The Tricky Illusion That Looks Faster Than Light
There are some things that look like they’re moving faster than light when we view them through a telescope. How is this possible?
Nothing can travel faster than light. This is an innate law of the universe which can never be broken. But if you’re not careful when looking through a telescope, you could be fooled into thinking that this universal law is being violated.
Take a look at this image on the left. It’s a series of observations made by the National Radio Astronomy Observatory (NRAO) in the 1990s, a jet of hot gas being fired from a quasar. In this image, you can see one green blob of gas moving over about a six-year period. The scale on the bottom indicates that the green blob traveled about 35 light-years over those six years.
How is this possible? The theory of relativity clearly prohibits moving faster than light, and yet here is an image of a gas jet doing exactly that. Maybe the bottom scale is wrong? Nope. We know how far away the galaxy is and we can calculate these distances very accurately.
It turns out that this image is a type of optical illusion arising from the fact that space is 3-dimensional, while our images are not. The gas jet in the photo is actually not headed sideways like it appears. Instead, it’s headed almost directly toward us.
In this video by Sixty Symbols, Professor Mike Merrifield looks at another example of this phenomenon:
Source:http://www.popularmechanics.com/space/deep-space/a26355/apparent-superliminal-motion/