Whether you ask trained physicists or the average lay person, the most widely known law of the universe is that objects cannot exceed the speed of light.
Even if someone doesn’t know precisely what the speed of light is (299,792,458 meters, or 983,571,056 feet, per second), they understand that it is extraordinarily fast and that nothing can go faster.
This universal speed limit introduces a lot of very difficult challenges.
For example, accurately studying the far reaches of the universe is impossible because anything we can see through telescopes is already millions, or billions, of years in the past.
Also, while we dream of being able to travel to distant stars, the speed of light makes that very impractical since it would take generations to get there.
Of course, sci-fi writers and scientists alike are always looking for ways around the speed of light, including things like warp drives.
Some people, however, have suggested that there are simple things that dramatically exceed the speed of light around us all the time.
One common way that this can be illustrated is by using a shadow.
If you take a flashlight and shine it on the wall, then run your finger over the front of the light, you will see the shadow travel across the wall.
The further you are from the wall (assuming your flashlight is bring enough) the further the shadow will have to go to get from one end to the other.
What happens if you shine a very bright light onto the moon and repeat the experiment?
If it took you a fraction of a second to move your finger across the flashlight, your shadow on the moon would take a fraction of a second to travel across the surface of the moon.
By continuing to scale this up, it is easy to see how it would make the shadow appear to travel much faster than the speed of light.
The problem with this theory, however, is that it is nothing more than an illusion.
The shadow is not moving, but instead it is the photons of light that are being interrupted.
You can repeat this type of experiment using a light, however. If you have a powerful laser and wave it across the roof of a massive dome that is 1 light year away, once it reached that dome it would appear to travel much faster than the speed of light.
Michio Kaku is an astrophysicist and explained what is happening on Big Think:
“Just the image of the beam as it races across the night sky is moving faster than light, but there is no message, no net information, no material object that actually moves along this image.”
While it looks like the laser is moving, it is actually just separate photons of light that were sent out from different origins that are reaching the dome at different times.
So, it seems that the speed limit of the universe is still safe. For now.
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