The LightCone in the "3D"

[neutrino]

How does the light"cone" appear if we include the 3rd dimension of space into the picture?

[selfAdjoint]

As a sphere growing from a point at present in both forward and backward time. The "cone" with a 3-D cross section is now a 4-D object, and you can't embed it in 3-space. That's why we do the 2-D cross section in diagrams.

[HallsofIvy]

What do you mean by "appear"? You can't draw 4 dimensions in 3 dimensional space so you can't "see" it in that sense.

[thomate1]

As we can project the an 3D image on a sheet of paper, can we project a 4D object to the 3D world, not atleast to a sheet of paper. I have heard that George Gamow gave some notes about that in his book 1,2,3 infinity