28
PHYSICS OF THE IMPOSSIBLE
arrays, but in sophisticated patterns so that light would bend smoothly
around an object.
Next, scientists will have to create metamaterials that can bend
light in three dimensions, not just for flat two-dimensional surfaces.
Photolithography has been perfected for making flat silicon wafers, but
creating three-dimensional metamaterials will require stacking wafers
in a complex fashion.
After that, scientists will have to solve the problem of creating
metamaterials that can bend not just one frequency but many. This
will be perhaps the most difficult task, since the tiny implants that have
been devised so far bend light of only one precise frequency. Scientists
may have to create metamaterials based on layers, with each layer
bending a specific frequency. The solution to this problem is not clear.
Nevertheless, once an invisibility shield is finally made, it might be
a clunky device. Harry Potter's cloak was made of thin, flexible cloth
and rendered anyone draped inside invisible. But for this to be possible the index of refraction inside the cloth would have to be constantly
changing in complex ways as it fluttered, which is impractical. More
than likely a true invisibility "cloak" would have to be made of a solid
cylinder of metamaterials, at least initially. That way the index of refraction could be fixed inside the cylinder. (More advanced versions
could eventually incorporate metamaterials that are flexible and can
twist and still make light flow within the metamaterials on the correct
path. In this way, anyone inside the cloak would have some flexibility
of movement.)
Some have pointed out a flaw in the invisibility shield: anyone inside would not be able to look outside without becoming visible. Imagine Harry Potter being totally invisible except for his eyes, which
appear to be floating in midair. Any eye holes on the invisibility cloak
would be clearly visible from the outside. If Harry Potter were totally
invisible, then he would be sitting blindly beneath his invisibility
cloak. (One possible solution to this problem might be to insert two
tiny glass plates near the location of the eye holes. These glass plates
would act as "beam splitters," splitting off a tiny portion of the light hitting the plates, and then sending the light into the eyes. So most of the
PHYSICS OF THE IMPOSSIBLE
arrays, but in sophisticated patterns so that light would bend smoothly
around an object.
Next, scientists will have to create metamaterials that can bend
light in three dimensions, not just for flat two-dimensional surfaces.
Photolithography has been perfected for making flat silicon wafers, but
creating three-dimensional metamaterials will require stacking wafers
in a complex fashion.
After that, scientists will have to solve the problem of creating
metamaterials that can bend not just one frequency but many. This
will be perhaps the most difficult task, since the tiny implants that have
been devised so far bend light of only one precise frequency. Scientists
may have to create metamaterials based on layers, with each layer
bending a specific frequency. The solution to this problem is not clear.
Nevertheless, once an invisibility shield is finally made, it might be
a clunky device. Harry Potter's cloak was made of thin, flexible cloth
and rendered anyone draped inside invisible. But for this to be possible the index of refraction inside the cloth would have to be constantly
changing in complex ways as it fluttered, which is impractical. More
than likely a true invisibility "cloak" would have to be made of a solid
cylinder of metamaterials, at least initially. That way the index of refraction could be fixed inside the cylinder. (More advanced versions
could eventually incorporate metamaterials that are flexible and can
twist and still make light flow within the metamaterials on the correct
path. In this way, anyone inside the cloak would have some flexibility
of movement.)
Some have pointed out a flaw in the invisibility shield: anyone inside would not be able to look outside without becoming visible. Imagine Harry Potter being totally invisible except for his eyes, which
appear to be floating in midair. Any eye holes on the invisibility cloak
would be clearly visible from the outside. If Harry Potter were totally
invisible, then he would be sitting blindly beneath his invisibility
cloak. (One possible solution to this problem might be to insert two
tiny glass plates near the location of the eye holes. These glass plates
would act as "beam splitters," splitting off a tiny portion of the light hitting the plates, and then sending the light into the eyes. So most of the