The Size of Space | JTheory

Using the speed of light, we can visualise the vast distances of space that separate us from the planets, stars and galaxies throughout our massive universe.

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A JTheory Production
‘The Size of Space’

Author/Producer Jason Forbes

Music ‘Ofelia’s dream’ by Bensound


The size and scale of the universe is one of those things that us humans have trouble visualising, we often compare familiar sizes to each other with images like these. We can use this method for planets, stars and galaxies but what about the space in between? Time or speed being used as a dimension for distance is much easier to understand then an arbitrary value with no basis in nature,unlike like the day night cycle we all experience. ‘Half a days drive’ or ‘20 minutes down the road’ are popular phrases and the human brain does not need to visualize time and speed to grasp it easily.

1 astronomical unit [AU or UA] is the AVERAGE distance from earth to the sun [149.6 million kilometers], the parsec is also measured in Astronomical units [1 parsec = 648000/πAU about 206265 AU or 3.26 light years or 31 trillion km]. The Light-year is the distance that light travels in vacuum in one Julian year (365.25 days) It is perhaps the most popular unit because the speed of light is constant and is found in nature just like the day/night cycle on earth, so we don’t need to visualise light-speed as much as Astronomical units. i will be using the light-year unit to explain distance but keep an eye out for parsec values on screen if you prefer those.

Let’s start with something familiar, A human person is said to walk, on average, 1.39 meters per second. Quick enough to get you to the bathroom from anywhere in the house in under 20 seconds for most folks. Travelling outside of your home takes longer, so we use kilometers instead 1000 meters is 1 km.. The earth is 40,075 kilometers in circumference which means it would take about 334 days to walk around it ignoring oceans, mountains and sleeping or stopping.

Light zips around the earth around 7.5 times per second[299 792 458 m / s] and spends 1.26 second travelling from the moon to your eyes[384,400 km]. It takes 8 minutes for light leaving the surface of the sun to reach us here on earth or 8 light minutes. That means if the sun exploded we would only find out 8 minutes later. Our nearest star, Alpha Centauri C, aka Proxima Centauri is about 4.3 light years [268,770 AU] away from us. Meaning it takes 4.3 years for us to find out if that star has exploded compared to the 8 minutes for our own. NASA Voyager 1 spacecraft[First spacecraft to leave the solar system] is travelling away from the Sun at a rate of 17.3 km/s. If Voyager were to travel to Proxima Centauri, at this rate, it would take over 73,000 years to arrive.

Our galaxy is about 100 thousand light years in diameter [30660.14pc]and has roughly 100 to 400 billion stars with other estimates in the trillions, the distance to the galactic core of the milky way from earth is about 27 thousand light years[8278.238pc]. Current estimates put the number of planets in our galaxy at 800 billion to 3 trillion planets.

Our favourite galaxy other than our home milky way is andromeda [Messier 31[m31] at 2.5 million light years[780 kilo-parsecs] away from us. Andromeda measures 220 thousand light years across[ ] which is more than double our own milky way galaxy.Canis Major Dwarf galaxy has in recent times taken the lead as nearest galaxy to earth at only 25 thousand light years[ 7.7 kilo-parsecs] compared to the previous title holder, Sagittarius Dwarf Spheroidal Galaxy which is about 70 thousand light years[21462.10pc] from earth.
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