Sirius is about 9.0 light-years from Earth.

To reach the star by spaceship in 10 years (ship time), how fast must you travel?
How long would the trip take according to an Earth-based observer?
How far is the trip according to you?

8 days

To determine the speed needed to travel to Sirius in 10 years (ship time), we can use the formula distance = speed × time. Since Sirius is about 9.0 light-years away, we can set up the equation as follows:

9.0 light-years = speed × 10 years

To solve for the speed, we divide both sides of the equation by 10 years:

speed = 9.0 light-years / 10 years

Hence, you would need to travel at a speed of approximately 0.9 light-years per year to reach Sirius in 10 years (ship time).

Now, let's calculate the duration of the trip according to an Earth-based observer. We need to consider time dilation, which is the effect caused by traveling at speeds close to the speed of light. According to special relativity, as an object moves faster, time slows down for it relative to a stationary observer.

Since the spaceship is traveling at a significant fraction of the speed of light, time dilation occurs. To calculate the time dilation, we can use the equation:

time dilation factor = √(1 - (v^2/c^2))

Where:
v = spaceship velocity
c = speed of light

Given that the spaceship needs to travel 9.0 light-years in 10 years (ship time), we already know the rate of travel of the spaceship is 0.9 light-years per year from the previous calculation.

Using the time dilation equation, we can solve for the time dilation factor:

time dilation factor = √(1 - (0.9^2 / 1^2))

time dilation factor = √(1 - 0.81)

time dilation factor = √(0.19)

time dilation factor ≈ 0.435

Therefore, the time dilation factor is approximately 0.435.

To find the trip duration according to an Earth-based observer, we multiply the ship time by the time dilation factor:

Trip duration = ship time × time dilation factor

Trip duration = 10 years × 0.435

Trip duration ≈ 4.35 years

According to an Earth-based observer, the trip to Sirius would take approximately 4.35 years.

Finally, to calculate the distance of the trip according to you (the Earth-based observer), we multiply the speed of the spaceship by the ship time:

Distance = speed × ship time

Distance = 0.9 light-years per year × 10 years

Distance = 9.0 light-years

According to you, the distance of the trip to Sirius is approximately 9.0 light-years.