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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?
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this post was submitted on 29 Apr 2024
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If “energy equals mass”, shouldn’t we be gaining mass from the sun too 🤔
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
I thought plant biomass was obtained from the air (CO2/carbon sequestration?) and water.
You need photosynthesis to do that
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 🤔
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.
Wow - that’s what I meant. Not sure how I managed to get it backwards.
And to think I fretted so much over using “astronomically” and “minuscule” together 🤪
We do, an infinitely small amount. Remember you gotta divide by c².
Isn’t this just a matter of units though?
Like we could define our own units such that 1 unit of e equals 1 unit of m.
I have no clue what units that c^2^ formula are actually in 😕
c is the speed of light, so you can use any distance over time unit. But most commonly it's given as 299 792 458 m/s
So you can't since m is multiplied by c and c isn't equal to 1.
Actually you can.
Oof - I have to rethink everything I thought I knew about E=mc^2^ 🫠
I’ve always discounted c^2^ 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.
Ok - This is literally the origin for me. 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 ....
~~> energy equals mass~~
~~That doesn't mean energy has a weight.~~
~~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...
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.
Oooh…Good point. And now I have conflicting responses.
This one makes the most intuitive sense to me but ¯\_(ツ)_/¯
One more thing to connect both responses.
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.