You cannot measure its length but you can measure its slope and intercepts.
There is no real world flat surface which goes on forever. It is a geometric idealised concept. So, since there is not even a first such thing, there cannot be another.
In nature, nothing. Even a ray of light is bent by gravity.
No. For example, the fraction 1/14 goes on forever when written as a decimal. (.0714285714285714285714285714285...)
There is no highest number. Even if the numbers end from sight, the arrows mean that it goes on forever.
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