Scale

The Sun is ~1,392,684 km in diameter. That's hard to envisage.
The Earth is ~12,750 km in diameter. that's also hard to envisage (although, travelling around the World in a plane is kind of within our brain's capacity to envisage.
Pluto is ~2300 km in diameter. That's a decent plane flight, within distances we talk about on Earth, but still hard to visualise.

The distances between these bodies, I think, are too big to visualise;

Sun to Earth = ~150,000,000 km.
Sun to Pluto = ~ 5,874,000,000 km. (on average, it is an elliptical orbit)
Sun to nearest star (Proxima Centauri) = ~4.243 light years = ~ 40,142 x10^12 km = ~ 40,141,750,100,000 km (40 trillion km!)

For whatever reason (fun) it is interesting to scale things down to try and give perspective to these sizes and distances.

So, if the Sun was the size of a basketball (dia. 238.5mm) then the Earth would be ~2.2mm and located about 25.6m away. You can picture that. It might surprise a lot of people how much bigger the Sun is than the Earth and just how far away it is. Although now we start to have the reverse of the problem: realising how small a human is on that 2.2mm sized Earth!

Pluto is a mere ~0.4mm about the size of a grain of castor sugar (not granulated but castor - not sure about other places, but in the UK, castor sugar is finer than granulated - granulated is about 0.8mm diameter, hence 2x bigger than the scaled Pluto). Scaled Pluto is located 1km away from the basketball-sized sun! That's getting hard to picture. I can picture 1 km, but I can't picture a grain of sugar 1km away.

But the best bit is that the nearest star (Proxima Centauri) in this scale is a whopping 6875 km away! ****ing far, even on this scale!

Its this scale that so many people fail to realise. Its this scale that is going to keep the fantasy of travelling to distant planets and stars (and galaxies) exactly that, a fantasy, at least for a very long time until maybe one day technology moves somewhere that we just cannot predict yet. 

I don't want to seem negative, just realistic. I'll still enjoy science fiction.