# What percentage of the universe do we know

• B

## Main Question or Discussion Point

Hello.
First of all, I must say that I'm new to this forum, so I apologize if I'm posting in the wrong section.
I'm a 17 year old with not that much knowledge about physics, so if what I'm talking about makes no sense or is completely stupid, just let me know.

A couple of days ago I asked myself: Is it possible to say what percentage of the universe do we know? (note: I'm talking about the whole universe, not just our observable universe)
At first I said that it is not possible to answer such question since it implies that we know what 100% of the universe is. If the universe is, indeed, infinite, that means we can do some math, as 100% = infinite.
https://scontent-frt3-1.xx.fbcdn.net/v/t34.0-12/14642996_1165564973536187_187242484_n.png?oh=18cc2d1f2867750971fa0dff9a00899c&oe=57FC053B
No matter what value we give to X, the answer will be the same, that is infinite. With this in mind, does it mean that what we currently know about the universe represents an infinite amount? And if so, it means that, as X increases, the result will still be infinite. That means that no matter how much we progress, how much more we learn about the universe, we will still know as much as we currently know... which doesn't really make sense, since we obviously increased the amount of information we have about it.

jbriggs444
Homework Helper
2019 Award
Why not start with a simpler question: What percentage of your left big toe do you know?

bapowell
We can't know anything scientific about what can't observe.

• jim mcnamara
Drakkith
Staff Emeritus
A couple of days ago I asked myself: Is it possible to say what percentage of the universe do we know? (note: I'm talking about the whole universe, not just our observable universe)
It is not possible, as we don't know the size of the entire universe.

At first I said that it is not possible to answer such question since it implies that we know what 100% of the universe is. If the universe is, indeed, infinite, that means we can do some math, as 100% = infinite.
I don't think your math is valid. As far as I understand, infinity represents an ever increasing quantity, not a single value. You cannot say 100% equals infinity since there are a never-ending number of values for infinity. You also couldn't say 100% equals 2 and 4.

Chronos
Gold Member
You could pose the question as x+y =1, where x is the observable universe, y is the unobservable universe and 1 is the sum.. Given 'y' is always unknown, the question is undefined.

• Stephanus
timmdeeg
Gold Member
If the universe is, indeed, infinite, that means we can do some math, as 100% = infinite.
The math you can do is simply
$x/\infty=0$, wherby $x$ ist finite.

Therefore you can't talk about a percentage of the infinite universe depending on the size of the observable universe.

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On the other hand, the universe might not be infinite, nobody knows.
However it still remains pointless to discuss percentage of an unknown quantity.

• jim mcnamara and jbriggs444