FEATURE: How Would You Know if You Were on Another Planet?

So, I finally got the chance to watch the latest ‘Predators’ movie. The movie opens with seven of the worlds leading ‘killers’ falling to the ground, into a mysterious Jungle. About thirty minutes into the movie, the characters realise that they are on another planet (or moon) when they reach the edge of the Jungle and are greeted with a panoramic view of what appears to be two gas giants and a collapsing moon.

Predators - the new movie

This got me thinking, “How would you know if you were suddenly on another planet, if nobody told you?" "What would it feel like to be on another planet?" Well, using my studies of astrophysics in conjunction with my extensive (and borderline-scary) knowledge of geeky science, I thought I’d try and put you onto another planet, using nothing but the magic of vocabulary!

'Whoa, doc, that’s heavy!’

As you stand up in the jungle, the first clue to your extraterrestrial relocation would come before you opened your eyes, before you even take a breath. Just pause for a minute. What do you weigh? Well, whatever your weight, it is dependant on the mass of the planet on which you stand. On Earth, with its meagre ‘1G’, you know exactly what you weigh. And every day of your life, every muscle in your body does its job under 1G. The result is that if there’s even the slightest “disturbance in the force” of gravity you know about it.

You even notice minute 'G' shifts in an elevator

Think about it, in a rapidly accelerating car – you feel it. In a lift (elevator), your body alerts you the second the lift starts moving. This is down to your remarkably keen sense of familiarity with gravity. No doubt you take this for granted as most of the time you experience the same boring ‘1G’. The most extreme that most Humans ever face in day to day life is in an airplane on take-off and landing. Now, guess how much ‘G’ that is? Only 1.2G 

So if you woke up tomorrow on another planet, you would know about it. It just wouldn’t feel right; you would feel a little heavy, or light, or that you were moving in a way you didn’t understand.

You see, it is virtually impossible to find another planet with exactly the same mass and density of Earth; that’s like an only child trying to find a random person identical to them – it’s not gonna happen. 

'Pressure – pushing down on me!’

 If the gravity didn’t get you, or by some miracle you found an identical planet to Earth in terms of mass/density ratio, then you’d probably still notice the pressure. Again, you spend your entire life in an atmosphere with very little variation. Few of us are mountain trekkers or deep sea divers, so few of us have had the experience of a noticeable change in atmospheric pressure.

But, again, on another world, the odds are overwhelmingly high that you would feel a strange change in pressure. If it was higher, you would suddenly feel like you were being squeezed, very slightly. If it was too low, you would start to ache very quickly, as your muscles and tissues would not be providing the necessary cohesion to keep you comfortable.

'I see the light!’
 
If you missed those early signs, you may catch this one. It shouldn’t take the hovering gas giants in the sky to alert you that the glowing ball you see is not Earth’s sun.

You see, our view of the Sun is provided by a combination of many factors, including:

• Its size
• Its composition
• Its distance from us
• Our atmosphere’s composition (which serves as the ‘lens’ that we see the sun through)

There are other factors. But you can imagine that, again, it would be extremely unlikely that you would find another planet with all the same properties as the above. This means that the sky would always seem strangely different; the colour of the sky, the hue, brightness and size of the sun, it would all just seem wrong.

'I can taste it!’

Another clue to your other-worldly predicament would be the air. Again, we have a delicate balace of chemicals here on the surface of our fair planet. We breathe a combination of 78.09% nitrogen, 20.95% oxygen, 0.93% argon, 0.039% carbon dioxide, and small amounts of other gases.

Interestingly, pollution makes up a very small percentage, so over 99% of what we breathe is unchanged no matter where we are on planet earth.

But, again, if you take an excursion to another planet, you would very quickly notice even a subtle difference in this combination. Studies have shown that changes of as little as 1% can lead to noticeable fatigue, changes in mood, and can even cause suffocation.

Those are the main ways you would know you were not on planet earth, without even touching on obvious things like alien plant-life and wildlife. It would simply feel strange. But isn’t it an exciting prospect? Wouldn’t you love to explore such strange new worlds? Even in our solar system, there are worlds that would be simply fascinating to visit. 

Titan

For example, Saturn’s moon, Titan. Did you know that if you were on the surface of Titan, the combination of the lower gravity (0.14G) and thicker atmosphere would mean that you could stand on the surface, without a space suit, and if you flapped your arms you would fly like a bird?

Of course, the temperature is extremely low, so you would need a good winter coat and a nice hat. But as along as you had that and an oxygen supply, you'd be fine! And the exciting thing is that one day, people will have that experience; the feeling of genuinely being on another world.
The brave men that visited the moon have come closest so far. Hopefully, within our lifetimes that dream will be realised fully.

All I know is that I’ll be mighty jealous of the people that do!