# 5.1 Voyager Program | Summary and Q&A

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November 8, 2021
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MIT OpenCourseWare
5.1 Voyager Program

## TL;DR

A discussion on the Voyager program, Alpha Centauri, and the different perspectives of time experienced by Alice and Bob in their journey.

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### Q: What is the Voyager program, and what was its original mission?

The Voyager program, launched in 1977, aimed to study planetary systems. It sent two spacecrafts that are still providing information about their surroundings in interstellar space back to Earth.

### Q: What is the destination in the course 8.20, and how fast does the spacecraft travel?

The destination in 8.20 is Alpha Centauri, the closest star system to our solar system. The spacecraft in the course travels at a constant velocity of 0.943 times the speed of light.

### Q: How long does the journey take from Alice's perspective?

From Alice's perspective, the journey takes 5.3 years. This is calculated using the distance of 5 light years divided by the velocity of 0.943 times the speed of light.

### Q: How long does the journey take from Bob's perspective?

From Bob's perspective, the journey is Lorentz contracted, taking only 1.67 years. This is calculated by dividing the distance of 5 light years by the gamma factor of 3 and then dividing by the velocity of 0.943 times the speed of light.

## Summary & Key Takeaways

• The Voyager program, initiated in 1977, sent two spacecrafts to study planetary systems and are now exploring interstellar space, providing valuable information back to Earth.

• In the course 8.20, the mission is to reach the closest star system, Alpha Centauri, and its planet, Proxima B, using a spacecraft that can travel at 0.943 times the speed of light.

• Alice, on Earth, observes Bob's journey taking 5.3 years, while Bob experiences a Lorentz contracted journey, taking only 1.67 years due to the effects of special relativity.