Life expectancy of protons etc

 In modern physics (as described by the Standard Model), most of these particles are considered either stable or have extremely long or unknown lifetimes. Here’s a clear breakdown:

⚛️ Proton

• Stability: Effectively stable (no confirmed decay observed)
• Experimental lower limit:
  Lifetime > 10³⁴ years (proton decay has never been seen)
• Meaning: If protons decay, it is extraordinarily rare and beyond current detection limits.

👉 So for all practical purposes: proton = stable

⚛️ Neutron

• Free neutron (outside nucleus): unstable
• Lifetime: about 880 seconds (~14.7 minutes)
• Inside nucleus: stable (bound neutrons do not decay easily)

👉 So:

• Free neutron → decays into proton + electron + antineutrino
• Bound neutron → effectively stable in stable atoms

⚛️ Electron

• Stability: No decay observed
• Experimental lower limit:
  Lifetime > 6.6 × 10²⁸ years
• Meaning: Electron is considered fundamentally stable

👉 So: electron = stable

⚛️ Quarks

Quarks cannot exist freely (they are confined inside hadrons like protons/neutrons), so their “lifetimes” depend on type:

Up & Down quarks (most common, in matter)

• Stability: Effectively stable inside protons/neutrons
• No independent lifetime (cannot exist freely)

Heavier quarks (strange, charm, bottom, top)

• Unstable
• Lifetimes vary:
• Top quark: ~10⁻²⁵ seconds (fastest decaying particle known)
• Others: ~10⁻¹² to 10⁻¹⁰ seconds range

🧾 Summary Table

Particle	Lifetime
Proton	> 10³⁴ years (stable in practice)
Neutron (free)	~880 seconds
Electron	> 10²⁸ years (stable in practice)
Quarks (u, d)	confined, effectively stable inside hadrons
Heavy quarks	extremely short (10⁻²⁵ to 10⁻¹² s)

🧠 Key insight

• Proton, electron → stable building blocks of matter
• Neutron → stable only inside nuclei
• Quarks → mostly unstable individually, but confined in matter

If you want, I can also explain why proton decay is predicted in grand unified theories (GUTs) or  what would happen to the universe if electrons were unstable.