe the overall ‘curve’ of space to be very close to flat. I’m talking the geometry of space; two parallel rays of light do not ever cross or diverge. For this to happen, there needs to be a certain average density of mass.
Wikipedia has the mass of the observable universe listed as 1.5×10^53 kg, although this can go up to 10^60 kg at the higher ends.
If we plug the Wikipedia numbers into the Schwartzchild radius formula: r = (2GM) / (c^2)
Where G is the gravitational constant, M is our mass, and c is the speed of light:
r = (2 * 6.67408 * 10^-11 m^3 kg^-1 s^-2 * 1.5*10^53 kg) / (299792458 m/s)^2 r = 2 * 10^43 m^3 s^-2 / 8.988 * 10^16 m^2/s^2 r = 2.225×10^26 meters r = 23.52 billion light years
Wikipedia lists the radius of the observable universe as 46.5 billion light years.
So… given the Wikipedia numbers, the universe would need to be half the size it is now to be a black hole. At these scales, being within an order of magnitude is… fine.
If we bump up the estimate of mass to only 3x10^53 kg, then the Schwartzchild radius equals the size of the observable universe.
So it’s within the margins of error of our current estimates that the Schwartzchild radius of our universe would be the current size of our universe.
Im_old@lemmy.world 2 days ago
Approximately
MycelialMass@lemmy.world 2 days ago
Light from stars tells us how big they are then adjust for things that don’t emit light by looking at how objects move (i.e. gravity). Objects in this case not necessarily being single entities but often groups of things like entire galaxies. This is basically how dark matter became a thing. Scientists were like “hey theres waaaay more gravity moving things around but we dont see any objects causing it…”
Swedneck@discuss.tchncs.de 2 days ago
but like, the whole point of black holes is that time and space switch places, which means all the matter/energy inside them is packed in a single infinitely dense point
that’s a pretty big thing to ignore
ubergeek@lemmy.today 2 days ago
It’s less than time and space switch in a singularity, and more that they are “undefined”.
Like dividing by zero.
faultyproboscus@sh.itjust.works 2 days ago
It’s more complicated in ways that aren’t intuitive.
Yes, at first glance, it appears that everything would continue to collapse down to a singularity. But a singularity is literally a failure of our model of physics. It’s like dividing by zero- the result is nonsense. It’s not an actual object.
From our perspective, time is stopped at the event horizon of a black hole. The singularity never forms because there isn’t time for that to happen. If you fell into a black hole, would a singularity form as you are crossing the event-horizon? Maybe. Maybe Hawking Radiation is a thing and you’re cooked by a wall of radiation as the collapsing object literally evaporates beneath you.
Keep in mind that high densities are needed for stellar black holes to form. An event horizon would form around the solar system if it was filled with air- and yes, there are black holes of this size.