This physics question has bugged me since I was around 15 years old.
The sun is constantly giving us energy. Admittedly, a lot of it is being emitted back. But some of it stays on Earth. Does this energy contribute to increase Earth’s mass since E=mC(squared)?
If yes, then I have another question. Once space travel becomes common, will this result in earth losing some of its mass in the form of fuel and rocket parts and travellers on board?
Will these changes in mass result in change in temperature and gravity etc due to change in size of the planet’s core?
In: Physics
The Earth actually radiates *more* energy into space than the sun radiates towards us.
This is fairly easily proved: The temperature stays about the same, but heat is produced in the core by radioactive decay. This means that there must be a net heat *loss* to maintain the constant temperature.
*However*, the Earth loses mass from its atmosphere and gains mass from falling space rocks all the time. Scientists estimate a net *loss* of mass between these processes.
We do gain some mass from falling meteorites, but we lose more as helium and hydrogen escape from our atmosphere into space. (net loss of 55k tons per year).
The difference between sunlight absorption and re-emission should be negligible. In fact we’re losing more energy than we’re gaining that way just because of all the heat still trapped deep underground that’s slowly escaping.
As for making a difference to the overall mass or gravity, not a meaningful one. Maybe if something large hits the planet, otherwise you’ll have to get into the seventh or so digit of Earth’s mass to see a difference after billions of years.
Very slightly yes. The heat energy which is held in the Earth from being warmed by the sun does translate, via relativistic effects, to a slightly higher total mass.
But everything which has heat, emits some thermal radiation, and the more heat it has, the more radiation it puts out. So, there’s kind of an equilibrium effect at work. Heating the earth up hotter just makes it glow brighter in the infrared, so the excess heat is lost faster. So it’s not like the extra mass ever really accumulates.
There are a bunch of more factors. Like earth collects dust and rocks from space while losing light gasses that escape the upper layers of athmosphere. In total earth gains a little weight over time, but it’s very small compared to it’s total mass.
It isn’t.
But not for the reason you thjnk, since in the grand scheme of things energy is very diluted, and adds very little to mass compared to matter, and even then earth radiates more energy than it gets from the sun, as it has a secondary energy sources from radioaactive decay in the core, and compression heating.
Earth’s mass is impacted far more by by meteorites falling in, and solar winds slowly tearing away at the uppee atmosphere close to the poles, where the magnetosphere doesn’t protect it.
The end result is a net mass loss, from loss of gas.
Latest Answers