Here vacuum does not mean low pressure, it means lack of substance. If you use a strong pump to depressurize and seal a glass bottle you still get a bottle wit

Here vacuum does not mean low pressure, it means lack of substance. If you use a strong pump to depressurize and seal a glass bottle you still get a bottle with air inside; you can easily see that there is air inside because if you submerge it in water or oil and break the seal you will see air bubbles coming out. If you were to try the same with a glass bottle full of water, you will find that is is much much harder to pump the water out than is it to pump the air out. This is perfectly compatible with the impossibility of an actual vacuum. The experiment that subverted this view had to use mercury to be practical at the time[1] In this experiment you essentially use the weight of mercury to pump mercury out of a glass bottle and since air cannot traverse mercury nor glass [2] then it must truly be a full vacuum. [3] [1] https://en.wikipedia.org/wiki/Torricelli%27s_experiment https://en.wikipedia.org/wiki/Torricelli%27s_experiment [2] This is false, mercury evaporates, quantum tunneling exists, gasses likely can be dissolved in mercury and material are porous. [3] In some sense you could say that the photons in the bottle make it not a vacuum, as they have mass or also that particles spontaneously appear from a base energy noise or a lot of other oppositions to that being a real vacuum. Still it is definitely a different thing from just low pressure air.