4 ms·

"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

by nyc111 2y ago

"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.

deleted 2y ago
[deleted]
klodolph 2y ago
“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.
- nyc111 2y ago
  "'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?
  - tsimionescu 2y ago
    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.
    - etcd 2y ago
      What is our current speed?
      - ithkuil 2y ago
        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".
    - DHRicoF 2y ago
      > 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-speed-of-light/ https://bigthink.com/starts-with-a-bang/speed-limit-below-sp...
  - icehawk 2y ago
    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???
    - rbanffy 2y ago
      I’d need about 40 minutes.
antonvs 2y ago
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.
- nyc111 2y ago
  "Any massless particle must move at the speed of light" Does not change my argument. Human body is not a massless particle.
  - dcow 2y ago
    No, but it does betray your lack of formal exposure to the topic.
  - icehawk 2y ago
    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.
  - yarg 2y ago
    Read the formula: https://en.wikipedia.org/wiki/Lorentz_factor https://en.wikipedia.org/wiki/Lorentz_factor
  - rbanffy 2y ago
    Which means you can approach the speed of light, but never travel at this speed in space.
nyc111 2y ago
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?
- mftrhu 2y ago
  > 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.
- itishappy 2y ago
  Why don't you? Here's a calculator: https://gregsspacecalculations.blogspot.com/p/blog-page.html 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 https://en.wikipedia.org/wiki/File:Roundtriptimes.png
  - shiroiushi 2y ago
    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.
ndsipa_pomu 2y ago
> 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.
mr_toad 2y ago
> Saying "close to the speed of light" changes nothing. https://en.wikipedia.org/wiki/Oh-My-God_particle https://en.wikipedia.org/wiki/Oh-My-God_particle

by nyc111 2y ago

deleted 2y ago

[deleted]

klodolph 2y ago

“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.

nyc111 2y ago
"'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?
- tsimionescu 2y ago
  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.
  - etcd 2y ago
    What is our current speed?
    - ithkuil 2y ago
      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".
  - DHRicoF 2y ago
    > 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-speed-of-light/ https://bigthink.com/starts-with-a-bang/speed-limit-below-sp...
- icehawk 2y ago
  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???
  - rbanffy 2y ago
    I’d need about 40 minutes.

antonvs 2y ago

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.

nyc111 2y ago
"Any massless particle must move at the speed of light" Does not change my argument. Human body is not a massless particle.
- dcow 2y ago
  No, but it does betray your lack of formal exposure to the topic.
- icehawk 2y ago
  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.
- yarg 2y ago
  Read the formula: https://en.wikipedia.org/wiki/Lorentz_factor https://en.wikipedia.org/wiki/Lorentz_factor
- rbanffy 2y ago
  Which means you can approach the speed of light, but never travel at this speed in space.

nyc111 2y ago

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?

mftrhu 2y ago
> 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.
itishappy 2y ago
Why don't you? Here's a calculator: https://gregsspacecalculations.blogspot.com/p/blog-page.html 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 https://en.wikipedia.org/wiki/File:Roundtriptimes.png
- shiroiushi 2y ago
  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.

ndsipa_pomu 2y ago

> 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.

mr_toad 2y ago

> Saying "close to the speed of light" changes nothing. https://en.wikipedia.org/wiki/Oh-My-God_particle https://en.wikipedia.org/wiki/Oh-My-God_particle