Google Earth In 4D

Rockgod writes to tell us about Google Earth's latest expansion. From the article: "Google skipped right past the third dimension and landed directly in the fourth (time) by offering historical maps on Google Earth. Now you can travel back in time — for example, I am looking at the globe of 1790. Don't expect detailed high resolution photography from days gone by, but it's still interesting to see old maps overlaid on the satellite imagery of today." I suppose a link to Earth4 would have been good.

Comments

Pangea?

[Ingolfke]

Where's pangea? Come on Google... get with the program.

Re:If it's not spatial it's not 4D

[chrisb33]

While I agree that 4D is being used more as a buzzword than anything else, time is in fact considered as a fourth dimension in physics. You can look at special relativity if you want to understand how time and the spatial dimensions can be "interchanged":

In the geometry of special relativity, a fourth dimension, time, is added, with units of c, so that the equation for the differential of distance becomes:
ds^2 = dx_1^2 + dx_2^2 + dx_3^2 - c^2 dt^2
If we wished to make the time coordinate look like the space coordinates, we could treat time as imaginary: x4 = ict . In this case the above equation becomes symmetric:
ds^2 = dx_1^2 + dx_2^2 + dx_3^2 + dx_4^2

Special relativity goes on to say that you can exchange time and spatial coordinates using the Lorentz transform, which preserves the length of the 4D position vector.

If the special relativity example seems too bizarre, just think in terms of locating an event. If I wanted you to come to my party, I would tell you 4 pieces of info - the x,y,z, and t coordinates of the party. Each of these degrees of freedom is a dimension.


What's much more annoying to me are the "4D" shows that are 3D plus some user interaction (getting water shot at you or something like this). That is a misuse of "4D".