Massing the point

by Andrew Irving (on Thursday 16th June 2016)*

Believe it or not, when it comes to Science, finding the right answer turns out to be the easy part!

But molding the right question – now that’s a whole other business…

What is gravity?

Honestly, gravity is pretty hard to define. But the popular answer is `it’s a force’.

What is a force?

Basically, forces are just names we give to `whatever is responsible for some physical action(s)’.

So asking what gravity `is’ doesn’t tell us much. Instead, maybe we need to ask something like the following:

What does gravity cause?

In short, gravity makes apples fall to the ground (yum) while keeping our planet and the Sun just close enough for our warmth and life (both good) yet distant enough to prevent Earth being sucked into oblivion (thank you gravity).

Before we get too excited, let’s be clear: this is knowledge, not understanding! We’re still not asking the right question – let’s have one last go.

What’s happening physically when we cite gravity?

Well, loosely gravity is the attraction all things with mass (e.g. stars, planets and apples) experience to one another.

But wait, light is also affected by gravity. And light has no mass at all!

So what’s really going on?

Well, gravity is not about mass per se, it’s about energy.

Mass-Energy equivalence

Mass-Energy equivalence

But as anything with mass has energy too (thank you Einstein), we may never have realised this without light.

Thank you, light!

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* This blog was based on the YouTube video entitled ‘What is gravity?’ by Minute Physics.