I’m wondering if interstellar travel is possible. So I guess the starting point is figuring out FTL travel.
In: 1302
The heavier something is (or “the more mass something has”), the harder it is to make it move. It’s easy to move a marble but tough to move a boulder, right?
Light has *no mass*. This means that it moves as fast as is possible. Anything else with 0 mass would also move as fast as possible; there’s nothing specifically special about light here.
This also means that anything with mass – any amount of mass, at all – *can’t* move as quickly as light, because its own mass slows it down.
People are talking a lot about causality. I like to think about the speed of light as the exchange rate between time and space. If you Max out your speed in space, you stop moving in time. If you were to go faster, then you would be in negative time and causality would break down.
It is not possible. Are you talking about for humans or for any particles? Unfortunately, despite science fiction, light speed will never happen. Why? Think of the speed of light as a universal “speed limit.” Matter cannot move faster than the speed of light because of the laws of the universe. Beyond your technological hold backs, light does not move through time. The faster you go through space, the slower through time you move. Time does not exist at the speed of light, because to light it is instantaneously at it’s starting point and ending point. If you have the ability to go faster than the speed of light, you have essentially created time travel, and will reverse time.
IF we were able to travel at the speed of light it would take 63,000 years to reach the nearest planet not in our solar system. So not very useful regardless. The only way to make interstellar travel doable is through a wormhole. We’d have to be lucky enough for one to be placed close enough to travel though. The movie interstellar is all about this. Unfortunately, since we are bound by our 3 dimensions (technically 4 with time) we can’t create a wormhole. Only something from a higher dimension can do this and create this passage for us. And that’s never happened before but hey crossing my fingers
You cannot travel faster than light because light moves at the speed of causality.
The speed of causality is the basis of time itself; if something could move faster than it, then things could happen before the thing that caused them to happen, happened.
*Why* the universe is this way is a much harder question, possibly even the greatest question in human history, because at this point we’re talking about the bare fundamentals of reality itself
I find it useful to remind myself that the “speed of light” is a bit of a misnomer. We should use “speed of causality”. We have yet to observe anything happening faster than that speed, denoted *c*. Its just that light is a very common thing that moves at the speed of causality, so we started calling it that, but plenty of other things move at that speed as well (gravity, information, anything with zero mass).
Everything would like to traveling at the speed of causality, but having mass slows us down. That is what mass is.
Next time you are at a cocktail party, find a physicist and get drunk with them. I find that they don’t bs you and pretend to know things. They just admit that we don’t really know why all the rules change at the quantum level. That we don’t know if the universe is made out of discreet smallest units like atoms, or if it is turtles all the way down, or a complete analog soup. We don’t know why light sometimes acts as a particle, and other times like a wave. And….it seems to act differently if we are watching it? WTF? ([https://en.wikipedia.org/wiki/Double-slit_experiment](https://en.wikipedia.org/wiki/Double-slit_experiment))
Future generations of humans will look back on us, and pity our ignorance the same way we look back on the ignorance of ancient peoples.
Are there more than 3 spatial dimensions? Is it possible to harness gravity itself and use it as a propulsion mechanism? WTF is dark matter? What is outside the simulation? Are only living things conscious or can the universe sense itself? Uhhh, what is consciousness anyway?
Tachyons are the least of our curiosities.
For the same reason squarer-than-square shapes are impossible. A square is already as square as it gets (4 equal sides, 4 90 degree angles). The speed of light ultimately comes from the *geometry* of the universe, and while getting into the weeds on that is well beyond ELI5, I hope this little example helps show why it’s actually a nonsense question.
The speed limit of the universe is causality, not light. In other words, the “speed of light” is the maximum speed that Event A can impact Event B. For example: if the sun suddenly stops existing, it would take 8.3 minutes for Earth to notice in terms of things like gravity and light. The event has to propagate through time and space, and the maximum speed at which it can do this is 299,792,458 metres per second, aka the “speed of light”.
Photons (light) aren’t restricted by mass, so they will zip around at the maximum speed of causality.
Since the “speed of light” is the maximum speed an event can propagate through time and space, you can’t travel between the sun and the Earth in less than 8.3 minutes, because that means you would arrive before causality catches up.
Faster than light travel is NOT impossible thanks to time dilation. What’s impossible is for observers to see you moving faster than light.
For example if you moved exactly the speed of light and traveled to a star that is 100 light years away and back the trip for you would be INSTANT, because at the speed of light the time stops completely!
But when you get back to Earth you find that while for you were away just a second 200 years passed on Earth.
This also means that time machines are only half impossible. You can go forward, but can’t go back.
edit: There is still one “small” problem of actually surviving the acceleration, needing infinite energy and having infinite mass while traveling at the speed of light.
This is limit of our universe. Just like we can’t make 361° circle we can’t travel faster than light.
Scientifically going faster than light means you will have a hard time seeing the road, then you might swerve into the opposing lane causing an unsafe environment on the space-highway
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