# Math Question Too Long For Thread Title (Calculating A Spacecraft's Speed Through Space) **URL:** \ **Category:** Factual Questions\ **Created:** [March 2, 2019, 4:01pm UTC](https://boards.straightdope.com/t/math-question-too-long-for-thread-title-calculating-a-spacecrafts-speed-through-space/830437 "2019-03-02T16:01:30Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![HeyHomie](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/heyhomie/32/207_2.png) [@HeyHomie](https://boards.straightdope.com/u/HeyHomie)\ **Post date:** [March 2, 2019, 4:01pm UTC](https://boards.straightdope.com/t/math-question-too-long-for-thread-title-calculating-a-spacecrafts-speed-through-space/830437/1 "2019-03-02T16:01:30Z")
The Voyager 1 craft is traveling at 17km/s. Exoplanet Ross 128b, which is suspected to be capable of supporting life, is 11 light years away. How long for Voyager to reach Ross (although I don’t know if it’s even headed that way, but you get my point). Can someone give me a formula for how long it would take Voyager to travel a light year? ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [March 2, 2019, 4:09pm UTC](https://boards.straightdope.com/t/math-question-too-long-for-thread-title-calculating-a-spacecrafts-speed-through-space/830437/2 "2019-03-02T16:09:47Z")
The formula is t = d/v, where t is time, d is distance, and v is velocity. That still leaves some unit conversions, but as it happens, [Google’s calculator](https://www.google.com/search?source=hp&ei=nqp6XNarOJfc-gTD2ac4&q=11+lightyears+%2F+%2817+km%2Fs%29&btnK=Google+Search&oq=11+lightyears+%2F+%2817+km%2Fs%29&gs_l=psy-ab.3...498.14537..15964...0.0..1.266.4334.0j22j4......0....1..gws-wiz.....0..35i39j0i131j0j0i3j0i22i30j0i13j0i13i30j33i299j33i22i29i30j33i160.KWgUUjMvaFM) will do those automatically: It comes out to almost 200,000 years. ---
**Author:** ![HeyHomie](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/heyhomie/32/207_2.png) [@HeyHomie](https://boards.straightdope.com/u/HeyHomie)\ **Post date:** [March 2, 2019, 4:22pm UTC](https://boards.straightdope.com/t/math-question-too-long-for-thread-title-calculating-a-spacecrafts-speed-through-space/830437/3 "2019-03-02T16:22:24Z")
> [@Chronos](#): > > The formula is t = d/v, where t is time, d is distance, and v is velocity. > > That still leaves some unit conversions, but as it happens, [Google’s calculator](https://www.google.com/search?source=hp&ei=nqp6XNarOJfc-gTD2ac4&q=11+lightyears+%2F+%2817+km%2Fs%29&btnK=Google+Search&oq=11+lightyears+%2F+%2817+km%2Fs%29&gs_l=psy-ab.3...498.14537..15964...0.0..1.266.4334.0j22j4......0....1..gws-wiz.....0..35i39j0i131j0j0i3j0i22i30j0i13j0i13i30j33i299j33i22i29i30j33i160.KWgUUjMvaFM) will do those automatically: It comes out to almost 200,000 years. That’s Voyager to reach Ross, or Voyager to travel a light year? ---
**Author:** ![74westy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/74westy/32/3950_2.png) [@74westy](https://boards.straightdope.com/u/74westy)\ **Post date:** [March 2, 2019, 4:44pm UTC](https://boards.straightdope.com/t/math-question-too-long-for-thread-title-calculating-a-spacecrafts-speed-through-space/830437/4 "2019-03-02T16:44:57Z")
Is the Sun’s gravity not slowing V-ger? ---
**Author:** ![DPRK](https://avatars.discourse-cdn.com/v4/letter/d/4491bb/32.png) [@DPRK](https://boards.straightdope.com/u/DPRK)\ **Post date:** [March 2, 2019, 4:45pm UTC](https://boards.straightdope.com/t/math-question-too-long-for-thread-title-calculating-a-spacecrafts-speed-through-space/830437/5 "2019-03-02T16:45:51Z")
Just to point out, actual Ross 128 is heading this way at 31 km/s and will swing by (within several light years; not 1, though) long before 200,000 years will have elapsed. ---
**Author:** ![engineer\_comp\_geek](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/engineer_comp_geek/32/504_2.png) [@engineer\_comp\_geek](https://boards.straightdope.com/u/engineer_comp_geek)\ **Post date:** [March 2, 2019, 5:03pm UTC](https://boards.straightdope.com/t/math-question-too-long-for-thread-title-calculating-a-spacecrafts-speed-through-space/830437/6 "2019-03-02T17:03:10Z")
> [@74westy](#): > > Is the Sun’s gravity not slowing V-ger? Technically yes, but practically, not much at this point. Voyager 1 entered interstellar space in 2013, and Voyager 2 entered interstellar space last year. The spacecraft needs to get about halfway between us and another star (Alpha Centauri, for example) before the sun ceases to be the most dominant gravitational object affecting the craft, but at this point the interstellar wind probably has more of an effect on the spacecraft’s motion than the sun’s gravity. Poking around on google, I found a post where someone claimed to have done the math, and figured out that in the next 30 years, Voyager 1 will slow down by about 1 mph. I didn’t check the math, but I think that’s in the general ballpark. ---
**Author:** ![Darren\_Garrison](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/darren_garrison/32/92_2.png) [@Darren\_Garrison](https://boards.straightdope.com/u/Darren_Garrison)\ **Post date:** [March 2, 2019, 5:58pm UTC](https://boards.straightdope.com/t/math-question-too-long-for-thread-title-calculating-a-spacecrafts-speed-through-space/830437/7 "2019-03-02T17:58:24Z")
Voyager 1 is 145 AU out, and gravity falls with the square of distance, so V1 is being pulled back twards the sun with 1/21025 the accleration that Earth experiences at 1 AU. Earth experiences 0.006 m/s[sup]2[/sup], so V1 is experiencing around 1/3,500,000 of a meter per second deceleration from the sun. ---
**Author:** ![74westy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/74westy/32/3950_2.png) [@74westy](https://boards.straightdope.com/u/74westy)\ **Post date:** [March 2, 2019, 6:36pm UTC](https://boards.straightdope.com/t/math-question-too-long-for-thread-title-calculating-a-spacecrafts-speed-through-space/830437/8 "2019-03-02T18:36:22Z")
> [@engineer\_comp\_geek](#): > > Technically yes, but practically, not much at this point. Voyager 1 entered interstellar space in 2013, and Voyager 2 entered interstellar space last year. The spacecraft needs to get about halfway between us and another star (Alpha Centauri, for example) before the sun ceases to be the most dominant gravitational object affecting the craft, but at this point the interstellar wind probably has more of an effect on the spacecraft’s motion than the sun’s gravity. > > Poking around on google, I found a post where someone claimed to have done the math, and figured out that in the next 30 years, Voyager 1 will slow down by about 1 mph. I didn’t check the math, but I think that’s in the general ballpark. > [@Darren\_Garrison](#): > > Voyager 1 is 145 AU out, and gravity falls with the square of distance, so V1 is being pulled back twards the sun with 1/21025 the accleration that Earth experiences at 1 AU. Earth experiences 0.006 m/s[sup]2[/sup], so V1 is experiencing around 1/3,500,000 of a meter per second deceleration from the sun. Two very good answers that fought ignorance without making me feel stupid. Thank you both.