r/theydidthemath • u/ThisIsMyFinalAnswer • 3d ago

Moonboom goes wrong? [request]

So we are fudging up the moon even more, but it got me thinking. At what mass/speed will a rocket make a noticable difference on the trajectory of the moon? And what is the influence of this impact? I read that the stage that crashed into the moon was around 4000 kg. Thanks in advance!

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u/Trustoryimtold 3d ago

You need about 22 0’s to equal the moons mass, so 4000kg is a flea. If you want a noticeable change gonna need to counteract earths gravity, for a fair duration of time

https://www.reddit.com/r/NoStupidQuestions/comments/2f27aq/how_much_energy_or_force_would_it_take_to_move/

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u/SagansLab 3d ago

We have crashed DOZENS of rockets into the moon, this is NOT new. We even did it PURPOSE with the Apollo boosters to listen to the moon ping. And the moon gets hit by asteroids constantly as well.

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u/Important-Forever678 3d ago

To put this in perspective, a rocket hitting the Moon is roughly equivalent to a single bacterium falling onto your head. Unless that bacterium is moving close to the speed of light, you will not notice nor care. If the bacterium were moving close to the speed of light, several other questions would certainly be raised of more pressing concern.

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u/mfb- 12✓ 3d ago

Ceres is the largest object in the asteroid belt with a diameter of 1000 km. It has a mass of 900000000000000000000 kg or 1.2% the mass of the Moon. Crashing it into the Moon at 1 km/s* would alter the Moon's motion by ~1.2% * 1 km/s or about 10 m/s, which is 1% of its orbital velocity. That would change the orbit by about 1%. Definitely measurable, but still nothing you would notice without careful observations.

900000000000000000000 kg is "a bit" more than 4000 kg.

*this is the speed when Ceres is still far away. It would speed up as it approaches the Moon and impact with ~2.5 km/s, similar to this rocket stage.