Use lemons to detect ghosts in your house

Yet another hilarious Instagram reel where this woman (who could otherwise thrive as a fashion model) claims to be an astrologer and numerologist has some super weird theories. One of them being- Slice lemons and put them in a glass of water. If they sink, there’s “negative energy” in your home. Quite evident that this woman has never attended a science class in her high school. So here’s a refresher:

Let's dive into the physics behind the sliced lemon's behavior using some formulas.

*Buoyancy and Density*

1. Archimedes' Principle:

Fb = ρVg

Where:
Fb = Buoyant force (upward)
ρ = Fluid density (water)
V = Volume of the lemon slice
g = Acceleration due to gravity (9.81 m/s²)

1. Density formula:

ρ = m/V

Where:
ρ = Density of the lemon slice
m = Mass of the lemon slice
V = Volume of the lemon slice

*Initial Floating*

Assuming the lemon slice has a density (ρ_lemon) slightly lower than water (ρ_water), and considering the air pockets within the slice:

ρ_lemon < ρ_water

The buoyant force (Fb) equals the weight of the lemon slice (F_weight), allowing it to float:

Fb = F_weight
ρ_water * V * g = ρ_lemon * V * g

*Eventual Sinking*

As water absorbs into the lemon slice:

1. Mass increase: m_new = m_old + Δm (water absorbed)
2. Volume increase: V_new = V_old + ΔV (water absorbed)
3. Density increase: ρ_new = m_new / V_new

The lemon slice's density becomes greater than water's:

ρ_new > ρ_water

The buoyant force decreases, and the weight of the lemon slice exceeds the buoyant force, causing it to sink:

F_weight > Fb
ρ_lemon * V * g > ρ_water * V * g

*Key Variables*

- ρ_lemon ≈ 0.87-0.95 g/cm³ (lemon density)
- ρ_water ≈ 0.998 g/cm³ (water density at 20°C)
- V ≈ volume of lemon slice
- g ≈ 9.81 m/s² (acceleration due to gravity)