/sqt/ - Stupid Questions Thread: Solar Flux Edition

Could we terraform the Sahara with ice asteroids? Like if we rigged them up with rockets to slow their re-entry so they didn't just melt

The sahara isn't hot just because its a desert you know, the ice asteroids will just end up melting once they land and the water will boil away. It's the sun that fucks up the region

finally, a question worthy of this thread

why humans' bellybuttons are so easy to spot while it is so hard to see other mammals' bellybuttons? I heard other animals have the mom chew off the umbilical cords and then the baby's bellybutton will just become a flat and small scar, but why is it that humans' bellybuttons aren't flat too?

Hello, why we say closed and bounded interval ?
If an interval is closes, he is necessarily bounded, no ?

[0, infinity) is closed

Bounded means that there is a finite intervall that includes that intervall.
eg. [2,3] is included in [1,4] so it is bounded.

Closed means all point are really inside the intervall.
eg. [1,2] means that all number that are greater then 1 and smaler then 2 are in the intervall, including 1 and 2.
The open intervall (1,2) means that all number that are greater then 1 and smaler then 2 are in the intervall, not including 1 and 2.

There is no speciall relation between bounded and closed.

There are intervalls which are closed and un/bounded, un/bounded and open and even intervalls which are closed and open.

>It's the atmospheric circulation that fucks up the region
FTFY
subtropical ridge (high pressure bands at ~25-30 N and S) causes extremely low precipitation, producing bands of deserts at those latitudes

But not bounded*

Some group theory stuff:
First problem:
I kinda have a problem comparing groups like the rubik's group to groups like integers.
Things like the Rubik's cube group, seem to be a set of transformations on a set of states, whereas the integers are an operation with two inputs.
The way I resolve this in my head, is to define the integer group, to be the set of integers as well as the set of functions [math] \{x+n\in \mathbb{Z} \to \mathbb{Z} : n \in \mathbb{Z}[spoiler][/spoiler]\} [/math]...if that makes sense.
Is this the general sense?
None of my texts seems to go too deep into it.

But what does associativity mean in this case?
That [math] f \circ g [/math] is in the set of transformations?
Does this form another group with [math] \circ [/math] being the operator?

Question 2:
Generators
Soo my text says that [math] 1 [/math] generates the integers.
Does this mean you start from a certain value and keep applying this transformation to get the entire set? Or you can start from any value? Or are these equivalent?

Moving on from that, does the positive integers generate the positive rationals group (under multiplication)?
And finally. wth are the generators for the real groups under addition and multiplication (sans zero ofc)?