# You travel to one outer and one inner planet and back home again. Your journey takes about 7 years, 8 months. To which planets did you travel?

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### 1 Answer

There are a lot of variables with your question. Since the speed at which you are travelling is not stated, I could answer that you traveled to any inner and outer planet that you wanted to travel to. Mars, for example, is only 4 light minutes from Earth and Jupiter is roughly another 30 light minutes past that. You could conceivable make those two planets and back in under 90 minutes no problem.

The other variable to consider is the other planets' positions relative to Earth. This obviously changes since Earth and your two target planets all revolve around the sun.

A third variable to consider is how much time did you spend at each planet? Any time collecting data? Or just taking a quick picture and turning around?

I'll assume you are doing a manned mission based on the phrasing of your question. That rules out the speeds achieved with space probes like New Horizons. The space shuttle's orbital velocity is just under 18,000 miles per hour. Unfortunately that doesn't get you on your way to another planet. So let's bump the speed up to just over Earth's escape velocity: 28,000 mph.

To simplify things I'm going to make your inner planet Mars, because it is on the way to the outer planets. At the speed of 28,000 mph you will reach Mars in 210 days and Saturn in 3.6 years. Turn around and come home and that means your trip took 7.2 years. That's 7 years and 2.4 months. Since you needed proof of your journey, you spent one month at each planet taking pictures while in orbit. Now your total trip is 7 years and 4.4 months. The initial question said your trip took "about 7 years 8 months." So based on the speed of current manned spacecraft and distances to planets, I'm thinking that you traveled to Mars and Saturn.

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