If we took material like rock from space and got it back to Earth enough times, would Earth grow as a planet?
As the title says. I’m actually thinking about this hard with my friends because everything that’s produced on Earth stays on Earth so it doesn’t change size, but what if it’s not from Earth but it stays on Earth?
Yes the mass will change. It's a part of some Sci Fi tropes that for highly populated planets that the same mass of people coming on just match those coming off. Or else the planet will shrink or grow
One of the proposed methods for terraforming Mars is to lob a bunch of icy rocks at it. That would increase its mass but more significantly also the energy of the falling rocks would convert to heat and melt the ice into water. So enough energy to increase Earth’s size would also heat the surface and kill life.
This happens naturally in the form of meteors streaking through the sky. Each one of those is adding a tiny amount of mass to the planet.
But you’ve got me wondering about something now. When a large asteroid hits the planet, it obviously adds its own mass, but it also kicks up a lot of debris into space. Some percentage of that will reach orbital escape velocity and never come back. But I honestly don’t know if there is a net mass increase or decrease after such an event? We’re generally concerned about other more pressing matters in such a scenario!
unless the meteor is a rogue moon, the mass gained/lost is negligible compared to other particles interacting with the atmosphere or radiating (in and out), processes which are constantly happening.
for example, just the sun contributes some 200 tons every year (We also radiate out about the same mass that comes in). in 7.5 million years, that equals the asteroid that killed the dinossaurs (an event which happens way less often). So yeah, maybe the mass changes for a while, but even then, the dinossaur-killing asteroid is 0.000000000001% of earth’s mass… If we had one meteor like that everyday for a billion years, we would get some 20% extra mass.
(rough numbers I calculated just know, double check please)
Everytime we launch something into space the mass of Earth itself decreases by that amount. There is also energy trade off with the mass stealing a bit of earth’s momentum/energy for it to continue as well.
Overall, we’re talking about absolutely micro, if not smaller changes in mass and energy and it ultimately has zero affect on anything.
Would it really be a net negative though? Earth constantly has things burning up in the atmosphere. It turns into dust, gas and energy but it still is added.
Also long term you shouldn’t have a negative change in mass. That would be against entropy
I mean yeah. If you add stuff to a ball of stuff it get’s bigger.
Currently Earth is actually losing mass at around 55.000 tons per year. (100.000 tons loss due to air escaping to space but gaing around 45.000 tons in dust and meteorties falling on it).
I’ve always discounted c2 as “just a number” and didn’t consider it was a number of specific units 🫣
This is actually very common and I even remember physics teacher basically using the words “don’t worry about it, it’s just a really big number”, because their point was to imaging the big amount of energy you could get from very little mass.
But I mostly blame old documentaries about atom bombs that just threw in the absolute basics to make what is basically explosion porn.
My 8th grade “physical science” teacher told us this.
Yeah, that checks out. It is an interesting concepts that can peak student’s curiosity, but to early to really get into quantum mechanics. So for people that don’t further pursue an interest in physics, that’s often the last impression they are left with.
I had the fortune to have a physics professor as a dad. I carried a laminated double sided periodic table since elementary school. We didn’t even have chemistry of physics until secondary school …
We do. The sun’s energy is locked in plants via photosynthesis, which is then processed by herbivores and passed further down the food chain. That energy exists in form of chemical compounds which are then broken down to release it during digestion.
In terms of numbers tho, it’s probably a negligible fraction of the Earth’s mass
Sure, but the implication was that plant mass comes from the sun. Maybe some negligible fraction of percent is but nowhere near the majority.
The sun’s energy also goes into heat all over the planet. I’m just trying to understand how any of that energy might manifest as mass in a tangible way.
Or maybe it’s just the case that the amount of energy needed to create mass is astronomically minuscule.
🤔 I suppose that’s the principle behind atomic bombs 🤔
Or maybe it’s just the case that the amount of energy needed to create mass is astronomically minuscule.
It would actually be an astronomically large amount. An atomic bomb will turn a very tiny amount of mass into a tremendous amount of energy. And that’s with a nuclear process that is way more efficent then a chemical one like photosynthesis.
But from pure physics standpoint a carbon atom and an O2 molecule will have a teeny-tiny bit more mass than a CO2 molecule (which is why combining or burning them together will release some energy). So doing the reverse and splitting up a CO2 molecule into it’s parts will generate a little bit of mass.
It means it is physically possible to transition energy to mass and vice versa. Sunlight hitting the earth does not add any weight.
Edit: turns out that part was wrong
Also, earth radiates heat out to space. At a rate of (aaaaaaaaalmost, because of the greenhouse effect) 100% of the energy we get from the sun. If it didn’t, earth would be a few million degrees hot by now…
Energy itself doesn’t have mass. Mass is interchangeable. But we do gain mass by a very kittle amount when it is stored (by plants or solar panels you know). So both answers checks out. Mass can be converted to large amount of energy and large amount of energh can be converted to little amount of mass.
Energy don’t have weight but, it does have an effect on the curvature of space the same way matter does. In fact one of the proposed methods to create artificial blackholes is to put enough photons into the same place. It’s easier than getting matter together as photons don’t interact with eachother.
However the point is correct that light energy will only impart an insignificant amount to the earth’s pull.
No, it literally does mean that. If you put light in a box of mirrors the total weight of the box will literally increase by an amount equal to the energy of the photons. If you put some radioactive material in a theoretically perfectly sealed box from which no heat or light could escape, and weigh it while it decays into radiation, the weight will not change.
This applies to all forms of energy. A spring is heavier when compressed. An object gets heavier when you spin it, or heat it up. Sunlight hitting the earth most definitely makes it heavier. In fact, the sun hits the earth with about 4.4*10^16 watts of power, corresponding to about 0.5 kilogram per second.
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