Push Me – Pull You

Pushing-22.4.17-BlogWhen you push something, it moves away from you. That’s just common sense and it was described by the great physicist, Sir Isaac Newton, in his 2nd law of motion way back in the 17th Century. But, believe it or not, scientists have now created a substance which does exactly the opposite – if you push it, it moves towards you!

How can such a thing happen? The answer is negative mass. Just as an electric charge can be either positive or negative, the same is theoretically true of mass. In everyday terms, mass is the same as weight (although weight is really caused by gravity’s effect on mass – but that’s another story!).

As you might expect, matter with a negative mass behaves in a different way to matter with a positive mass (everything we come across in the ‘real’ world). When a force, like a push from an arm, or the pull of gravity, acts on positive mass it causes it to move in the direction of the force. But things with a negative mass move in the opposite direction.

Floating-22.4.17Negative mass wasn’t easy to make! First the scientists from Washington State University had to take some rubidium atoms and cool them to absolute zero – that’s 273⁰ below freezing. In these conditions the atoms move very slowly and start to behave as if they were waves rather than particles. Lasers were then used to ‘kick’ the fluid which behaved just as something with negative mass was predicted to.

More experiments have to be done to confirm the findings. But, if they are true then we will be able to recreate in the lab conditions found in black holes and neutron stars. There might also be technological implications, like anti-gravity devices, but these (if possible at all) are a long way in the future.

If you love science then you’ll find quite a few articles on the topic in Nature Matters. There are also many quizzes on Science in the educational area of our site, each one written for a different level of understanding (click on the relevant curriculum from KS1 to GCSE in the sidebar). Why not take a look?

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