Editing 1125: Objects In Mirror

{{comic
| number    = 1125
| date      = October 24, 2012
| title     = Objects In Mirror
| image     = objects_in_mirror.png
| titletext = Universes in mirror, like those in windshield, are larger than they appear.
}}

==Explanation==
"Objects in mirror are closer than they appear" is a required, although marginally ridiculous, "safety warning" required to be engraved on passenger side mirrors of motor vehicles in the USA, Canada and Korea. These mirrors in these countries are typically the only ones that are slightly convex, making objects appear smaller (and farther away) than their true size. Other countries often have convexity in driver-side and passenger-side rearview mirrors to give a larger field of view, at the cost of natural distance proportions of the mirror image, without making any statements about it on the mirror itself using engravings.

This comic is a reference to the phenomena known as {{w|redshift}}/{{w|blueshift}}. Due to the {{w|Doppler effect}}, objects that are moving toward an observer appear bluer than they actually are (known as blueshift). Objects moving away from the observer (e.g. objects viewed in the rear-view mirror of a moving vehicle) appear redder than they actually are (known as redshift), and thus the objects are in reality bluer than they appear. This is generally relevant only in terms of high speed motion such as observation of the expansion of the universe in astrophysics. The joke is that the relative speed of any object visible in a side-view mirror would create an insignificant and unobservable redshift.

Another possible explanation is that the redshift refers to the actual reflection itself.
As photons are reflected in a mirror, momentum is transferred and thereby they lose a very small amount of energy. This loss of energy results in a slight redshift of the light. (This effect is similar to {{w|compton scattering}})


Edwin Hubble was an astronomer credited ({{w|Stigler's law of eponymy|amid some controversy}}) with "{{w|Hubble's Law}}," which states that a Doppler shift can be observed for objects in deep space moving with relative velocity to Earth and that their velocity is proportional to their distance from Earth. Probably the most famous application of the law was measurement of relative velocities of galaxies, such as those seen in the picture known as {{w|Hubble Deep Field}}, taken by the {{w|Hubble Space Telescope}}. The results proved that most galaxies keep getting farther apart as a result of expansion of the universe. This is one of many pieces of evidence supporting the {{w|Big Bang}} theory.

The title text references that we see the universe as it was in the past (due to the distances involved and the speed of light), when it was smaller than it is today. It may also be a reference to comic [[1110: Click and Drag]].

== Transcript ==
:[View of a car mirror and outside view of landscape, with clouds and mountains. The mirror reads "Objects in mirror are bluer than they appear."]
:Edwin Hubble's car

{{comic discussion}}
[[Category:Cosmology]]
[[Category:Physics]]
[[Category:Comics with color]]