Physicists often bring up the idea that traveling faster than the speed of light can cause time-travel paradoxes, which is why faster than light travel is important.
The speed of light is the only speed that's the same for all observers, making it the limit of the speed of information.
Misconceptions about the speed of light being a limit stem from Einstein's theory of Special Relativity.
Particles can travel at the speed of light without infinite energy if the Higgs field is condensed and they become massless.
The Higgs field slows down particles that have mass and its condensed form is Lorentz-scalar invariant.
Traveling faster than the speed of light can cause time-travel paradoxes.
Physicists have noticed time order reversal in relation to faster-than-light travel.
There are problems with the idea of faster-than-light travel, including the causality paradox and the fact that our current theory of space-time doesn't work with quantum theory.
We need a theory of quantum gravity to understand the possibilities of faster-than-light travel.
It's currently implausible that any argument about faster-than-light travel would survive in a theory of quantum gravity.
Intelligent life exists on other planets, but they haven't contacted us because we haven't figured out how to send information faster than light.
The idea that the speed of light is a limit comes from Albert Einstein's theory Special Relativity.
The speed of light is the only speed that's the same for all observers, and it's the same in vacuum.
Light moves away from an object with a speed of light, no matter how fast the object is moving.
It's impossible to catch up with light, and it has a consequence that you can't move faster than the speed of light.
The energy needed to accelerate an object to the speed of light is infinite, which means that only massless objects can move at the speed of light.
The speed of light plays a special role in Einstein's theory because it's the only speed that's the same for all observers, making it the limit of the speed of information.
Misconceptions About the Limit of the Speed of Light 00:38
The idea that the speed of light is a limit doesn't mean that faster than light travel is forbidden in Einstein's theory.
The theory is entirely compatible with faster-than-light travel.
The problem seems to be that you can't accelerate from below the speed of light to above the speed of light.
The idea that infinite energy is needed to reach the speed of light is suspect because we have a counterexample that proves otherwise.
Counterexample to the Claim that Infinite Energy is Needed 07:12
To understand the counterexample, you need to know where mass comes from.
Mass comes from the Higgs field, which is a field that permeates all of space and gives particles their mass.
The Higgs field is like molasses, and particles moving through it experience resistance, which is why they have mass.
But if the Higgs field had a different value, particles could move through it without experiencing resistance, and they would be massless.
In this case, they would also move at the speed of light, which means that massless particles don't need infinite energy to move at the speed of light.
Therefore, the claim that infinite energy is needed to reach the speed of light is incorrect.
Most of the mass in objects around us is not actually mass, but rather binding energy.
Almost all of the mass of an atom is in its nucleus, which is made up of neutrons and protons.
Neutrons and protons are each made up of three quarks, which do have mass, but when added together, the sum is far less than the mass of the neutron or proton.
Most of the mass of neutrons and protons comes from the strong nuclear force that holds them together, which we interpret as mass because of E=mc².
Microscopically, most of an object is not mass, and most of a person is made up of pure energy.
Electrons and quarks do have masses, but they are very small.
These masses come from the Higgs field, which is a field that fills the entire universe and drags on particles.
The Higgs field is not to be confused with the Higgs boson.
The Higgs field's condensed form is what gives fundamental particles mass.
In the early universe, particles did not have mass because the Higgs field was not condensed.
The Higgs field condensed when the universe cooled, and this phase transition called “electroweak symmetry breaking” happened about 10^-11 seconds after the Big Bang at a temperature of 10^15 Kelvin.
The energy released in this phase transition was finite, which is important because if it hadn't been, we wouldn't be here.
Physicists often bring up the idea that traveling faster than the speed of light can cause time-travel paradoxes.
The argument is that if Alice observes a spaceship going faster than the speed of light, then Bob, who is moving relative to Alice, would see the spaceship going back in time.
This is because Bob sees different events happening simultaneously due to his relative motion.
Time Order Reversal for Faster Than Light Travel 14:40
In special relativity, events that happen at equal times are on straight lines for Bob, not on horizontal lines.
Bob sees the order of events as egg first smashing to the ground and then gets dropped.
For Bob, the time order of faster than light ship is reversed.
The time travel argument is correct in special relativity, but it is not in general relativity.
Imagine that there is a spaceship that can go faster than light and according to you, it goes back in time.
If you send a message to your younger self not to watch this video, then you'd never have sent the message in the first place, so did you or didn't you watch it?
This type of construction is also called a time-like closed loop, and it's a loop in time.