Talkradar UK, you called me out. Now I respond!

On this weeks Talkradar UK my comment criticising the zero-g missions in Halo and Killzone was received with some…confusion by the hosts. They proceeded to challenge me to defend my claims and prove my scientific girth (just for you, Cundy) by shedding light on the issue of gravity in space. I will now do so, one erroneous comment at a time.

Dave “Hooters” Haughton: “There’s no gravity in space, otherwise the shuttle would just fall back down. It must only kick in when you get very close to something big like a planet.”

OK, first of all, yes there is gravity in space. The sun is 150,000,000 km away, yet we are held in place by its gravity. So, gravity works in space, period. In fact, the Moon's gravity reaches Earth all the way across the 238, 000 mile gap and moves the sea around. Humans call this "the tides".

So, unequivocally, there is gravity in space. It does not “kick-in” when you get close to a planet. The moon is over 200,000 miles away, the Shuttle is just 200 miles way. So the Shuttle is definitely held by the Earths gravity. So why does it not fall down? The answer is the same as why the moon does not fall down: because it is in orbit.

Let's be clear: Orbit is not "a place where there is no gravity". Orbit is the name for when something’s ‘forward’ speed exactly matches the gravity that is tugging on it, leaving it in perpetual freefall. Let’s demonstrate this visually.

Imagine a cannon. You fire a cannon ball very slowly (A on this lovely diagram). The cannonball falls down. Why? Gravity pulled it down.

Now fire it harder (B). Still falls down and hits the ground. But what if you fired it so fast that the Earth’s surface curved away at the same rate as it was falling (C)?

As long as there’s no air resistance, you’d just keep falling round, and round, and round…. You get the picture.

That’s what is happening to the moon, and the shuttle. They are falling due to gravity, they just never hit the planet. And all the occupants inside do not feel gravity because they are freefalling. Imagine being in a lift, plummeting to Earth. You’d float in the middle. That’s what happens aboard spacecraft. Its not really “zero-g”, it is actually “micro-gravity”.

Matt Cundy: “Would a man in space be attracted by gravity to his spaceship?”

Actually, yes. It’s just that it would be by such a small amount that it would take years to “hit the bottom”.

Gravity seems strong, but it is weak. Think about your biceps. With your puny human bicep, you can lift up, let’s say, an apple. The ENTIRE PLANET EARTH is pulling that apple, yet your little bicep can easy cancel out the entire planets gravity!

So what’s the problem with those levels on Killzone/Halo?

My main problem is inconsistency. You see, in those levels, the ‘artificial gravity’goes offline. Fine. So why does everything slowly drop to the floor? Its like normal physics, but slower! That’s not micro-gravity!

The other big problem is that debris and dead bodies float, while everything else falls slowly to the ground! WHY??! A guy is stood (how, if there’s no gravity?!) on the ‘ground’ in those levels and as soon as you kill him he’ll suddenly begin to float!

Why do dead bodies float? Do they obey some new, different laws of physics? If so, I’ll be staying away from graveyards. One can only imagine the thousands of coffins floating off to the sky!

I guess the problem is the burden of knowledge. Like a Doctor watching Casualty, or someone with any grasp on facts watching Fox News. A little knowledge is a dangerous thing!