Time is a dimension, but not like space

"This is the underlying reason why, when you move at speeds that approach the speed of light, you start to experience phenomena such as time dilation and length contraction:"

This is not even possible in pulp science fiction. In order to be able to move with the speed of light you need to transform yourself into a photon. Only a photon can move with the speed of light. Saying "close to the speed of light" changes nothing. You need to be light to move with the speed close to the speed of light. Macroscopic objects cannot move with speeds approaching light speed.

“Close to the speed of light” means, like, 99% of the speed of light. You can even see the speeds listed on the graphs, which are given as a fraction of c.

You might want to look up the word “approach” in a dictionary.

> Only a photon can move with the speed of light.

Any massless particle must move at the speed of light. Gluons, the carrier of the strong force, are another example.

"Any massless particle must move at the speed of light"

Does not change my argument. Human body is not a massless particle.

"'Close to the speed of light' means, like, 99% of the speed of light"

So, you are saying that it is possible to accelerate human body to 99% of speed of light without transforming the body into a massless particle?

Yes.

It will never be possible to get to 100%, but I principle anything below that is possible. Not just 99%, but 99.99999999% or however many you want.

Of course, it's not actually feasible, you would need galaxies worth of energy to do so.

But for something like 10% or even 50% of the speed of light, it's not even that implausible.

No, but it does betray your lack of formal exposure to the topic.

And it can't move at the speed of light. It can approach the speed of light which isn't the same thing as moving at it.

Yes.

Gven the average mass of a human body at 66kg: (((1/sqrt(1-((0.99c)^2/c^2)))--1) 66kg * c^2) = 50,000PJ

which is the amount of electrical energy the entire US produces in 0.287h???

Read the formula: https://en.wikipedia.org/wiki/Lorentz_factor

What is our current speed?

Our current speed is 99.999999% the speed of light, according to some frame of reference, 10% according to another frame of reference and 0% according to another.

A lot of work is done by the words "get to" which is colloquial for "accelerate".

I guess you guys found a way to accelerate human body to the speed of light without disintegrating. Why don't you prove your technique first with G-forces?

> accelerate human body to the speed of light

Nothing with mass can have the same speed as light, but you can trivially accelerate a human body - or something similar - to a speed which is arbitrarily close to it, without risking anything from the G-forces involved.

You just need to do it very slowly.

That is, in any case, neither here nor there, since this is a thought experiment used in a discussion about the effects of moving at a speed close to c - people in thought experiments are stronk.

Which means you can approach the speed of light, but never travel at this speed in space.

I’d need about 40 minutes.

> Not just 99%, but 99.99999999% or however many you want.

Badly enough, even that's not true.

We have a frame of reference given by the cosmic microwave background. When you move faster and faster at some limiting speed will create pions that will slow down the particle creating an effective slower max speed.

https://bigthink.com/starts-with-a-bang/speed-limit-below-sp...

> This is not even possible in pulp science fiction

Incorrect - anything is possible in pulp scifi.

> In order to be able to move with the speed of light you need to transform yourself into a photon. Only a photon can move with the speed of light.

Incorrect - any massless particle will move at the same speed as light.

> Saying "close to the speed of light" changes nothing. You need to be light to move with the speed close to the speed of light.

Incorrect - it's perfectly feasible to accelerate particles to over 99% of the speed of light. e.g. the LHC can accelerate protons to 0.999999990 c. Also, it's not possible for massless particles including photons to move at anything other than the speed of light in a vacuum, so "close to the speed of light" is not possible unless the object has mass.

> Macroscopic objects cannot move with speeds approaching light speed.

Incorrect, though humans haven't been able to accelerate macroscopic (e.g. visible to human eye) objects to more than approx 0.064c (Parker Solar Probe), it's just a question of using enough power to accelerate the relevant object. There's no reason to think that a black hole accretion disk couldn't easily accelerate a lump of matter to more than 0.99c.

Why don't you? Here's a calculator:

https://gregsspacecalculations.blogspot.com/p/blog-page.html

1G of acceleration (which I'd hope you agree is survivable by humans) over an extended time period can easily reach relativistic speeds.

    1 day   .0028c
    1 week  .02c
    1 month .086c
    1 year  .77c
    2 years .97c
    3 years .996c
    4 years .9995c
    5 years .9999c

The thing stopping us from doing this today is economics, not physics. Current rockets have about enough fuel for minutes of acceleration, and fuel requirements increase exponentially due to the tyranny of the rocket equation. If you skip the need for fuel (laser propulsion?) and find some way to decelerate (laser cooling propulsion???), then interstellar travel to pretty much anywhere becomes entirely reasonable within human lifespans.

https://en.wikipedia.org/wiki/File:Roundtriptimes.png

> Saying "close to the speed of light" changes nothing.

https://en.wikipedia.org/wiki/Oh-My-God_particle

I think you're handwaving away the other issues with physics that make near-lightspeed travel effectively impossible for humans. How exactly do you propose sustaining 1g acceleration for 5 years, for instance? You can't just "skip the need for fuel". Lasers aren't perfectly collimated and spread out over distance. Even an Epstein drive from The Expanse will eventually run out of fuel. The other big problem is: how exactly do you deal with collisions with space debris? Even at the speeds we currently travel, micrometeorites are a problem, but at 0.9999c, even stray hydrogen atoms (which deep space is full of) are going to destroy your ship.

Honestly, Star Trek way back in the 1960s was pretty brilliant at getting around many of these technical problems by inventing "warp drive".

Even if we somehow magically solved our economic problems overnight, that isn't going to make relativistic speeds feasible for humans anytime soon, if ever.

I'm definitely handwaving away the difficulty, but I did explicitly speak to these concerns.

We really can skip the need for fuel, for example. Sails (with or without lasers) are a technology we have proven in the field. Lasers do lose collimation over distance, but you can reach relativistic speeds before then (I'd argue that .02c from 1wk of 1G is relativistic). That won't get you to the center of the galaxy (or solve the deceleration issue), but there are proposals being reviewed today to use lasers to send probes for a flyby of Proxima Centauri.

https://www.nasa.gov/general/swarming-proxima-centauri/

https://en.wikipedia.org/wiki/Breakthrough_Starshot

But we don't need science fiction tech for this to work, we just need impractical amounts of fuel. Starship only has enough fuel to last 10m? Just send 50k starships and you can burn for a year. Tyranny of the rocket equation requires additional fuel to push all that fuel? Just send another billion Starships or whatever. Going too fast and now the interstellar medium hits like high-energy cosmic rays? Just send more shielding and fuel. This assumes we can build and fuel billions of Starships, which is certainly infeasible, but I'm calling this an economics issue as we have these technologies today.

If we want to get really sci-fi, I'd point you towards stellar engines. The thought process here is that the Earth already provides radiation shielding, and the Sun already burns fuel to provide massive amounts of energy, so we might as well just make use of what we got! Add mirrors to concentrate the Sun's light in one direction, and our entire solar system becomes an interstellar spaceship. It might take millions or even billions of years, but the Sun has enough fuel to accelerate the whole system to about .27c.

https://en.wikipedia.org/wiki/Stellar_engine