By Sybille Hildebrandt
Although water covers 70 percent (click here) of the Earth's surface, water is actually a rare substance that represents just 0.05 percent of the Earth's total mass.
Water has nevertheless played a crucial role in the emergence of life on Earth. Without water, the Earth would in all likelihood be a dead planet.
The amount of water on the planet has not always been the same, however. A research group at the Natural History Museum of Denmark has discovered this by measuring how hydrogen isotope ratios in the oceans have changed over time.
"The water that covered the Earth at the dawn of time contained more of the lighter hydrogen isotope than the heavier hydrogen isotope, known as deuterium, than it does today,” says Emily Pope, a post doc, who has played a central role in the study.
“By examining how the ratio of these isotopes has changed, we have been able to determine that over the course of around four billion years, the Earth's oceans have lost about a quarter of their original mass."...
Here we are now with the knowledge Earth loses mass over time. It loses mass in the way of helium molecules and hydrogen molecules and that hydrogen is linked to water.
Besides the Earth out-gassing helium and hydrogen there is also a universe comprised of the same molecules
This graph displays (click here) the different values of the deuterium-to-hydrogen ratio (D/H) in water observed in various bodies in the Solar System.
The horizontal blue line shows the value of the ratio in Earth's oceans, which has been determined to be 1.56 ×10-4. The green square shows the value of the ratio measured in CI carbonaceous chrondrites, a class of meteorites found on Earth, which are believed to originate in the outer asteroid belt....
Pretty cool stuff, isn't it? The point is mass is finite in the 'average' universe. There are scientists that measure an expanding universe, but, the real question is does an expanding universe me there is additional molecules added to it's mass or is it simply moving outward and making the 'universe as a bubble' larger.
For now, Earth's molecules are finite and we lose some of the over time.
