Question

Choose the best answer to each of the following. Explain your reasoning with one or more complete sentences. If we sent one of our current spacecraft to a nearby star (besides the Sun), the trip would take about (a) a decade; (b) a century; (c) 100,000 years.

Short answer

The trip would take about 100,000 years (option c).

Step-by-step solution

Understand the Problem

We need to determine how long it would take for a current spacecraft to reach a nearby star other than the Sun. To do this, we'll consider the average speeds of current spacecraft and the distances to the nearest stars beyond the Sun.

Examine Spacecraft Speeds

Current spacecraft, like the Voyager probes, travel at speeds of approximately 17 kilometers per second. This is a high speed but still limited compared to vast cosmic distances.

Consider Nearby Star Distances

The nearest star system, Alpha Centauri, is about 4.37 light-years away from Earth. We need to calculate the time it would take for a spacecraft traveling at Voyager's speed to reach it.

Calculate the Time Taken

First, convert the speed to a yearly distance: \(17 \text{ km/s} \times 60 \text{ s/min} \times 60 \text{ min/hour} \times 24 \text{ hour/day} \times 365 \text{ day/year} = 536,723,200 \text{ km/year}\). The distance to Alpha Centauri is approximately \(4.37 \times 9.461 \times 10^{12} \text{ km}\) (since 1 light-year is roughly \(9.461 \times 10^{12} \text{ km}\)).

Solve the Calculation

Divide the distance to Alpha Centauri by the yearly distance covered by the spacecraft: \(\frac{4.37 \times 9.461 \times 10^{12}}{536,723,200} \approx 81,000\) years. This is a rough estimate of the travel time.

Select the Correct Answer

Given the calculated travel time, the answer closest to 81,000 years is (c), which states 100,000 years. This accounts for the large scale of interstellar distances and spacecraft current capabilities.

Key concepts

Alpha Centauri Distance

Alpha Centauri is the closest star system to us, other than our own Sun. It is located approximately 4.37 light-years away from Earth. This might not sound far when we talk in terms of space, but on a human scale, it is immensely distant. To give some perspective, the distance from the Earth to the Moon is about 384,400 kilometers, which is quite small compared to a light-year. A light-year is the distance light travels in one year, which equates to about 9.461 trillion kilometers. Therefore, multiplying this by 4.37 gives us the vast distance light covers to reach Alpha Centauri.

Current Spacecraft Speed

Current spacecraft, like the renowned Voyager probes, cruise through space at speeds of around 17 kilometers per second. This equates to roughly 536,723,200 kilometers per year. While it sounds rapid, this speed is quite slow when scaled against the backdrop of vast cosmic distances.

Some faster Earth-bound objects exist, like certain particles in accelerators, but for manned and unmanned spacecraft, this speed limit displays the technological boundaries we face today. The challenge is to develop propulsion systems that can significantly increase these speeds to make deep space travel feasible within human lifetimes.

Interstellar Travel Challenges

Space travel to other stars is filled with challenges.

• Distance: The sheer distances involved make current spacecraft speeds impractical for timely human travel.
• Propulsion: Increasing speed without harming the spacecraft or its occupants is crucial.
• Energy: Finding sustainable energy sources to power long journeys is essential.
• Navigation: Long-duration navigation requires precision to avoid collisions with space debris or asteroids.
• Sustainability: Life support systems need to be self-sustaining for many generations if people are onboard.

These challenges go beyond engineering, encompassing biological, psychological, and logistical aspects.

Light-Year Calculation

A light-year is a unit of distance used in astronomy. It represents how far light can travel in one year. Since light moves at about 299,792 kilometers per second, it travels vast distances in one year, approximately 9.461 trillion kilometers. For calculations involving space travel and distances to stars, this measurement is critical. It provides a comprehensible scale for astronomers and scientists to work with.

For our example, the distance to Alpha Centauri requires converting this light-year distance into kilometers to understand how long a spacecraft, like the current ones, would take to travel these immense distances. It is a daunting number, but it helps frame the magnitude of interstellar travel for students and enthusiasts alike.