The Sun is losing mass, and at a rate fast enough that it’s forced us to change the way we measure astronomical distances.
Is Earth Gaining Mass Or Losing Mass?
We generally think of the Earth as having a constant mass. On a basic level that’s true, but the Earth’s mass does change very slightly. So is it’s mass increasing or decreasing? The short answer is we don’t know.
Galactic Scale
How do you weigh a galaxy? With planets we can measure their distance from the Sun and their orbital speed. By observing their motion in detail we can calculate their mass very precisely. For binary stars we can use a similar method. Observe the size of their mutual orbits and their orbital period, and by Kepler’s laws you can determine their mass. We can’t do that with galaxies, so what do we do?
Dying Light
Photons are massless. We know they are massless because particles with mass can’t move at the speed of light. We know that special relativity works, and the speed of light is the same in all frames of reference, and special relativity only works if photons are massless. Except…
Accentuate the Negative
There’s news on the web that cosmologists have proven the existence of negative mass. The news is based upon an article that recently appeared on the preprint arxiv, and has not yet been peer reviewed. The article in no way proves the existence of negative mass, but rather demonstrates the theoretical possibility of a form of negative mass within general relativity. In other words, it is an interesting “what if” paper rather than applied astrophysics.
Give and Take
How do we determine the mass of a star? One way is to look at the motion of binary stars. Their motion due to their mutual attraction allows us to calculate their masses by their orbits.
Massive Issues
We all know that many objects (atoms, cats, us) have mass. What you probably don’t know is that there are multiple different types of mass, and this has real physical (and astrophysical) consequences.
Seen and Unseen
When we look at our galaxy, we find it has more mass than the matter we see. Much more. This is the first clue that there must be dark matter in the Universe.
Equivalent Principles
The equivalence principle states that everything falls at the same rate in a gravitational field. But what about antimatter? We think it would fall just like regular matter, but we haven’t yet been able to put that assumption to the test.