5 ms·

lfuller is right. For example, if you have a ship capable of continuous acceleration at 1g, you can reach any point in the universe on the order of ~50 years.

ikeboy 12y ago
Can you continuously accelerate at g for 50 years without going over the speed of light? According to wolfram alpha http://www.wolframalpha.com/input/?i=speed+of+light%2Flittle+g http://www.wolframalpha.com/input/?i=speed+of+light%2Flittle... it would take a year to get to the speed of light at 1g (if my equation was right.) Then you can't speed up anymore.
- pdonis 12y ago
  > it would take a year to get to the speed of light at 1g (if my equation was right.) It isn't. Wolfram Alpha apparently doesn't know about the relativistic rocket equation. Try here: http://math.ucr.edu/home/baez/physics/Relativity/SR/rocket.html http://math.ucr.edu/home/baez/physics/Relativity/SR/rocket.h...
- gizmo686 12y ago
  Your equation is correct in a Newtonian universe, but does not consider relativistic effects. Generally when we talk about an object's acceleration, we are talking about its acceleration in its own reference frame. By definition, an object's velocity in its own reference frame is always 0, so acceleration does not become more difficult (ignoring the fact that the surrounding matter will be impacting you at higher speeds). From the perspective of an outside observer who is not accelerating, time would appear to slow down on the accelerating object, and the outside observer would record a decreasing acceleration.
  - readerrrr 12y ago
    Fun fact, from the perspective of the observer on the ship, time outside the ship would also appear to slow down.
  - ikeboy 12y ago
    So why is it difficult to maintain a constant acceleration? Is 1g really that impractical right now?
    - snowwrestler 12y ago
      I'm being accelerated at 1g right now and I'm about 40...so in another decade or so I should be able to get to anywhere in the universe! Jokes aside, there's no fuel source we know of that would allow a ship to accelerate continuously for 50 years at 1g.
    - gizmo686 12y ago
      1) Maintaining an acceleration requires fuel. 2) Even though you don't observe yourself moving at increasing speeds, you do observe the rest of the universe moving at increasing speeds. This means that small particles impacting your ship will hit it with increasing energy.
- readerrrr 12y ago
  After a year of acceleration at 1g, a stationary observer would observe a speed of 215184620 m/s or 71.7% the speed of light. After two years: 89.9% After four years: 97.2% After eight years: 99.3%

ikeboy 12y ago

Can you continuously accelerate at g for 50 years without going over the speed of light? According to wolfram alpha http://www.wolframalpha.com/input/?i=speed+of+light%2Flittle+g http://www.wolframalpha.com/input/?i=speed+of+light%2Flittle... it would take a year to get to the speed of light at 1g (if my equation was right.) Then you can't speed up anymore.

pdonis 12y ago
> it would take a year to get to the speed of light at 1g (if my equation was right.) It isn't. Wolfram Alpha apparently doesn't know about the relativistic rocket equation. Try here: http://math.ucr.edu/home/baez/physics/Relativity/SR/rocket.html http://math.ucr.edu/home/baez/physics/Relativity/SR/rocket.h...
gizmo686 12y ago
Your equation is correct in a Newtonian universe, but does not consider relativistic effects. Generally when we talk about an object's acceleration, we are talking about its acceleration in its own reference frame. By definition, an object's velocity in its own reference frame is always 0, so acceleration does not become more difficult (ignoring the fact that the surrounding matter will be impacting you at higher speeds). From the perspective of an outside observer who is not accelerating, time would appear to slow down on the accelerating object, and the outside observer would record a decreasing acceleration.
- readerrrr 12y ago
  Fun fact, from the perspective of the observer on the ship, time outside the ship would also appear to slow down.
- ikeboy 12y ago
  So why is it difficult to maintain a constant acceleration? Is 1g really that impractical right now?
  - snowwrestler 12y ago
    I'm being accelerated at 1g right now and I'm about 40...so in another decade or so I should be able to get to anywhere in the universe! Jokes aside, there's no fuel source we know of that would allow a ship to accelerate continuously for 50 years at 1g.
  - gizmo686 12y ago
    1) Maintaining an acceleration requires fuel. 2) Even though you don't observe yourself moving at increasing speeds, you do observe the rest of the universe moving at increasing speeds. This means that small particles impacting your ship will hit it with increasing energy.
readerrrr 12y ago
After a year of acceleration at 1g, a stationary observer would observe a speed of 215184620 m/s or 71.7% the speed of light. After two years: 89.9% After four years: 97.2% After eight years: 99.3%