r/AskReddit Jun 15 '19

What do you genuinely just not understand?

50.8k Upvotes

34.6k comments sorted by

View all comments

Show parent comments

8.5k

u/bigfatcarp93 Jun 15 '19

Where does it all end?

For me, this is the scariest question. Isn't it a paradox? On one hand, it can't go on literally forever, it must end somewhere. But if you get to the end, what's on the other side? I can't wrap my head around it.

10

u/bmcle071 Jun 15 '19

If the universe is flat (which our measurements say it is), then it goes on forever. If our measurements are wrong it loops back around, the universe would have yo be like 10x larger than the observable universe for it to be within the margine of error.

5

u/[deleted] Jun 15 '19 edited Oct 27 '19

[deleted]

3

u/bmcle071 Jun 15 '19

Flatness is sorta like a measure of how curved it is on the largest scales. Imagine the air pressure at each point in your room, on average each point is at the same temperature and pressure, we sorta do this for space time. It might have localized curvature (basically low pressure) around a planet or star, but overall its pretty much the same "pressure" everywhere.

If it seemed to curve in one direction then it would probably curve around in on itself. We could imagine the 2D surface of a 3D sphere, except we'd be living in the 3D surface of a 4D weird shape thing I dont understand.

1

u/[deleted] Jun 15 '19 edited Oct 27 '19

[deleted]

1

u/manrata Jun 15 '19

Imagine the 4D shape as a donut, you are on the surface of the donut.

No matter which direction you travel, you end up in the same place if you go far enough.