Einstein
once called the speed of light “The Universe’s speed limit”. He claimed that
traveling faster than the speed of light would violate the causality principle.
For the layman, that means cause and effect. An example of this would be a
bullet hitting a target before the trigger was even pulled.

Accelerating
to light speed or exceeding it would also violate certain fundamental energy
conditions. It could even allow for time travel.
So why can’t
anything go faster than the speed of light?
Before we
can dive into that, we have to know what the speed of light actually is, what
it means, and clear up some common misconceptions regarding this “universal
speed limit“.
The speed of
light, (or the speed of a photon) in a near-perfect vacuum is exactly 186,282
miles per second. We perceive photons (light) traveling at this speed because
they are massless, or have no ‘weight’ (but they do have kinetic energy, more
on that in a bit).
Every
particle in our universe (including photons) moves or ‘swims’ through what
scientists call “the Higgs field”. As a result of this interaction, particles
acquire their mass. Different particles interact with the Higgs field with
different strengths, which is why some particles are heavier (have more mass)
than others. Photons move through but do not interact at all with the Higgs
field.

Universal
speed limit: Since photons don’t
interact with the Higgs field, it means they aren’t bound by any speed limit.
They’re free to move at the fastest possible speed – their own “light” speed.
Why isn’t the speed of light slower or faster than 186,282 miles per second?
It’s because that exact speed is a fundamental constant of our universe.
Wondering
why light doesn’t travel at a different speed is like wondering why gravity
isn’t reversed or what it would be like if our universe only had 2 spatial
dimensions instead of 3 (4 if you include time). Those constants, along with
the speed of light, were set in place when our universe was created at the
moment of the big bang.
Particles
that have mass require energy to accelerate them. The closer to the speed of
light you get a particle; the more energy is required to go faster. This is
because the particles themselves get more massive in proportion to the
increased velocity. In short, the faster you go, the heavier you get.
Thanks to
this inconvenient truth, if you wanted to accelerate a single electron to
‘light speed’, you would need an infinite amount of energy due to the electron
becoming infinitely heavy. There isn’t enough energy in the entire universe to
propel just a single electron to the speed of light.
One of the
methods Einstein used to help formulate his theory of special relativity was to
visualize what the universe would look like from the perspective of a photon.
Einstein saw that life as a photon would be quite bizarre. For instance, if you
were a photon, time would have no meaning to you. Everything would appear to
happen instantaneously.

Spark of Photons:
Imagine for a moment that you are a happy little photon created by a star in
another galaxy some 4 billion light-years away. From my perspective here on
Earth, it took you exactly 4 billion years to travel from that star until you
reached my retina. From your perspective, one instant you were created and then
the next, you are bouncing off or being absorbed by my eyeball. You experienced
no passage of time. Your birth and death happened instantaneously.
This is
because time slows for you as you get closer to light speed, and at it, it
completely stops. This is also another reason why nothing can go faster than
light. It would be like slowing down a car to a stop and then trying to go
slower than completely stopped.
One should
think of the speed of light as ‘infinite speed’. A common misconception is
thinking the speed of light is just like any other finite speed. The speed of
light is only finite from the perspective of the outside observer; from the
perspective of a photon, it’s infinite. If you move at exactly the speed of
light you could go anywhere, no matter how far, in exactly zero seconds.

There is at
least one real-world example of superluminal (faster than light) travel. It’s
cheating a bit, but it occurs when light passes through water.
Remember,
nothing can go faster than 186,282 miles per second, but the photons that
normally travel at that speed can be slowed down. An example of this can be
seen in water where light is slowed to 3/4th of its normal speed.
In nuclear
reactors, the charged particles emitted off radioactive rods through the water
they are submerged in exceed this reduced speed.
Because the
particles contain an electric charge, they emit energy called Cherenkov
radiation. Any particles they bump into becoming radioactive, giving the water
an eerie, mysterious blue glow.

It’s an
interesting question that many people may not think about. Does gravity also
have a speed and if so, what is it?
Speed of
gravity: Gravity does, in fact, have a
speed. The speed of gravity is technically the same as the speed of light.
The reason for this speed is the same reason why light travels at the speed it does. It’s simply a fundamental property of spacetime itself. If the Sun were to disappear right this instant, the earth would continue its orbit for 8 minutes (the time it takes light to reach Earth from the Sun) before the orbit would be perturbed by the Sun’s absence.
The reason for this speed is the same reason why light travels at the speed it does. It’s simply a fundamental property of spacetime itself. If the Sun were to disappear right this instant, the earth would continue its orbit for 8 minutes (the time it takes light to reach Earth from the Sun) before the orbit would be perturbed by the Sun’s absence.
So to sum
up, nothing can travel faster than light because the speed of light can be
thought of as infinite speed. To match or exceed it would be to go infinity
miles per second/hour. A loop-hole does, in fact, exist, however. The loop-hole
requires a control or warping of the fabric of spacetime itself which we’ve
touched on in a previous article. (See: “Why aren’t we exploring the galaxy
yet?” and “What is a warp drive?“)
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