- News

There are factors that are causing Earth to both gain and lose mass over time, according to Dr Chris Smith, a medical microbiologist and broadcaster who tries to improve the public understanding of science.

Using some back-of-the-envelope-style calculations, Dr Smith, with help from physicist and Cambridge University colleague Dave Ansell, drew up a balance sheet of what's coming in, and what's going out. All figures are estimated.

• It's getting lighter, by about 50,000 tonnes in mass each year, but not due to space dust

Some factors include:
• Gains: Mostly dust (like an asteroid, above) falling from space, plus increased energy from increases in the planet's temperature
• Losses: Mostly hydrogen, plus some helium and a tiny amount of lost energy

Activity - finding space dust • Micro meteors and particles falling from space land on roof
• They are washed with rain water into water butt
• Run a magnet round sludge at bottom of butt
• Any iron rich particles in there are probably from space
Credit: Dr Chris Smith, Cambridge University

Relevant teacher resources from the National STEM Centre eLibrary include:

Stardust
This Science upd8 resource revolves around the topic of the universe. A mission brings space dust back from the tail of a comet. The dust may reveal secrets about the origins of the universe and life on Earth. Students must defend the mission's $200 million price tag and produce a graphic to support their talks. Age: 11-14

Pupil Research Briefs – Astro-science Briefs
This Pupil Research Brief (PRB), designed by a team at the Centre for Science Education, supports the teaching and learning of astro-science at GCSE and Scottish Standard Grade levels. The briefs include, Collision course, Cosmic web site, ET phone Earth, Shooting stars and Star trail. Age: 14-16