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The universe is expanding, at a rate which I believe is heading past the speed of light. This limits our ability to reach galaxies further away from us as they

The universe is expanding, at a rate which I believe is heading past the speed of light. This limits our ability to reach galaxies further away from us as they are speeding away faster than we could conceivably travel since our engines would of course be bound by the speed of light. Some more info: https://www.forbes.com/sites/startswithabang/2016/06/10/can-the-universe-expand-faster-than-the-speed-of-light/#64e0a9473605 https://www.forbes.com/sites/startswithabang/2016/06/10/can-...

chongli 7y ago
That’s the case for the galaxies furthest away from us. Closer galaxies are receding less quickly and Andromeda is actually coming towards us.
- lioeters 7y ago
  Indeed, and will merge with ours to become..the Milkdromeda (TBD) galaxy. Looking forward to the fireworks. https://en.wikipedia.org/wiki/Andromeda%E2%80%93Milky_Way_collision https://en.wikipedia.org/wiki/Andromeda%E2%80%93Milky_Way_co...
  - cobbzilla 7y ago
    Humans (assuming we are still around) will have to watch from another planet: the collision will happen in ~4.5 billion years [1], and Earth will be uninhabitable long before then [2]. [1] https://en.wikipedia.org/wiki/Andromeda%E2%80%93Milky_Way_collision https://en.wikipedia.org/wiki/Andromeda%E2%80%93Milky_Way_co... [2] https://en.wikipedia.org/wiki/Timeline_of_the_far_future#Future_of_the_Earth,_the_Solar_System_and_the_universe https://en.wikipedia.org/wiki/Timeline_of_the_far_future#Fut...
    - saagarjha 7y ago
      Plus it’ll take quite a while to complete.
    - chongli 7y ago
      If we can figure out how to solve our political issues and become a eusocial species, we may be able to build some generational starships. In 4.5 billion years we could potentially colonize many of the planets in the habitable zone of stars in the Milky Way. Sure, it could take millions of years to cross the galaxy, but we could grow exponentially (like lily pads crossing a pond), at least until other limiting factors kick in.
    - lioeters 7y ago
      That second link I'd read through before, but oh my, you're right there's a number of critical events ahead: an ice age around 50k years from now; in ~300mil years (oh cool never noticed this before), "All the continents on Earth may fuse into a supercontinent"..resulting in another glacial age; in 700 mil years, "The death of most plant life".. Also realized, there won't be much "fireworks", since apparently the stars are far enough apart that the merging of two galaxies won't cause much collision. Still fun to imagine things on that scale, especially in light of some of NASA's beautiful photos of colliding galaxies (like https://www.nasa.gov/image-feature/goddard/2019/hubble-s-dazzling-display-of-2-colliding-galaxies https://www.nasa.gov/image-feature/goddard/2019/hubble-s-daz...).
hunter2_ 7y ago
Why would some things be bound by the speed of light and not others? I always thought of this limitation as an all-or-nothing law.
- ajuc 7y ago
  Everything that moves is bound by the speed of light. But when you create space between 2 points they can appear to move faster than the speed of light, despite not actually moving - it's just that there's new space created between them, so the distance between them grows faster than the speed of light.
- michelpp 7y ago
  Everything that moves through space is bound by the speed of light. But space itself is expanding at a rate such that two distant points can move away from each other faster than the speed of light. Think of it like two ants on opposite sides of a balloon, one ant starts moving toward the other as fast as it can go, but then you start to inflate the balloon. The distance between the two ants expands faster than an ant can move and they'll never meet.
  - rpq 7y ago
    Thanks for this clarification.
  - troubler 7y ago
    So, we can calculate speed of Earth relatively to our segment of space, right? Can you do the calculation and tell us speed of Ether Wind, please?
- lordnacho 7y ago
  Not an expert but the speed of light limitation seems to be derived from special relativity considerations the constancy of that speed and the use of light to carry information about events. So a train cannot accelerate to beyond c because of this. But not every phenomenon is limited by this. As an example if you shine a torch at a really far away rock the dot can move faster than c transversally when you wiggle the torch. But the actual light is going at c to the rock and back to you.

chongli 7y ago

That’s the case for the galaxies furthest away from us. Closer galaxies are receding less quickly and Andromeda is actually coming towards us.

lioeters 7y ago
Indeed, and will merge with ours to become..the Milkdromeda (TBD) galaxy. Looking forward to the fireworks. https://en.wikipedia.org/wiki/Andromeda%E2%80%93Milky_Way_collision https://en.wikipedia.org/wiki/Andromeda%E2%80%93Milky_Way_co...
- cobbzilla 7y ago
  Humans (assuming we are still around) will have to watch from another planet: the collision will happen in ~4.5 billion years [1], and Earth will be uninhabitable long before then [2]. [1] https://en.wikipedia.org/wiki/Andromeda%E2%80%93Milky_Way_collision https://en.wikipedia.org/wiki/Andromeda%E2%80%93Milky_Way_co... [2] https://en.wikipedia.org/wiki/Timeline_of_the_far_future#Future_of_the_Earth,_the_Solar_System_and_the_universe https://en.wikipedia.org/wiki/Timeline_of_the_far_future#Fut...
  - saagarjha 7y ago
    Plus it’ll take quite a while to complete.
  - chongli 7y ago
    If we can figure out how to solve our political issues and become a eusocial species, we may be able to build some generational starships. In 4.5 billion years we could potentially colonize many of the planets in the habitable zone of stars in the Milky Way. Sure, it could take millions of years to cross the galaxy, but we could grow exponentially (like lily pads crossing a pond), at least until other limiting factors kick in.
  - lioeters 7y ago
    That second link I'd read through before, but oh my, you're right there's a number of critical events ahead: an ice age around 50k years from now; in ~300mil years (oh cool never noticed this before), "All the continents on Earth may fuse into a supercontinent"..resulting in another glacial age; in 700 mil years, "The death of most plant life".. Also realized, there won't be much "fireworks", since apparently the stars are far enough apart that the merging of two galaxies won't cause much collision. Still fun to imagine things on that scale, especially in light of some of NASA's beautiful photos of colliding galaxies (like https://www.nasa.gov/image-feature/goddard/2019/hubble-s-dazzling-display-of-2-colliding-galaxies https://www.nasa.gov/image-feature/goddard/2019/hubble-s-daz...).

hunter2_ 7y ago

Why would some things be bound by the speed of light and not others? I always thought of this limitation as an all-or-nothing law.

ajuc 7y ago
Everything that moves is bound by the speed of light. But when you create space between 2 points they can appear to move faster than the speed of light, despite not actually moving - it's just that there's new space created between them, so the distance between them grows faster than the speed of light.
michelpp 7y ago
Everything that moves through space is bound by the speed of light. But space itself is expanding at a rate such that two distant points can move away from each other faster than the speed of light. Think of it like two ants on opposite sides of a balloon, one ant starts moving toward the other as fast as it can go, but then you start to inflate the balloon. The distance between the two ants expands faster than an ant can move and they'll never meet.
- rpq 7y ago
  Thanks for this clarification.
- troubler 7y ago
  So, we can calculate speed of Earth relatively to our segment of space, right? Can you do the calculation and tell us speed of Ether Wind, please?
lordnacho 7y ago
Not an expert but the speed of light limitation seems to be derived from special relativity considerations the constancy of that speed and the use of light to carry information about events. So a train cannot accelerate to beyond c because of this. But not every phenomenon is limited by this. As an example if you shine a torch at a really far away rock the dot can move faster than c transversally when you wiggle the torch. But the actual light is going at c to the rock and back to you.